Thursday, September 26, 2013

New US Mediumwave Files Uploaded

A new US Mediumwave Pattern Reference, produced by Radio Data MW, has been uploaded. You will find it at the top of the right sidebar under LATEST US MEDIUMWAVE FILES. Radio Data MW, a program I have been working on for the last few years, accomplishes this mapping process.

Included is a complete set of GoogleMap-based, HTML-driven maps which show the most current pattern plots of all licensed US mediumwave broadcast stations from 540 - 1700 KHz. The set includes all frequencies for the indicated services: Unlimited, Daytime, Nighttime, and Critical Hours. Individual maps are grouped by channel frequency: 540, 550, 560 KHz, etc.


See the link at the top of the right sidebar under LATEST US MEDIUMWAVE FILES.

I will attempt to make this a regular feature on RADIO-TIMETRAVELLER, with regular yearly updates. The sidebar at the top right will have the most current links. The link will change for each new posting, so I would avoid copying and pasting it into a forum or other web page. Come to the main page of this blog instead.


The maps are HTML-based, so no regular install is necessary. Simply unzip the downloaded file and click on the individual map file to run. The map will open up in your web browser. They are self-contained, with image icons embedded right into the code. You must have an internet connection to view the maps.


Using the actual FCC database files Radio Data MW will auto-generate an interactive HTML pattern map, showing the pattern plots for all stations included at the discretion of the user. A complete set of mediumwave pattern maps can be generated in a matter of minutes. Radio Data MW generates a real pattern plot based on ground conductivity, ground dielectric constant, and can display actual (but approximate of course) signal level boundaries for Local, Distant, Fringe, Extreme mV/m levels, or any custom mV/m level chosen by the user.

The online Google Maps API is used to generate and plot each station on a map of the US. An accurate flag pin is placed at each transmitter location, and in satellite view may be zoomed in to see the actual transmitter site. Map flags are color-coded to indicate Unlimited, Daytime, Nighttime, and Critical Hours services. Each flag has a tooltip-type note, and when hovered over with the mouse will display a note on the station.

A pattern plot for each station is generated and displayed. Each pattern is calculated using standard formulas used by the FCC to compute the base values at one kilometer, and field strength formulas at distance based on the works of many people over the years. See Field Strength Calculations: A History and Field Strength Calculator One, previously posted on RADIO-TIMETRAVELLER.

Finally, an accurate ray path can be drawn from all transmitters to a user-specified receiving location by inputting latitude-longitude coordinates. Super-imposed on the pattern plots, the ray paths show the listener where he or she falls on each station's pattern, a handy guide to knowing where you stand.

Note that these maps are web-based. As stated, they use Google Maps and thus require access to Google. In order to view them you need a connection to the internet. In desktop or laptop use, they have been tested in the Internet Explorer, Firefox, Chrome, Opera, and Safari browsers. If using Internet Explorer, best results are had with the latest version. Chrome works best.

These maps will work on some tablet or phone browsers. I have tested them on an Android device and it's handy to be able to display them while DXing outside or on the road. Some browsers will not allow pinch-to-zoom, where others will. Some browsers don't render the map controls correctly. Response is fair to poor on the tablet or phone due to the sheer number of HTML lines and processing required to render the maps. Such is the current state of tablet and phone browser rendering.

Hope you enjoy these pattern maps and find them useful.


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Stephen said...

Hi, Bill.

I've been wondering how your DXing adventures have been going. I was hoping to read about your trip east from AZ to NY, for example. Also I'd like to suggest another idea for a future trip - what about taking a northern route, say, including IL, MN, ND, etc? I'd love to find out how your truck radio does with stations like WNAX, KFYI, CBK, etc. :)

73, Stephen


Hi Stephen,

Long time no hear. Hope you have been well.

I must apologize for no blog posts this last year. I have gotten away from the writing but perhaps will do some this fall or winter.

I was indeed in AZ last winter. Will be making the trip again soon from NY to AZ, but unfortunately heading across the midwest again (I-70). One day I may take that northern route as I need just 4 of those northern tier states to complete all 48.

Have been working on mapping nighttime signal patterns over the last year and may have some downloadable files in the next few months.

Take care and good DX to you,


Stephen said...

Hi Bill,

Good to hear from YOU! I've been alright, for the most part. My latest radio acquistions are the Tecsun PL-398bt, which I like quite a bit (once I've discovered an undocumented way to change how it behaves on desensing on the front end), and the CC Pocket, which is a fair bit of a disappointment. Oh, and I have a Superradio that I got used, as well as a filter-modified SRF-M37W (but I just broke the belt clip on it the other day) and a second PL-606 to replace one with a broken display. I'm thinking about maybe getting a PL-310 (b/c of videos that show it has that same "feature" as the 398bt) but I'm not sure yet.

Oh, I should explain about that feature. :) So I have a local station on 1130 that reads 75 dBµ and one on 1170 that on peaks (it uses MDCL so it varies) is about 80 dBµ. Between the channels, it normally reads about 43 dBµ on 1110 and 1190 and 45 dBµ on 1150. KDIS is audible, but extremely quiet on 1110 even with the volume maxed out, KTLK is almost undetectable on 1150, and KGBN is very faint on 1190.
So, I go into SW, start scanning with the VF button, then quickly give the tuning knob a jab-rotate down. The background noise jumps up much louder, and my signal display goes to 00/00.
I then switch back to AM, and 1110 KDIS is now reading around 22/16 or so in the +/- 1 kHz BW mode, and sounds just about as loud as the local stations, just much noisier. The noise just about covers up KTLK on 1150, but I can sometimes make out the offset het which indicates another station on 1150 (in this case, the one in Mexicali), and 1190 KGBN is readable too, again with the Mexicali het underneath. The blank channels in between are just as loud as the local stations. In this mode (which I'm not sure what to call it), I don't get the 41/00, 45/00 or even 50/00 in between the stations, but the signal strength drops off much more once you tune off a local's channel.
I'm not sure if the PL-380 can do it, though. I'm not able to test on mine because of the broken tuning knob. I find I frequently break the knob on it - this is like the 2nd or 3rd time, hence another reason I'm considering a PL-310 because of its different tuning knob configuration. Actually I'd like to get a vertically-oriented one - kind-of like the shape/size of the CC pocket but with all the other features that the Tecsuns have, especially including that one I discovered that I described up above.

Oh, okay. I'll be honest and say I'd been starting to wonder if something had happened to you, maybe you had passed away, become the LATE Bill, or something like that. (I think I'd seen a post from you on ultralightdx or abdx on yahoo, I forget which, but it'd been a while.) Glad to hear you're still around. :) I look forward to more blog posts. Got some ideas of things you may write about? Any chance you'd write about your DXing on the trips this past winter?

Ok. So do you think you'll be tuning in 630, 650, 760 and 850 early on to see how far east those stations reach when not enhanced by what happened during your mw daytime dx tale story a few years ago? :) Also what route(s) did you take last winter? Or is that an answer for an article you may be writing?

Ahh, that sounds very interesting. :) Would that be the skywave patterns, I'm guessing? :)
Also I'd be interested in seeing some groundwave patterns at different signal strengths, too - for example the default ones in your field strength calculator program, plus a few others maybe - or even be able to pick custom fields to display. Also being able to put in a location (gps coordinates) on a map and have it show the calculated fields at that location would be quite nice. :)

Stephen said...

Also on another forum, someone posted a link to a coverage map of 540 CBK which I thought was quite interesting. :)

You take care too, and even better DX to you. :) So what do you think would be some of your best catches? A few memorable ones for me, in no particular order, have been:
594 JOAK - Tokyo, Japan - dug out from under my local KOGO and its IBOC a few years ago, using a PL-380 and SAT.
1240 KALY - Albuquerque, NM - heard on a 90s-vintage Panasonic RQ-SW20 (and probably SAT) nearly a decade or so ago, out from under my local 1240's unmodulated carrier. (I'm close enough to my 1240 that it owns the channel at night unless I null them, and they were opposite direction from KALY so not nullable.)
1230 XEEX - Culiacan, Mexico - heard on an SRF-59 in the early morning, complete with an ID in Spanish (faint but alone on the channel) not 5 seconds after I put the headphones on! I'd just woken up around 5am local - had gone to sleep with the radio on a different station entirely.
910 KWDZ - Salt Lake City, UT - heard on one of my Tecsuns around Thanksgiving weekend after Harold Camping's failed predictions, out from under my local 910 KECR which was experiencing automation / network issues. KWDZ has a deep null toward me, and KECR is almost aimed right at me.
840 WHAS - Louisville, KY - was listening to Dave Ramsey on KXNT almost a couple years or so ago when I suddenly heard a few WHAS mentions in the background station as it faded up and KXNT faded down. I have since heard the station a few other times.



Hi Stephen,

Nice to know you're still in the hobby. Thanks for the update on your latest radios. Interesting about your desense trick. I'll have to try that one on my PL-380.

No, I'm okay. Have had less inclination to write lately, so no posts on the blog. It is time consuming and I've been involved in other outside activities beyond radio. Have done a little work on the program this summer with the intention of getting nighttime skywave plots going. Am getting close but things keep cropping up like rewriting pre-existing code.

The route this year will be Rochester-Cleveland-Columbus via I-90 and I-71. Columbus-St.Louis-Kansas City-Denver via I-70. Mostly I tune from about 1100 KHz down. Long distance stuff during the daytime is almost always at the bottom end. I'll probably follow 650 KHz all the way across. It is sparsely populated. WSM in Nashville (50 KW) is the big one but suprisingly fades quickly to the northwest leaving open the possibility of hearing KGAB (8.5 KW) out of Cheyenne, WY. Denver on 850 KHz, KOA, usually shows up about Salina, Kansas about 400 miles out of Denver. Often little KHOW-630 (5 KW) is in there as well. I'll try to take some notes :-).

Interesting pattern graphic on CBK-540. Dated 1939, but still accurate and detailed. BTW, I have the full Industry Canada AM database unpacked and coded.

Nice DX catches by the way! That WHAS one is great!


Stephen said...

Hi Bill,

Yes, I am. I've kinda laxed off on the active DXing a little, but I'm still into it some. :) And, also, I think that trick only works on some Tecsuns. I know my PL-398bt and now-defunct PL-398mp do it, and I've seen a couple youtube videos of the PL-310 doing it. I'm not able to do it on my PL-606, though, my PL-380's tuning knob is broken, and I don't have other models to test it.
Also, I wonder if the PL-880 is like that natively? I've seen a couple youtube videos where I saw the signal strength dBµ on AM or SW below 14 dBµ. Normally I have to do that desense trick on my Tecsuns to get that, otherwise the minimum is 15 dBµ.
Also I've noticed it doesn't work miracles, either. If I'm close to a 50 kW station whose 50/00 desense is covering up a station that would otherwise be listenable, it'll still be covering it up after doing that trick. Also I've seen dBµ numbers drop significantly on moderately strong stations when they're desensed by a blaster.

Ahh, I'm glad to hear it. :) And I look forward to seeing those nighttime skywave plots. :)

Okay. :) I'll look forward to your report when you post it. :) Hey any chance you might be able to get audio or video recordings of some highlights?

So is there any chance you might also have Mexican stations on it soon, too? Sometimes it throws me off when I'm looking at the maps and I don't see Mexican stations that I know put strong signals into the US. :)

Thank you. :) A couple of my desired eastern targets are 760 WJR (would be a challenge with my local KFMB just 7 miles away) and 1180 WHAM.



Hi Stephen,

Question. I noticed you mention one or more of your radios will show dBµ in excess of 63. My PL-380 maxxes out at 63. I seem to remember the old version PL-310 registered higher dBµ too. I wonder if the PL-310ET currently selling will read higher than 63?

Seems I don't do much DXing anymore unless I am in the truck and on the road. WJR-760 might be a possible catch for you around KFMB. It comes in here weakly during the daytime at 294 miles distance. WHAM-1180 would be an excellent catch for you. That one is only about 8 miles from here. It has an interesting looking 410 ft. tower.

I do have an audio recorder so it would be possible to get some audio. Have toyed with that idea before (posting some). Maybe, if there is time, to weed through more stuff!....

Mexico basically doesn't have a mediumwave database like the FCC and Industry Canada does. They produce a nice .PDF file of their stations but no antenna array data. That makes it impossible to develop graphical patterns. The FCC does catalog Mexico in their database, but the information is woefully out of date for foreign countries in this hemisphere.



Stephen said...

Hi Stephen,

Hi Bill,

My PL-380 maxes out at 63 dBµ too, but apparently Gary DeBock of Puyallup, WA, has (or had) one that would go higher. There's a picture of it showing 85 dBµ on his local station 1450 KSUH, but I'm having difficulty finding it now. (It was posted a couple years ago, and I suspect it may have been an early model PL-380.)
I'm not sure what the cap is on the PL-310ET, but I would like to find out.
The Tecsuns I have, other than the PL-380, usually max out at 98 dBµ. They're already compressing the signal though - I notice this starts happening in earnest when the dBµ is in the 80s. For example, I'm 9.3 miles from 1170 KCBQ and 7.3 miles from 760 KFMB, and both show around 80 dBµ when they're running 50 kW. I have to get within about 1000 feet to 1/4 mile or less from the sites for them to continually show 90 dBµ or above.
Sometimes when I'm fairly close but not THAT close, when I first tune it in, it might flash something like 94 or 95 dBµ, then drop down to around 89 (or even 85) next time the chip/display refreshes. Also, on some occasions, when hitting the radio with a very strong signal and the display updates before the desense kicks in, I've seen it flash 99 dBµ a few times, or even cycle around to like 07 or 13 or so. (I'm guessing the maximum cycle-around flash-reading would be 27, which would represent 127, but I haven't confirmed it.)
Anyway, for me, a radio that maxed out at 63 dBµ would be pretty useless on that function, considering I'm often in areas that have many stations that far exceed that level.

So what does 1180 WHAM, being 8 miles away, indicate for you? For me, as I said, 1170 KCBQ at 9.3 miles indicates around 78-80 dBµ or so. Their DA_ERP toward me (unless there's a better term for how I calculate it) is about 111.33 kW.

I calculated that as follows...

KCBQ's Augmented RMS is 2,628.2 mV/m @ 1 km.
It's a 187.33° heading from the antenna array to me, according to the FCC search results for the coordinates I entered. (32° 45' 38.3" N, 116° 56' 45" W)
The augmented field at 1 km is 3,737.73 mV/m at 185°, and 4,132.53 mV/m @ 190°.
The trasmitter power is 50 kW.

That gives the result when "searching" it via Google.

The 50 is the transmitter power, the long fancy part from 4132 to 37.73 is my interpolating the pattern data to get a more exact field toward me in the DA, the 2628.2 is the non-directional RMS value and of course you square it when doing the calculation. A simpler example that I've used before when estimating their signal toward me would be 50*(3750/2500)^2, which would result in 112.5 kW DA_ERP.

How do you do your ERP calculations? Do you base it on a constant 305.78 mV/m @ 1 km for 1 kW base for the non-directional part of the equation, or do you take the actual FCC data RMS value into account?

Ahh. My DXing has been pretty much completely random. I did go to a few sites back in June one day to compare some radios. The first site was the front of the driveway at the KCBQ/KECR transmitter site around 7 am, the second was in front of the fire station just east of Cameron Corners, CA (east of the Highway 94 & Buckman Springs Rd intersection) for a few hours in midday, the third was on one of the sidewalks behind the Santee Trolley / Transit center around 6 pm.
I had the Tecsun PL-398bt, Sony SRF-M37W (modified filter), CC Pocket, Sangean DT-400W (borrowed from my dad) and SAT. Due to time constraints I was only able to test the CC & Sangean at the KCBQ site and in Santee, but I had more time to test most of the radios at Cameron Corners. (I only tested the SAT with the PL-398bt.)

Stephen said...

I recorded videos of the vast majority of the tests. I put together several comparing the DT-400W and CCP between the KCBQ site and Cameron Corners, also adding in the M37W at CC in the videos. They're supposed to show how I get better reception out in the "sticks" on some fringe stations than being near the "big sticks", in spite of being closer to the target stations. Also the DT-400W was able to still receive many stations near the big sticks that the CC Pocket could not hear in spite of its DSP selectivity. And, in some cases (especially toward the higher end of the band), my SRF-M37W was more sensitive than the other two at CC.

Mexico basically doesn't have a mediumwave database like the FCC and Industry Canada does. They produce a nice .PDF file of their stations but no antenna array data. That makes it impossible to develop graphical patterns. The FCC does catalog Mexico in their database, but the information is woefully out of date for foreign countries in this hemisphere.I've noticed that about the Mexican database. :/ I wonder if there's some way to get it in there though. Sometimes I notice the data is fairly accurate on, but it too doesn't seem to show pattern data. Speaking of pattern data, based on my own obervation, 1090 XEPRS is directional fulltime, but pretty much all the online sources I'm aware of say it's ND daytime. Also there's confusion on 950 XEKAM's transmitter power output, with none of the online sources (except maybe that PDF which I haven't checked recently) showing it as 20 kW daytime, which it announces on the air. (I understand enough Spanish to be able to ID a station, and I think it's not a bad idea for DXers who often target stations in a specific language, or frequently receive stations in said language, to at least learn some things in that language to make them easier to ID.)

I suppose you could look at the map and google street view if available to try to work out how many towers there are, and by perspective calculation figure out the approximate electrical height of the towers. That, however, would probably be just a weee bit beyond the intended scope of your program / data, as would the inclusion of Australia, Europe, Africa and Asia into your data. ;)




Hi Stephen,

Was out this morning and just worked this up for you.

"I'm not sure what the cap is on the PL-310ET, but I would like to find out."

Maybe someone on the ABDX or Ultralight group would know? I'd be interested too.

Single mast WHAM-1180 (50KW at 8 miles) maxxes out at 63 dBµ on my PL-380. Calculated received mV/m at my location is about 91 mV/m over 8 mS/m ground conductivity. I don't think it is much more than 63 dBµ because I can null it to 49 dBµ.

I tried your desensing fix trick on my PL-380. It didn't work, as you expected. Thanks for the tip, though, I will remember it for next time and next radio.

Yep, I sure wish Mexico would publish their mediumwave data. To calculate array patterns and gain, you need:

1. Tower heights and type (normal,top hat, sectionalized, etc.)
2. Tower spacing.
3. Tower orientation from the reference tower.
4. Tower phasing from the reference tower.
5. Field ratios of each tower (percent of full power applied to each tower).

It would be fruitless to try to estimate these values.

The gain and ERP calculation separately.




Hi Stephan,

Okay, on to the ERP and gain calculations...

First of all, all gain and ERP calculations are based on the gain a tower or array has over (or under) a perfect quarter wave monopole. A perfect 1/4 wave monopole at 1 KW output will produce a 305.768 mV/m field strength at 1 kilometer. Looking at field strengths (FCC values) for various 1 tower installations, you will notice that some are greater than 305.768 and some are less. It is simply a matter of antenna efficiency, or more properly, apparent tower length in relation to that 1/4 wave length at the station frequency. Lengths longer than 1/4 wave will have higher field strengths at 1 km, those shorter than 1/4 wave will have lower. WHAM-1180, for instance, has a value of 376.59 mV/m at 1 km (even though 50 KW, remember it is based on a 1 KW output). You can bet that it is significantly taller than 1/4 wave, and it is - it's .492 of a full wave, almost half a wavelength, or 410 ft. tall.

So, taking the published mV/m values for all stations, we can calculate the actual mV/m value for single tower installations (omni-directional), or use the FCC chart for arrays to interpolate the value in our direction. Using these values, we can also calculate effective radiated power (ERP).

This is how I do it in Radio Data MW.

If 1 tower:
RMS is published by the FCC, but for 1 tower installations it is based on 1 KW output at 1 kilometer.

rms = RMSTheoretical ...published by FCC

You can calculate the actual rms at 1 km thusly:

mVm = rms * Sqr(power_KW)
return_MVM = mVm ...actual mV/m at 1 km, 1 tower

You can calculate the actual gain and power ERP at 1 km thusly:

dB_gain = 20 * Log(rms / 305.768)
dBW = 10 * Log(power_watts) + dB_gain ...dBW = dB above 1 watt
return_power = 10 ^ (dBW / 10) ...ERP, 1 tower

If multiple towers:
RMS is published by the FCC in chart form, by azimuth. An overall RMS is also published, but this is based on a different calculation.

The actual FCC RMS calculation for your azimuth (the chart) uses return_ratio and k_factor and is a complicated formula.

FCC calculation:
RMS = return_ratio * k_factor
return_MVM = RMS ...actual mV/m at 1 km

Better to use the published FCC value from the chart.

From the chart:
rms = RMSTheoretical ...or more accurately can be RMSStandard or RMSAugmented, published by FCC

You can calculate the actual gain and power ERP at 1 km thusly:

base_mVm = 305.768 * Sqr(power_KW)
dB_gain = 20 * Log(rms / base_mVm)
dBW = 10 * Log(power_watts) + dB_gain ...dBW = dB above 1 watt
return_power = 10 ^ (dBW / 10) ...ERP, multiple towers

All Logarithms are base 10 of course.

Proof showing that the above formulas work:
Using 50 KW WHAM for example.

We are calculating gain over "base" power (using "base" voltage, being that of a 1 KW output to a single 1/4 wave radiator = 305.768 mV/m @ 1 km).

Power = V^2 / R

Solve for R at base voltage:

R = V^2 / Power
.00000186988(resistance) = .305768^2(volts) / 500000(watts)

Now solve for power gained (in ERP) at FCC measured mV/m (376.59 mV/m):

75844.45(watts ERP) = .37659^2(volts, published rms) / .00000186988(resistance)
Resistance always remains unchanged of course.

You will get the same ERP (75844.45 watts) using the single tower formula, above. The antenna gain for WHAM is 1.81 dB in the top formula.

Hope this helps.



Stephen said...

Hi Bill,

I consulted youtube re: the PL-310/ET, and found a few videos that showed dBµ readings well in excess of 63. - PL-310 ET - hits 95 dBµ around 5:59, refreshes display about every second - PL-310 - hits 72 dBµ around 1:48, refreshes every second - PL-310 - hits 67 dBµ at 1:30, refreshes every 2 seconds - PL-310 - hits 79 dBµ at 1:13, refreshes every second

Interestingly, this PL-380 - - flashes 84 dBµ at 14:29 (and shows other higher-than-63 levels), and refreshes every second. Mine caps at 63 and refreshes every 2 seconds.

Your PL-380 pretty much definitely caps at 63 dBµ. (This could be confirmed by going up to the tower of your nearest / most convenient station - if it's still 63 dBµ it's definitely capped there.)

On my PL-606 and PL-398bt, here are some examples of readings and calculations over 63 dBµ:

760 KFMB day - 7.3 miles, 5 kW ND, 714.152 mV/m @ 1 km (RMS is 304.17 mV theoretical for 1 kW, I did "(304.17*1.05)*sqrt(5)" to get "standard" figure) toward me, 8 mS/m ground - calc'd ~ 45.89 mV/m (93.23 dBu), indicates 72 dBµ

760 KFMB night - 7.3 miles, 50 kW DA, 2034.95 mV/m @ 1 km (40.51 kW; RMS 2260.755 mv) toward me, 8 mS/m ground - calc'd ~ 130.77 mV/m (102.33 dBu), indicates 81 dBµ

910 KECR day - 9.3 miles, 5 kW DA, 667.33 mV/m @ 1 km (5.08 kW; RMS 662 mV) toward me, 8 mS/m ground - calc'd ~ 27.57 mV/m (88.81 dBu), indicates 67 dBµ

910 KECR night - 9.3 miles, 5 kW DA, 961.8 mV/m @ 1 km (10.53 kW; RMS 662.8 mV) toward me, 8 mS/m ground - calc'd ~ 39.74 mV/m (91.98 dBu), indicates 70 dBµ

1130 KSDO day - 6.3 miles, 10 kW DA, 1075.36 mV/m @ 1 km (10.447 kW; RMS 1052.1 mV) toward me, 8 mS/m ground - calc'd ~ 64.4 mV/m (96.18 dBu), indicates 75 dBµ

1130 KSDO night - 6.3 miles, 10 kW DA, 1244.647 mV/m @ 1 km (12.92 kW; RMS 1095 mV) toward me, 8 mS/m ground - calc'd ~ 74.54 mV/m (97.45 dBu), indicates 76 dBµ

1170 KCBQ day - 9.3 miles, 50 kW DA, 3921.7 mV/m @ 1 km (111.33 kW; RMS = 2628.2 mV) toward me, 8 mS/m ground - calc'd ~ 124.1 mV/m (101.87 dBu), indicates 80 dBµ max (MDCL makes it vary by 3-4 dBµ)

1170 KCBQ night - 9.3 miles, 2.9 kW DA, 994.26 mV/m @ 1 km (7.63 kW; RMS 612.9 mV) toward me, 8 mS/m ground - calc'd ~ 31.46 mV/m (89.95 dBu), indicates 68 dBµ max (MDCL varies it)

I skipped 600 KOGO (~68 dBµ), 690 XEWW (~69 dBµ) and 1360 KLSD (~66 dBµ) as the ground conductivity changes along their paths, and I don't know how to use your field strength calculator program to deal with that.

Your 91 mV/m figure on WHAM is about 99.18 dBu. At an apparent 21 dB difference in my above figures between calculated dBu and displayed dBµ, my radios (other than my PL-380) would theoretically be indicating about 78 dBµ.

However, I've found that some situations can greatly change that scale, especially being in close proximity to stations.

I also think that being out in the sticks can make some difference. For example, my reading at Cameron Corners fire station on 1390 XEKT, the strongest station there, was 48 dBµ. The station is 5 kW non-directional, and 14.78 miles away from there. Since I don't know the specific antenna data, I'm assuming the standard 305.78 mV/m for my calculations, and multiplying by 1.05 to get the standard pattern RMS. This results in a field at 1 km of 717.93 mV/m.

Over the 4 mS/m ground out there, that results in a calculated field of 2.67 mV/m or 68.53 dBµ. Well looks like it's still about 20-21 dB different, so maybe it's still fairly linear at the lower signal strengths.

Stephen said...

So, let's check a higher level example. On CA-67 across from the KCBQ site, I remember getting 91 dBµ there a year or two ago, at ~ 0.47 mi, 228° from KCBQ. The FCC data says max field is 5280.6 mV/m at 227°, so using that calculation and 8 mS/m, I get a field of - well, I can't do it with your program cause it's under 1 km. So, since it's 741.6 meters, we'll do it a different way: 5280.6/741.6*1000 results in 7120.55 mV/m, or 137.05 dBu. This is a 46 dB difference.

I generally find that this type of severe desensing really gets going when your strongest stations are in the 80s dBµ indicated range, or around/over 100 dBu actual field. Sometimes the radio will briefly flash something like 95 dBu, then snap down to the mid/upper 80s, if you're getting fairly close to the station. Once you get close enough, it quits trying to drop the display down to the upper 80s, and just stays above 90 at whatever it is.

Also, I've been able to null stations a lot deeper than 14 dBµ (63 - 49).

In this video - - I take 1170 KCBQ down to 15/00, then upon signal restoration it jumps back up to 82/25 then 80/25.

In this video - - 760 KFMB goes down to 15 dBµ, then later peaks at 92 dBµ. At 0:58 when I quickly re-orient the radio for the strong signal, you hear a brief burst of overload/distortion in the audio. The display doesn't catch up to it in time, but usually I find the audio starts to distort when you're indicating about 95 dBµ or so. (This distortion sounds severe enough to me that it was very possibly 98 or even 99 dBµ or higher, had it been caught on the display.)
However, I suspect that the results of this one are being skewed, due to using house wiring as an inductively-coupled antenna. (There is an electrical outlet hidden by my hand.)

Oh, and another thing - when you have a situation where it starts off indicating something like 93 dBµ then snaps down to 87 dBµ, I think the modulation of the strong pest has everything to do with that. For example, if I tune in to Mark Levin's show on 760 (he often has long silent pauses; I suppose Family Radio would work too as they usually have silence between songs) during a silent period, it'll stay at 93 until he starts talking, at which time it drops at the next display refresh. Also, if I'm listening to another weaker station on the Tecsun (and monitoring 760 on another radio), it'll have moderately good reception during 760's silent period, then at the moment Mark opens his mouth, it suddenly gets noisy, and often drops 10, 15, maybe even 20 dBµ or more on the signal strength in some cases. In some cases this even affects stations halfway across the band, like 910 KECR, 1070 KNX, possibly 1170 KCBQ and maybe even 1360 KLSD to a lesser extent. (Btw at my house this is when boosing 760's signal with the aid of the SAT.)

I generally find that the desensing drops off slower as you tune higher than the offending station, than as you tune lower. I also notice this with normal PLL radios - a mega-strong station on, say, 800, might be about as strong on 700 as it is on 1000 or so, for example, and a sufficiently strong station (like being near the KCBQ site) would cause the strong station to semi-weakly occupy every single otherwise-blank channel on my normal 450/455-IF PLL radios.\

Yeah, with the data we have, it would be fruitless to try, or at least very difficult, to incorporate Mexican data, although I do wish it could be done somehow. One example is 620 XESS and 1030 XESDD, which use the same single tower. At my house they both are within a dB or two of each other, IIRC, somewhere in the low 40s or so, daytime. At Cameron Corners, 620 is 37 dBµ and 1030 is also 37 dBµ. At Jilberto's in Pauma Valley (Hwy 76 & Pauma Reservation Rd) on the PL-380 (which I find indicates about 3-4 dB or so less than the PL-606 and PL-398bt), 620 is 15/17 (hitting the minimum 15 dBµ display), and 1030 is 20/22.

Stephen said...

Well those are interesting calculations - it will probably take a while for me to fully grasp them. :) I notice you're using the standard 305.768 mV/m figure in determining the ERP. When I'm calculating directional arrays, I use the RMS figure specified for the station. This means that for a given field strength in my direction and a given transmitter power, a station using half-wave antennas would have a lower "ERP" than a station using quarter-wave antennas.

For example, take three 1 kW stations with a 700 mV/m field toward me. The first uses 1/4-wave antennas and has an RMS of about 305 mV/m, the second uses 1/2-wave antennas with an RMS of about 381 mV/m, and the third uses Franklins with an RMS of about 512 mV/m. (Obviously the patterns would be different, too, but we're only calculating one azimuth here.)

1*(700/305)^2 = 5.267 kW "ERP" with the 1/4-wave towers
1*(700/381)^2 = 3.376 kW "ERP" with the 1/2-wave towers
1*(700/512)^2 = 1.869 kW "ERP" with the Franklin towers

Is there a different term I should use when doing those calculations and specifying them that way? I think of it as ERP relative to using that station's particular transmitter and antenna system in non-directional mode vs directional mode, or something like that.

I've noticed what looks like an interesting discrepancy. If you look up 1360 KLSD on the FCC query - - it says the tower's electrical height is 184.5°, yet the theoretical RMS is only 312.21 mV/m for 1 kW. The tower itself is more like about 270° tall to give extra height for the FM stations mounted atop it, but the upper part is detuned from the AM side. Any idea why that discrepancy could be there?

Also, 850 KOA - - shows 362.1 mV/m with a 207.8° tower, but it says "lin resistor".

Anyway, I was wondering about something recently ... Is your Radio Data MW program yet able to put out a calculated list of the top 2 (or possibly 5 in some cases) field strengths on each frequency at a particular location?

(In my case I'm thinking 32° 45' 38.3" N, 116° 56' 45" W, as that's the approximate coordinates of my backyard makeshift shack.)

Alternately, maybe every station above 1 µV/m, except when you have stations over 5 mV/m in which case only include the one strongest station. (The FCC rules say indirectly that a station's 5 µV/m contour is not supposed to overlap a class A's 100 µV/m contour on co-channel, but I've heard that in some places it's possible to pick up stations weaker than that, so I arbitrarily picked 1 µV/m.) If a frequency has no stations at/above the threshold, then the strongest ones within 6-10 dB of whatever is there.

Stephen said...

Alternately, if that'd be too big of a list (I'm guessing it could include several hundred stations), I'd be especially interested in the following stations fields (the Mexican ones are optional):

560 KBLU
580 KSAZ & KMJ
590 KTIE
610 KAVL
680 KNBR
700 KALL
720 KDWN
750 KOAL
770 KCBC
780 KAZM
810 KGO
840 KXNT
870 KRLA
880 KKMC
890 KIHC & KDXU (also there's a TIS at Cabrillo National Monument that's intermittently active - used to be called KPB792 I think but I didn't find it in FCC's data last time I looked a while back.)
900 KALI
920 KPSI (beware XESDA)
930 KHJ
940 KFIG (beware XEWV)
970 KNWZ
990 KTMS (beware XECL)
1010 KXPS (beware XEDX)
1020 KTNQ
(is it possible to map approximately where in San Diego area 1030 XESDD and 1040 KURS are equal strength, and what the approximate field is?)
1050 KCAA (beware XED)
1100 KFNX
1110 KDIS
1140 KNWQ
1150 KTLK (beware XERM)
1160 KSL (beware XEQIN)
1180 KERN
1190 KGBN
1200 KYAA
1220 KWKU
1230 KXO & KYPA
1250 KZER & KNWH
1260 KMZT
1280 KFRN
1290 KZSB & KKDD
1300 KROP & KAZN
1320 KKSM
1330 KWKW
1340 KCLU (beware XEAA)
1350 KTDD
1370 KWRM
(is it possible to map approximately where in San Diego area 1390 KLTX & XEKT are equal strength, and what the approximate field is there?)
1400 KESQ & KKZZ
1410 KCAL
1430 KWST & KMRB
1440 KFNY
1460 KTYM
1480 KVNR
1490 KGBA & KSPE
1510 KSPA
1520 KUNX
1530 KFBK
1540 KMPC
1560 KNZR
1570 KPRO
1580 KBLA & KMIK
1590 KVTA (beware XEHC & XEYX)
1600 KAHZ
1620 WNSB415 (or does your program not do TIS's?)
1650 KFOX
1670 KHPY

Well I guess that's a longer list than I was anticipating making. :) Many of those, except foreign language and Catholic stations in some cases, would be some of my desired daytime DX targets.




Hi Stephen,

Thanks for the messages. Let me digest some of what you wrote and get back to you on your questions.

I'll also get something together for you using your latitude-longitude coordinates. I have some work I'm doing on the program right now, but will see what I can come up with in the next few days.

I'd need an email address for you if you can encode it somehow.




Hi Stephen,

Thanks for the research on the Tecsun PL-310 and its upper dBµ range. I may be tempted to order one of these this winter.

I will do some calculated dBu comparisons (from the program) against some dBµ readings on the PL-380 and see if there is any linear correlation. That may have to wait till next week when I'm out of town and away from the dense RF around here.

I may have mentioned this before. Normal formulas don't work to calculate mV/m level closer than 1 km. Figures given start at 1 km and are reduced from there as you go out in distance. OSHA may have some computation to get RF levels in Volts as you get within feet of a mast. Remember, there is no perfect receiver that will ever handle the extreme signal levels standing quite near a tower.

Okay on the nulling ability. Will do some more experiments on that. I'm sure I can produce a deeper null than 14dB as you say. That was just WHAM's situation.

The Mexican data in the FCC's database may be accurate enough to produce some meaningful results on certain stations. depends on how out of date it is.

Your calculations are wrong for multiple towered arrays:

1*(700/305)^2 = 5.267 kW "ERP" with the 1/4-wave towers
1*(700/381)^2 = 3.376 kW "ERP" with the 1/2-wave towers
1*(700/512)^2 = 1.869 kW "ERP" with the Franklin towers

They won't give you power gain this way. They may be used as below in the next set of formulas for single towers:

For single towers of course the mV/m measurements would be different.

1*(305/305)^2 = 1 kW "ERP" with the 1/4-wave towers
1*(381/305)^2 = 1.56 kW "ERP" with the 1/2-wave towers
1*(512/305)^2 = 2.81 kW "ERP" with the Franklin towers

You must compare all to the standard 1/4 wave at 305 mV/m.

First, the "700" you used above would not be the same for each array. It would be higher for the 1/2 wave and Franklin towers. Secondly, the formula won't work for multiple towers as is.

Below is probably the simplest way I know for multiple towers.

First calculate the base mV/m for the multiple towered array:

base_mVm = 305.768 * Sqr(power_KW)

Now use it in the following computation:

kW*((mVm_coming_at_you/base_mVm)^2) = kW "ERP"

You must establish a base mV/m to work from on multiple towered arrays. 305 is not correct unless power is 1 kW.

Be sure to pay attention to parenthesis here. Multiply the entire squared result by the kW at the start of the line.

Or, calculate the dB gain using the formula I gave in a previous reply and then calculate the new power (ERP) using it. I had a need to know the dB gain, so I went that way with the formula.

"Is your Radio Data MW program yet able to put out a calculated list of the top 2 (or possibly 5 in some cases) field strengths on each frequency at a particular location?"

Yes. As many as you want and at whatever mV/m threshold you want. Multiple ground conductivities are fully accounted for at all distances within the US.

On the KLSD-1360 discrepancy. Not sure what gives here. Normally the mV/m level would be higher than 312, more like 380. The tower is just over 1/2 wavelength. The 312 figure is what the station reported to the FCC, so I assume it is accurate. There may be other factors involved. The same situation may exist with KOA-850, Denver. We have to go with the published figures, as had to be technically verified at some point along the line.



Stephen said...

I would appreciate that, knowing the signal strengths (I'm guessing mV/m, uV/m and nV/m depending on strength, and/or maybe dBuV/m - btw I can't type the "mu" character on my phone) of stations coming in here. :') Any chance that in the future, skywaves could be included? (So that for example I could determine my best chances/times of hearing, say, 1180 WHAM, 774 Melbourne AU, 1521 Saudi, or 1230/1240 Chicago area?) Or does the variability of the ionosphere make it too complicated?

As for my email address, lemme try this... Each thing in parentheses should run together, for example the first 3 are "piano"
(Name of greek character representing 3.14159...) (1st letter of English alphabet) (opposite of "yes") (another name for a performer of a musical instrument or a professional sport) (WCBS's frequency in 10s of kHz) (singular of the thing you use to unlock a door) (the "at" symbol) (the email service of a major search company founded by Larry Page & Sergey Brin)
Alternately, the Ascii character codes are:
You can type each one by holding alt, typing the numbers on the numeric pad (the number row above the letters doesn't work for this) then releasing, repeating for each group.

I'm almost tempted to get a PL-310ET, too. I originally didn't like the way the tuning knob protrudes, but considering how many times I've broken my PL-380's knob, I think the 310's design may be easier to repair when I break it. (I also wish the whip antenna was better designed on those Tecsuns. I've broken just about every single whip on a Tecsun I've had, except a second PL-606 that I haven't used much.)

Actually, though, I'd really prefer a vertical-oriented radio. I almost like the CC pocket's interface, but it's not quite sensitive enough for me, and suffers badly from desense. I crank the volume all the way up on 1110, for example, and can barely hear it in a quiet (audio) environment, and in a noisy area (again, sound) forget it, even with headphones.

Another one I'm eyeing at a distance, although NOT at its current price (! - I'd consider it at maybe $50-70 shipped though), is the PL-880. In a video or two I've seen of it, I've seen dBu readings below 15, and I suspect its desense characteristics may be different than the smaller Tecsuns.

I'll look forward to those dBu comparisons. I'm guessing you may get somewhat skewed numbers at the low end of the AM band - I've heard those are more deaf down there. Also, yesterday I was at my sister's new house a couple miles from KOGO-600 and KLSD-1360. I had calculated the signal strengths of those two stations, and iirc they're both around 150 mV/m or so. However, 600 was reading around 76 or 78 dBu on my PL-606, and 1360 was either 84 or 87 dbu, I forget which now.

Stephen said...

BTW, my PL-398bt had something go wrong with the AM antenna yesterday. I'm suspecting the ground is disconnected or something, cause I can still weakly hear some locals and it's still directional. (For example, 760-KFMB which is normally 72 dBu daytime was showing, iirc, 8 dBu.) I've recorded several videos comparing reception barefoot vs with SAT vs with utility ground, and am still working on editing them (cutting them out of the continuous videos then combining as desired). Idk when I'll upload to youtube (it'll be set as unlisted most likely) but hopefully soon.

I think you have said that. I wonder if there is a way to calculate it, for example, if you're close enough to completely overload a SDR (so the entire spectrum shows a pegged signal, and any content is so distorted as to be completely undiscernable) with no antenna/ground connected.
Well, it'd be nice to have one that could get weak first-adjacents as long as you're outside the danger zone for safety. :) An example would be the hypothetical situation where a 50kW Class A on 1500 would need to monitor a 1kW class C on 1490 for EAS in the studio. (Assume the studio is a couple hundred feet from the tower - I've heard the safety/danger zone is about 25-35 feet or so for a 50kW or something like that. Also as you probably know, on 1st adjacents, the 0.25 mV/m isn't supposed to overlap the 0.5 mV/m.)

I too would like to do more null experiments, although I'd prefer to do it in a place where I have just one strong station that's like 88 dBu and everything else is 30 and below (not because of desense).

Hmm.. ok. :/ I guess I'm doing it a different way - maybe I should call it something else like eQuivalent Transmitted Power?
The way I'm doing it, if the field toward me at 1 km equals the published RMS field at 1 km, then the power toward me is the published transmitter power. Should I be calling it something else, or is it still totally wrong? For non-directional stations, the transmitter power is considered by me to be the power toward me, regardless of the type of antenna used. Hmm... :/




Hi Stephen,

I have skywave field strength calculations pretty well done at this point. I've been working on the skywave mapping this summer. Getting close there. Skywave calculations turned out to be a bit simpler than groundwave, all told. I was surprised. The FCC has a pretty good formula which calculates for a time of sunset +6 hours, which would be roughly midnight, or "deep" dark, and well past the ionospheric anomalies you get around sunset/sunrise. Your distance from geo-magnetic north also comes into play. The further away, the less effect of the magnetic pole on mediumwave.

Got your email address. Thanks.

The nice thing about the PL-360, beyond being vertical, is that it has an external antenna jack which defeats the ferrite rod. Might still consider that one too.

I agree, the Tecsun PL-880 is way over-priced for my taste. I would consider one if it dropped to about $80.

Did some RSSI (dBµ reading on the PL-380) comparisons with calculated dBu. They are different and not linear. For a '380 reading of 15-20 dBµ the calculated dBu is nearly 2.5 to 3 three times higher. For higher '380 readings above 20 dBµ the calculated dBu is more near 1.5 to 2 times higher.

After thinking about it, it dawned on me that dBu is computed using 10 * Log(..) and RSSI dBµ is computed using 20 * Log(..). That's probably the difference.

Played a little with the nulling on the PL-380. Best null so far was 50 dBµ down to 18 dBµ. Not bad.

Still making program adjustments. I need to write a sort for skywave levels so I can make a nice list in received field strength order.




Hi Stephen,

"Hmm.. ok. :/ I guess I'm doing it a different way - maybe I should call it something else like eQuivalent Transmitted Power?
The way I'm doing it, if the field toward me at 1 km equals the published RMS field at 1 km, then the power toward me is the published transmitter power. Should I be calling it something else, or is it still totally wrong? For non-directional stations, the transmitter power is considered by me to be the power toward me, regardless of the type of antenna used. Hmm... :/"

You will see different power directed at you depending on tower height and/or multi-tower array characteristics. If the mV/m level is higher at your azimuth, then the power coming at you is higher. If mV/m is lower, then power is lower. Thus the meaning of 'effective' radiated power (ERP). a.k.a. 'equivalent'.



Stephen said...

Hi Bill,

I saw your post & the subsequent thread in the ultralightdx group about DSP radios that exceed 63 dBµ. Here are some of my videos showing my radios exceeding that - many of them hitting 98 dBµ. (I'm unable to post to that yahoo group.) - PL-398bt - 1130 KSDO is 70 dBµ at 0:43, 910 KECR is 72 dBµ at 0:59 - 1170 KCBQ is ~ 80 dBµ on PL-398mp in first part of video. (This is a demo video to show how desense changes on PL-380 on 1200 at 1170's pattern change.) - 1170 KCBQ is ~ 81 dBµ on PL-398mp in first part of video. (This is a demo video to show how desense changes on PL-380 on 1190 at 1170's pattern change.) - 760 KFMB is 84 dBµ on PL-398mp in first part of video. (This is a demo video to show how desense changes on PL-380 on 780 at 760's pattern change.) - PL-398mp - 1170 is in the upper 80s and low 90s as I start tuning off in +/- 6k mode. (This is a demo video showing the skirt selectivity I would like to have in a radio - going from full signal at -6 kHz to nothing at all at -8 kHz. I would have done -7 kHz but my hand missed that step on the tuner. I accomplished this by pinching the antenna leads together for the first part of the video, then letting go of them at the last, disconnecting the antenna.) - PL-398mp - 600 KOGO is around 96 dBµ, but tuned to 603 (a TP frequency) as I cycle through the bandwidths. - PL-398mp - 910 KECR - 96 dBµ - PL-398mp - 910 KECR - starts off at 65 dBµ, then as I bring it up to the SAT & utility pole it pegs at 98 dBµ. - PL-398mp - 910 KECR - mid 90s dBµ. (This is a demo video to show the audio pumping / soft muting I get even on some very strong signals. Several times you'll see the S/N at 0 dB with the signal at 94 or 95 dBµ.) - PL-398mp - 760 KFMB - starts at 81 dBµ, then pegs at 98 dBµ as I bring it to the SAT & Utility Pole 7.2 miles SE of the transmitter site. - PL-398mp - 760 KFMB - 98 dBµ, about 50 feet or so from one of their towers. The signal strength here on the barefoot radio is about the same as with the SAT+Util setup 7.2 mi SE in the above video. - PL-398mp - I have WHAS under KXNT in parts of this video, but at around 0:53, KXNT peaks at 78 dBµ. - PL-398mp - 600 KOGO - 95 dBµ; IBOC on 612 is 68 dBµ - PL-606 - 760 KFMB - hits 92 dBµ briefly at 1:20. (I get a "null" down to 15 dBµ at 0:51. As I un-null at 0:59 the audio briefly distorts like it's overloading. I think if the display had refreshed at the right time it would have at least indicated 98 dBµ for a second.)

Stephen said... - PL-606 - 1170 KCBQ - starts at 81 dBµ, then pegs at 98 dBµ (and on the 2nd harmonic!) when I bring it to the SAT + utility pole. This boosted signal, 9.2 miles S of the transmitter site, is STRONGER than the barefoot signal portions in the 2 next videos below, just a few hundred feet from the site! - PL-606 - 1170 KCBQ hits 98 dBµ a few hundred feet from the TX site, and on top of that I boost it with the SAT + utility pole for an extra overload crunch test. As it gets close to the pole it's overloaded so much that the audio gets through the "muting" that normally happens when you have moderate overload. - PL-606 - 1170 KCBQ hits 98 dBµ again, same scenario as above. In this one, at 3:38, the DSP chip cuts out (blanking out the signal display for a few seconds until I move it away, although you can still momentarily hear the audio while the radio's still next to the antenna). This particular overload is so severe that the buttons are unresponsive even after moving away. I had to remove the batteries to power off the radio, then wait something like 15-20 minutes before I was able to resume operating the radio. - PL-606 - 1110 KDIS hits 71 dBµ with the SAT + utility pole at 0:25 - PL-606 - 830 KLAA hits 87 dBµ with the SAT + utility pole at 0:27 - PL-606 - 640 KFI hits 82 dBµ with the SAT + utility pole at 0:51 - PL-606 - 600 KOGO hits 79 dBµ with the SAT + utility pole at 0:38 - PL-606 - 1170 KCBQ is overloading at 98 dBµ, except during the nearly 10 seconds it's off the air during pattern change. - PL-606 - 760 KFMB, several pattern changes pasted together. Most of the time the signal is 98 dBµ, but briefly at the change at 0:03 it indicates 7 dBµ, which should really be 107 dBµ, then snaps back to 98 dBµ. - PL-606 - 1170 KCBQ - goes from a 15 dBµ null at 0:16 to an 82 dBµ peak at 0:31. - PL-606 - 1000 KCEO is 74 dBµ with the SAT + chainlink fence at 0:35. - PL-606 - 910 KECR is 68 dBµ, 1170 KCBQ is 82 dBµ. (KCBQ can be heard in the background of KECR.) - PL-606 - 910 KECR is 67-68 dBµ, 1170 KCBQ is 81 dBµ. (KCBQ is heard behind KECR.) - PL-606 - 910 KECR is 67 dBµ, 1170 KCBQ is 81 dBQ. (KCBQ is heard behind KECR.) - PL-606 - 1550 XEBG hits 86 dBµ with the SAT + utility pole at 0:37 - PL-606 - 1070 KNX hits 80 dBµ with the SAT + utility pole at 0:34 - PL-606 - 990 XECL hits 65 dBµ with the SAT + utility pole at 0:38. (During the SAT-only portion, KTMS Santa Barbara is clearly audible under XECL, but almost disappears when the utility pole is added.) - PL-606 - 740 KBRT hits 87 dBµ with the SAT + utility pole at 0:56 - PL-606 - 1170 KCBQ hits 94 dBµ briefly when first tuning in, then then drops to 88 dBµ. (This is a demo video to show how desense changes on 1160 when 1170's carrier cuts off briefly at 0:53, recorded a couple miles or so SE of the transmitter site.


Hi Stephen,

Thanks you for the very comprehensive video list. I have gone through some of them. Looks like the displays wraps around at 100 (example: 107 shows 07) as you said. I sometimes see the SNR at 00 on a strong dBµ. Perhaps that is the point of extreme overload.

Someone in the ultralightDX group confirmed that the PL-310ET does go higher than 63 dBµ so that might be a possible buy in the future.

Still working on code here. Have been wrapped up in Equation of Time code for sunrise/sunset calculations. Will send you a station list when I get through those changes.

Thanks again and 73s,


Stephen said...

Hi Bill,

From my experience, the display normally caps at 98 dBµ. However, if a strong signal happens to "suddenly" turn on right at the moment the display refreshes, it will temporarily indicate higher (including wrapping around - I'm guessing the cap would be (1)"27"), until the next refresh cycle brings it back down. (Sometimes it's also the radio desensing, cause sometimes I've seen 95 or 99 dBµ while momentarily hearing the audio "crunch" like it's overloading, then it drops down to, well, sometimes 89, sometimes 77, it depends on various factors that I haven't yet figured out.)
And sometimes I think even 98 dBµ isn't high enough for a sustained reading. Also, I've noticed that they start really desensing above about 82-84 dBµ or so. (If you tune off-frequency without doing that special trick I discovered on the PL-398 series, your "blank" channels would be indicating 49/00.) In the 80s dBµ range, I can go from like 7-9 miles from a 50 kW station to 1/4-1/2 mile from it, and my sustained readings will generally stay within around 82-89 dBµ or so, most often around 84-87. The closer I am to the station, the wider my "49/00" on blank channel desense spreads. When I'm within something like a mile or two (I haven't figured it out exactly), I start getting 50/00 on nearby blanks, and they too spread with decreasing distance. At around 1/4-1/6 mile or so, when I'm getting above 95 dBµ, the 50/00 is spreading about as wide as an FM channel or two, and the 49/00 is almost across the entire band. (It generally spreads higher than lower, btw.)

Ahh, okay. I'll be looking forward to that list when you have it ready. :) Hey are you in AZ yet?




Hi Stephen,

I've looked at the software manual for the DSP chips some time ago, and the dBµ range is 0-127, so theoretically, you could get a reading way up to 27! That would be one whopping signal, though the desense would take over long before that.

Still in NY. Headed across country Thursday morning. Will be in Denver the 22nd for ten days or so. Won't be in AZ til about Oct 10 or so.


Stephen said...

Hi Bill,

Thanks for sending me the mw list. :) It seems fairly close to what I experience, with a few differences.

I think the desense takes over somewhere in the 80s dBu range or so. This past Sunday I went to Santee for a memorial service, and on the way there we were going by the KFMB transmitter at Hwy 52 and Mast Blvd. I put my Tecsun PL-606 and PL-398bt up to the window to compare signal strengths as we were approaching and driving by. (Btw my PL-398bt has something wrong with the antenna - signals that are 80 dBu on the PL-606 are 15 dBu or less on the PL-398bt.)

We were going by fairly quickly so I couldn't set up to video it, but I remember that as we were still some distance away, the PL-398bt was reading around 13-15 and the 606 in the upper 70s or so. As we got closer, the 606 went higher up into the upper 80s, then as it got to like 88-89, it kept snapping down to 85, climbing to 88, down to 86 up to 90, etc, until we got close to the tower where it peaked and briefly held at 92. (I think the actual "hot" tower for the day pattern was on the other side of the freeway.) Meanwhile, the PL-3908bt, as we came closer, kept climbing, up into the 20s, 30s and I think it peaked around 40-something or so but I don't remember now.

One of these days I'm hoping to plan another trip to a transmitter site with the two radios. I'm thinking I'd start at a place where the signal is about 72 to 78 dBu or so on the PL-606, then as I approach the station keep monitoring it on both radios until I get to the fence outside the towers.

One possible station I'm considering trying this with is 600-KOGO, and another one is 1450-KFSD. A third possibility is 1170-KCBQ but it shares a site with 910-KECR so that might contribute a little to the desense too. But, last time I was near KOGO's site, I wasn't able to get close enough for the radio to overload (as in have distorted audio on-channel, which usually happens when your sustained reading is over 95 dBu or so.)
KFSD is omni, and I can get within like 10-15 feet of the tower so I should be able to get significant overload and check the desense there. Also, KPRZ's desense shouldn't be too much of a factor there.
KOGO is low on the band, and generally I find desense isn't nearly as bad on the low end. KLSD is close by, but way up on 1360.
As for KCBQ, they share a site with 910 KECR so idk how that would do for affecting desense, also 1130 KSDO and 760 KFMB aren't all that far away either. KCBQ can overload even a few hundred feet down the street, though, due to its powerful signal and directional antenna. Interestingly, one time I was visiting the on-site studios with my dad a month or two ago, toward the back of the property ... and the signal about 100 feet or so from a tower there was a good bit weaker than out at the street more like 300-400 feet from the towers. :o

Stephen said...

Hey I was just thinking, another thing that might help for planning DX outings... Is there a possible way to make a map (I'm primarily interested in San Diego county, maybe Southern California & nearby areas) that has an overlay that shows what the strongest signal in that particular area is?
I'm thinking of like a color-gradient transparent overlay, meaning where the map is a certain color, the strongest signal is between X and Y. I suppose the gradients could be done at 3 or 6 dB intervals or something like that.

Also, I'm thinking to keep the complications down, only show the areas where the strongest signal is up to 78 dBu (7.94 mV/m) or so. Also, it'd help if there was some way to include Mexican data. For example, if you only included US data, then I think it might show Tecate, CA (yes it exists, but is only a little village compared to the city in Mexico) as being a fairly good DX spot. BUT, there are quite a few strong Mexicans received there, including 1390 XEKT which is a local there. At the bus stop near the border crossing, I've noted signals up in the upper 70s dBu range on the PL-606, which would translate to nearly 100 dBu in the real world.

So far my DXpeditions have been to Cameron Corners, the Viejas outlet center east of Alpine, and Jilberto's Taco Shop in Pauma Valley. At the 1st and 3rd one the strongest signals were in the mid 40s dBu range or so, and in Alpine it was close to 60, as indicated on the radio. I'd like to find a place where the strongest signals are below 15-20 dBu or so, so I can try out big antennas combinations (some of which may have 60 dB or mmore of gain) without the radios overloading. :)

But, then, that still wouldn't help for if I wanted to do a TP DXing excursion to the coast, where pretty much along the entire coast you might have stations upwards of 90-100 dBu (31-100 mv/m) or more. I've heard that DXers usually get better results by the ocean, but since where I live going to the ocean means going to where the local pests are really strong (except the inland transmitter sites), I guess it'd be better for me to go out in the back-country desert to do my DXing?

Hope you have a good trip. :) Please be sure to update us when you can on the DX you hear along the way. :)

73, Stephen

Stephen said...
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Stephen said...

Oh, also, I went outside earlier today and took signal readings on my defective-antenna PL-398bt vs my PL-606, with the Select-A-Tenna vs. barefoot. (Btw something happened recently to it, idk what, but I suspect maybe the ground connection or one side of the antenna got disconnected from the board.)

Below is a table of the readings I got. The Freq and Call columns are self-explanatory. "st398" is the PL-398bt with the Select-A-Tenna, "st606" is the PL-606 with SAT, "bf398" is the barefoot PL-398bt, and "bf606" is the barefoot PL-606. "s:6>3" is the difference between the PL-606 and PL-398bt with SAT, and "b:6>3" is the difference barefoot. On the signal readings, for weak signals I noted what the dB (S/N) reading was during non-modulation (between sentences), which is usually when it's the highest. For the MDCL stations (1170 and 1210, iirc), those are the maximum reading I see. In most cases, the readings are in yy,zz format, as shown on the display. On a few, I did xx/yy - on those, the first number is the extra-high reading I get when first tuning in, the 2nd number is the signal strength it settles to after the initial desense kicks in. The "xxxxx" readings on the barefoot PL-398bt column means the signal was not heard at all. (Weak ones like 00,02 were very weak, such that I couldn't understand any audio even with headphones, but the signal was still doing something with the muting circuitry. Also, stations that weren't heard at all even with the SAT on the PL-398bt aren't included, even though there are quite a few that are easily audible on the barefoot PL-606.)

Also, I noticed that with the SAT, the strongest signals on the defective PL-398bt happened when I had it sitting directly on top, but with the PL-606 I had to hold it a few inches away from the SAT.

freq | call | st398 | st606 | bf398 | bf606 | s:6>3 | b:6>3
----- | ----- | ----- | ----- | ----- | ----- | ----- | -----
540 | xesurf | 18,25 | 74,25 | xxxxx | 54,25 | 56 | xx
600 | kogo | 33,25 | 86,25 | 00,09 | 67,25 | 53 | 67
620 | xess | 05,18 | 59,25 | xxxxx | 40,25 | 54 | xx
640 | kfi | 11,22 | 65,25 | xxxxx | 45,25 | 54 | xx
690 | xeww | 33,25 | 87,25 | 02,13 | 68,25 | 54 | 66
760 | kfmb | 37,25 | 90/88 | 01,15 | 70,25 | 51 | 69
800 | xespn | 24,25 | 74,25 | 00,02 | 55,25 | 50 | 55
830 | klaa | 03,17 | 53,25 | xxxxx | 34,25 | 50 | xx
860 | xemo | 22,25 | 74,25 | 00,02 | 55,25 | 52 | 55
910 | kecr | 35,25 | 86,25 | 00,12 | 67,25 | 51 | 67
950 | xekam | 23,25 | 74,25 | 00,02 | 55,25 | 51 | 55
1000 | kceo | 10,24 | 62,25 | xxxxx | 43,25 | 52 | xx
1030 | xesdd | 09,23 | 58,25 | xxxxx | 40,25 | 49 | xx
1040 | kurs | 16,25 | 71,25 | 00,00 | 51,25 | 55 | 51
1070 | knx | 15,25 | 66,25 | xxxxx | 46,25 | 51 | xx
1090 | xeprs | 18,25 | 70,25 | 00,02 | 50,25 | 52 | 50
1130 | ksdo | 41,25 | 92/88 | 06,21 | 75,25 | 47 | 69
1170 | kcbq | 46,25 | 94/91 | 11,24 | 79,25 | 45 | 68
1210 | kprz | 20,25 | 74,25 | 00,02 | 54,25 | 54 | 54
1270 | xeaz | 13,25 | 68,25 | xxxxx | 48,25 | 55 | xx
1310 | xec | 08,23 | 63,25 | xxxxx | 43,25 | 55 | xx
1360 | klsd | 25,25 | 81,25 | 00,09 | 62,25 | 56 | 62
1390 | xekt | 08,22 | 62,25 | xxxxx | 41,25 | 54 | xx
1420 | xexx | 12,25 | 65,25 | xxxxx | 45,25 | 53 | xx
1470 | xercn | 23,25 | 75,25 | 00,09 | 55,25 | 52 | 55
1550 | xebg | 02,17 | 55,25 | xxxxx | 34,25 | 53 | xx
1630 | xeut | 15,25 | 66,25 | xxxxx | 45,25 | 51 | xx
1700 | xepe | 21,25 | 73/72 | 00,05 | 51,25 | 51 | 51