Editor's note: The newest version of the pattern set (2024) is available. See the link at the upper right of this page.
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. 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.
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.
INSTALLING
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.
HOW THEY ARE PRODUCED
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.
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.
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.
INSTALLING
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.
HOW THEY ARE PRODUCED
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.
37 comments:
Great work! Just one comment: On regional channels coverage maps overlap a lot and it's often difficult to see which contour belongs to which station. Since the pattern reference is probably mostly for DX-ers, could it be an idea to use a higher signal reference to make the contours smaller (and thus less "interfering")?
Thanks, Bjarne. Glad the maps are helpful to you.
There's a couple of things I can do to improve the confusion in the overlap. I do have the ability to draw radial lines from the transmitter to the plot edge. Unfortunately, it increases file size and I purposely left these out to make the files smaller.
As you indicated, I could also increase the signal reference level. That should take care of it.
I'll have a look at it and make some changes in the next database build.
Thanks again,
Bill
Bjarne,
One problem I just thought of: if the signal reference level is raised too far, above a certain level the skywave plot will disappear. This occurs just above the "distant" level, or a little greater than 0.5 mV/m. I'll work with it.
Bill
Thank you for sharing this excellent work with us!
Rather than changing the signal reference level for the regional channels how about a feature that by clicking on one station flag would then show only that stations coverage? Perhaps be able to click on several to get a comparison, etc.
Hi Zygmunt,
Thanks for your suggestion. I'll need to have a look at the generated web code and see if it's feasible.
Thank you,
Bill
I love these maps! :)
One feature that would be nice would be to be able to select a custom mV/m level, and % on skywave. :) That, and maybe showing the field based on a specified location, combined with Zygmunt's idea of being able to show only selected stations. Also what about showing a few different mV/m levels, with shaded color coding based on signal strength?
Also, being able to show skywave on day patterns (cause sometimes that does happen in the daytime) would be nice. Also what about critical / specified hours patterns (like 850 KICY Nome, AK), and the few USA-licensed stations in the west Pacific on frequencies not divisible by 10?
And, so far I have no trouble at all displaying the maps. I'm on a cable connection (Cox), and I'm running Chrome (also have Firefox and Opera available but haven't tested with them except an accidental click into FF when I meant to use Chrome, and it was fine there too), on PCLinuxOS 64-bit KDE Fullmonty, viewing on a Dell 24" 1080p monitor, with an i7-4790K CPU, 16 GB DDR3-1600 RAM and a 256GB Crucial M550 SSD. :) (I almost think I could load all of them in separate tabs if I wanted to.)
Hi Stephen,
Glad you like the maps are they are useful to you.
Good ideas, all. Unfortunately there is no formula calculation done at all on the HTML side of things. All maps are created offline according to inputted parameters, plot points calculated there, then the HTML is created en-masse to display the map. It would not be feasible to do the calculation side of things in the HTML code. It would be thousands and thousands of lines of code because it would have to have FCC database access, record sorting ability, etc., as well as sheer number crunching. The program that creates these maps, and does many other things, is some 50,000 lines of code, impossible to recreate in an HTML page.
Zygmunt's idea of switching patterns on and off may be possible. I'll have a look at that one at some time.
1. Being able to show skywave on day patterns?
I can produce maps that show skywave on day patterns together. It's one of the inputted parameters offline. It would be possible to include both, though being able to switch on and off would be imperative.
2. Critical / specified hours patterns (like 850 KICY Nome, AK), and the few USA-licensed stations in the west Pacific on frequencies not divisible by 10?
KICY-850 does show both daytime and critical hours plots. Any critical hours plots can be found on the daytime maps. It will be the smaller plot circle inside the daytime circle, where applicable. If you are referring to PSRA or PSSA authorizations, I have no plans on implementing plots for these.
The Guam stations (both x10 KHz and not divisible by 10) are on the plots, though I see the daytime plots are screwed up. That is undoubtedly due to M3 map segment errors somewhere. I guess I have more to fix!
Bill
Stephen,
Forgot to add, you can find the odd Guam, etc. stations, like 567 KHz on the 560 KHz map. The 560 KHz map has everything from 560-569.999 KHz. Likewise for other x10 groups.
Bill
Hi Bill,
I was just thinking a little earlier this morning. What about having several different mV/m levels? You could select them with checkboxes, or if it's only practical to display one at a time, with a drop-down selector. (I suppose you could implement a ctrl+click method for multi-select on the menu-style selector, too, instead of the individual checkboxes.)
I'm thinking the options would be in 10 dB increments, "snapped" to levels divisible by 10 dBuV/m. For example, maybe starting with 10 dBuV/m (3.16 uV/m), then 10 uV, ~30 uV, 100 uV, ~300 uV, 1 mV, 3 mV, 10 mV, 30 mV, 100 mV, 300 mV and 1 V/m (120 dBuV/m). For the skywave plots, maybe only use the 10 uV (20 dB) to 3 mV (70 dB) plots, but also be able to select 50% or 10% skywave.
If that's too many plots, then I guess you could do every 20 dB, maybe starting with 10 uV (20 dB), then 100 uV (40 dB), 1 mV (60 dB), 10 mV (80 dB), 100 mV (100 dB) and 1 V (120 dB), with skywave being 20, 40, 60 and 80 dB or 30, 50, 70 dB.
Also, considering how far out some of the lower-field-level plots would go and the massive overlap that would ensue, I'd suggest implementing it along with Zygmunt's idea of the switchable station patterns.
Speaking of % time on skywave, what really does that mean? Does 50% of the time mean that half the night the signal is that good or better, or something else? And what about 10%? Or, for example, sometimes I'll see a skywave signal several dB stronger than I normally see it due to a propagation peak that maybe lasts a minute or two, then I never see that strength again that week. What about those types of anomalies?
Thanks for the tip re: viewing "split" frequencies on the maps that share the 2nd digit & more left of the decimal. :)
73, Stephen
Hi Stephen,
Thanks for your comments.
Creating multiple mV/m level plots would certainly be possible, and of course it's possible and not hard to create the data points for those in an HTML document. You are talking 12 plots per station. For perhaps up to half a dozen stations per map that would work, but not so for many beyond that as it makes the HTML files too big. Even as it is today, the current files tend to choke most tablets and some slower laptops. File size is averaging about 500 KB each already, very large for an HTML file. The graveyard frequencies with all their stations are in the 3 MB range and really bog a computer down.
The HTML/Google Maps operation (the HTML files) are simply plotting data points. They are created externally by a Windows program, my Radio Data MW program. To actually calculate all these data points in the HTML itself is not the way to go. Javascript is an interpreted language and is inherently slow. You wouldn't want to run massive computations in HTML/script anyway. It must be done outside of the HTML. So you must produce an HTML map object with all or most of the computations already done.
The simplest thing is to continue to create fixed plots and perhaps switch selected plots on and off through a checkbox system of some sort. Sometime when I have some time I will have a look at what this entails.
You asked, 'Speaking of % time on skywave, what really does that mean? Does 50% of the time mean that half the night the signal is that good or better, or something else? And what about 10%?'
You are essentially right. 50% means that the signal will be received at this level (the particular map level calculated was 0.25 mV/m) approximately 50% of the time during deep darkness hours (Sunset+6). 10% would mean that the signal would be received at 0.25 mV/m only 10% of the time during these hours. Common formulas exist for 50% and 10%, I have not seen others for any other percentage values. Skywave plots for nearer to sunrise or sunset are a wholly different thing and the mechanics are very different. That math is VERY complicated.
You asked, 'Or, for example, sometimes I'll see a skywave signal several dB stronger than I normally see it due to a propagation peak that maybe lasts a minute or two, then I never see that strength again that week. What about those types of anomalies?'
The formulas don't account for these extremes, though they are possible as you have seen. Possibly many effects are coming into play just at the perfect time, or maybe weird ducting in the troposphere, etc. Not something easily calculated.
Bill
Stephen,
More on your extreme signal strength anomaly.
Interestingly, at the 50% reception figure, the skywave forumlas start to fail about the 1 mV/m level, producing no distant plotting point, meaning that there is basically no skywave propagation at the 1 mV/m level to be had at 50% of the time. Of course that means for some value less than 50% of the time you might see 1 mV/m or even greater.
The thought process can get confusing.
Counter-intuitively, the 10% plots are bigger than the 50% plots for the same mV/m value. For example, 50 KW KOA in Denver gets into western Ohio at 0.15 mV/m at 50% of the time and the plot edge stops there. The 10% plot shows KOA getting into central New York state at 0.15 mV/m at 10% of the time. Of course in NY, reception of KOA would be further complicated by even stronger and close stations on 850 KHz.
Bill
Hi Bill,
Would it be possible to consider having two versions of the maps available? One would be the basic version like what you have now (or maybe with one extra level added if desired), and the other one would be the more feature-rich version.
Apparently I still need to figure out how to access the maps on my phone (Samsung Galaxy S Relay 4G) - I'm getting file access denied in Chrome (testing with the 1490 kHz night plots file), even though I downloaded the zip and saved it to my SD card. The previous maps worked fine in the past, though. I think I was using FireFox then, but now I don't like using it, because some sites I visit (like youtube) do something to the phone if I use FF that makes it respond extremely slowly, have weird graphics anomalies on the display, etc, and I have to force-reboot (remove/replace the battery while unplugged) to get it back to normal.
Any idea when/if that Radio Data MW program may be made available?
Ahh, thanks for the skywave % explanation. :) Oh, and I'm wondering if those % take into account other anomalies in the other direction, like aurora, excessive sunspots, acts of war/God, etc?
Some examples of "extreme" signal strengths I've had, from my location (32° 45' 38.32" N, 116° 56' 45.05" W), include, as indicated on my PL-606 or other similar Tecsuns:
720 KDWN - "62 dBu"
740 KCBS - "58 dBu"
840 KXNT - "62 dBu"
1160 KSL - "56 dBu"
1180 KERN - "58 dBu"
1530 KFBK - "57 dBu"
1580 KMIK - "64 dBu"
There could be an error rate of a couple dB, as I'm going on memory. Also this is using only the built-in ferrite antenna.
On my PL-606, in that range of signal strengths, a 58 dBu signal seems to correspond to 10 mV/m. (This is based on 1170 KCBQ, which is around 120-130 mV/m daytime here, indicating about 80-81 dBu, and 1130 KSDO at ~60-65 mV/m indicating about 75 dBu.)
I'm not surprised that the 10% plots are bigger for the same received signal level. It stands to reason, at least in my mind, that a signal would be more rarely received at a higher level, and as you get farther from a station, particular DX is rarer. For example, I think you're in AZ right now, right? You probably get nightly listenable reception of stations like 820 WBAP, 870 WWL, 1040 WHO, 1080 KRLD, 1110 KFAB, 1130 KWKH, 1170 KFAQ, 1200 WOAI, and 1500 KSTP, right? Well, it's rare here that those signals are strong enough to listen to if at all, at best. I have locals on 1040, 1130 and 1170 as well, and of the aforementioned big guns on those frequencies, WHO is the only one I've heard. (I did hear CKWX once when KSDO was off.)
Stephen
Also, re: my strong night skywave signals, I forgot to mention something. Signal levels of "48 - 54 dBu" (3.16 - 6.3 mV/m) are frequently/consistently seen (except in propagation fades) on some of my closer / stronger skywave signals, including 660 KTNN, 680 KNBR, 700 KALL, 770 KKOB, 810 KGO, 830 KLAA, 890 KDXU, 960 KKNT, 1560 KNZR, plus the ones already mentioned.
Also I've seen upwards of 58-60 dBu on 1110 KDIS in the late afternoon before their pattern change, and in the early morning after the switch to daytime mode, and I've heard 1550 KUAZ fairly strong around sunrise/sunset while they're on the air. (Hey I wonder if they could be an inspiration for the subject of another "oddities" post? It seems they use a similar transmitter facility (50 kW, omni, big/efficient antenna) that some Class A stations use, but they're authorized for daytime operation only. I wonder if there are any other stations like that?)
Wow, Stephen, you have been busy! :-)
'Would it be possible to consider having two versions of the maps available?'
Currently the creation process allows for up to 5 plots per station per service (5 daytime and 5 skywave). They are 2.5 mV/m (local), 0.5 mV/m (distant), 0.15 mV/m (fringe), 0.05 mV/m (extreme), and one custom mV/m. Additionally, you can plot skywave at either 50% or 10% levels. It might be nice to add one or two extra custom mV/m levels particularly for skywave. I'm out of room on the form though. I'll have a look, no promises. Honestly, I'm not looking to spend too much more re-engineering design time on the program, just minor changes. It has occupied a huge amount of my time in the last 5 years and realistically I need to move on.
Hope you get your phone to work for the maps. Small devices do tend to bog down though.
'Any idea when/if that Radio Data MW program may be made available?'
Not sure. There are still many small fixes on the list. I'm still fooling with a separate offline mapping process. No documentation has been done. That's many, many hours of work just there. I may kick it out on the public before I get too old and cash out, if you know what I mean. I'm no youngster anymore. 67. For the immediate future, probably not.
'Oh, and I'm wondering if those % take into account other anomalies in the other direction, like aurora, excessive sunspots, acts of war/God, etc?'
No, they don't. Those are pretty hard to predict. :-)
Bill
Haha, maybe a little, Bill. :)
Ahh, okay. Hmm....
Hey I was thinking. Could you maybe do 5 custom levels (replacing the 4 fixed plus 1 custom) for the maps? If so, then my suggestions would be as follows:
Day:
100 dB (100 mV/m)
80 dB (10 mV/m)
60 dB (1 mV/m)
40 dB (0.1 mV/m)
20 dB (0.01 mV/m)
Night:
70 dB (3.16 mV/m) 10%
54 dB (0.5 mV/m) 50%
40 dB (0.1 mV/m) 50%
28 dB (0.025 mV/m) 10%
14 dB (0.005 mV/m) 10%
Or, if you have to keep the levels you already have, plus one custom, then I suppose for daytime you could do the 2.5 mV, 0.5 mV, 0.15 mV and 0.05 mV (if you could change this to 0.025 that'd be nice), and add maybe a 15 or 25 mV/m as the custom level.
For nighttime, if you keep the normal ones, how about...
2.5 mV/m (68 dB) 50%
0.5 mV/m (54 dB) 50%
0.15 mV/m (43.5 dB) 50%
0.05 mV/m (34 dB) 10%
0.005 mV/m (14 dB) 10%
A couple ideas I was also thinking re: the night skywave plots. What level would you need to have the closest one, so that for a typical 50 kW station it shows the "propagation peak" strength (I think 10% would be close) within, say, 300-500 miles or so? And, for the farthest one, what about showing, for example, reception of east-coast stations (at least the big ones) in Europe and Africa, and west-coast stations in Asia and Australia? (As in, trans-oceanic reception predictions.)
For the day plots, I'd prefer the closest one (if not picked from ideas above) being the range at which even a dirt-cheap radio can get a perfectly clean signal even with electrical devices (plasma TVs, CFL lights, unshielded computers (although mine does fairly well at not radiating too much so far based on my limited testing), etc), with some radios like the Sony SRF-M37W having the stations being like 50-100 kHz wide before they start reducing in volume as you tune farther off. For the farthest contour, I'm thinking a level that with a large loop antenna or longwire and a decent receiver, you might hear a carrier. :)
Well, it worked previously, so I'm thinking I must be doing something wrong. (Maybe I should test it with one of the Mexican Class A channels?)
Ahh. I do hope it's not priced out of reach for hobbyists. Something like $100 or even $50 for a copy would be way out of reach for me, even if it's super customizable, etc. And yes you are a youngster - well at least compared to my parents. :) My dad's 68 (he worked as an engineer at KECR-FM while he was in college, then his main line of work had to do with more of something like military type radio engineering through his working like until just a few months ago when he retired), and my mom is 71. Oh, and I guess you wouldn't want to consider, for example, something like the open source community.....?
Haha I'm not surprised it doesn't predict those all that well. :p so I'm also guessing you can't predict my likelihood of receiving 594-JOAK at my location, being 7.7 miles from 600 KOGO's IBOC-infected 5 kW site. And, yes, I have received it once, a few years ago, and yes KOGO was on with its IBOC. :)
Stephen
Hi Stephen,
Have thought of a possible way to add extra custom levels, it may be fairly easy to just stack the inputs in one text box since they are manually entered. Anyway, I'll have a look and see what it entails as far as changes go. It's a slow go process here, and I only work on this program when the mood strikes and I have the time.
Some comments on your plot list:
Day:
100 dB (100 mV/m)
100 mV/m - Plot not very accurate at this level. Too close to transmitter (~1-2 km for a 1KW station). Plot formulas are meant to plot distant patterns (many wavelengths), meaning many kilometers away. They are not accurate at close ranges.
80 dB (10 mV/m)
60 dB (1 mV/m)
40 dB (0.1 mV/m)
20 dB (0.01 mV/m)
0.01 mV/m - Though a signal will exist at this level, you will never hear it in a portable. Buried in the noise.
Night:
70 dB (3.16 mV/m) 10%
3.16 mV/m - way too high a level for a skywave plot for most stations except the highest power ones like 25KW or more. Formula produces either totally inaccurate results or zero result for lower powered stations. In other words, no skywave exists at the 10% level for this mV/m value.
54 dB (0.5 mV/m) 50%
40 dB (0.1 mV/m) 50%
28 dB (0.025 mV/m) 10%
14 dB (0.005 mV/m) 10%
0.025 mV/m and 0.005 mV/m - interesting to see on a plot, huge plots, but you will never hear this level on a portable. Buried in noise.
You asked, 'What level would you need to have the closest one, so that for a typical 50 kW station it shows the "propagation peak" strength (I think 10% would be close) within, say, 300-500 miles or so?'
The skywave formulas don't work this way. The absolute highest propagation peak could be anything. Unpredictable.
Open source community? Maybe. Don't know of an open source community that is into radio propagation. Maybe the Hams. This is way down the road though. This is still my hobby program. :-) Can't give it away yet.
Bill
These are great maps. You are more than welcome to incorporate these maps into the REC Broadcast Query tools (recnet.net) will full attribution. REC currently provides propagation curve support for FM and TV but we do not provide any AM curve support even though we have the full AM database (both FCC and Industry Canada) available and you can look up AM stations.
This might help those who want to view the data for only one station at a time.
Myself, I have very little experience with AM. I am more of an FM person but it would be cool to add these maps and perhaps with the right coding, we could do the multi-contour support that some here are asking for.
Michi Bradley
Founder: REC Networks
=m
Hi Bill,
If adding extra custom levels for the map is possible then that would be nice. :) Your comment "only ... when ... I have time" reminds me. How's your DXing been in AZ this winter, and what was the trip out like? (That probably should be answered with another blog post instead of a comment here maybe.)
Hmm... is there any strong-signal level that would work for the close-in plots? I'd like to see contours where you might be getting 50/00 desense from an AM station across the width of an IBOC FM channel on the PL-380, for example, or, where on a radio like the SRF-M37V or even the DT-400W, it'd still be just as "loud" about 50-80 kHz off-channel, or, maybe where it's still a full-quieting signal on a cheap pocket radio and it hampers its ability to DX anything within a couple channels either side.
For example, a station like KCBQ might not even "reach" the extreme northeast corner of Santee, KFI wouldn't make it to the I-5 / CA-91 interchange, KNX may or may not make it to I-405, etc.
Or, if that's too close, then, for example, at my location, I'd only be within the specified contours for KSDO and KCBQ, barely for KFMB, and a little outside for KOGO, KECR and KLSD, for example.
Basically on the close-in plot I'd like to see the level within which even a selective radio would have trouble DXing near there, or something like that.
As for the farther plot ... well, I don't know what the fields would be, but on a portable I have sometimes heard stations well outside the 0.15 mV/m contour. I know you don't currently have Mexican stations listed, but, for example, at Cameron Corners, CA, I've heard listenable signals from 1090-XEPRS -- http://transition.fcc.gov/fcc-bin/amq?list=0&facid=166706 -- in spite of being like 3-4x outside their 0.5 mV/m night groundwave contour. (Btw they run directional fulltime, using the night pattern.)
Here's an example video, part of which shows XEPRS's reception at Cameron Corners - https://www.youtube.com/watch?v=9x7t5PhLrhA
Also, when using larger antennas inductively coupled to portables, I've heard stations well beyond that sometimes.
Hey, that reminds me. Would it be too much to request a few semi-abridged lists based on a few locations I've gone in the daytime to try DXing or testing radios? :) A list of coordinates (locations) is below, along with the general location (town) name, and the purpose for the visit. For the most part I'm thinking just daytime lists, maybe something like 4 or 5 or so stations per frequency, regardless of field intensity.
32-37-46.4 N, 116-28-7.4 W (Cameron Corners, CA - DXpedition)
32-50-29.8 N, 116-42-8.8 W (east of Alpine, CA - DXpedition)
33-19-44.9 N, 117-0-3.3 W (Pauma Valley, CA - DXpedition)
32-50-33.8 N, 117-1-32.0 W (Santee, CA - selectivity testing) - night would be preferred on this one, as I was testing my radios at night.
32-53-37.9 N, 116-55-40.5 W (Lakeside, CA - selectivity testing)
34-4-19.9 N, 117-17-55.2 W (San Bernardino, CA - selectivity testing)
Re: Night -- Ahh, hmm... is there still some way to show, on one end of the strength spectrum, the plots where you have nearby skywave blowtorches - the ones where, say, 10% of the time, it's basically full-quieting on a pocket-sized portable? (For example, at my location, it might show me just barely being within KDWN, KCBS, KXNT, KFBK and KMIK's "blowtorch" contours.) And on the other (weak) end, what about "predicting" trans-oceanic reception, like WBAL, WQEW, WTIC, WPTF, WFLF, WFED, etc. in Europe and Asia, and KTCT, KFMB, KMIK, KEIB, KMJ, etc. in Asia and Australia? I've "heard" WQEW some time ago on an online receiver somewhere in Europe, and also a few other stations as well.
Ahh, well, I was thinking maybe 10% would get us somewhat close to a semi-peak or something. (I'd think that 90% of the time the signal would be less than that, for example.) What contour, for example, might a typical 50 kW Class A station have at like 300 miles, at 10%?
Ahh, well it's of course up to you what you do with it. :) I'm no programmer, but would love to be able to try some reception scenarios sometime, for example, maybe use it to plan DXpeditions, like looking where on a map the weakest signals are.
OH!! :) Another thing I just remembered! How difficult would it be to come up with a map that shows what the strongest signal is at a particular area? It wouldn't need super high resolution, like maybe only 6-10 dB steps or so, and maybe it could be limited to only show areas where the strongest signal is less than 5 mV/m groundwave or 1.5 mV/m 50% skywave or something like that, idk.
73, Stephen
Hi Michi,
Thanks, glad you like the maps. And thank you for the invitation. I will consider it for the future.
I am working on some changes to the plotting routines right now. I do have the ability to create separate maps for each station at various plotting levels. Please note that these maps are fixed - they do not automatically update with station changes in the FCC database. They must be recreated each time changes occur.
Bill
Hi Stephen,
I haven't really done any DXing this winter from Arizona. I bought a new place this winter and have been busy working on it. My programming goes in spurts. I may put in a lot of time for a couple of weeks, then not much of anything for a month or more.
The trip out was good, and uneventful. Did a little DXing from the road. I have a partial blog post written. I should get back to it.
You asked:
'is there any strong-signal level that would work for the close-in plots?'
I'm looking into that. The groundwave plots at 1-2 miles distant can be ragged and erratic. The skywave plot formula just does not work at all for anything less than about 50 kilometers. For certain levels out past 50 km that don't work, the key is to jimmie the percentage value to something other than 50% or 10%, if that's possible. I'm looking into that too.
You asked:
'Would it be too much to request a few semi-abridged lists based on a few locations I've gone in the daytime to try DXing or testing radios?'
Give me the latitudes-longitudes in decimal format so I don't have to convert them and pick your favorite one. I'll get you one anyway.
Bill
Hi Stephen,
You asked:
'Re: Night -- Ahh, hmm... is there still some way to show, on one end of the strength spectrum, the plots where you have nearby skywave blowtorches - the ones where, say, 10% of the time, it's basically full-quieting on a pocket-sized portable?'
Well, anything above about 2 mV/m should be full quieting in a small radio. Just generate the skywave plot for 2 mV/m at 10% should do it. If you are within the plot boundaries, you have your scenario.
You asked:
'What contour, for example, might a typical 50 kW Class A station have at like 300 miles, at 10%?'
You would have to manually experiment with the mV/m levels when generating the plot to determine this.
You asked:
'How difficult would it be to come up with a map that shows what the strongest signal is at a particular area?'
Radio Data MW already does that. First you have to set your location to the latitude-longitude you wish. It will then recalculate all signal levels and produce a list.
Bill
Hi Bill,
Ahh, that’s nice, a new place in AZ I’m assuming? :) Is it also in Quartzsite, or somewhere else?
I look forward to reading the post. :)
Re: the close-in plots, I commented on another post about OET Bulletin 65 and supplement A, about RF exposure guidelines close to a transmitter, and they seem to have some formulas. I wonder if they might give some ideas?
Also I was thinking, for the skywave when you have the “too-close” situations - what about using the groundwave strength for those cases? And maybe there’s a way, in a transitional zone, to figure out how to calculate the combination of skywave and groundwave. Also what about cases where you get out of groundwave range, but aren’t far enough for skywave yet, maybe something might need to be fudged there a little, too. Then for farther distances, like trans-oceanic or inter-continental DX, what about multi-hop skywave? And for all skywave distances, wouldn’t the configuration of the antenna system used have an effect on the vertical radiation shape? (I’m guessing that’s already factored in though?)
Ok, here’s the list of lat-lon’s, in decimal.
32.6295556°, -116.4687222° -- DXpedition, near Cameron Corners, CA
32.8416111°, -116.7024444° -- DXpedition, near Viejas Outlet Center (E of Alpine), CA
33.3291389°, -117.0009167° -- DXpedition, near Pauma Valley, CA
32.8427222°, -117.0255556° -- selectivity testing, near Santee, CA (night preferred)
32.8938611°, -116.9279167° -- selectivity testing, near Lakeside, CA
34.0721944°, -117.2986667° -- selectivity testing, near San Bernardino, CA
The most preferred ones would be the Cameron Corners and Pauma Valley lists, as I’ve had a few DXpeditions at both sites and have recordings of the stations received there. The Cameron Corners site is fairly close to Mexico, though, so many of the stronger Mexican stations aren’t going to show on your list until there’s some way to add Mexican data. (I wonder if mwlist.org may be of any help there? although you’d still need specific pattern data; maybe David Eduardo on the radiodiscussions.com or radioinsight.com boards may have some ideas on how to get it accurately?)
If you choose to do the others as well, a little heads-up on the Santee and San Bernardino sites may be in order -- they are closer to individual towers than the distance between the towers in the arrays for KFMB and KTIE, respectively. My very rough calculations estimate that the field strength of those stations at those sites would be rated in hundreds of volts per meter. The Lakeside site isn’t quite so close to individual towers, but the use of the longwire antenna seems to boost the signal to a level such that if I was close enough to have the same signal without the big antenna, the field might be more like tens of kilovolts per meter, I’m guessing. :o
With whichever one(s) you do, I only need 2 or 3 stations per frequency regardless of the minimum, and only one time - daytime for all except Santee. Frequencies would as usual be 10 kHz steps between 540 and 1700 (adding 530 for the night one maybe, leaving it off for day ones as you don’t seem to have TIS stations factored in yet). I’m thinking each list would be about 234 or 351 stations. Generally just 2 per frequency should be sufficient, but in cases where multiple stations are within 3 to 6 dB of the strongest on that frequency, then 3 may be desirable. On the close-to-station ones, having the 2nd-place one listed for those frequences would be interesting too, to see what would theoretically be heard there if the transmitter was off the air. :)
Hmm… actually, 2 mV/m still has some significant noise on some of my small radios. :)
http://youtu.be/UMyhL0rdu3Y?t=1m36s -- 740 KBRT (2.095 mV/m) -- Tecsun PL-398mp -- switching TX sites. Listen to beginning of clip for Catalina signal
If you listen earlier in the clip, the signal is about 15 dB stronger, coming from Catalina before the site change.
http://youtu.be/Jt6_Li9_fKk?t=2m17s -- 1000 KCEO (2.64 mV/m) -- Panasonic RQ-SW44V
http://youtu.be/KKvW2NO3CJk?t=4m14s -- 1000 KCEO (2.64 mV/m) -- Panasonic RQ-SW20
http://youtu.be/ctIjTeFDWkc?t=1m53s -- 1000 KCEO (2.64 mV/m) -- GE Superadio III (Wide)
http://youtu.be/ylEOx3TRNVg?t=15m43s -- 1000 KCEO (2.64 mV/m) -- Tecsun PL-398mp
http://youtu.be/d7S15FZHrLk -- 1000 KCEO (2.64 mV/m) -- Tecsun PL-606 -- barefoot, then SAT, then SAT + Chainlink Fence
The Panasonic RQ-SW44V just barely hears any trace of signal on KCEO. The RQ-SW20 is better, though. (I think they're basically almost the same radio as far as selectivity, but the RQ-SW20 is much more sensitive.) Even the Superadio has some audible noise. In the PL-606 video, the noise is dramatically reduced when the SAT is added.
http://youtu.be/Jt6_Li9_fKk?t=3m34s -- 1210 KPRZ (11.34 mV/m) -- Panasonic RQ-SW44V
http://youtu.be/KKvW2NO3CJk?t=5m39s -- 1210 KPRZ (11.34 mV/m) -- Panasonic RQ-SW20
http://youtu.be/ctIjTeFDWkc?t=1m13s -- 1210 KPRZ (11.34 mV/m) -- GE Superadio III (Wide)
The RQ-SW44V is fairly noisy here with the 11.34 mV/m signal. Even the RQ-SW20 still has a little too. The Superadio III has a little too, along with splash from 1170 KCBQ.
http://youtu.be/Jt6_Li9_fKk?t=4m10s -- 1360 KLSD (31 mV/m) -- Panasonic RQ-SW44V
http://youtu.be/KKvW2NO3CJk?t=6m38s -- 1360 KLSD (31 mV/m) -- Panasonic RQ-SW20
http://youtu.be/ctIjTeFDWkc?t=45s -- 1360 KLSD (31 mV/m) -- GE Superadio III (Wide)
http://youtu.be/tRJfqtUe3LE?t=8m6s -- 1360 KLSD (31 mV/m) -- Tecsun PL-398mp
http://youtu.be/tRJfqtUe3LE?t=8m18s -- 1360 KLSD (31 mV/m) -- Sony SRF-M37W
The RQ-SW44V still has moderate noise, in spite of the fairly strong 31 mV/m signal.
http://youtu.be/nnmLc4mdmjg?t=1m00s -- 760 KFMB (46.9 mV/m) -- Coby CX-70
The Coby CX-70 still has a little noise here (ignore the plane overhead). (If you look through the clip, you'll also see its selectivity is quite poor, for example 910 KECR is still heard on 1000 KCEO, and I think 1170 KCBQ runs into 1360 KLSD.)
http://youtu.be/Jt6_Li9_fKk?t=3m24s -- 1170 KCBQ (123 mV/m) -- Panasonic RQ-SW44V
http://youtu.be/KKvW2NO3CJk?t=5m24s -- 1170 KCBQ (123 mV/m) -- Panasonic RQ-SW20
http://youtu.be/nnmLc4mdmjg?t=2m42s -- 1170 KCBQ (123 mV/m) -- Coby CX-70
http://youtu.be/ylEOx3TRNVg?t=12m12s -- 1170 KCBQ (123 mV/m) -- Tecsun PL-398mp
Even with this fairly strong 123 mV/m signal, the RQ-SW44V still retains a little noise.
Also, the above clips may give an idea for the targeted plot contour for the occasional blowtorch skywave signal. (Ignore the weaker radios - the CX-70 and RQ-SW44V, for this one.) If I had to guess or pick one, I think I’d be looking at something like the 10 mV/m 10% skywave signal, or maybe the 1% or 0.1%?
Also, I was thinking, re: a map that shows the strongest signal, and a suggestion, if it’s possible. My idea is 2 maps, one for daytime & one for nighttime, that are basically kind-of like a terrain / elevation map, but for signal contours. This could be used as a DXpedition planning guide, so someone could pick a location with the weakest pest within their desired traveling distance.
Basically, it would show the strongest field strength in the area, regardless of frequency. I’m thinking the contours could be in 6 dB steps, starting with 78 dBuV/m (7.94 mV/m), and going down to 24 dBuV/m (15.85 uV/m), if you wanted to keep it relatively simple. Maybe the areas in between the contours could also be lightly color-coded/shaded, with the “urban” areas (over 78 dBuV/m) and ultra-rural areas (below 24 dBuV/m) not being shaded at all. For nighttime, you could maybe go from 72 dBuV/m (3.98 mV/m) to 42 dBuV/m (126 uV/m), 6 steps. Maybe for areas where there are 2 stations within 6 dB of the strongest there could be one kind of crosshatch pattern, and if there are 3 or more within that range of the strongest, another pattern maybe?
I’ve been wanting to plan a daytime DXpedition to a rural area of San Diego county for some time now, and now that I have a car, I’ll have much more freedom to choose where to go. My previous DXpeditions have been limited to Cameron Corners, CA, Pauma Valley, CA, and east Alpine, CA, because of bus service available to those locations. I had also gone to Borrego Springs like 10 or so years ago, but I don’t recall recording anything, I didn’t have some of the radios then that I have now, and the bus no longer allows me to go and return on the same day. I do remember that it was probably summertime (was fairly warm, like over 100 degrees), 970 KNWZ was the strongest signal there, and 700 KALL (or whatever it was then) was audible on the RQ-SW20 with the Select-A-Tenna. Now that I have a car, though, I could go again, and I could also if I wanted to, go to other sites like Pine Valley, Julian, Cuyamaca Lake, or even other places. Maybe I could even hit a few sites in one day. (I don’t know if I could go to Quartzsite and come back all in the same day, though, and have time for DXing…) Anyway, having a map like I described above would help me plan the DXpedition, so I could choose a site with the weakest “strongest pest”.
Also, if there’s a way to have the map show more detail as you zoom in, then maybe you could do 3 dB or even 1 dB steps, and show urban signals up to and maybe over 10 volts/meter. (If I wanted to plan a coastal DXpedition, for example to try reception of TPs at a better location than home, I’d need to see some fairly high signal strengths. I’m guessing that I’d have to drive up to like past Santa Maria or so to find a place where the strongest pest is less than 5 mV/m or so. I’d prefer if I could to go to a place close enough so I could leave my house early in the morning, get to the coastal site, DX, then come home by mid morning or so. :)
Stephen
Stephen,
You are a bundle of questions and suggestions which could keep me busy for years to come. :-)
You asked:
'Also I was thinking, for the skywave when you have the “too-close” situations - what about using the groundwave strength for those cases? And maybe there’s a way, in a transitional zone, to figure out how to calculate the combination of skywave and groundwave.'
Both of those have been accounted for when creating maps. The user has the choice of substituting the groundwave point if the skywave is either nil or the reception point is too close.
You asked:
'Also what about cases where you get out of groundwave range, but aren’t far enough for skywave yet, maybe something might need to be fudged there a little, too.'
This has been accounted for as well. Actually, skywave usually overlaps with the groundwave signal on many medium to strong stations. Skywave can start to show up in as close as 50 km or so.
You asked:
'Then for farther distances, like trans-oceanic or inter-continental DX, what about multi-hop skywave?'
Extreme distance, multi-hop skywave is a different situation. The skywave formulas I'm using are not as accurate outside of the northern-western hemisphere, as they are tailored for North America. And the simple skywave formulas in general are not accurate at extreme distances.
'And for all skywave distances, wouldn’t the configuration of the antenna system used have an effect on the vertical radiation shape? (I’m guessing that’s already factored in though?)'
Yes, the antenna system used has great effect on the vertical component of the radiation pattern. I calculate for 0 degrees.
On the charts:
'With whichever one(s) you do, I only need 2 or 3 stations per frequency regardless of the minimum, and only one time - daytime for all except Santee.'
I don't have control over that. The program produces a list of all stations that exceed a certain received threshold. Some frequencies may have none, some 1-3 or so stations, depending.
'Frequencies would as usual be 10 kHz steps between 540 and 1700 (adding 530 for the night one maybe, leaving it off for day ones as you don’t seem to have TIS stations factored in yet).'
TIS plotting isn't possible. They don't submit any pattern engineering data. I suppose you could treat all of them as a point source.
Thanks for the multitude of clips, but I can't possibly listen to them all. Skywave formulas for 10 mV/m @ 10% would produce few plots at all, and only for the highest powered stations. KOA-850 (50 KW) Denver, for instance, shows some 10 mV/m, 10% skywave at 75 miles. You would see little or none at those levels for lesser powered stations.
You asked:
'Also, I was thinking, re: a map that shows the strongest signal, and a suggestion, if it’s possible. My idea is 2 maps, one for daytime & one for nighttime, that are basically kind-of like a terrain / elevation map, but for signal contours. This could be used as a DXpedition planning guide, so someone could pick a location with the weakest pest within their desired traveling distance.'
Creating maps with the strongest signal is already possible. I can sort station data pretty much any way one would like. I've recently added the ability to choose any and as many contour levels one would like.
You asked:
'Also, if there’s a way to have the map show more detail as you zoom in, then maybe you could do 3 dB or even 1 dB steps, and show urban signals up to and maybe over 10 volts/meter.'
Again, I can create any map you like. It just must be done offline. I can't do it in the HTML page. It just isn't possible to do it there. You can't cram that much software to change maps on the fly into an HTML web page.
The only other future change I'll be looking at is the ability to turn on and off selected plot displays on the web map page. I may have a go at that this summer when I get more time.
Bill
Bill, :)
Skywave only as close as 50 km? I don't have an audio recording readily available, but a year or two ago when I went to one of the night monitor points for KCBQ (around 0.6 mV/m at about 5.7 km, iirc), I was hearing fading on the signal immediately after sunset, and it wasn't because of KLOK or KFAQ, as they were pretty much absent. This fade was erratic like skywave, not steady like offset co-channel. What might that have been?
Ahh, ok, on the charts. I look forward to what you might be cooking on it. :)
Re: TIS, I suppose you could assume they're 10 watts into a 15-meter antenna, but there are some that employ leaky cable with a certain field strength requirement, also. So that'd make it a bit complicated. I think they're usually all omnidirectional, though, at least the ones using vertical antennas. (Figuring out which is which is probably beyond the scope of your work with the program at this point, though. :/ )
Re: Skywave at 10% -- I came across this post by "Schroedingers Cat" on radiodiscussions - http://www.radiodiscussions.com/showthread.php?685134-Your-quot-Go-To-quot-Nighttime-Station&p=6035168&viewfull=1#post6035168 - an excerpt from his post (he's referring to eastern Michigan I think): "As I recall, I measured the peaks of WMVP, WOWO, and WCKY at around 10 mV/m, which corresponds closely to the theoretical 6% skywave curves in the 1960 NAB Handbook." That's basically what I'm looking for, for strong skywave peaks or something like that. :)
Could you elaborate on what you mean with "creating maps with strongest signal"? Maybe an example map showing southern California or San Diego county or something? Or what do you mean?
Ahh, that'll be interesting to be able to show/hide the various plot displays. :) Hopefully it shouldn't be too much of a resource hit on my computer to show some details on those ;) (i7-4790K CPU, 32 GB RAM, Windows 7 Pro, etc...)
73, Stephen
Hi Stephen,
"Skywave only as close as 50 km?" The skywave formulas peter out if less than about 50 km (or about 35 miles distant). There could be some very small amount of skywave signal (maybe reflection from somwehere else?). Not sure what happened to you on that occasion.
Yeah, TIS would be difficult. No consistancy, like you said. Even so, skywave is not strong enough to plot with any formula I have. On a 10 watt station, groundwave peters out to about 0.15 mV/m (distant) reception at about 17 miles.
One of my jobs this summer will be to look further into skywave formulas which attack a lower percentage of reception, like Schroedingers Cat's reference in his 1960 NAB reference post. A 6% or less formula would be nice to find. The 10% plot on a 50 KW omni-directional station shows up at about 85 miles out. I know at a lower percentage it would be even further.
"...creating maps with strongest signal". I mean I just pick a frequency or frequencies, do a run on the database, sort stations by received strength for a given receive location, create the HTML maps for the list and create the plots.
Don't know what you mean by "show some details". I plot a point every degree. That's as fine a detail in the plot ring as I can manage.
Bill
Hi Bill,
Well, one person mentioned on another board several years ago something about me being in a deep null for the pattern at that particular spot. (He said something like 5.68 km to the 0.63 mV/m contour is pretty deep, and there could be phasing issues or something like that.) I kind-of remember it being on radiodiscussions, but I can't seem to find the post right now otherwise I would have linked it.
Also, speaking of phasing/etc, yesterday when I was driving east on I-8 toward Pine Valley, I was listening to 910 KECR, which has a pretty severe null to the east. Once I got past around Los Coches Rd or Lake Jennings Park Rd (about where the speed limit changed to 70 which traffic was already exceeding anyway), I started hearing fades on KECR, along with the type of audio distortion you normally get at night when you have one sideband fading out, or skywave/groundwave interference. (This was around 1 pm though.) Around the west side of Alpine or so, I started hearing the co-channel fading from the Mexicali station on 910 being underneath, and fairly abruptly after I passed by Viejas Casino, coming up on the CA-79 exit or thereabouts, the Mexicali station came up on top. Both stations battled it out to Pine Valley. Then, heading to Julian, they traded, but KECR was somewhat better in Julian. (There were some spots where KFRN's signal was cleaner, if weaker, than KECR.) Later, on the way home going through Santa Ysabel and heading toward Ramona, KECR was quite well on top, but after their pattern change they dropped off and were hit with interference even south of Ramona.
Yeah, seeing more capability on the skywave plots would be interesting.
Well, as for a map showing strongest signal, I figured I wasn't explaining myself well enough, so I made a concept map of contours, just to give an idea of what I mean.
https://plus.google.com/photos/118228966367965758611/albums/5484707295038138721/6121203122195899682?authkey=CIer0efojpPg8AE&pid=6121203122195899682&oid=118228966367965758611
It basically shows San Diego and Imperial counties, and parts of some surrounding area. I took a screenshot of Google Maps and imported it into GIMP. Then, I by hand drew some contour lines around places where I know stations are. I should note that they are NOT at ALL intended to be anything remote to accurate in my drawing, it's just a concept image. Then I filled in with shading. I was working in separate layers. For the contour lines, I set the layer opacity to 64%, and for the shading I set it to 16%. Once I was finished drawing it, I selected the portion of the image I wanted (my “working copy” included west to Santa Maria, almost north to Bakersfield, included Barstow, Prescott, Phoenix, missed Tuscon, included Yuma, missed Ensenada), used the “copy visible” and “paste as new image” functions to make the image you see at the link.
Here's a listing of the colors I used to represent what field strengths. You could do some variations of course, but it just happens to be the way I set it up.
90 dBµV/m – 31.62 mV/m - #ff00ff (255,0,255) (magenta)
84 dBµV/m – 15.85 mV/m - #ff007f (255,0,127)
78 dBµV/m – 7.94 mV/m - #ff0000 (255,0,0) (red)
72 dBµV/m – 3.98 mV/m - #ff7f00 (255,127,0) (orange)
66 dBµV/m – 2.0 mV/m - #ffff00 (255,255,0) (yellow)
60 dBµV/m – 1.0 mV/m - #7fff00 (127,255,0)
54 dBµV/m – 0.501 mV/m - #00ff00 (0,255,0) (green)
48 dBµV/m – 0.251 mV/m - #00ff7f (0,255,127)
42 dBµV/m – 0.126 mV/m - #00ffff (0,255,255) (cyan)
36 dBµV/m – 0.063 mV/m - #007fff (0,127,255)
30 dBµV/m – 0.032 mV/m - #0000ff (0,0,255) (blue)
In the shaded area, the field strength is up to that strength. For example, at a spot where the maximum field strength anywhere on the dial is 2.7 mV/m, the shading would correspond to the 3.98 mV/m color. Inside the 90 dBµV/m contour, I just shaded it kind-of like a gray color.
Also, I might have liked a wider range (like 1 µV/m to 1 V/m) and finer resolution shading (like every 3 dB or even 1 dB the color changes), but since I was doing this by hand and not with the aid of a specialized program, I just made it relatively simple.
Is it possible for your mapping program to generate something similar to that, but accurate? Mine does take into account some Mexican stations (for example the high-field around Tecate represents a wild guess of 1390 XEKT), but misses some Vegas stations and others just cause I wasn't trying for super accuracy, just a concept.
73, Stephen
Stephen,
I've experienced some weird phasing situations myself. In Rochester, NY, I am within 1.2 miles of two 5 KW stations and one 1 KW station. There are spots where the signal on one or another will drop out to almost zero while driving.
I now understand your strongest signal map and color coding ideas, thanks for explaining it and for the sample graphic. I'm currently creating multiple plots and using different colors for the plot edge line itself, and using a single grey-like color for the fill in. I've been back and forth in fooling with this color thing before. It's difficult to present options for using different colors past a few plot levels. It gets overly complicated. I'll give it some more thought to see if there is a different way I can do it. Your color selections are varied and a good choice. Thanks.
Shading in minute dB variations really isn't practical at this point. It requires too many computations. A select few would be better from the computation standpoint, say up to 3-5 or 6 different values, and I can already do that.
73s,
Bill
Bill,
I've experienced something like that I guess, in the major lobe of a broadcast station right by their transmitter site!! :o For example, in these two videos, as I'm approaching the longwire antenna that I use to give a boost (for overload/selectivity testing :p) ...
https://www.youtube.com/watch?v=fEMLcEqCu3E
https://www.youtube.com/watch?v=kEIU3mP5f38
... well, first I start with the radio nulling the station, then I turn toward it and it overloads. I then walk toward where my makeshift antenna setup is (I have the SAT tuned to the station's frequency on the ground by the utility groundwire), and there's a bit of a fade (and that type of distortion), then it quickly comes back up and REALLY overloads, briefly blanking out the audio. When I get within an inch or two of my antenna setup, it takes the overload to yet another level. (I suppose there isn't a way to calculate what field strength would be required to produce that level of signal with just the internal ferrite loopstick, is there, or using a receive antenna whose total length if you stretched the wire out was under 0.05 µm ...)
Ahh, that'd be interesting to see your multiple plot ideas. Any chance you might be able to at least post a sample soon? :)
Re: picking colors, I noticed the color picker in GIMP, at least the ribbon on the right side, seems to be like a rainbow that fades smoothly from red to orange to yellow to green to cyan to blue to magenta and back to red. (Then on the left you can go with less brightness or saturation if desired.) With maximum saturation/brightness, the color values start at 255,0,0 for red, then the green comes up (to 255,255,0), then the red fades down (to 0,255,0), then blue fades up (to 0,255,255), then green fades down (to 0,0,255), then red fades up (255,0,255), then finally blue fades down and it's back to the starting red value. I was generally using red or somewhat purple for the strong signals (because they'd be most likely to prevent DX) and the blue for the weakest signals, leaving a gap between blue and purple so as not to have a strong signal color be too similar to a weak signal color. (I suppose instead of going purple after red, you could alter the saturation/brightness and go for a darker red for the ultra strong signals if you were shading it that fine.)
So, maybe you just want to do 6 values for now. If so, what do you think of something like this?
80 dBµV/m = 10 mV/m = magenta (#ff00ff ; 255,0,255)
70 dBµV/m = 3.162 mV/m = red (#ff0000 ; 255,0,0)
60 dBV/m = 1 mV/m = yellow (#ffff00 ; 255,255,0)
50 dBµV/m = 316.2 µV/m = green (#00ff00 ; 0,255,0)
40 dBµV/m = 100 µV/m = cyan (#00ffff ; 0,255,255)
30 dBµV/m = 31.62 µV/m = blue (#0000ff ; 0,0,255)
If you wanted maybe you could shift to go up to 90 dBµV/m (31.62 mV/m) or down to 20 dBµV/m (10 µV/m). I'm thinking those would be the values for the strongest signal map that I was talking about.
For individual actual station plots (like what you've been doing already, just adding more plot levels), I was thinking the same concept, but somewhat bigger steps between them, and possibly a bit varied in evenness, too. For example the strongest one might be maybe 5 V/m, then 250 mV/m, then 10 mV/m, then 2.5 mV/m, then 100 µV/m, then 2.5 µV/m or something like that, although having more than 6 steps would be nice to be able to get a little finer variation while having a wide range that goes from overloading your radio in a city to barely detecting a carrier in the desert with a longwire. For night, maybe a similar concept, but with the strongest two being groundwave local (maybe the 2nd one being about the practical limit for non-DX'ing listening to class C stations at night), the 3rd being the previously referenced 6% 10mV/m contour, and the weakest being the one that shows the exotic trans-oceanic reception. :)
(Sometimes I wish it was possible for me to experiment myself with some of the plots, considering the things I'd like to try with it. :) )
Stephen
How accurate are the skywave maps - average?
Hi Devyn,
The pattern maps are created using the identical formulas that the FCC uses in their regulatory code: CFR 47, Part 73.190, so they are as accurate as that. They were last evaluated in about 1991. The ITU has their own set of formulas dating back to the 1990s. The thing about the FCC's formulas is that they are tailored for Region 2, which is the western hemisphere, North American continent. We are a special case as we are the closest to the geomagnetic pole which causes a lot of problems in accuracy.
In general, calculating skywave accuracy is a crapshoot at best. Not all of the scientific community even agrees on the formulas available. Wang seems to have the latest and most accurate, at least claimed. I may try to implement this option as a secondary choice.
Bill
Hi - just a simple thank you for making this available! I appreciate all of the work you have put into this - I love being able to use these maps as a fun tool in my DXing! Thanks!
Hi Mark,
Thanks so much for your kind comments. Glad you like the maps. New and more accurate versions should be out this fall.
Bill
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