tag:blogger.com,1999:blog-4260200412608523752.post6462139869385734741..comments2024-03-26T05:51:25.820-04:00Comments on RADIO-TIMETRAVELLER: Notes On Mediumwave Loops And Wire AntennasRADIO-TIMETRAVELLERhttp://www.blogger.com/profile/05463280488316885706noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-4260200412608523752.post-26685989884281297992020-04-20T11:13:42.945-04:002020-04-20T11:13:42.945-04:00Hi Steve,
For receive purposes, using 75 ohm coax...Hi Steve,<br /><br />For receive purposes, using 75 ohm coax instead of 50 ohm won't matter much. I've used 75 ohm TV cable for years for receiving on the HF bands - 30 MHz and below. Transmitting or VHF/UHF work would be a different story. The 75 ohm to 50 ohm mis-match is a 1.5:1 mis-match, which coincidentally is also a 1.5:1 SWR (Standing Wave Ratio) in the ham radio transmitting world. That's usually about at the edge of acceptability for transmitting in the HF range.<br /><br />The impedance transformation of 450 to 50 ohms is a 9:1 ratio of course. It is based on the windings ratio and is equivalent to the square of the windings ratio. If the input side (the 450 ohm side) has 3 times the number of turns than the output side (the 50 ohm side), then the turns (windings) ratio is 3. 3 squared = 9, so the impedance transformation is 9:1.<br /><br />For 75 ohms, you'd need an impedance transformation ratio of 6:1 (450/75). The square root of 6 is approximately 2.5, so you'd need a turns ratio of 2.5 from input to output. 10 turns to 4 turns would do it.<br /><br />Understand that the 450 ohm figure for the longwire may vary greatly above or below this figure depending on the frequency you are receiving. In other words, the impedance presented at the end of the wire is frequency dependent. The original concept of a longwire was a wire of several wavelengths. Casually, someone throws an odd length of wire out a window and calls it a longwire. If your end-fed "longwire" is anywhere near one-quarter wavelength of the frequency being received, you probably are looking at an impedance of 20-75 ohms, not 450 ohms. An end-fed halfwave length of wire might present itself around 1000-2000 ohms. The point I'm trying to make here is that the 9:1 balun is there just to get you in the ballpark, matching-wise.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-38754178212680016412020-04-19T17:19:24.426-04:002020-04-19T17:19:24.426-04:00EXCELLENT explanation. I'm 58 and still was n...EXCELLENT explanation. I'm 58 and still was not aware of what it meant to match the impedance and why that's important. Tremendous amount of signal loss if you don't in some cases. So I will buy a 9:1 magnetic "unun" to attach the long wire to.<br /><br />Does it make any difference if the coax is 75 ohms rather than 50 ohms and if I wanted to match to exactly 75 ohms, what should I do?<br /><br />The other question is at the radio end. If the radio's input is 50 ohms and the coax is 75 ohms (RG-6), anything to be concerned about?Steve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-31808119661169429932020-04-19T15:11:28.821-04:002020-04-19T15:11:28.821-04:00Hi Steve,
A balun is merely an impedance transfor...Hi Steve,<br /><br />A balun is merely an impedance transformer, transforming one impedance to another. Impedance is the net vectorally-combined resistance and reactance of an AC or RF circuit at a certain frequency.<br /><br />Maximum signal is transferred (and I might add with minimum distortion) if the impedance is matched between input and output of a circuit. Not sure how old you are but in the old days of Hi Fi the audio enthusiast always made sure his speakers were matched to the stereo's speaker output. If the stereo had an 8 ohm speaker connection, you made sure you used 8 ohm speakers, not 16 or 32 ohm speakers. Maximum signal would be transferred to an 8 ohm speaker, and also as important, minimum distortion would result.<br /><br />The same is with radio and antennas. Typical longwire antennas might have an inherent impedance in the neighborhood of 450 ohms, or more. Old radios which had a single antenna post for a longwire usually made sure that the input was designed around 450 ohms. The coax inputs or mini-jack inputs of most receivers are usually designed around an input impedance of about 50 ohms. If we connect a longwire to one of these inputs we are creating a series circuit of 450+50 or 500 ohms at the input with our "tap" at the 50 ohm point above ground. Ohm's law tells us that we are only getting 50/500 or one-tenth the signal available from the longwire. This is remedied by the impedance matching transformer or by the antenna tuner. Properly matched, we get the full signal off the longwire.<br /><br />In the ham radio world, good matching is even more important when transmitting to an antenna. A poor match results in the antenna reflecting some or most of the power right back at the transmitter. These reflections also exist on receiving antennas when mis-matched.<br /><br />Some radios seem to be a little more tolerant of antenna mismatch, some not. I have the SDRPlay RSP1a SDR receiver here and I find it not tolerant at all of antenna mis-match. Many radios, however, will respond favorably by hooking up any sort of wire to them.<br /><br />Hope that explains it a little better.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-87207985654611973212020-04-19T14:20:01.036-04:002020-04-19T14:20:01.036-04:00Hi Steve,
The Pi type tuners work quite well for ...Hi Steve,<br /><br />The Pi type tuners work quite well for longwires. I used to have a homemade one which I used for years on the ham bands for both transmit and receive. That style can match about anything.<br /><br />MFJ's page for their tuners is here:<br /><br />https://mfjenterprises.com/collections/all/mfj_tuner<br /><br />Though essentially they are mostly for ham use, they will work for receiving as well of course.<br /><br />Yes, an ATU will have the additional advantage of giving you some bandpass or signal peaking as well as matching, so they could be used in conjunction with a 9:1 balun.<br /><br />Grove Electronics (they also published the magazine Monitoring Times years ago) used to sell quite a few receive tuners. I have the TUN-4 which is quite nice and will tune from below the AM band to 30 MHz. You can often find these and the others on eBay. Here is the old Grove catalog:<br /><br />https://www.americanradiohistory.com/Archive-Monitoring-TImes/Grove-Catalog/Grove-1989-02.pdf<br /><br />I usually grounded my 9:1 balun at the one end. I'm not so sure it made a huge difference overall, but for static discharge sake I did it.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-84430166017303247732020-04-18T19:43:44.627-04:002020-04-18T19:43:44.627-04:00I googled "9:1 magnetic balun" and see t...I googled "9:1 magnetic balun" and see that these can be purchased, actually.<br /><br />So now I'm getting more interested being there are pre-made solutions.<br /><br />I understand from the blog these should ideally be mounted close to the ground with a short wire going to the ground rod.<br /><br />If I do use an ATU with that, I suppose that can't do anything but help.<br /><br />What I don't understand though is how the balun works. I understand it helps match the impedance between the long wire and the coax coming into the back of the ATU. What I need to understand better is the value of matching impedence. Just trying to get a condensed idea of this. What is the result of good matching vs. bad matching?Steve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-52328143758104750822020-04-18T19:18:01.910-04:002020-04-18T19:18:01.910-04:00Thank you for the link. My listening interests are...Thank you for the link. My listening interests are MW to SW. So, the low end of AM to the high end of HF is what I would like to set up for. I have listened recently to SW stations I was able to pickup that are in the 5-6 MHz range.<br /><br />I was looking at some Palstar tuners that have the Pi configuration with two continuous, fine-tuned variable caps and one continuous, fine-tuned variable inductor.<br /><br />I'd like to buy a nice one that would work well with a longwire.<br /><br />I'm not too confident in assembling very much on my own but prefer to buy something that works very well.Steve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-3218132091031470142020-04-18T11:49:25.685-04:002020-04-18T11:49:25.685-04:00Steve,
Inductive coupling to a radio's ferrit...Steve,<br /><br />Inductive coupling to a radio's ferrite loop can easily be done.<br /><br />Find an old piece of ferrite bar or rod and close-wind 15-20 turns of insulated wire on it. Ground one end to the earth and connect the other end to the longwire. Then couple the ferrite bar/rod to your radio's ferrite antenna. You can even run it through a length of coaxial cable, though better results will be obtained by using the 9:1 balun where the longwire connects to the end of the coax (outside).<br /><br />My 25 ft. vertical is set up that way. Picture the vertical as a simple end fed longwire (fed at the bottom and insulated from the ground). It is attached there to the 9:1 balun and through the balun to the coaxial cable. The 50 ft. coax cable runs to the inside of the house where the center and shield of the coax is connected to the 15-20 turn winding around that spare piece of ferrite bar/rod.<br /><br />Sensitivity can then be adjusted by the closeness of the coupling to the radio.<br /><br />Be aware, most of these radios are easily overloaded by excessive signal. It shouldn't take much of a longwire to do that.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-67159727606513358092020-04-18T11:35:33.396-04:002020-04-18T11:35:33.396-04:00Hi Steve,
Not sure of your listening interests, w...Hi Steve,<br /><br />Not sure of your listening interests, whether they are shortwave or AM broadcast or? I see the CCRadio SW has an external AM/SW antenna connector. I'd try a direct connection to a longwire first. It may be all you need. Experiment.<br /><br />Good or even better results can sometimes be had with other matching devices like an antenna tuner which will also do the matching something like a balun would. MFJ https://mfjenterprises.com/ has quite a few which can be used for simply tuning odd lengths of wire. Google will produce many results for antenna tuners. They can be made pretty simply with a variable capacitor and some hand wound coils.<br /><br />Try not to overthink this but experiment and see what gives good results.<br /><br />For AM broadcast DXing I prefer inductive coupling right into the radio's own ferrite antenna. Matching is pretty well taken care of then and good signal transfer is also accomplished, and often without the overloading that occurs when directly connected by some form or another.<br /><br />An example of a 9:1 impedance transformation balun can be found at <br />https://m0ukd.com/homebrew/baluns-and-ununs/91-magnetic-longwire-balun-unun/<br /><br />Rather than a balun, this is really what they call an "un-un" as it transforms between unbalanced input (the longwire) to unbalanced output (the coax input of the radio). This circuit is actually the same circuit as the RF Systems magnetic balun I have. It takes a high impedance (the longwire) and transforms it by a 9:1 ratio down to a lower impedance (usually the radio's input connector). Note that radios with external longwire posts like your CCRadio SW may already be set up for high impedance input. It depends on the input circuitry used in the radio.<br /><br />Be careful directly connecting wire to any of these radios. Modern chip electronics is not so forgiving as the old tube stuff from my generation. I have fried several radios with static discharge.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-14649424792255448672020-04-18T00:25:20.915-04:002020-04-18T00:25:20.915-04:00Currently I have a CCRadio-SW but I plan on buying...Currently I have a CCRadio-SW but I plan on buying several new radios including the Eton Elite Satellit when it comes out in July.Steve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-72462577957588117402020-04-17T09:50:52.902-04:002020-04-17T09:50:52.902-04:00Hi Steve,
Which receiver or receivers are you wan...Hi Steve,<br /><br />Which receiver or receivers are you wanting to connect a longwire to? The whole balun thing might be irrelevant depending.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-19679069693597275342020-04-16T21:04:56.053-04:002020-04-16T21:04:56.053-04:00Hello Bill,
I appreciate all the detail you provi...Hello Bill,<br /><br />I appreciate all the detail you provided and my focus has changed because of it.<br /><br />One subject I don't know anything about is baluns.<br /><br />I don't know of a quick guide to tell me what is best to use.<br /><br />Is there some measurement to look for that works better with certain frequencies?<br /><br />Thanks again!<br /><br />SteveSteve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-32415566096370638262020-04-16T09:47:36.935-04:002020-04-16T09:47:36.935-04:00Hi Steve,
For the details and properties of Litz ...Hi Steve,<br /><br />For the details and properties of Litz wire you might look up Gary DeBock on the Ultralight DXing group on groups.io and read the posts on that subject. He has developed the Ferrite Sleeve Antenna or FSL and has quite a bit more knowledge than me of Litz and it's properties with ferrite. Basically the idea of Litz wire is to reduce the skin effect of current running on the outside of a single wire diameter. By using many strands, each strand carries current throughout the totality of the wire. Personally I have a simpler mindset about antenna building and use whatever is available. I'm an old time ham from the early 1960s.<br /><br />On the longwire, use the largest diameter copper wire possible (the smallest gauge in #). Insulated or not, it doesn't matter as long as you keep uninsulated wire away from conducting objects. #24 telephone wire will work but is a little slim for a longwire. Anything from 12 gauge to 20 gauge would be OK. Best results will be had by running the antenna through some sort of matching device or tuner to the radio. People's disappointment in antenna performance often stems not from the antenna but from the mis-match to the receiver. In the winters in Arizona I run a 25 ft. vertical on the AM broadcast band, matched with an RF Systems magnetic balun, and it blows the socks off anything else I have.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-9205024623541634462020-04-15T20:41:23.822-04:002020-04-15T20:41:23.822-04:00Given they are insulated, do the individual strand...Given they are insulated, do the individual strands of the Litz wire act almost like individual antennas?<br /><br />Does the dB combine at the end where it's soldered together?<br /><br />If it works that way I would happily spend the money as opposed to un-insulated strands where the signal stays mostly on the outer edges of the wires.<br /><br />I'm not on a budget, so let's say if you wanted to build the best performing long wire, what kind of wire would you use?Steve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-78027001400048165282020-04-15T10:06:52.705-04:002020-04-15T10:06:52.705-04:00Hi Steve,
Yes, for ferrite windings Paul suggests...Hi Steve,<br /><br />Yes, for ferrite windings Paul suggests Litz of 46 gauge strands (multi strands). Of course for a long wire, use any wire convenient, not Litz wire. Stranded or solid copper wire preferably. When winding box loops, I have good luck with 4 conductor telephone cable which is about 24 gauge. Strip 25 ft. of telephone cable and you get 4x 25 or 100 ft. of 24 gauge wire.<br /><br />BillRADIO-TIMETRAVELLERhttps://www.blogger.com/profile/05463280488316885706noreply@blogger.comtag:blogger.com,1999:blog-4260200412608523752.post-11595733895696316092020-04-14T21:26:04.035-04:002020-04-14T21:26:04.035-04:00This is incredibly interesting. So you're sayi...This is incredibly interesting. So you're saying Litz wire composed of 46 gauge strands, not just a single strand wire of that diameter, correct? So I was wanting to build a long wire antenna of at least 200' (actually going over 500' was my original plan so I could get a full wavelength near the top of the broadcast band). What actual wire would I use for that (how many 46 gauge strands)? I need a really good antenna that covers 1.7 to 30 MHz and plan to use a good antenna tuner.<br /><br />Steve Sybesma<br />Brighton, COSteve Sybesmahttps://www.blogger.com/profile/15559352738777040878noreply@blogger.com