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I have a question about what kind of a reliable cheap wire I can use for a backyard long-wire RECEPTION ONLY antenna that is inconspicuous enough that neighbours and my wife don't complain too much about it. I have about 12m or almost 40 ft to work with if I go diagonal, or two 30 ft sections if I make a 90-degree dipole, and would be clipped on to my Tecsun SW radio or plugged into the ext. antenna input (or into my laptop's SDR dongle).
One end of the wire would be going to my upstairs 2nd floor bedroom window and in to my radio, and the other end would be at the diagonal part of my backyard (opposite corner fence post) perhaps 5-6 ft off the ground, and likely pass through the branches of a tree along the way which is in that corner. Distance from bedroom window to fence is roughly 40 ft at ground horizontally, but with the diagonal rise it may add another few feet.
The wire should be thin enough that I can slip it through my window which I would then shut on it, and not too obvious to see, yet strong enough that it won't easily break. In the past I've used telephone wire strands (solid copper insulated) but I feel they are not flexible enough and would tend to snap if I tensioned them, and I can't always see the break because the insulation keeps it together on the outside even though inside conductor may have separated. I've also used braided insulated wire, not sure what gauge but I'm sure it was pretty cheap 30 AWG spools available of 50 ft. I don't need the wire to be tensioned, I expect it to sag anyways a bit.
Do you recommend insulated vs. non-insulated? What gauge would you recommend? I've seen copper, there is also just bare steel wire spools that I've seen (solid, not braided) but I believe they are shorter sections so I'd have to connect several together (how would that affect the antenna reception).
The other question is do I make an "L" like a dipole and send out two wires at right-angles... If I do, I can get about 30 ft on each wire, with 90-degree between them. How do I then connect it up at my radio? Do I just tap the middle of the wire and clip to my external radio antenna, or do I cut it and feed it into the ext antenna jack (which has 2 terminals). Any ideas, suggestions would be helpful. I'll see if I can upload a satellite photo at some point so you can see.
Any advice would be appreciated to get my hobby back up to some level since the house move without upsetting off my family too much.
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Get a decent diameter polyester hollow braid and thread insulated extra-flexible wire + Dyneema kite line (for tensile strength) through it using a very long fid, then 'milk' the braid down onto the core and call it a clothesline!
Insulated multistrand CCS wire could also work if it passes the S.O's clothesline 'sniff' test.
Put the block and tackle to let it down / tension it at the far end so your lead-in can be fixed.
There are commercially available 'shut in the window' feedtroughs used for satellite systems, but you might do better to use a fairly short length of copper foil sandwiched between two wider pieces of Kapton tape, joined to the end of your exterior lead-in. -
Thanks for the suggestions. I've attached some potential options (single and dipole) that may be feasible but if you have any other ideas, please let me know. These are running "in the air" but I could run it along the house and fence to make it look less obvious, which I assume will degrade performance with all the bends and such.
I've included a 3D and top-down view with relevant measurements and angles.
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"Honey, let's plant a tree."
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If you make a square loop you will get a loger antenna.
Make some fiberglass poles like the thin ones used flr electic fences.
Put the poles on top of your fence and also on top of your house on the side facing you back yard.
Put a thin stainless wire on top of the poles and feed the center down to your window.
Call it a bird repellant to prevent the birds flying over your back deck and dropping
For feed-line you can use two parallel RG59 taped together so that they have the exact same length. The screens on the coaxses have to be connected together a at the ends. The two coaxes are connected to the opposite ends of the loop.
The feed-line will work as a 150 ohm ladder line.
I have this kind of setup at my cabin. The antenna is very god at RX and TX. On RX its very quiet with low noise levels. -
I've "mocked up" a square loop design (see attached picture). It's about 9m x 12m (30x40ft) giving the perimeter length about 140 ft. As you can see in the picture, I have to run it along the fence and jump it to the house, will need to go up a bit to clear the windows and around the bend in the middle of the house wall... so it's not exactly square and will have some 90-degree bends in it. Hopefully this will not affect performance too much. I've drawn the 2 coax coming out the window vertically to meet the loop ends.
Easiest thing would be to pin it along the edge or top of the fence without any "stand-offs", just with some plastic cable staples hammered into the wood. Nobody will see it. It may be visible when it jumps off the fence and runs along the side of the house horizontally and up to our bedroom window but the family might think it's just electrical or satellite cable or security camera wires.
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in most case long wire is a bad choice, especially if you want reception only antenna. I think in your case the better choice is use a small active antenna with RF-choke on the coax cable to cut-off noise from your house. Such antenna can be built as a small vibrator (dipole or just a small piece of wire) with a low noise amplifier.
Also you can use magnetic loop or ferrite rod antenna, but their con is that they have very narrow bandwidth and needs to tune for specific frequency. If you want to listen another frequency you're needs to tune it again.
In any case, you're needs to use RF choke on the coax cable between antenna and your home, it needs to cut off noise from your house, otherwise you will get a lot of noise received by your coax cable from your home equipment (such as computer and other home electronics). And keep your antenna as far as you can from any buildings and mains line. Especially from those buildings which have home electronics inside.
Note that large antenna needs a large distance to the noise sources. But smaller antenna has weak signal and requires amplifier. Amplifier should be placed on antenna side.
Since you don't have a lot of space, it's better to use a small antenna with active amplifier. The best location for your picture is the center of your field. At least 4 meters from any wall. Just put a short piece of wire and low noise amplifer at that point. The height should be as high as you can, to keep it as far as possible from the ground. In your case 4 meters height will be good enough.
Since your space is limited with max 4 meters to noise source, you can expect about 4*2*pi=25 meters = 11.9 MHz with no noise from buildings. It still can works at lower frequency, but they will be affected for a little by noise sources in the buildings around antenna.
You can start to experiment with mini-whip like this:
https://www.aliexpress.com/item/1005003172328123.html
or this:
https://www.aliexpress.com/item/1005001424710676.html
I didn't tried exactly this circuit, but at a glance it should works ok. You can experiment by adding a small wire to that mini-whip, about 0.5-1 meter length. Don't forgot to put ferrite RF choke on the coax cable, one near antenna and one near enter into building. -
here's another idea for you
https://swling.com/blog/2020/12/how-to-build-a-simple-linear-loaded-dipole-for-low-noise-shortwave-radio-listening/
I tested it and it works well, place the feedpoint, suspended with a rope, at 1m or more from the house and lay the two arms in a V shape to the end supports, keep the arms ends at 1m or more from the supports, the antenna will be fed from coax from the feedpoint to the inside and connected to the receiver using an adapter plug, the antenna may be suspended using pulleys (for the ropes) so that it will be easily lowered in case of need, also, choosing a relatively thin 3-wire conductor with a neutral color will reduce the visual impact
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If you are making the first proposed balanced, L shaped antenna, or a dipole of any kind, ideally you should feed it with a "bal"un, a balanced to unbalanced RF transformer.
If you are building a one-wire antenna that works against the ground beneath it, use a un-un. For SWL reception you can use the one you have which I think is made out of a minicircuits part. Which are good. They do the job they are supposed to. Just dont use it for transmitting, even QRP. . For QRP, you can make a unun that proabaly would handle up to 5 watts out of a single toroid ring core like a FT-50-43 For any more than 5 watts, use a larger toroid core.
If you want to use @AW's dipole, I suspect you would have good luck with one like the elecraft BN2, which can be designed to be switchable to allow 1:1 or 4:1 winding ratio. You can make one yourself from two binocular cores, and by all reports its very good. Its very efficient and broadband, it works well from 1.5 to 54 MHz. If the radio you are using has a built in antenna tuner the balun may help you match to it. It is connected via BNC jacks. Lots of portable-oriented ham radios now use BNCS for quick, portable operation, that is strong and convenient. But you might also want to use SMAs with very low power transmitters of any kind of receive setup. Use good quality, thin, insulated copper wire. multiple turns may get cramped, then use thinner wire. I often use the copper wire from cat5 cable for baluns. At least you know the insulation has low loss. For receive it can be thin wire. Or use enameled copper wire, any size that fits well in there..
The rectangular binocular cores work very well. They aren't at all expensive either. Kitsandparts.com is a very good source for these magnetic cores. They are affordable and fast to ship. The first one that I built used two of these It works great. More recently I built one using two of these. It works quite well - for receiving with a dipole- this design is really good for any dipole, but I am debating with myself whether I should use a heavier duty DPDT slide switch. The tiny DPDT switch that I have is supposed to be rated at 10 amps but I just dont see it actually handling that much. Its ebay junk, basically. It would melt. or short out, I am fairly sure. My first clue that it wouldnt be suitable was when I discovered tht these micro toggle switches had muchy higher resistance than the ones I bought at least 35 or 4 years ago when I was first getting into electronics. I know they are quality switches but I would prefer to use a new one. I don't want my switchable balun to suffer a failure thats preventable. Better to get a beefier switch to start out with.
If I was going to build a 9:1 unun to use for a ham station (i.e. transmitting someday) I would use a big ferrite toroid and (teflon insulated?) well tinned copper wire that would be able to handle some power. Probably a
http://toroids.info/FT240-43.php would likely handle up to several hundred watts. (Not the full legal limit, it might get too hot) It would be smart to doube check the temperature with a non content thermometer. If you are planning to transmit as much as a kilowatt into it I would use those FT240 size big toroids, but stacked, in other words, use two of them next to one another treated as one. There is quite a debate online over what materials to use, for different kinds of antennas. (unresonant or resonant) Some suggest using #53 material.. some using #33 (I think) I dont know enough about their performance to make that call! All I know is that #43 is what I see suggested the most. Speaking of the number 43...
A 43 foot vertical wire made out of very strong thin woven insulated grey wire. with a 9:1 unun with a counterpoise and ground will work well as a low visibility general purpose antenna for HF down to several MHz but I would experiment with different lengths and configurations too since you are not transmitting on ham bands - the reason that length was picked. So feel free to use different lengths, and different configurations. Use a un un to connect any monopole, and a balun for any two legged balanced antenna. You can use many kinds of toroid cores thats suitable for RF use. You might even be successful with an iron core magnetic. youhave of suitable ferite material (better for broadband transformers) I have used the most common #43 often for these. Thats the material used in noise suppressing beads which can substitute for an HF toroid core well. Many of us already have some lying around.
Or use any length wire, 43 feet does not resonate on any ham band so that may not be the best length for swls who probably care more for lower frequency reception if tiy have the space, do your best to string an antenna that best uses it.
A unun attempts to match a single wire to an unbalanced feedline like a coax cable. It will smooth our the reception and may improve your reception markedly, reducing noise substantially, anyway that is what its intended to do. If you have a two wire (dipole or loop) antenna use a balun to connect it to your feed line. Like the elecraft schematic. I have had really good luck with that balun design and its easy to make.
To make the unun use three wires and a #43 spit bead as your toroid core, make 12 loops through the split bead Twist the three wires together, use the thinnest strong wire you can find. Or use two split beads and nine loops around. If you like lower frequencies more use twelve or more. The cost of this unun should be a dollar or less. Connect it to your receiver using any suitable coax cable. For HF, RG-174 is fine. Try to use the best ground you can find, or as a counterpoise a wire laid on the ground as long a wire as you can manage. If you use an RF choke around the feed coax put it close to your receiver rather than near the feedpoint. Because the coax cable is the ground side of your antenna.
To make the balun out of split beads instead of binocular cores use four identical split beads (out of the same batch if possible, and use two beads as you would a binocular core. You can use a single or two binocular cores for the switchable balun. The "original" Elecraft BN-1 was made with just a single binocular core, I think.
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Im using a loop antenna that i got last week and works great getting better listening than my 2 discone antennas up 30feet.https://www.banggood.com/GA-450-GA450-Loop-Antenna-SDR-Short-Medium-Wave-Radio-Antenna-SW-2_30-30MHz-MW-522-1710KHz-p-1893431.html?cur_warehouse=CN&rmmds=search
Discone,s are mainly for my uniden scanners.the GA450 LOOP is good for 80m up to 27mhz CB band,not real good for MW band.Not bad for a loop thats only 20 cm
I have the loop in a old tripod with a wooden Rake pole about 8 feet tall about 15ft out from my Shack window.Its not water proof so if rain does eventally come i will
put it in the shed.About 1 week i am getting a bigger loop thats water proof, MLA-30+ from Tecsun radios.Still amazed how a 7.8 inch loop works so good. -
Im using a loop antenna that i got last week and works great getting better listening than my 2 discone antennas up 30feet.https://www.banggood.com/GA-450-GA450-Loop-Antenna-SDR-Short-Medium-Wave-Radio-Antenna-SW-2_30-30MHz-MW-522-1710KHz-p-1893431.html?cur_warehouse=CN&rmmds=search
Discone,s are mainly for my uniden scanners.the GA450 LOOP is good for 80m up to 27mhz CB band,not real good for MW band.Not bad for a loop thats only 20 cm
I have the loop in a old tripod with a wooden Rake pole about 8 feet tall about 15ft out from my Shack window.Its not water proof so if rain does eventally come i will
put it in the shed.About 1 week i am getting a bigger loop thats water proof, MLA-30+ from Tecsun radios.Still amazed how a 7.8 inch loop works so good.
If you want to go for a loop antenna, then consider this one
http://www.kk5jy.net/rx-loop/
it can be easily built for pennies and will serve you well, if you don't want to build your BalUn (as described at the above page), you may buy a ready made one
https://www.nooelec.com/store/balun-one-nine-v2-barebones.html
and just add a small waterproof box to enclose it, then, willing to add a preamplifier to turn the antenna into an active loop, you may just add this one
https://www.nooelec.com/store/lana-hf-barebones.html
the combo will work MUCH better than any "chinese" antenna, including the poorly designed MLA-30+ which suffers by a number of issues, if you're curious about them, see here
https://www.g8jnj.net/activeantennas.htm#MLA30
so, my suggestion is to skip those "chinese" stuff and, not willing to sheet out too much money, go for the very simple, cheap and effective loop suggested above
HTH
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@AW
Thank you! Years ago I made a mag loop using a single flat tape-shaped loop made with foil on a piece of plastic from a shade for a sliding door, It worked really well. I want to try it again, this site gives me an incentive to do so. I still have some of this broad plastic, however unfortunately I only have shorter pieces of it now.
However I can probably use several of them, glued or taped together.
I also want to try Martin's twisted figure 8 (90 degree offset) loop. Cool. I also want to try to make a dedicated preamp for HF loop experimentation. Asssted wit NANAVNA to determine the best components to use for the front end.
If you plan to be spending a lot of time fooling around with antenna designs, a very wide range receiver is very useful because with any given antenna it gives you an almost instant, visual indication of where it performs the best.
A hackRF One could likely do this for you well. Although I dont know how well the Chinese ones work in the low HF range, Or maybe a Rx-888 mkii or just an rx-888 would be better.
Even if the frontend is fairly deaf atlow frequencies, an HF up converter could likely help quite a bit.
Its hard to argue with a receiver that pulls in 1-6000 MHz. If the HF doesnt work well, hook it up to a upconverter which will shift the entire HF range up to 100+ MHz. Its the ability to visualize 20 MHz at a time that makes it useful.
I find it hard to believe that a really small loop will pull in low frequencies well, but who knows, I could easily be wrong. I have had very good luck recently with an approximately 1 meter across active tuned loop made with Monster Cable and PVC tubing and a MiniCircuits MMIC LNA with 4 BVAM109 varactors replacing the capacitor. Fed very simply with a voltage divider and an RF choke. The varactoirs draw almost no backwards current, being diodes..
Some generic switching diodes might also work. LEDS too tend to have a wide capacitance range when not conducting. (hooked up backwards) Electrical tuning saves a lot of hardship with mechanical tuning, as well as the cost of variable capacitors is much much higher than the cost of variable resistors..
(even fancy ones with reduction gears) The Q can be very high, allowing one to have a very narrow bandwidth and preselection. A magnetic loop with very high Q is ideal for shortwave listening. Thats my favorite way to listen.
It would even be possible to make a controller that would remember the (varactor back-bias voltage bias settings for different frequency ranges and follow your tuning of a radio.)
That eliminates the main drawback people give against "magnetic" (tuned) loops. IMHOP magnetic loops rule.. I love their narrowbanded nature.. Especially in winter, long winter nights.. there is nothing like the super quiet magnetic loop for hearing signals from the other side of the world in amazing quiet. At least for me, where I live.
I found myself hearing fishermen on boats in the Indian Ocean speaking local languages on SSB marine band..
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For discreet long-wire, there are a couple of places that sell a copper+kevlar wire
https://www.ebay.co.uk/itm/255255426762?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=255255426762&targetid=1279609265486&device=c&mktype=pla&googleloc=9044937&poi=&campaignid=9445986145&mkgroupid=123611895558&rlsatarget=pla-1279609265486&abcId=578896&merchantid=6995734&gclid=CjwKCAiA3L6PBhBvEiwAINlJ9Nt0L7qkiF8lzU6rNZPVlkSiooICXoYtz2wYdIlqI5sCpEAgKKjWCRoC4nUQAvD_BwE
https://www.hfkits.com/product/koper-kevlar-antenna-wire/