Ham Radio - Experimenting with a loop on the ground receiving antenna
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- เผยแพร่เมื่อ 15 ก.ค. 2024
- I spent some time exploring this low noise receiving antenna concept and tried a variation on it by lifting it slightly off the ground.
Web link to source design:
www.kk5jy.net/LoG/
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Great video, Kevin. Thanks for putting this together. Just as a FYI, in the case of matching transformers, the impedance matching ratio is based on the SQUARE of the turns ratio. Since you have 2-turns on the primary and 6-turns on the secondary, your turns-ratio is indeed 1:3, but the impedance ratio is 1:9, or 1:(3^2). Again, thanks for the video. 73 Ken -- WBØOCV
👍 Thanks 😊
I enjoy the antenna videos. I figure about 40 more years working with HF and I might have a little clue on the magic of antennas. Thanks Kevin.
Great test Kevin. I appreciate all the hard and rigorous work you do to test out different stuff for the Ham community. 73s from Sweden.
Nice video! I also have a LOG with a home brew balun made with a BN73-202. Its size is 60 meters and laying flat on a wet clay soil. I'm very pleased with it here in a suburbia because of the fairly high QRM levels from different sources.
You can use SDR-console for good signal evaluation, as you will notice in the attached pic. You will notice the signal meter showing the SNR and at the bottom of the screen the signal history is showed with the white line following the actual signal strength and the yellow line showing the base noise level. SDR-console also has a built-in video recorder with sound, which I always find very useful. You can change the metering on S-points, dB and dBm, but the SNR will always be measured in dB.
I like the items you are covering on your TH-cam channel, including the Linux video's.
73' Ron - on2ron
Great vid. Thanks! I have been using LoG for over a year and I like it (4mX4m square about 10m away from my house. Connected with 75 ohm TV coax). This not "one antenna to rule them all" but rather an antenna you should have in your arsenal. Especially if you live in a city. It works great for 80m local traffic and local AM. You will be very surprised when you leave it for a night on FT8 (40, 20 and even 15m)
I love your ideas makeing antennas it's nice to see you Kevin too keep them coming please...
Your a mad man Kevin. You've long ago inspired me to experiment and tweak designs to see of they can be adapted to the applications I want. Experimentation is half the fun. Doing the experimentation and sharing with us here, even if its a no go is what I enjoy about your channel. Keep-em coming my friend. I look forward to the next video.
Long awaited video!!!
I use a home brewed small loop antenna for Ham radio. I live in a senior citizen facility and they will not allow outside antenna. It is a three story, four wing, concrete seel construction. I fight electronic noise. The loop helps me to keep me busy with ham radio. I live on the first floor. Concrete and steel above and below me. But I do communicate.
Often wondered about this exact comparison. Take away seems to be it helps a little with weak signals and substantially reduces local sources. Many thanks.
Great video Kevin! Very informative!
very interesting experiment . i have done similar testing with my Alex loop in the past with SW , RX
According to many experts the transformer is there to protect the radio from the high voltage and current that build up on the antenna and prevent the feedline from becoming part of the antenna.
If I am not mistaken, 2 turns at the primary, 6 turns at the secondary make a 3 × 3 impedance transformation ratio, or 9:1, which ratio is well known by random-wire users ;)
looks fun Kevin, I am pretty sure the isolation transformer is to keep the common mode from the shack off the feedline as that would cause a degradation in SNR, also might try to peak the signal with a tuner as that will drive surrounding signals/noise down and keep the desired signal up, bigger wire = bigger aperture. keep experimenting!
One of the Net Controllers on the OMISS nets runs on at his QTH in the Phoenix area. He says his noise floor is an S9 without the loop and he finds it almost to copy anyone without it. He says with the loop he is down to a S4 and hears everyone.
I suspect that much of the better noise performance you observed from that loop on the ground is because of that isolation transformer. If more people used those things, they'd isolate the antenna from the transmission line better. Some will insert TWO isolation transformers, with a 1:1 for the receiver to the coax and another isolation transformer for the loop. This also keeps common mode energy from coupling in via the transmission line.
Some loop designs I've heard of have smaller diameters than you used, and a good pre-amp with an appropriately decoupled linear power supply at the loop. Keep in mind that resonance isn't really what we're after here.
Again, I think the biggest help is when you get the antenna away from all the noise sources and ensure that they can't couple in to your receiver system. That is what improves the signal to noise ratio. I suspect that had you installed a PA0RDT Mini-Whip with appropriate decoupling, it would be as good.
73,
DE AB3A
Mini whip is great antenna but needs careful installation. I have found if you think of it as a RF probe it is easier to understand.
Before settling on a a final spot it is best to move it around to find a local position where wanted signals are maximised and unwanted noise minimised. Unlike a magloop which needs to be mounted no more than two metres off ground, Miniwhips need to be four to five metres above ground on a metal (conductive) pole. In both cases quadshield coax works best as feedline.
I use both a magloop and miniwhip separated by about 8 metres horizontally in a low noise HF diversity set up. It is great to be able to switch back and forth to get the best receive signal. Often the noise on this Rx setup is 20dB below that on the transmit antenna.
For AM listening however, I prefer a ferrite sleeve antenna and have had good results with that swling.com/blog/tag/ferrite-sleeve-loop/
I use separate vertical and horizontal antennas for transmit (and receive comparison).
It looks like the it's just even acrost the board, try Building a 15-foot by 15-foot square and run it horizontally 5 foot off the ground with a 7 degree slope to the horizon , and a little amp at the feed point, feed point in the middle of a 15 toor not the corner and a 4:1 ballon, and your noise should drop
Interesting, maybe try some shortwave broadcasters as well. The one's I've seen on the net also often use a preamp at the antenna as well. Really interesting experiment, must try one next time out in the country.
Always cool stuff to see and learn here. Thanks man!
I sure I had that kind of room!
73 de N2NLQ
Interesting experiment but I'm not sure it would be high on my personal antenna priority list. Hope the A/C is keeping that RV livable.
I find where the loop on ground is very helpful is in high noise environments. I have s9 plus noise on 40 and below but on the loop it’s way down and I can actually hear stuff. But if I compare it to my 20m delta loop I almost always find my delta loop better.
I have also used a long piece of terminated coax (sometimes called a snake antenna) on the ground. The key is to terminated it on the far end and to cut the shield on the near end, so it basically acts as a folded long-wire on the ground. It works OK as a broadband, stealthy receive antenna. Also interested trying your loop
I also had tried wspr on my "snake" and had similar results, it radiates but not well. It's OK for WSPR, you might get some CW or digital contacts. I would never suggest trying ssb using it.
Cousin to the Beverage antenna? I helped set up a Beverage for a 160m event. Worked well!
Thanks man. Glad you did this and not me.
Can I suggest making a Beverage antenna and experimenting with that?
Did you know *underground antennas* are a thing? Lots of material to find on those, on the web.
OK, Carriers on either side of AM Stations can be the digital AM. The same is true for FM. For FM the digital is -20 dB. I don't know about the AM specs. The conclusion of quieter antenna is the same as I have observed. I don't remember if you said it was insulated wire. Laying on the ground, it would need to be insulated.
Hi Kevin. I will be looking for a small loop antenna for my town house attic farm for use this upcoming winter. I have a lot of man made noise here in my area in a suburb of Chicago. Let’s see what I come up with.
Large amounts of wire above earth pick up a lot of static electricity. Isolation transformer prevents this getting into your Rx where it could damage the front end.
Given space available I think you would be better off with beverage antennas, long wires one to four metres above ground pointing in directions of interest
en.m.wikipedia.org/wiki/Beverage_antenna
These operate in travelling wave mode and can have very good performance.
I lives in urban city in Orange County CA. I have inverted L antenna, it seems lower I make it, quieter it get. unlike VHF antenna, where I need to put it up above roof lines of neighbours. if I put HF antenna below Roof line of neighbour it become quieter. I guess, I just have to receive signal from up above, not from side way. AG6JU
Thanks for another very informative video. I am wondering if your results may be related to having so much more wire than recommended by KK5JY and therefore more capture of noise. Did you try using the recommended 15 foot square?
73 de Arnie W8DU
Correct me if I'm wrong but I think the lotg is bidirectional so that would effect some of the stations you're receiving
dunno if you have done this or not but a comparison with a BOG (beverage on ground) and a beverage would be awesome!
Would it work as a receiving antenna in a two-antenna diversity setup?
Nice video Kevin. I have been pondering installing a small ground loop for my RSPdx SDR receiver, but one of my concerns is that I have an EFHW antenna about 35 feet above it in the trees. When I look at the free space path loss at 3.5MHz between the two antennas assuming 0dBi gain, it is only a bit over 3dB, so I am concerned about taking out the frontend of the RSPdx receiver. My guess is that the antenna gain for this loop is well below 0dBi, but I am not yet ready to blow things up..I think that I will us my nanoVNA to measure the path loss between the two antennas before I start dumping power into my EFHW. but I am curious if you had a chance to look at the coupling between your two antennas. Thanks!
Great video, I just subscribed to your channel. What program is displaying the waterfall/spectrum on your screen?
GQRX.
I put one on the ground last fall and the noise definitely went away, but so did everything else. If the other station was no on a amp, I could not hear them. I probably had wire that was too small. I tore the antenna out, but kept the transformer and plan on putting it back in the yard this summer. I could hear Jim W7CPT out of Washington on 40m (about 700 miles to SW Montana). But most other stations disappeared. What size wire did you have on your spool? DE Gene N7ARO
How would it compare to a small active receive loop ...or a magnetic loop I wonder?
Hi! I have this kind of ground loop antenna for RX. If you live in the city with a lot of noise it makes the difference. It killls the local strong noise. Not so good to receive DX signals but for signals on lower band in radious of cca. 1000 km isn't bad. I have abt. 20m of wire in square configuration abt. 10 cm above the ground. Made the transformer but never tested without or different winding ratios.
So for local receiving on lower bands does the job. If somebody wants DX reception will not work well. In this case beaverage or other antennas maybe better choise.
73 Andrej - s57rw!
Very interesting. I'm thinking of trying one for LW/MW. What's the software on your PC screen when you're transmitting about 20 minutes into the video?
That's called WFWIEW It's a free and open remote software for icom radios. I have a video on it.
th-cam.com/video/BZxW9AESIBk/w-d-xo.htmlsi=MbYrcCydB8248mBq
Thanks. Good experiment nd report/evaluation. Ever considered VLF reception? Eg. USN VLF transmits, etc. You have the room that I don’t an endeavor/experiment of that size real estate wise.
I'm very interested in exploring VLF. Here in Kingman, there is BPL in use and the whole lower end of the spectrum is noise from it. I'm working on antenna options though. Once I move back down to Quartzsite in September I'll be looking to do some VLF RX.
👍
Have you tried Stan Gibilisco's clever noise reduction circuit?
Do you have a link? I checked his youtube site and googled it and was unable to find it.
Would you please share the link of stan’s video? Thanks
A little higher, and it's an eruv.
ya know what you should make? an HF Yagi. since you got the room, might as well try, right?
I'm already tripping over things in the RV, I wouldn't have anywhere to store it when I go south in a couple of months.
I would like to make a 3 element 40 meter yagi though, full half wave elements strung between masts. 6 of them.
whats giving your 705 an extra 20 watts?
The little MX-P50 amplifier I have. There are three videos about it on my channel.
Remember, like in real estate, it's location, location and location; meaning height. Ron W4BIN
Gulf war H under sand
I use LOG antennas all the time. The vertical lines are voltage measurements not power measurements. Can't just measure the height of the signal peak over the baseline on the dipole and call that the ratio compared to the loop. It is signal power of the signal audio compared to the noise floor audio for the two antennas.
When length of your LOG approximates or exceeds 1 Lambda at the highest frequency you no longer have a LOG antenna. You just have a really low antenna (NVIS).
The transformer you wound is good for 80 and 40 - maybe usable at 20 but other losses are setting in with the 73 mix above that frequency..
My 80/40/20 loops are 60 feet (give or take a few feet) with a loop every 90 degrees. I use the 2T primary and 6T secondary with 73 mix binocular cores at RG6 (200 to 300 feet of run each)
But for 160 the choking action (inductance) of 2/6T windings is too low and losses escalate. You will want to use at least 3T primary and 9T secondary. And the 77 mix would also help reduce losses due to low inductance of the windings. And maybe the next size up for the ferrite core to increase the inductance.
cheers - Doc