A good concise presentation with a lot of in-depth information, thank you. Hi to all VK4ZOW here ,I have built many loops in the past and had good results and failures. So my best performing RX loop ended up as a diamond box frame loop compound wound with 80mt of fine NON insulated copper coated MIG wire( no static in dry weather) spaced at 30-50mm apart on a crucifix system approx. 4mt sides made of varnished pine (big but not heavy ) and the smaller feed loop as per Freq formula is located at the top apex of the loop and held in place with fishing line like an inverted pyramid feed at the apex .So now the tuning cap is at the bottom of the diamond. I also incorporated band tuning by soldering jumpers to various turns on the main loop near the tuning cap and fitted a ten position SW and another to SW to the gangs of the cap so to SW in and out the capacitance. It for me is the best loop yet and works from 160mt to 10mt and very sharp and directional as well. Foot note I did not use a cap on the input feed to keep the weight down, but in saying that I may make a vary-cap tuning arrangement to tune the whole thing from my shack just for RX. I built and fitted LNA .2 DB noise with 30 DB gain with 2 Schottky diodes for front end protection. Now the my 757-gx radio is pulling out signals across the ham band.
I really appreciate your great efforts! Your theory explanations are wonderful even for us non-math guys. As a BCB dxer from long ago, nothing beats a loop.
Agreed, the untuned loop from video 1 with refinements depicted in video 2 is the way to go. Thanks for the informative series, I learned a lot. I've recently moved into my first (owned) domicile. My previous landlord was delighted to observe the decommissioning of my array of wire antennas. With the new home, it's on to a whole new world of possibilities of antenna systems. I plan to deploy several long wire type antennas here, the tree supports are excellent (but very high). Far taller than I can manage with a thrown tennis ball or basic slingshot. A drone purchased from Amazon has arrived which I will be attempting to utilize for antenna installation. But something inspired by these videos might be perfect on my back roof.
Last year I experimented with using a 8 feet diameter loop (basically a wire nailed to the wall) with my broadcast band crystal set as I don't have a tree nearby for an inverted L antenna. The inductance of the loop came out around a couple of microhenries (just as in your case). Instead of using a coupling loop, I just connected the loop antenna in series with the main inductor and made it part of the resonant circuit of the crystal set. It worked, however the Q of the tuning tank went down significantly. I suspect that the long antenna wire adds a lot of DC resistance.
Very informative, thanks. I'm hoping I can fit a 100 watt TX loop to my balcony as it's all the space I have. RX loops are easy, it's the capacitor on tunable loops that becomes a problem when transmitting anything beyond 20 watts or so. What are your thoughts on this can I ask? 73 KD2ORG
Very nice, I liked it. I'm building an antenna now, what do you think about the issue of the coax that will be inside the big ring for proximity and distance from the ring? Any trials on this? Thanks
Nesting the pickup loop inside the big loop is not terribly critical on RX only loops, because you losses are better tolerated. A single loop about half of the area inside the large resonated loop and spaced away a bit or even centered will minimize capacitive effects. You want pure inductive coupling. Of course the double Faraday shield is helping you here too. In a low noise environment I doubt that any of this would make much difference. You could just use wire and no Coax except for the amplifier output.
RG-59 is what I have and alot of it. On the outside loops should I use the outside braid or tie them together? Newbie to loops here and learning. Thanks for a great series!
Mike do you have a link to the schmatic for the universal test oscillator you show at 1.54 in this video? Im unable to find a vfo unit covering this range. 73 for Christmas and 2022. Keep up the videos, always a real good watch!
You can use a noise bridge, or a Grid Dip Oscillator. Instead of using a coupling loop, what about using a gamma match or a ferrite matching transformer?
