AM Loop Antenna from PVC Pipe 

Same

Crystal radios are near enough to magic.

These days about 1/2 the AM band is taken up by COAST overnight. WHAS-840 is 50KW (day and night) and can be heard in most of the country - but Kentucky is college basketball country and the post game shows can preempt the COAST broadcast on many nights. Or, sometimes there are technical problems... I am building this to get the show from a dozen or more other stations just in case one might be down. Hopefully some of these stations are still broadcasting in HD too! Not to mention if your town came under some sort of an apocalypse! :-O Then a battery operated radio and this antenna could save your life!

+Eric's garage Broadcast TV is alive and well. We ditched cable 6 years ago. Lot's of Internet based content for sure, but there is an antenna for the TV as well, and we get almost 40 stations. The other interesting thing is that over-the-air content is not compressed nearly as much as cable or satellite. The HD picture is beautiful compared to what we used to have on cable. When people come over to visit they ask if I have a 4K set :)

Thank you! All the best to you and yours in the new year as well.

As explained by Matt in reply to other comments, the directionality of the loop is broadside-null. To receive a station at best signal, the loop should be such that the station is in the same plane as itself. Because it works by phase difference between its two vertical sides.

The math is a big tricky to get exact but close is good enough with a variable capacitor to tune with the inductance.

Or get a 100pF and a 220pF fixed capacitor and a ON-OFF-ON switch.

That's correct. The only reason I put the whole radio inside my loop is because it's own antenna is internal

Thanks! Some good ideas there. Really any glue will work. Superglue is the best substitute for the PVC cement, but even good old Elmers white glue would be fine. As for collapsible: I like the idea. Best bet is likely to make the "X" frame with a pin between two legs so that it would fold flat. You do need to be careful about introducing metal into the build though. It can throw off the calculations for the loop.

Sure can. Anything non-conductive will work just fine.

Very well. I have a video or two on the press. Added a keyless chuck to handle smaller bits, and really have no complaints.

The coupling is magnetic, so if you want to get the signal onto coax or some other transmission line then you need a small loop placed where I had the radio. This is what you connect to the coax, twin-lead, etc. The design of the small loop is touchy, but you can pick them up cheaply enough. Any small loop advertised as an AM antenna will work. Your primary problem is that you need to be able to access the tuning capacitor and to rotate the loop. If you're remote mounting the loop outdoors, then you have to motorize and then weather-proof both of these. At that point I think I start looking into Beverage antennas if you have the room.

Larger loops do "catch" more signal, but in practice you have to go much bigger to make a noticeable difference. The number of turns and the spacing are related, and more isn't better. They have to be the right mix for the loop to tune to the frequency you want. The calculator in the video description is the best way to experiment with different combinations.

Matt Heere, okay. I will build it the way you showed. Thanks!

Thanks for the heads on the DX page. I'll have to go find that. 73's - N3NWV

Your video was posted on DX SOCIETY (The world of radio), a Facebook page dedicated to DXing by José Maranhão, one of the best DXers in Brazil.

Hi Grant. What you're describing sounds like a beverage antenna. Loops share some of the characteristics of a beverage, but they have much higher Q (they are more sensitive to tuning) and they don't have the S/N ratio benefits. If you have the room for a beverage and the tuner, then that's the way to go. The loop is a better choice when you have less room.

Long live Long Wave !

If you made a 2’ box loop, meaning that from center to center would each be only 6 inches per side, then merely increasing the number of loops wouldn’t do the trick. The inductance of the loop has to match the range of your chosen frequencies, in this case the AM broadcast band from 500-1700 KHz, and that inductance must be correct to tune it with a 10-360 pF tuning capacitor as shown. To maximize the power of that tank (tuning) LC circuit, two feet per side, or 8 feet per one complete winding is in fact a highly efficient amount when wound 11 times. Yes, you could make the loop antenna any dimensions you like, but you’d still have to match inductance and capacitance to tune the band you want to monitor. I even made made an equilateral triangular loop with each side measuring 2’8”, or a total of 11 feet per one complete wind, with a total of 8 windings that beat out my earlier box and cylindrical am loop antennas. Experiment and have fun. One thing really helps though: The larger your tuning capacitor (physical size, not capacitive range), the more selectivity (fine tuning) you will have on the antenna.

Well it's essentially the same antenna. Using a ferrite core let's you shrink the loop, which is helpful if you intend to install it inside a radio. Big antennas catch more signal though.

@@MattHeere Thank you! I thought, ferrite was a crucial part in this construction, now much has been clear.

For AM broadcast that's 530 kHz, so a 1/4 wave is 464 feet tall. Best of luck.

One wire goes to the ground or metal body of the variable capacitor. Each cap has 2 terminals going to the plates. Only use 1. it does not matter which one. With the loop unconnected use a meter and test the body and one of the plate terminals and the frame of the cap for shorts. Make sure the cap is turned somewhere in the middle.

What channel range are you interested in? UHF or VHF? The Gray-Hoverman antenna is an outstanding antenna. I have built 2 or 3 versions of them and they all performed like a champ on weak UHF signals. The last version I built is known as the gold standard.

@@Bruce_Wayne35 I am interested in the VHF and UHF. The VHF is because I live in a location where there are still a few channels that I would like to get and UHF all the way to 52 channel. I got what I need for the antenna build and am going to start. Not sure what is the gold standard ??? Nice to hear from you Sir. v

@@victoryfirst2878 It's what the members of the Digital Home Canada discussion board/inventors chose to call it. The gold standard version was the highest gain UHF version of the Gray-Hoverman antenna. It covers channels 14 to 51 and has usable gain beyond that a bit, so it would still work great on 52. They're easy to build. Even a sloppy build will amaze you with good performance. A double-bay version will have around 16 dbi gain.

I've updated the link at the end of the description to point to a working calculator for square loops. It will let you experiment with size, row count, and the capacitor values to see the effect on loop tuning. The model of capacitor does not matter for this application, only the range of values it provides.