Loops Megaloop FX - Loop Size Question

[Merovingian]

For a while I have been hearing good things about the Megaloop FX. I currently have a Wellbrook loop which I assume, as been doing good so far, I'm not sure since I have nothing else to compare it to and I have no other experience with other types of long wire, random wire, ect. . . antennas. I have been receiving signals with it for the last year, that is all I can say at the moment. I have seen some YouTube videos of people receiving DMR broadcasts as well as others with their SDR radios and their signals seem to be very "clean" and reception strong. Those people are often in Europe so they may be closer to the transmitter than I am here in the US but they are often using a random wire or long wire antenna of some sort to receive their signals. I have a little room for a long wire antenna, maybe 100 feet or so but it would not be very convenient to install nor easy to put up, it could be done I suppose if I "really" needed/wanted to.

I have been thinking of sticking with magnetic loop antennas since they would be a lot easier and more convenient to put up where I am and with what I would have to do to install it. My Wellbrook loop came with a 1 meter aluminum "hoop" for the antenna element, I'm guessing that was chosen for shipping, cost and performance for a given space reasons, maybe the internal amplifier is optimized for that size as well, I don't know. . . I was wanting better signal reception performance so I was looking at the Megaloop FX since it gives the option of different sized flexable loops, I don't know what the size limit is for this antenna. The megaloop FX is a little expensive so I have a few questions for those that know or have had experience with many different antennas.

For reference as to what I like to do: I like to listen to everything in general, I don't have anything specific in mind I want to receive or monitor so I would be listening between 1kHz and 30MHz. One day I may want to listen to HAM guys talk, some other time I may want to receive a weather fax transmission, maybe I want to listen to a distant radio station, or try to decode a digital signal, ect. . . In the future I may also want to try to use my Wellbrook and a Megaloop FX, if I buy it, for diversity reception.

#1. The Megaloop FX has the option of a 5m and 10m loop. I also found a site that someone is selling a 20m option for the antenna. If I were to buy the antenna with the 5m cable would that be just as good or better, compared to my Wellbrook? Or would say the 10m or 20m provide a notably better signal reception because it is bigger?

#2. Is there a limit to the loop size? If I wanted to make my own 30m or 50m loop for some reason, would that work even better? Or beyond a certain size there is not much noticeable difference?

#3. How about shape? I've seen people make it a diamond shape. Does it just have to be some sort of roundish shape to work well? Or does it have to be a perfect circle? Or could I take a 20m loop and stretch it out to a flattened oval shape almost like a folded dipole and still have it work well?

#4. Does a long wire antenna just provide a better signal because it is a long piece of wire better tuned electrically to one or many frequencies? It dose seem hard to imagine that my tiny by comparison Wellbrook does as good as it does with it just being a 1m diameter loop versus the actual signal wavelength that may be hundreds of feet long or kilometers long.

Thanks for your time.

 

[ka3jjz]

1. The larger sized loops tend to change the rules a bit; the rule that I have always been taught was that when a loop exceeds 1/10 wavelength on a given frequency it tends to act more like a dipole than a loop. Their greater capture area means more signal; how quiet it would be I haven't a clue. It seems to be garnering some good reviews, although the 3 step attenuator and FM bandstop filter gives me pause as to how linear that amp would be across such a huge tuning range. If you live in an urban area, expect to have to fiddle with this. And also insure the amp is grounded; there is a lug for this.
2. See answer above
3. Any symmetrical shape would work, but circular seems to be the most popular. However I've seen squares and they seem to work just fine.
4. Be careful here; you're falling into the trap of comparing a wire antenna to a loop. Simply put, the comparison is not valid. When you are working with a loop you should expect a better signal to noise ratio - i.e. less noise as part of the signal. It will NOT be the same as a long wire (and even that term has to handled with a bit of care). A 100 foot long wire (notice I separated the 2 words) mounted well off the ground will likely resonate well across most all of the HF spectrum (with all other restrictions being equal) - however you will NOT get the noise reduction or directivity of a loop. On the flip side, propagation might favor the wire one day, the loop the next. Having 2 (or more if you are fortunate) antennas for HF is an advantage because of this. Not everyone can put up a 100 foot random wire (or inverted L if you like). There are several other designs set up for smaller lots that work well; the Vibroplex PAR is just one of many

Mike

 

[Merovingian]

1. The larger sized loops tend to change the rules a bit; the rule that I have always been taught was that when a loop exceeds 1/10 wavelength on a given frequency it tends to act more like a dipole than a loop. Their greater capture area means more signal; how quiet it would be I haven't a clue. It seems to be garnering some good reviews, although the 3 step attenuator and FM bandstop filter gives me pause as to how linear that amp would be across such a huge tuning range. If you live in an urban area, expect to have to fiddle with this. And also insure the amp is grounded; there is a lug for this.
2. See answer above
3. Any symmetrical shape would work, but circular seems to be the most popular. However I've seen squares and they seem to work just fine.
4. Be careful here; you're falling into the trap of comparing a wire antenna to a loop. Simply put, the comparison is not valid. When you are working with a loop you should expect a better signal to noise ratio - i.e. less noise as part of the signal. It will NOT be the same as a long wire (and even that term has to handled with a bit of care). A 100 foot long wire (notice I separated the 2 words) mounted well off the ground will likely resonate well across most all of the HF spectrum (with all other restrictions being equal) - however you will NOT get the noise reduction or directivity of a loop. On the flip side, propagation might favor the wire one day, the loop the next. Having 2 (or more if you are fortunate) antennas for HF is an advantage because of this. Not everyone can put up a 100 foot random wire (or inverted L if you like). There are several other designs set up for smaller lots that work well; the Vibroplex PAR is just one of many

Mike

Thank you for the information, it was very helpful! If I do buy it I may consider getting the 5m version then, that is already a lot bigger than the Wellbrook. I would probably have to get some PVC or something to give the loop some support to keep it somewhat round, a diamond shape would be easier though I imagine, especially since it may not affect reception at all.

Hummm. . . the Vibroplex PAR, I have not heard of that, I will look into that as well. Thanks you again.

 

[ka3jjz]

Here's some links - for the PAR and a couple of other ideas for wire antennas for small lots. You can do a Google search on the EWE and you will find out more about it...

Par EndFedz® EF-SWL receive antenna

Vibroplex, Bencher, GHD and Hi-Mound Morse Code keys. INRAD headsets, microphones and filters. Par EndFedz EFHW antennas, Spiderbeam fiberglass poles. mAT-TUNER automatic antenna tuners, Easy-Rotor-Control rotator controllers, DX Patrol receivers

www.vibroplex.com

EWE Antenna review :: DXing.info

Mike