Out of boredom like usual I decided to play around with loop antennas again and read up on delta loops. They can be setup for vertical or horizontal polarization and even can have a high, medium or low angle of radiation depending on where you feed it with coax... w5sdc.net/delta_loop_for_hf.htm
From what I read they have about 3dB of gain on the broadside of the antenna and with the low angle of radiation it could make a great antenna for shooting your signal towards the location you want with no loss of gain in the other directions over your basic vertical dipole.
I am going to try one out for FM broadcast just for fun in the basic triangle configuration. I rather use it as a receive antenna once properly tuned up but will definitely give it a try for transmitting. If it works as good as it sounds on paper I will keep it around for camping trips since it could make an excellent low profile antenna that could even be hung from a tree and no one would even notice.
Anyone else here ever give this antenna any thought?
So far the dimensions I calculated for 96.9MHz would come out to..
Total wire length of all 3 triangle sides - 10' 4.4" 75ohm matching coax length - 1' 8.8"
Found this by simply... 1005 / MHz = Wire total in feet for complete triangle ( * 12 for inch) ((1005 / MHz) / 4) * .67 = 75ohm length in feet ( * 12 for inch)
.67 is the 75ohm coax velocity factor The 75ohm piece of coax is there to transform the 100ohm impedance of the loop down to 50ohm for your usual coax impedance. Will let you all know my results after I play around.
3 hours later and I whipped together the antenna out of a wooden dowel for the bottom of the triangle and used some light copper wire with the top of the triangle hanging by a thumb tack in the wall. Ran the 75ohm matching coax coming out of the corner of the triangle to my regular 50ohm line and from that into the SWR meter and transmitter. Crossed my fingers, flipped the power (transmitter set to 1/2 watt) and... 1.2:1 SWR!
Mind = Blown.
I did not believe what the meter was telling me since I did not even try to cut and tune the antenna and literally just threw this thing together in like 15 minutes so I checked with a field strength meter and it was pegged around the whole room. Tuned the transmitter from the bottom of the band to the top and SWR was mostly flat around the whole band only going up towards the highest and lowest frequencies.
Next I connected the antenna into my FM radio and that was amazing. Not sure if the moon was aligned just right or if the antenna Gods are looking after me but just about every channel on the radio was picking up a station with near full quieting. Was even able to hear a low power college station 60 miles away that I normally can not pick up well. Compared the radio connected to this antenna to my DX398 with its built in whip and the difference was nothing short of jaw dropping.
This is now going to be my official DXing antenna for FM. I am just going to thumb tack the triangle antenna to my wall and just leave it as is. Almost wish I could try a permanent version of this outside for transmitting but it would look ridiculous having a giant triangle sitting on top my tower and the J-pole I got up there now works alright. No need to fix what is not broke lol.
I highly recommend anyone here who wants to really pull in those distant FM stations try this setup. I will post a quick computer drawn picture with dimensions later as an aid for anyone interested. This really is not any harder to quickly wire up than a dipole but does take up more room and becomes awkward to place in the room because of the shape but completely worth it.
I can only imagine how well this would work on lower frequencies and from what I read many ham radio operators swear by this antenna so it must work really well down on HF if you have the space.
Have you ever tried a MOXON for DXing on 87.5-108, or even used it for tx? After building one, I have made a rough comparison between that and a 3 ele. Yagi-Uda, and found both were about the same. They're still "alive", but aren't being used for ages.
My DX antenna is seldom used 8 ele. TRIAX (Danish) that had to be removed off the AR 300 XL rotator a month or so ago as this one got stuck with lots of corrosion. In sum, a cheap piece but also a very bad quality one.
Have you ever tried a MOXON for DXing on 87.5-108, or even used it for tx?
Not yet but now that you mentioned it I will have to experiment with it sometime in the near future. In a few days I will get a 100' roll of stranded copper wire and see what all different configurations work like. So far I am absolutely amazed by the reception on this delta loop and was equally amazed how well it worked for transmitting while only <15' off the ground.
I am going to try a delta loop on 11 meter CB band and see how well that works. Good thing is I can run this antenna indoors and should still be able to get a strong signal out while low to the ground.
Quick note.. I originally fed the delta loop at the bottom corner for vertical polarization and it worked great as observed and noted above. There were many websites saying the proper place to feed it for vertical polarization is 25% up from the corner for vertical. Well I tried that and found out real quick that it did not perform as well on all stations. So not sure exactly how people came to the 25% conclusion but it did not work for me. I find it is best fed directly off the corner with the matching coax either hanging down or sideways away from the antenna. I wonder if this has something to do with partially including horizontal artifacts that supposedly are detrimental to the overall design, however most radio stations use circular polarized antennas so maybe somehow this strange interaction or "design flaw" is somehow a blessing when it comes to DXing? Either way I am going to feed it off the corner and not 25% above or below the corner as sites suggest. It just works better!
Is it pratical, I mean using a Delta Loop for the 87.5-108 band?
It surely resembles the K9AY, which can be fed up or down depending on how one erects it. In my two cases, both [elevated] K9AYs are bottom fed, triangular shaped, each using 4 loops, 25 m perimeter. These are my main tools for LF/MF DXing. One of the K9AY has 2 loops with 2x25 m in series so as to increase sensitivity.
The ones below are those I mentioned, plus one other I tried and still have, but it's just standing there, not used at all.
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