First test, after you put an antenna up, is the SWR; this will show you how well is the antenna matched to your transmitter and feeder cable, and if it correctly resonates on the required frequency. Here is a plot of the SWR on both antennas between 24 and 31 MHz; target for minimum SWR is around 27500 and where SWR is over 5 I haven’t measured further. Power used was 10W.
As you see, the Delta loop has tuned very well and the minimum SWR is 1.5 wich is decent in my book. With the Ground plane though we have weird figures: two SWR minimums and a very wide bandwidth; why is that ? Because although it resonates correctly (it’s pretty much symmetrical around 27.6 MHz), the resonance impedance is different that 50 ohm, probably due to the fact that the radials are not at the correct angle. This can be corrected but it will of course tighten the frequency band of the antenna, as now it should work OK in the 12m, 11m and 10m radio bands and with correct impedance the minimal SWR will come down to almost 1 but won’t stay below 2 for more than 1-1.2 MHz.
Using the both antennas for DX work, the Ground Plane seems superior: signals from distant stations are a bit higher and the noise floor is actually lower, wich is should have been one of Delta Loop’s strong points. In it’s defense I could say that it sits about 2.5 meters lower than the Ground Plane and for some local stations using horizontal polarised antennas the signal reports have actually improved considerably, without degrading too much for those with vertical polarisated antennas. All in all, the Ground Plane seems to be a better DX antenna, probably due to it’s lower takeoff angle, although if I would put both antennas to exactly the same height and use 100% vertical polarisation for the Delta Loop it might come very close.
Pages: 1 2