Skywire Loop Antenna aka W0MHS Loop Skywire aka Full Wave Loop Antenna Observations by Jason Buchanan - N1SU

13-Mar-07 - Updates to original article

• A 544' length of wire is fine for operation on 160 meters through 20 meters. My tuner has a lot of trouble tuning the loop at 15 meters and higher. At 15 meters it starts tuning the feed line and the RF is difficult to control. 17 meters will tune ok but it's on the upper limit of my tuner's ability to tune with "comfort." The tuner becomes very "touchy" when tuning for the sweet spot of low SWR on the upper bands.

• 544' is comfortably resonant at 1.847kHz, 3.694kHz, 7.389kHz, 14.779kHz and 29.558kHz.
• 560' is comfortably resonant at 1.794kHz, 3.589kHz, 7.178kHz, 14.357kHz and 28.714kHz.
• 565' is comfortably resonant at 1.778kHz, 3.557kHz, 7.115kHz, 14.230kHz and 28.460kHz.

As of March 2007 the solar cycle is great for the length of my loop since 15, 12 and 10 meters are out of action. In a couple years the cycle will begin to swing in favor of 15 meters and i'll lengthen the loop.

Noise is greatly reduced with the loop compared to my dipoles. My dipoles are mounted on a pole at the end of the house and some of the noise may be due to their height (35 feet for the dipoles vs. 30 feet for the loop) and close proximity to the house and stuff inside. The loop is 40 feet or greater from the house in most places. The noise on 20 meters is sometimes reduced as much as 1 S unit when using the loop compared to the dipole (even at 3:00am when nothing in the house is on). Once in a while a station may be slightly stronger with the dipole but the noise is stronger too - weaker stations are easier to copy with the loop due to less noise.

Polarity plays a strange role. Buy a good copper knife switch with porcelain base and give yourself the means to quickly switch the polarity for A/B testing. I've found that the characteristics of the loop change considerably when you flip the polarity. On 20 meters my loop tends to try to radiate from the ladder line if the polarity is switched in one direction but works perfectly fine in a different direction. I just noticed this a few weeks ago but haven't had the time to nail it down. My 2-year old son keeps me busy with other things but eventually i'll figure it out.

Performance is exceptional as compared to a dipole but in some cases the dipole is better. The dipoles I have are mounted at approximately 35-38 feet, the loop is approximately 30 feet. Stations that are within 15 miles of my house usually perform better with the dipole - sometimes the loop won't hear them at all but DX stations are considerably stronger. I notice on the 20 meters WinDRM weekend net that a station 15 miles away from me will be S7 with the dipole and S3 or worse on the loop, yet the DX stations are always equal or better with the loop. The local station can't hear me well with the loop either but the local station copies me perfectly with the dipole. Remote DX stations report an improvement using the loop compared to the dipole. My grandfather Rod W4BI in southern Florida is considerably stronger when I use my dipole (technically it's an inverted vee with the center conductor angled 45 degrees to the ground) but DX to Washington state is far better on the loop. I'm in the Boston area so you can get a rough idea of the distances.

The loop really, really cuts the mustard on 160, 80 and 40 meters. Knowing what I know now, I probably would have cut the wire for 560' feet to make the upper bands work better and kept an eye on the tuner to make sure it wasn't getting hot - the only reason I would have done this is laziness so I wouldn't have to bother with splicing more wire in as the cycle improves. But 544' is fine - nothing to work on the upper bands right now anyway. I tried adding more ladder line to lengthen the feed line but that didn't seem to have any effect. I tried making the feed line shorter and that didn't seem to have any effect either. It works great as is so i'm leaving well-enough alone. hi

Performance Observations