Friday, April 3, 2015


I was looking at possibly incorporating  a loop style antenna into my station.  The Flex 6300 has a transverter input which will QSK at 100+ wpm silently.  I discovered this while watching N4LQ's video describing QSK in his 6300.  I had been thinking about how to proceed on a separate RX antenna and of course the Flex boys use Waldo at all the hamfests

It's a running joke perpetrated by W5GJ and W4TME "Where's Waldo" followed by a pic of Waldo out behind the convention center somewhere.  Waldo is a Pixel magnetic Moebius loop antenna which is largely impervious to noise and works quite well at the hamfests.  I did a little research and found the competition was loop antennas made by Wellbrook in England.  So what to choose?  There are a couple of fairly extensive shootout tests exploring the behavior between the 2 antennas.  In some Wellbrook seems clearly superior and in other tests Pixel is the winner.  So which did I choose?   Neither.  Both the Wellbrook and the Pixel loop antennas are quite expensive in the $400 -$500 dollar range and both seem to need a rotor.  Just in general it offends me to pay $500 for a receive only antenna.  

Wellbrook has some other options, a medium aperture and large aperture device.  I looked at the large aperture device, the ALA100 and it hooks to a 20M loop (as in 60ft circumference) which is pretty big.  I next looked at the medium aperture device  the ALA100M and it hooks to a loop between 3 and 10M in circumference.  Now your talking.


My 23ft circumference loop

The ALA100M is a preamp, a power injector which ships power down the coax and a little brick supply.  If you choose to supply your own voltage NOTE, the center pin is neg and the outer ring is pos so be careful.  

The loopwas made from a couple of 3/8" 8 ft pieces of fiberglass from Maxgain ($5.50 per acquired at Orlando hamfest) and the center these arms are zip tied to Is a thin light $1 piece of circuit board material (1ft x 1 ft) obtained locally at a surplus store.  The wire around the perimeter is some #14 bare copper I had laying around.  So the loop cost me $12 and the ALA100M was $232 plus shipping, half of the $500 price tag and I can see no need for a rotor.  The whole loop is about 2 lbs.   I had a 25 ft fiberglass post in the back yard so I secured the loop with a couple of hose clamps and away we go!

Loop on 160

Lightning noise source off the FL coast of my house

160M inv-L

The little program on the left is DDUTIL and gives a readout of peak and ave S meter readings.  Also you can see which ANT is being used as it reads out in red in one of the system boxes in DDUTIL.  Bottom line much lower noise both to the offshore lightning and the local line hash -85 dBm vs -105 dBm  Big improvement!

80M full size vert


On 80M the difference is -91 dBm vs -113 dBm on the loop

These are shots of V6Z on 40M this morning  

V6Z on 40M 1/2 wave vertical 

V6Z on Loop

-98 dBm vs -118 dBm notice the intensity of V6Z's signal on the second shot vs the first.  In the first I could tell he was there but he was not copy-able.  On the second shot he was Q5 even though still very weak.  I tried the loop all the way up to 10M where I was greated by a VK6 perfectly copy-able on the loop but uncopy-able on my 55ft dipole on that band.  

I made a little demo video, worth a look if your considering a RX loop antenna.  I would consider phasing a pair of these on the diversity receiver of a 6700, if I had a 6700.  I'm very pleased.  I made a toggle macro between ANT1 and XVTR on my Genovation keypad so all I have to do is push one button to compare.

73  W9OY