The SULA antenna

[rayb]

Very good Andrew. Well, it was just an idea I had that seemed to have a possiblility of working. That's how we advance the state of the art... come up with an idea and test it. Thanks for your reply. Your work saves someone from spending time and physical effort that won't produce the desired results.

73,
rayb

[Andrew (grayhat)]

Very good Andrew. Well, it was just an idea I had that seemed to have a possiblility of working. That's how we advance the state of the art... come up with an idea and test it. Thanks for your reply. Your work saves someone from spending time and physical effort that won't produce the desired results.

73,
rayb

it isn't forbidden by the way, if you want try the two configs and see it by yourself, but ensure to run the check at LW, MW, SW and, if you want VHF and UHF (up there the pattern will be reversed)

[rayb]

I just might try it in a few weeks since better weather isn't too far away. Good tip about making sure the test is on more than one band. I wouldn't think it would be of much use at LF, but MF through 30 mhz would definitely be in order. I have better antennas for vhf and higher.

rayb

[Andrew (grayhat)]

I just might try it in a few weeks since better weather isn't too far away. Good tip about making sure the test is on more than one band. I wouldn't think it would be of much use at LF, but MF through 30 mhz would definitely be in order. I have better antennas for vhf and higher.

rayb

Well, Ray, the SULA works fine for the HF bands and above, going below the gain drops quite dramatically but the cardioid pattern remains; and going up to V/UHF the pattern is reversed, that is, instead of being aimed toward the feedpoint it's aimed toward the resistor and at those higher frequencies the SULA start having some relevant gain, getting back to the coax routing, I tested it in NEC and Ollie (13dka) confirmed that, routing the coax "inside" the loop, causes the cardioid pattern to become deformed and the nice backside "null" more or less disappears, so if you want "the real thing" the coax should be left "dangling" outside, if you want nothing forbids adding a (PVC) pipe down the mast to hold the coax coming from the feedpoint, but in general I don't think it's needed, aside for aesthetic reasons; the most important parameters when building/installing the sula are:

The size of the loop
The coax routing
The height of the bottom corner from ground (or ground plane), 3m is optimal
The use of a preamp offering 20 (or more) dB gain

if the above is respected, the SULA will work as it is designed to, I'll also refrain that the SULA is not a "magnetic" loop so, while it can be tried indoors, it isn't designed to work well in such a setup