The SULA antenna

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rayb
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Re: The SULA antenna

Post by 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
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Andrew (grayhat)
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Re: The SULA antenna

Post by Andrew (grayhat) »

rayb wrote: Tue Feb 28, 2023 5:29 pm 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) :D
rayb
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Re: The SULA antenna

Post by 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
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Andrew (grayhat)
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Re: The SULA antenna

Post by Andrew (grayhat) »

rayb wrote: Tue Feb 28, 2023 9:02 pm 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
Martyn77
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Re: The SULA antenna

Post by Martyn77 »

hello .... a curiosity .... how does it behave towards the high portion of the HF? like in 15 and 10 meters amateur radio?...thanks and congratulations for everything!
13dka
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Re: The SULA antenna

Post by 13dka »

Welcome to the forum! Well, the "null" isn't quite as deep on 10m as it is on the lower bands but it still does what it's supposed to do. On upper end of HF it has the least losses (for the shortwave band that is, it starts getting gain when you go higher) and generally performs very well on 15-6m.

Image

TBH, when I tested the SULA last year it was usually at night, when the upper bands did not have many signals. I did record one short clip on the freebander band with some blokes from the UK to compare that to the amplified YouLoop I brought to the dike as a reference.



Beyond shortwave it gets even better. Here's the SULA on the airband, receiving an ATIS station in 200+km distance (EDDV), due to "marginal" (on the Hepburn Tropo Index scale) tropo conditions on VHF (also much 2 closer ATIS stations later in the clip via enhanced groundwave). It performs like a dedicated antenna up there, despite only 3m height (but then again, this is super flat country):



Here's the SULA pointed at the GRAVES radar near Lyon, France during the Perseids 2022:



I could also receive a lot of echoes from aircraft passing through the GRAVES beam, likely everything that crosses that section of the sky at night, so it should be quite sensitive. Anyway, I'm looking forward to do more tests on the upper HF in the much more enhanced conditions this year!
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Andrew (grayhat)
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Re: The SULA antenna

Post by Andrew (grayhat) »

Martyn77 wrote: Wed May 17, 2023 7:18 pm hello .... a curiosity .... how does it behave towards the high portion of the HF? like in 15 and 10 meters amateur radio?...thanks and congratulations for everything!
Hi there, Martyn, welcome on this forum.

Regarding your question, I hope 13dka answer included the infos you were seeking for, I'll just add that regarding coax matching, the SULA will have a good match on the whole HF spectrum and that to get full performance from the SULA it's important to follow the build and installation instructions by the book
Martyn77
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Re: The SULA antenna

Post by Martyn77 »

thanks to both of you, I'll try my hand at building it and I'll tell you...unfortunately my conditions are what they are as a space for antennas...the best is a balcony practically closed on 3 sides...I have an active loop similar to ala1530 that up to 2 meters is fine, @Andrew I'm also looking for an alternative to the "tuttobalcone" for ranges from 20 meters upwards, in case the condominium makes a fuss about installing the wire and related supports outside the wall of the balcony...thanks again!!!
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Andrew (grayhat)
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Re: The SULA antenna

Post by Andrew (grayhat) »

Martyn77 wrote: Thu May 18, 2023 3:06 pm thanks to both of you, I'll try my hand at building it and I'll tell you...unfortunately my conditions are what they are as a space for antennas...the best is a balcony practically closed on 3 sides...I have an active loop similar to ala1530 that up to 2 meters is fine, @Andrew I'm also looking for an alternative to the "tuttobalcone" for ranges from 20 meters upwards, in case the condominium makes a fuss about installing the wire and related supports outside the wall of the balcony...thanks again!!!
Hi there again, if you want to try the SULA follow the directions here

viewtopic.php?p=427#p427

and ensure to build it exactly as indicated, including the way the coax is routed and all the other details, they aren't there "by chance", as for the remainder of your post, if you have questions about other antennas than the SULA, please open a new discussion here, this one is dedicated to the SULA antenna and aimed at helping builders, thanks.
Martyn77
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Joined: Wed May 17, 2023 7:13 pm

Re: The SULA antenna

Post by Martyn77 »

ok!!! Thanks !!!
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