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Author Topic: 2 element, 2m quad as ISS omni?  (Read 14986 times)

K5TED

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2 element, 2m quad as ISS omni?
« on: July 10, 2014, 07:33:54 PM »

Pointed straight up, fixed. Thoughts?
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N4UFO

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RE: 2 element, 2m quad as ISS omni?
« Reply #1 on: July 10, 2014, 10:24:23 PM »

If it's 2 element, it's not an omni... Just the driven element by itself would be an omni; AKA a full wave loop. If you were after something like that I would just put up a squalo.  http://www.freqtester.com/_mgxroot/page_10760.html And, no, stacking would not help... just use one.  ;D

Not sure what you are after as I have never worked the ISS, but you might take a look at my comments in another recent thread about omni versus directional antennas for satellites. However if this is for "unmanned" monitoring where you won't be there to adjust the rotor, then, yeah a squalo or other omni would be a simple choice. Otherwise you might want to look at an eggbeater or Texas potato masher type antenna. At 2 meters, you can get away with a lot more than you would if UHF were involved.

But to directly answer your question, the problem with the quad is that it would be directional straight up. And the ISS will rarely fly directly overhead and even when it does it's only there for mere seconds. (As in less than 60.)

73, Kevin N4UFO
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K5TED

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RE: 2 element, 2m quad as ISS omni?
« Reply #2 on: July 11, 2014, 08:04:44 AM »

If it's 2 element, it's not an omni... Just the driven element by itself would be an omni; AKA a full wave loop. If you were after something like that I would just put up a squalo.  http://www.freqtester.com/_mgxroot/page_10760.html And, no, stacking would not help... just use one.  ;D

Not sure what you are after as I have never worked the ISS, but you might take a look at my comments in another recent thread about omni versus directional antennas for satellites. However if this is for "unmanned" monitoring where you won't be there to adjust the rotor, then, yeah a squalo or other omni would be a simple choice. Otherwise you might want to look at an eggbeater or Texas potato masher type antenna. At 2 meters, you can get away with a lot more than you would if UHF were involved.

But to directly answer your question, the problem with the quad is that it would be directional straight up. And the ISS will rarely fly directly overhead and even when it does it's only there for mere seconds. (As in less than 60.)

73, Kevin N4UFO

Good info. Thanks.

I'm not particularly interested in passes below 35 degrees, and more interested in the ability to put a good signal up when the ISS does pass at higher elevations. I've tried the 2m halo approach, and while it is OK, it suffers a lot on high passes. Looking at the typical 2 el quad pattern with about 75-80 degree beamwidth, and taking into consideration the recent article on using 2m/70cm Moxons pointed up, I'm wondering if a similar performance might be possible with the quad. It is planned to be a sort of "unattended" antenna on one of my remote receivers.

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WD9EWK

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RE: 2 element, 2m quad as ISS omni?
« Reply #3 on: July 11, 2014, 10:54:49 AM »

I'm not particularly interested in passes below 35 degrees, and more interested in the ability to put a good signal up when the ISS does pass at higher elevations. I've tried the 2m halo approach, and while it is OK, it suffers a lot on high passes. Looking at the typical 2 el quad pattern with about 75-80 degree beamwidth, and taking into consideration the recent article on using 2m/70cm Moxons pointed up, I'm wondering if a similar performance might be possible with the quad. It is planned to be a sort of "unattended" antenna on one of my remote receivers.

Have you tried the halo with a groundplane below it, about 1/4-wavelength?  That might help with the higher passes.  The Eggbeaters sold by M2 come with a groundplane kit, in part, to help with their coverage upwards.  The ISS signals should be strong enough to avoid the need of a preamp, but working SO-50 or other satellites would be challenging without one. 

73!
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Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/ - Twitter: @WD9EWK or http://twitter.com/WD9EWK

K5LXP

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RE: 2 element, 2m quad as ISS omni?
« Reply #4 on: July 11, 2014, 03:48:25 PM »

If overhead is all you're interested in, a quarter wave groundplane will work just fine.  I pick APRS from the ISS with one with ease.

Mark K5LXP
Albuquerque, NM
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N4UFO

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RE: 2 element, 2m quad as ISS omni?
« Reply #5 on: July 11, 2014, 04:08:11 PM »

Have you tried the halo with a groundplane below it, about 1/4-wavelength?  That might help with the higher passes.  The Eggbeaters sold by M2 come with a groundplane kit, in part, to help with their coverage upwards. 

The "squalo" I was referring to is mounted horizontal, Patrick... not sure a ground plane would work the same under it. And to be honest, Ted, I'm not sure if that is what you meant either; vertical or horizontal. But I'd have to say, I like Mark's idea of a simple ground plane. The pattern would only decrease reception DIRECTLY overhead and then I would think it would be so close as to not be a bother. As always, YMMV.  :D

73, Kevin
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N8HM

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RE: 2 element, 2m quad as ISS omni?
« Reply #6 on: July 11, 2014, 05:54:30 PM »

If it's 2 element, it's not an omni... Just the driven element by itself would be an omni; AKA a full wave loop. If you were after something like that I would just put up a squalo.  http://www.freqtester.com/_mgxroot/page_10760.html And, no, stacking would not help... just use one.  ;D

Not sure what you are after as I have never worked the ISS, but you might take a look at my comments in another recent thread about omni versus directional antennas for satellites. However if this is for "unmanned" monitoring where you won't be there to adjust the rotor, then, yeah a squalo or other omni would be a simple choice. Otherwise you might want to look at an eggbeater or Texas potato masher type antenna. At 2 meters, you can get away with a lot more than you would if UHF were involved.

But to directly answer your question, the problem with the quad is that it would be directional straight up. And the ISS will rarely fly directly overhead and even when it does it's only there for mere seconds. (As in less than 60.)

73, Kevin N4UFO

Good info. Thanks.

I'm not particularly interested in passes below 35 degrees, and more interested in the ability to put a good signal up when the ISS does pass at higher elevations. I've tried the 2m halo approach, and while it is OK, it suffers a lot on high passes. Looking at the typical 2 el quad pattern with about 75-80 degree beamwidth, and taking into consideration the recent article on using 2m/70cm Moxons pointed up, I'm wondering if a similar performance might be possible with the quad. It is planned to be a sort of "unattended" antenna on one of my remote receivers.



Don't limit yourself to passes above 35 degrees. The ISS has a very strong signal with it's 5 watts output, much more than most amateur satellites. If they ever get the Kenwood radio working again, it'll be putting out a massive 10 watts.
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K5TED

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RE: 2 element, 2m quad as ISS omni?
« Reply #7 on: July 13, 2014, 08:23:17 AM »

Seems like the 2 element quad pointed straight up is close to the same as a halo over ground plane.

There's a good pass today at around 2p CDT, so I'll try it out.

Incidentally, re the ground plane, I have a dual band ground plane with 30' of lmr400 and it is horrible on high passes. I have better luck with a VX7 and whip.
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N4UFO

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RE: 2 element, 2m quad as ISS omni?
« Reply #8 on: July 13, 2014, 02:48:44 PM »

Seems like the 2 element quad pointed straight up is close to the same as a halo over ground plane.

Well... a squalo/halo is essentially a half wave dipole bent into a square/circle, whereas a quad loop is a full wave antenna in a closed loop. The 'plane' of a ground plane is grounded... the reflector of a quad is not and is a parasitically tuned element. But more importantly, the spacing between the two will drastically affect the pattern. A quad is designed to enhance the pattern in one general direction. Perhaps if the distance between the loops were changed? I don't know. An antenna modelling guru could probably tell us. But it would be interesting to hear your results.

73 Kevin
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