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Hi all
I'm wanting to work satellite from the car. I have an arrow antenna at the moment, but just wondering how people feel about a 1/2 wave ground plane mounted on a vehicle. Obviously not going to outperform the arrow, but it would be a whole lot easier for the high passes. Grey nomad here, and quite often out of telephone range. I will also be running APRS via sat, so any suggestions on antenna solutions would be gratefully accepted.
vk6mmm@qsl.net
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OK, so the first thing I'd say here is that most dualband 2m/70cm antennas are a half wavelength at 2m. The problem comes with antenna pattern nulls at higher elevations, particularly on 70cm. I'd be more inclined to look at either a halo-type antenna for each band or a turnstyle, both of which are quite easily homebrewed.
Secondly, yes you can do it, but I'd be concerned about somebody charging down the highway at 100kph+ focusing on a satellite contact, playing with their knobs and not watching for me as a fellow road user.
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(20-11-2021, 10:01 AM)VK3DXE Wrote: OK, so the first thing I'd say here is that most dualband 2m/70cm antennas are a half wavelength at 2m. The problem comes with antenna pattern nulls at higher elevations, particularly on 70cm. I'd be more inclined to look at either a halo-type antenna for each band or a turnstyle, both of which are quite easily homebrewed.
Secondly, yes you can do it, but I'd be concerned about somebody charging down the highway at 100kph+ focusing on a satellite contact, playing with their knobs and not watching for me as a fellow road user.
Yep, I agree, too many distractions alright............ no I mean, stop and work the sat. I will also have a caravan in tow so setting up on a tripod is another option as I can just run coax out the door
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(21-11-2021, 06:15 PM)VK6MMM Wrote: Yep, I agree, too many distractions alright............ no I mean, stop and work the sat. I will also have a caravan in tow so setting up on a tripod is another option as I can just run coax out the door
For /P operation, your options open right up, from a handheld arrow-type yagi, to a fully automated system on a tripod (BTW, the Aldi bike workstands work really well). It really depends now on your budget and how much manual input you want to have. You can do it with unity gain antennas (halo, turnstyle, etc.), but a bit of gain really helps.
You can buy a dualband yagi from China via AliExpress for around $150 incl. GST, or go the genuine Arrow or similar.
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Actually, the turnstile has good response when the satellite is high in the sky, and is relatively poor when the satellite is at low angles, sort of reverse of the vertical ground plane. 73 Joseph
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Hi
An antenna well suited to the application is the Quadrifilar Helix Antenna as it is designed for satellite use. It does not have a null above it as usually found with vertical antennas which does not help when the satellite is directly overhead.
Some more information on the Quadrifilar Helix Antenna can be found at
https://www.rish.kyoto-u.ac.jp/digitalbe..._Guide.pdf.
73s
Igor
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Used to work MIR in the mid 90's using a dual band vertical on the car.
Diamond SG7500 or SG7700. Something like that. Was a while ago now
