How is the Comet CA-2X4SR antenna?

[WSCE741]

Has anyone tried testing the antenna when folded vs upright? 

I have this antenna, i was using it as a temporary base station and am looking to put it on my car now. I have a ford edge so i cant have it sitting upright all the time or ill be hitting my garage door / ceiling everyday (we have an old small farmhouse garage). Im curious though how well this antenna would perform (specifically TX) on both murs or gmrs if i ended up having to use it while it was folded down? 

[SteveShannon]

7 minutes ago, WSCE741 said:

Has anyone tried testing the antenna when folded vs upright? 

I have this antenna, i was using it as a temporary base station and am looking to put it on my car now. I have a ford edge so i cant have it sitting upright all the time or ill be hitting my garage door / ceiling everyday (we have an old small farmhouse garage). Im curious though how well this antenna would perform (specifically TX) on both murs or gmrs if i ended up having to use it while it was folded down? 

Try it. I think it’ll have a really screwy propagation pattern, perhaps mostly vertical, but without trying it you’ll never know. 
If you have an analyzer put it on first because the SWR will probably change as well. 

[WRYZ926]

I know laying the antenna flat on top of the roof is different from laying it flat in a back seat. But I know the 2x4SR does not work well when laid flat inside a vehicle. I have to agree that your propagation pattern will most likely be straight up in the air when laid flat.

[Socalgmrs]

Yea sorry to say that won’t work well at all. 

[WRXB215]

Horizontal is used a lot for HF where you get skip but I doubt it would be useful for UHF. Especially since you will loose some because of the change in polarization.

[WRUU653]

Aside from the performance issues already stated I imagine that in the folded down state it might be inclined to whip around in the wind at speeds spanking your car as you travel the highways and byways.

Okay I realize that probably wouldn’t be your use scenario. All kidding aside I would swap out to a shorter antenna while using parked in the garage, something that stays vertical but isn’t affected by the height restriction. 

[wayoverthere]

19 minutes ago, WRUU653 said:

All kidding aside I would swap out to a shorter antenna while using parked in the garage, something that stays vertical but isn’t affected by the height restriction. 

That was my thought as well. Curious what the pattern would be laid down, but in the end it boils down to folding and unfolding each time, or picking up a shorter whip.

Personally, I'd park and measure at the lowest clearance point, and go from there to see what my options were for whip length. The ubiquitous 1/4 wave is around 6" and pretty inexpensive (not much over $10 last I looked), and a solid option of you have the ground plane for it, and the no ground plane 1/2 waves are around 12", iirc

[Davichko5650]

12 hours ago, SteveShannon said:

Try it. I think it’ll have a really screwy propagation pattern, 

But won't "Some People" tell him it won't work????  But I'm with you, try it!  Be interesting to see how being folded down close to the vehicle body will affect SWR.

[dosw]

1 hour ago, Davichko5650 said:

But won't "Some People" tell him it won't work????  But I'm with you, try it!  Be interesting to see how being folded down close to the vehicle body will affect SWR.

I would have expected that laying it flat against the ground plane would cause it to reflect a lot. So I gave it a try. Standing up, at 465MHz, on a pizza-pan ground plane, it measured 1.6:1. Laid flat it measured 2.3:1. So it got worse, but not terribly so. Nevertheless, VHF and UHF FM is supposed to be vertical polarization. Orienting the antenna horizontally isn't going to really help anything except clearing your garage roof.

However, at 2m, it got much, much worse. Something like 5:1. I didn't write it down. But standing in the upright position, in the 2m band, it's down to about 1.2.1.

 

Your mileage may vary. Laying it flat against a larger ground plane, one with a radius large enough that the entire antenna is adjacent to the metal ground plane, is going to be a lot worse. Maybe bad enough that "some people" would be right. I know even in the vertical position, I was having reflection / high SWR issues when I put reflectix along side the antenna to cover the opening necessitated by a window air conditioner in sideways sliding windows.