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Author Topic: Multiple antennas and SWR?  (Read 503 times)
KG4LJF
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Posts: 15


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« on: May 28, 2001, 10:23:30 PM »

Ok, here's the deal. I have a 3' magnet mt. CB whip on my truck cab.

I want to put me a 1/2 or 1/4 wave 2M ham antenna up there with it.

Is it going to be possible to keep both antennas' SWR within a good performance range?

If not, what alternatives do I have so I can Ham and CB at the same time without affecting either radio's SWR?

Email if ya want. Thanks well in advance.
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VK2GWK
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« Reply #1 on: May 29, 2001, 05:57:06 AM »

Obviously in the US you do not need to need to know any antenna theory to get a license......
Antenna's do influence each other, so keep them apart as far as possible. On a truck cab you will not have much choice. So put the CB antenna on one side and the VHF one on the other.
The SWR is only an indication between the mismatch in impedance between the antenna and the feedpoint and/or cable. This impedance is influenced by nearby objects, size of the ground surface e.a. So move the antenna's around on the cab to get minimum SWR for each.
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WB6BYU
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« Reply #2 on: May 30, 2001, 03:34:25 PM »

If you use a 1/4 wave 2m antenna, there will be relatively little
interaction as long as the antennas are not too close together.
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RobertKoernerExAE7G
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Posts: 1435




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« Reply #3 on: May 31, 2001, 05:50:07 AM »

Take down the CB antenna.
Install your new ham antenna.  Adjust the ham antenna for minimum SWR.
Re-mount your CB antenna.
Check the SWR on your ham antenna and CB antenna.
Remove your CB antenna.
Have fun with ham radio.
When I first went from CB to ham, I had difficulty not using CB jargon -- I sounded like a CBer on two and ten meters.  It didn't go over too good with hams.

No joshing Josh, don't do both at the same time!  The receivers won't be to happy if you do.

Consider changing the info on your profile page, untill you find some aspect of haming you especially like.  

have FUN
Bob -- haming for 2.2 sun spot cycles
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W7DJM
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Posts: 1




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« Reply #4 on: June 24, 2001, 09:43:36 PM »

On business vehicles with various FM systems, you will routinely see several antennas for different systems mounted along the roof of a car, SUV, pickup, etc.   low band, high band VHF, UHF, and Cell antennas can and do all co-exist.  If the front end of the radio is of ANY quality, the Q and tuning of the antenna(s) off the band in use will reject the unwanted signal.  

It may in some cases affect your installation, but I'm betting it wont
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