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Author Topic: Multi-Purpose Dual Band Antenna  (Read 4397 times)
KC0VLX
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« on: February 25, 2011, 10:22:55 AM »

I'm considering the plunge into mobile 2/70 operation.  I'm also a Civil Air Patrol communications type with a CAP VHF transceiver that operates over 140-150 MHz.  I'd like to avoid having 2 antennas, if possible.  Is there a dual-band antenna that will cover the extended VHF frequency band with decent SWR?
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KG4RUL
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« Reply #1 on: February 25, 2011, 10:36:08 AM »

The bigger question is how do you switch the antenna between rigs?  If you leave both rigs connected to the antenna, to be able to receive simultaneously, you wil blow out the receiver of the other radio when you transmit.
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KC0VLX
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« Reply #2 on: February 25, 2011, 05:09:55 PM »

I planned to use a coaxial switch.
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K1CJS
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« Reply #3 on: February 27, 2011, 07:55:30 PM »

Given the right information and technical sheets, it is possible to tune many of the dual band antennas to transmit and receive on the bands you want them to--you just have to accept the fact that the antenna system will be slightly mismatched on both bands.

Bottom line is that you would be better off with two separate antennas if you want the full capabilities (power output wise) of your rigs.
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K0BG
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« Reply #4 on: February 28, 2011, 07:07:34 AM »

Absolutely.

The idea of using a switch is, shall we say, impractical. As stated, two separate antennas is the correct solution.

Remember too, placement is more important than the type (1/4, 1/2, or 5/8).
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VA3WXM
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« Reply #5 on: February 28, 2011, 03:32:43 PM »

Comet makes the CA-2xSR which is advertised as a more widebanded dual-band antenna for "search and rescue" use.  It claims a 140-160 MHz SWR of less than 2:1.

Realistically, a regular 2/440 dual-band antenna will probably work fine.
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K0BG
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« Reply #6 on: February 28, 2011, 03:56:51 PM »

Jeff, it is does work well, it means only one thing. Poor overall performance.
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VA3WXM
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« Reply #7 on: March 01, 2011, 08:59:56 AM »

Alan, I have no doubt.  Just pointing it out to the OP that such animal exists in ham radio marketplace.

If it were me I'd keep the CAP radio and the ham radio separate and use two antennas.
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AB2M
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« Reply #8 on: September 11, 2011, 08:54:08 PM »

I realize I'm late to this party, but wanted to add my 2 cents in case anyone else winds up in a similar circumstance.

Your average 2m antenna will generally work OK with CAP VHF frequencies (yes, even the new ones).   I use two of the same model dual-band antenna on my ham rig and my CAP EFJ and they both perform admirably.   I've used various other 2m antennas (J-Pole, Diamond 2m/440/6m/10m, 1/4 wave vertical) and had expected performance with each.   I've never thrown the analyzer on it, but I am always full quieting into the CAP repeater on low power and have excellent reception, so I haven't gone looking for a problem to solve. 

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K1CJS
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« Reply #9 on: September 18, 2011, 09:14:20 PM »

Even if you can find an antenna that would work OK, you still have one problem.  What if you key the radio that isn't connected at the time?  If you don't notice it right away, you run the risk of blowing the finals.  That one reason is more than enough to make you think twice about your decision to use a switch and one antenna.  Two antennas are MUCH better, just for that reason--protection.
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