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Author Topic: Sharing an antenna  (Read 3016 times)
KC8OYE
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Posts: 297




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« on: September 20, 2010, 07:15:21 PM »

I just got a base station antenna up. (JetStream JTB3 (Basicly a Diamond X50 copy))

anyway, I'd like to share it between my HT and my scanner.. it's it ok to use an antenna switch 'backwards' as such? (Two radios to a common antenna?)  and is there something specific I should be looking for? like a "grounds unused input" or such so that I don't start feeding 5w directly into the antenna input of the scanner?
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K5COV
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Posts: 3




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« Reply #1 on: September 20, 2010, 09:02:56 PM »

You can use a good switch either direction, it's just a switch. You should get a good one with as much isolation (at least 50-60db) and as little insertion loss as possible. The loss makes a difference with VHF/UHF, so stay away from switches that are "HF only". The ones that have a center position for ground is a good idea, but as with any antenna don't rely on it to protect you from lightning though. In my mind they are a precaution against static electricity more than anything. I have been using the ones from MFJ for years (http://www.mfjenterprises.com/Product.php?productid=MFJ-1702C). Not the very best but good for the money. I see that MFJ also has a new switch with gold contacts (!?) and slightly better specs but no center ground connection (http://www.mfjenterprises.com/Product.php?productid=MFJ-2702).

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AA4PB
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Posts: 13033




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« Reply #2 on: September 21, 2010, 04:56:24 AM »

I'd look for a switch that grounds the unused antennas. That way when you turn it around it will ground the unused radio connection. It should provide a little better isolation for the scanner while you are transmitting with the HT. Of course you've got to be careful not to key the HT when it is not selected on the switch.

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K1CJS
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Posts: 6061




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« Reply #3 on: October 22, 2010, 10:12:52 PM »

Even though you can do that, be careful to have the scanner switched off when transmitting.

I find its better to have the scanner on its own antenna--even if that antenna is a length of wire tied to its antenna connector.
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KD4LLA
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Posts: 465




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« Reply #4 on: October 23, 2010, 10:31:26 AM »

You would be far better off stringing some cheap TV coax and a bent hanger for a scanner antenna.  Key point here is, yes it can be done, but what happens when you forget to throw the switch and fry the HT or scanner?   Spend the $35-25 on separate coax and antenna instead of a switch.  I don't worry so much about grounding either.  I have had a scanner antenna (RS ground 1/4w plane) up for over twenty years and have never had any issues with lightning.  Besides, if my antenna takes a direct hit, my built in 1936 house will go up in flames too.

Mike
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