HAM Duplexer Question

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MesquiteWx

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Hello, I was wondering if anyone had any suggestions for how I could pull this off. I am trying to consolidate my antennas due to space limitations and what not and clean things up a bit. I have an iCom IC-7000 that I use as a base station. Then I have a dual band 2M/70cm iCom IC-2820H that I use both inside and in the vehicle. I have a Diamond X-300NA that I am using as a base antenna and I would like both those radios to share the same antenna. It is matched for 2M/70cm use. Now normally a duplexer would work but there is a problem with this. Since the duplexer is frequency bound I am going to lose a band on each radio. How could I share this antenna across both radios effectively?

-Thanks!
 

WB4CS

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Check out MFJ's antenna switch page: MFJ Enterprises Inc.
I believe they have a switch that can switch antennas to radios.

You could switch which antenna goes to which radio that's in use. The ones not in use would be isolated, but you couldn't use each radio/antenna simultaneously.
 

MesquiteWx

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Thanks, I have looked into some switches as an alternative. With the switches though I can only use one radio at a time correct? I was hoping if possible to be able to use both radios at the same time off the same antenna. I have separate antennas for each radio at the moment but things are getting crowded up on the tower and was trying to clean it up some and have the radios maybe share one antenna and still be able to use both radios at the same time. I am not even sure this is even possible but thought I would at least explore the option.
 

kayn1n32008

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Thanks, I have looked into some switches as an alternative. With the switches though I can only use one radio at a time correct? I was hoping if possible to be able to use both radios at the same time off the same antenna. I have separate antennas for each radio at the moment but things are getting crowded up on the tower and was trying to clean it up some and have the radios maybe share one antenna and still be able to use both radios at the same time. I am not even sure this is even possible but thought I would at least explore the option.

You are not going to be able to share one antenna between to radios in the way you want to. If you do, when you Tx on one and the other radio is hooked up, on the same band, you WILL damage to receiver of the other radio. Diplexers only work when the second radio is on a different band(a mono band UHF and a mono band VHF, using a diplexer can share a dual band antenna, or a dual band radio can share a monoband UHF and a mono band VHF antenna. Within the ham band you will not be able to share 2 VHF radios with the same antenna, or 2 dual band radios and be able to transmit and receive at the same time with both radios.


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Kirk

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I don't think a product to do what you want exists. When commercial sites combine antennas, they use combiners which are tuned to the frequencies used. All of the receivers are combined together and the transmitters are combined together on separate antennas.

It's hard to get around the problem of sending transmit power into receivers and killing them.

I'd look at adding a second tower. It's probably cheaper.
 

MesquiteWx

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Thanks guys you're right. This was the problem I was afraid of as you have stated. I didn't think there was a practical way and it was a shot in the dark. Never hurts to try in case there is a way I didn't know of which there isn't....LoL

I would love a second tower but, I don't have the room for a second one and I don't think the city would permit me have a second one. I have room on the one now, it is just cramp or at least for my style and I am kind of getting tired of looking at all the antennas so thought I would try to condense it some it possible.... I know what some are thinking. How can you get tired of having to many antennas. Lol I can live with the extra antenna for what it's worth.
 

prcguy

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I share two radios with one antenna using a Dow Key coaxial relay with 12v coil connected to the power supply on my primary radio. When the primary radio power supply is on it switches the antenna to the primary radio. When I'm not using the primary radio the antenna defaults to the secondary radio area.

There are versions of these relays that will handle 1kw or more to any frequency you would ever want to switch. Check Ebay for cheap prices.
prcguy
 

zz0468

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I once built a device that allowed multiple radios to use a single antenna at the same time. It involved a relay switching from transmitters to a receiver multicoupler, and each transmitter was switched through a multipole coaxial switch. There was a logic and relay driver board to do the controlling. It was more involved than just that, but it worked well and allowed several transceivers for different bands to share a single discone, and had extra multicoupler ports for scanners and things.

It wasn't cheap, and it was challenging to do all that RF switching with minimal loss.
 
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