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Anyone make a VHF/VHF duplexer?

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N7SAC

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I would like to run two VHF radios into a single antenna in my vehicle. Is there anyone out there that makes a VHF/VHF combiner or duplexer? If not I guess I'll just have to drill another hole :)


--Scott
 

N8IAA

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I would like to run two VHF radios into a single antenna in my vehicle. Is there anyone out there that makes a VHF/VHF combiner or duplexer? If not I guess I'll just have to drill another hole :)


--Scott
Looks like you'll have to get the drill out. I checked Diamond and Comet websites. No VHF/VHF duplexers or triplexers. Unless someone out there knows of another company that makes them up.
Larry
 

AK9R

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I would like to run two VHF radios into a single antenna in my vehicle.
Are you wanting to have two VHF radios that transmit from the same antenna? If so, then there's no easy answer. You'll need an antenna relay that cuts out the feed to one radio when the other is transmitting. Otherwise the transmitting radio will seriously overload the receiver of the other radio. If the frequencies are far enough apart, you could use pass-reject style of cavity duplexer like is used on repeaters, but they typically have very sharp tuning, so you'd lose the frequency agility of your radios. Oh, cavity duplexers for VHF are pretty big. A single cavity is typically about 4 inches in diameter and about 24 inches long. Also, again if your frequencies are far enough apart, there's a company in Canada called DCI (http://www.dci.ca/) that makes some nice RFI filters that might be sharp enough to block one radio from getting into the other.

If both radios are receive-only, a multicoupler would work. Some of the scanner dealers sell the Stridesberg (sp?) multicoupler. You could also do it on the cheap with a cable TV splitter.
 
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N7SAC

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I would not be transmitting at the same time however I would like to be able to monitor with one while using the other. Otherwise I would just use a switch.
 

zz0468

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If you're going to try the relay, you'd also want to add a sequencer to the PTT circuits of the radios to delay keying them until the relay switches. It wouldn't be expensive to come up with a scheme to allow two radios to share a single antenna, so long as you're content that one radio is deaf while the other is transmitting. A couple of antenna transfer relays and some semi-complex switching circuits would make it transparent to the user.

dbSPectra sells a control station combiner that will do exactly what you want, but it's going to be in the multi-thousand dollar class.

You're really just better drilling another hole.
 

N7SAC

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Thanks for all the info!

I think I'll probably just drill that other hole. I have 1 at the front of my Suburban and 1 at the back. The one up front is for VHF and the back one is UHF. I'll probably drill one in the middle and move the UHF antenna there. That way I have some decent space between the two VHF antennas.

--Scott
 

AK9R

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Three antenna mounts on a 'Burb? That's almost nothin'. You have plenty of roof space. I have ten NMO mounts in the roof of my Expedition. Once I drilled the first hole, I figured I better plan for expansion. Only using six right now.
 

prcguy

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Shakespeare makes an RF sensed latching antenna relay that connects two VHF radios to one antenna and whichever on you transmit on gets the antenna connected. These show up on Ebay all the time for about $30.
prcguy
If you're going to try the relay, you'd also want to add a sequencer to the PTT circuits of the radios to delay keying them until the relay switches. It wouldn't be expensive to come up with a scheme to allow two radios to share a single antenna, so long as you're content that one radio is deaf while the other is transmitting. A couple of antenna transfer relays and some semi-complex switching circuits would make it transparent to the user.

dbSPectra sells a control station combiner that will do exactly what you want, but it's going to be in the multi-thousand dollar class.

You're really just better drilling another hole.
 

n8emr

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Oct 20, 2005
Messages
498
You can find in marine (boat) catalogs RF sensing devices but when you switched to radio 1, radio 2 has no antenna attached so you cant transmit or receive, When you key radio 2 radio 1 is now dead. It works geat if you have radio's in two location such as an up or lower helm on a boat or driver position and rear of RV but doest work well if you want both radio's active. 2 antennas is the best solution .
 
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