two uhf's on one antenna

Submitted: Sunday, Apr 23, 2006 at 17:26
ThreadID: 33171 Views:2051 Replies:4 FollowUps:6
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hi gang

i have two uhfs in the 4by one acts as a spare in case one dies.

what i would like to know is can i have them both going to the same antenna via a splitter.
i dont intent to have both on at the same time but am concerned that the transmitting one my damage the other if the go via a splitter.

one is a 5watt the other 35 watts.

cheers
gra
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Reply By: Mad Dog (Australia) - Sunday, Apr 23, 2006 at 17:50

Sunday, Apr 23, 2006 at 17:50
Low loss coaxial switches are available, just make sure it's suitable for the frequency. If you have easy access to the back of both radios it would be cheaper to just unscrew the coax from one radio and connect to the other.
AnswerID: 168608

Follow Up By: Member - George (WA) - Sunday, Apr 23, 2006 at 19:09

Sunday, Apr 23, 2006 at 19:09
35 watts UHF ?? Where do you get one of them. I thought 12 watts was max. legal output, but I could be wrong
Cheers
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FollowupID: 423975

Follow Up By: hl - Sunday, Apr 23, 2006 at 19:32

Sunday, Apr 23, 2006 at 19:32
Hi,

On UHF CB, the maximum power is 5 Watts.

cheers
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FollowupID: 423983

Follow Up By: mcgra (VIC) - Sunday, Apr 23, 2006 at 19:37

Sunday, Apr 23, 2006 at 19:37
its a motorola unit

exgoverment same as the ones in the police cars i believe.

it can be set to a max of 40 watts with 100 channels

i have one mounted in the back and the other in the roof console so cables run under the floor coverings.

i will look into this channel selector, i saw one on ebay for 3 units to one anntenna but it was way to big for what i wanted

gra
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FollowupID: 423985

Follow Up By: Mad Dog (Australia) - Sunday, Apr 23, 2006 at 20:11

Sunday, Apr 23, 2006 at 20:11
two postion switch

tinyurl.com/qevk7
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FollowupID: 423996

Reply By: Mad Dog (Australia) - Sunday, Apr 23, 2006 at 19:26

Sunday, Apr 23, 2006 at 19:26
Probably a converted commercial or Ham rig. I've got one here that would do 45 if modified.
AnswerID: 168625

Reply By: Robin - Sunday, Apr 23, 2006 at 19:40

Sunday, Apr 23, 2006 at 19:40
Hi Gra

Can't do it with a splitter , because as you suggest power from one will damage the other.

It can be done automacitally using devices known as directional couplers which couple energy in the forward direction and cancel it out on a their 3rd port.

While there are low cost and broadband TV types devices available they are really meant for receiving , and would be marginal on 5watt and would be over powered by 35watt.

Robin Miller

P.S.
5 watts is legal max on UHF but there are many modified units around and commercial units that run a lot more power. While a few more watts
can be handy is basically not worth running a lot more power than the person
you are talking to because as long as both units are up to scratch you might send out a strong signal but can't here there weak reply signal.

I would go so far as to say that often in practise your range can be effectivily
reduced by using a high powered rig unless you are talking to a mate also with a high powered rig.

The reason for this is a little strange but its because primarily high powered units
are generally moded commercial units. Contary to what some believe commericial units as a class do not have more sensititive receiving sections to match the higher powered transmitter side.

Generally they are more concerned with reduction of interference effects with cute names like intermodulation etc. So actual receiver sensitivity is often less.

AnswerID: 168627

Follow Up By: Mad Dog (Australia) - Sunday, Apr 23, 2006 at 20:09

Sunday, Apr 23, 2006 at 20:09
Higher power is handy for hitting a distant repeater Robin.
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FollowupID: 423993

Follow Up By: Member No 1- Monday, Apr 24, 2006 at 08:01

Monday, Apr 24, 2006 at 08:01
they are also handy if one is part of a group running high power units
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FollowupID: 424048

Reply By: Member - Mike DID - Monday, Apr 24, 2006 at 16:19

Monday, Apr 24, 2006 at 16:19
You could connect your "spare" transceiver to a low-gain antenna inside the car - get a CB Handheld antenna with a BNC plug and plug it into a coax cable with BNC-UHF adapter.

This way you can use the 2nd CB to monitor a second channel reliably (scanning means you may miss a signal)

e.g. one on Ch11 and one Ch 40

Mike
AnswerID: 168720

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