Hi.
I should have read down a little further. If you can derive some type of a
switching voltage, it is probably possible to develop some type of switch
that disconnects all inputs except the one you are transmitting on. To be
really safe, it might be a good idea to either short the receiver inputs or
switch in some type of attenuator as there can still be a lot of capacitive
coupling across an open switch--maybe enough to make a delicate front end
just go away. Some radios are touchy.
I had an experience with this a number of years ago when I tried to load a
Gonset G50 into an antenna that was about 30 feet from the antenna that my
Kenwood TV506 6 meter transver6ter was connected to. Well, to make a long
story short, I smoked the front end of the TV506 with the Gonset G50, which
put out about 40 watts. I think that illustrates the potential problem.
73, de Lou K2LKK
At 04:37 PM 12/20/2007 -0700, you wrote:
>that is what i was thinking too.
>Except a duplexer seems to allow for use of two transmitters and receivers
>within the same band, but not the same band pass...in other words the
>filters have to be set up so that each transceiver can only talk or listen
>on a certain band width. without the two ever crossing.
>So for instance, i could have one transceiver on 144 to 146MHZ, and another
>transceiver on 146 to 148 MHZ, but neither radio could just go where ever it
>wanted between 144 and 148 without having to reselect the band pass for that
>radio.
>I guess what i am looking for mostly, is something that will trip a switch
>on all the ports as soon as i start transmitting on one radio.
>This will keep the rf from going directly into the other radios while i
>transmit.
>And, something that has a proper distribution amplifier built in so there is
>no signal loss with multiple receivers going off one antenna...
>I basically need a multicuppler for the receive side, but one that can
>except rf going back through it from the transmitter, and that will
>instantly shut down all receiving ports while that rf is going back through.
>A multicuppler usually will receive from say 50MHZ to 2GHZ, so the receive
>is certainly wide enough.
>A duplexer has fairly narrow filtering only a few megs wide usually.
>anyway, i'm still searching for what i want.
>73
>Colin, v a6BKX
>----- Original Message -----
>From: "Steve" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Thursday, December 20, 2007 8:08 AM
>Subject: Re: multiple radios, one antenna
>
>
> > A duplexer?
> >
> > ----- Original Message -----
> > From: "Colin McDonald" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Wednesday, December 19, 2007 6:53 PM
> > Subject: multiple radios, one antenna
> >
> >
> > here is a question for the list:
> > I want to have my main VHF/UHF transceiver hooked up to my single dual
> > bander, while at the same time using that same dual band antenna for
>another
> > transceiver and a scanner at the same time.
> > I don't want to have to manually switch the antenna over to the different
> > radios via an antenna switch.
> > What i need is some sort of distribution device that will allow me to
> > transmit on either of the VHF and or UHF radios, without damaging either
>the
> > other transceiver or the scanner. And then when there is no rf being
> > transmitted, to be able to have all 3 receive properly using the one
> > antenna.
> > My question is, is there such a device availible?
> > I know about distribution amplifiers for receive, but i don't know if you
> > can transmit through those, and i also need something that will prohibit
>any
> > rf getting back into the other radios.
> > I know that any receiver that is on the same band will be desensatized as
> > soon as I transmit, but i am not concerned about that since if i were
>using
> > a separate antenna, that would occur in the near field anyway.
> > I require such a device because i can only really have one good dual band
> > antenna at any height and i have several different rigs i want to be able
>to
> > use to monitor and transmit on, as well as listen on the scanner.
> > I know that in multi-frequency systems, such as a public safety
> > organization, or even public transit, they often have multiple radios on
>the
> > same band going at the same time for dispatch or communications purposes,
> > all using the same antenna....i suspect they use some sort of tuned
>cavities
> > to prevent desensatization...
> > I need a little box that i can plug my antenna into, and plug 3 radios
>into
> > the other side and not worry about my 50 watts of rf on VHF getting back
> > into the antenna jack of the other radios and blowing out the front ends.
> > any help is appreciated in finding a solution to my wishes.
> >
> > 73
> > Colin, V A6BKX
> >
> >
> >
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.5.503 / Virus Database: 269.17.5/1190 - Release Date:
>12/19/2007 7:37 PM
> >
> >
>
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.516 / Virus Database: 269.17.5/1191 - Release Date:
>12/20/2007 2:14 PM
Louis Kim Kline
A.R.S. K2LKK
Home e-mail: [log in to unmask]
Work e-mail: [log in to unmask]
Work Telephone: (585) 697-5740
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