Ray Hughes wrote: > I know that a duplexer I was looking at can fit into the chassis of the > GR1225. I believe it needs 4.5MHz separation between the frequencies which > should not be to big of a problem to get. > > > > I understand that the GR1225 has either a 25 or 50 watt output so > programming to the lower level should take care of one of the problems, I > hope. > > > > The only other radios that would be included in the Comm Van would be a 2 > meter Amateur Radio and a Marine Band radio, neither which should be > transmitting very much. > > > > The repeater would be our main radio used. > > > > One question that I did not realize and want to clarify is about the GR1225 > being a 16 channel radio. Are you saying that if a duplexer is used, it can > only be programmed for one RX and 1 TX freq and the other 15 channels are > worthless?
Yes. The duplexer is a very narrow device, by necessity. It likely will not allow varying more then 50-100 KHz from where it's tuned. So, for 155.1, 155.2 or 155.0 will be an extreme. Anything further away than that will not pass. > I guess that if this is the case, I would need to find a switch that would > allow me to bypass the duplexer and use the radio as a standalone unit. Will > this work? No. Some may suggest a pair of coax relays, one on the transmit leg and one on the receive leg. Don't do it! It will cause isolation problems as signal leaks across the relay contacts. There is no such thing as a coax relay with the isolation necessary for repeater use. > Also, is there a control head for the radio so I would not have to use the > Chassis front panel to operate the radio? This way, I could mount the radio > and Duplexer in a different type of chassis. > Maybe. Or at least an 'extended local' control to give you mic, speaker, and repeat on/off. (You need a way to either turn it off altogether or disable the repeat function quickly in case there is a problem.) My suggestion would be to have another mobile to use for any other freqs you may need other than the repeater itself. There probably still are some radios that are certified for both commercial (part 90) and marine. ------------ Jim Barbour
