I wanted to go UHF from the start, but until 2 days ago I was unable to locate info on backyard UHF pairs. info which I now have. the packet rigs are on 144.39 and 145.05, so not quite exactly 600kc separation.. I use the TNC-X and it does not have a "hold-off" input to sync with other devices without making modifications either in hardware or software, so I'm probably just going to filter it up real good and test with a spectrum analyzer to make sure all the intermod products are well suppressed.
_____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Brown Sent: Friday, November 02, 2007 9:07 AM To: [email protected] Subject: Re: [Repeater-Builder] UHF Radio recommendations ?? John, for your application I would suggest buying a GE Mastr II mobile UHF radio and modifying it for repeater use. It is very simple to configure, and all the info you will need is on the repeater-builder site. I have several of these units in service and have been very pleased with the results. If you do not care to do the modification yourself, purchase one of these units from the repeater-builder folks. In my experience they far out-perform the Hamtronics type units so far as reliability and desense rejection is concerned. I think you are on the right track for your system. As you might remember, I suggested this solution in the first place. Use a standard VHF duplexer to couple the two radios to the VHF input of a Comet or Diamond band splitter and couple the UHF duplexer for your repeater to the other port of the band splitter. A dual band antenna will complete the RF configuration with a minimum of difficulty on the RF side. To avoid complications on the two packet ports, I would configure the system to not allow transmission on both radios at the same time. Packet TNCs have an input to prevent transmission when a signal is being received, and you should be able to arrange logic to OR the receive signal DCD with the PTT on the other radio and supply this to the TNC as the DCD signal. Do this for each TNC, using the other TNC PTT signal. This will avoid the possible intermod product you will generate with the two transmitters keyed at the same time. If your two packet frequencies are exactly 600 kHz apart, the other 2 meter repeater owners in the area will apreciate it also. 73 - Jim w5ZIT John Barrett <[EMAIL PROTECTED]> wrote: The major problem I was having is resolved. I've finally got a UHF backyard pair for my portable repeater :-) No more hassling with trying to pack 4 radios into 1mhz of VHF bandwidth :-) Since there isn't a way to look at receiver specs and figure how much isolation is really needed, here I am asking - what is my best bet for radios to build a UHF repeater? I'm currently looking at a Hamtronics receiver/exciter pair with separate PA, but I'm pretty much open to anything I can get at a reasonable price (300-400 for both RX and TX, PA extra if needed). The repeater controller I will be using has PL built in, so the radios don't need it. I would prefer 50 watts or better output, 100w max. Size is important. I've only got about 16" of depth to mount this in, though there is a way I can get bigger than that if absolutely necessary. If the equipment recommended has any "front panel" controls, it needs to be 16" or less front to back. If no controls, then I have a lot more freedom in mounting. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
