At 8/30/2008 08:19, you wrote: >Bob - >Tell us more about how you did that & what filtering/protection you used? >(I've been thinking of a very similar project)
Any ol' crossband diplexer to split between the 2 meter & 440 bands (well, not quite "any": must have connectors on the unit - no pigtail leads, which will cause desense). In this example I used an Austin diplexer, though I found the loss to be higher than the Comet/Diamond equivalents. The antenna port of the 2 meter duplexer of course went to the VHF side of the diplexer. On the UHF side, I used a wide split mobile duplexer to multiplex in the 420 TX. That duplexer was tuned to notch 440 & 445 on the low freq. port & notch 420 on the high freq. port. The high freq. port of that duplexer went to the antenna port of another notch duplexer that duplexed the 445 TX & 440 RX. A splitter or 10 dB coupler went on the RX port of that duplexer for the 439 MHz link RX. There were also pass cavities on both UHF TXs & on the low freq. (RX) port of the 440 duplexer. The 439 link RX & 440 main RX freqs. were close enough that I could tolerate the small additional losses on the 439 channel that were due to the pass cavity being tuned to 440. Bob NO6B
