What power output level is the repeater station? The usual 110W? The 110W amp doesn't play well at lower power outputs. It tends to spur and the efficiency isn't great.
I'd first thought about putting a relay in the PA to twiddle with the main power output pot setting. I DO NOT like modifying the stock gear so that idea was immediately thrown out. I thought about using a couple of small relays to insert a 50 ohm attenuator in-line with the exciter to PA connection to reduce drive level which would reduce output level. The relays could be run off a wall-wort for the power fail switch over. This was somewhat attractive with the RCA connectors from the exciter to PA input. They are readily accessible and the scheme is reversible to stock. Before anyone screams, I realize both of those solutions would lead to the problem stated above. You could use two antenna relays to bypass the PA altogether and run 250 mW barefoot with the exciter. Would be very low output, but would last a very long time on batteries. For slightly higher power with the two relays you could insert a much smaller output rated PA (perhaps a GE M II 40W PA idled down) after the exciter. You probably want make sure you don't switch out a PA to no load while it's outputting power. Perhaps wait until a PTT off time frame. Any decent controller with a macro could accomplish that. As a side note, we removed our continuous duty 110W PA for servicing one time and substituted a 40W intermittent PA idled down to 20W. I don't think anyone on the repeater even noticed. Another option would be to utilize a secondary lower power transmitter (GE Phoenix?). Switch out the GE M II tx audio/ptt from the controller to the alternate TX and use one antenna relay to switch the RF over at the duplexer. Again taking care not to remove a 50 ohm load from an active transmitter. These may not be optimal, but I'd also like to hear of other suggestions. Ralph W4XE -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of drwoolweaver Sent: Tuesday, July 29, 2008 9:17 PM To: [email protected] Subject: [Repeater-Builder] Emergency Power Does anyone have a circuit to the reduce the power output of a VHF GE MASTR II repeater station when primary power is lost? I searched the messages and found some comments, but no circuit. Recommendations? David
