mpoole

Thanks to everyone who responded to my inquiry, very good info here.  I've just returned from taking the duplexer to a professional radio shop for tuning to 462.550.  The Fumie duplexer still has a 20 watt lose on TX.   It appear the Fumie is junk and the advise of the radio technician is to stay away from the cheap China duplexers.....all of them.  His minimal recommendation was a ICOM at a cost of $395.
 
I think I'm going to investigate using two antennas instead of a duplexer.  As long as I have signal separation to prevent bleed-over it will be less expensive and provide full TX power from the repeater.  We are moving forward to the next stage of our project.
 
Thanks again for your support!
Mike
WRJE502

Nice!  I'm in a mountainous area at 2150 ft running a 50 watt radio.  Because of a ridge interference that is 40 ft higher than my antenna I can't reach 1/4 mile in that direction.  As such I'm moving my repeater to a neighbor's work shop that is 120 higher than I am.   So yes, the higher the better.

Have you checked the SWR past the duplexer (checking the feedline and antenna?) Also check your jumpers, its possible you accidentally hooked swapped them and is often the problem.

RG8x isn't very good for short repeater runs let alone the length you are running, While I doubt thats causing your swr issue, it will greatly reduce the range of the repeater, especially at longer lengths. Personally I used LMR400 then upgraded to 600 which in my opinion is fine for running 30-40 feet up, though there are guys here who will demand 1/2" or 3/4" helix which for the type of install and the cost, I just dont feel its worth it.

If the SWR is good past the duplexer, then it would be reasonable to believe the duplexer is bad. Most flatpacks that I have seen are only rated to 45W for UHF band, and work best at wattages below 25W. `If you are putting 52W in you may have caused some damage to the internals, and could have damaged the repeater itself. So, I would try running low power, around 20W or so, and see if that gives you better SWR readings.

Last, I would recommend changing out the flatpack for a band pass/reject style duplexer. The difference will shock you for two reasons. #1, the Chinese flatpacks arn't made with the best quality and often have issues with them and are never tuned correctly. and 2) BP/BR duplexers seem to just work better than the flatpacks do.

Your duplexer is mis-tuned! It should be tuned to precisely the frequencies you are going to be using.
 
The entire purpose of the duplexer is to allow only a single frequency to pass with minimum loss, while supressing any other frequencies. The easiest way to explain this is with a picture. This image is from a VHF duplexer, but the principles are the same. Note that the green line represents the lower frequency of your pair and the red line represents the higher frequency.
 
It is important to note that any frequency lower or higher than the tuned frequency is quickly attenuated. This is precisely why you are losing so much power when you transmit: