[Yaesu] Yaesu AD-3 Duplexer Question

[Scott L.]

I have a Yaesu AD-3 on my FT-847 to use a dual band antenna, Diamond X-200A, and I have been having some problems with it.  For some reason if I transmit below 145 MHz it presents a high swr to the radio and the FT-847 will only produce about 10-15 watts out.  For example, a local repeater is on 145.110-, so I transmit on 144.510 and then the problem shows itself.  I don't have any trouble across the rest of 2m, and on UHF it doesn't present any problems.  

I checked the antenna with an SWR meter inline, no duplexer just straight from the 2m antenna connector to the swr meter, and all is well, about 1.2-1 SWR at 144.000MHz and the radio produces the full 50 watts.  With the Duplexer inline I get about 2.5-1 on the SWR and about 15-20 watts out.  I tried different antennas despite knowing that the Diamond is fine with the same results, I took the radio to my work bench and verified full power into a dummy load on all bands and more importantly from 144-145 MHz where I have been having the problem, so it appears to just be SWR related since the FT-847 senses the SWR and reduces output accordingly.

So that leaves the Duplexer as the culprit.  Is there anyway to adjust (tune) the VHF side of this Duplexer??  The passband seems to be a bit high, from 145-155 it will pass without any adverse problems, I tested from 148MHz to 155MHz using the DOT frequencies and my business mobile, which uses the usual red, purple, blue, and green dot frequencies, I don't have any further test equipment and my FT-847 is un-modified as it will always remain!  So I cant do much for extensive testing on the VHF side.

Anyone have the same problems?  Any suggestions other than sending it back to Yaesu?  I would like to avoid sending it out for repair or bringing it somewhere to be checked at all costs.  I cant afford to have someone work on it, and its not under warranty with Yaesu anymore.  Does anyone know how to service this thing and get it back to the low end of 2m?

Thanks and 73,

Scott, KB0NLY