Should duplexer be tunnd for maximum output

[Flameout00]

I have a few Motorola GR1225'S and was doing some experimenting with one. I have a cheap spectrum analyzer and thought I was getting the (flat pack) duplexer tuned pretty darn close. On low power, the r1225 is putting out about 23.7 watts directly from the radio and was only about 15 watts from duplexer. I realize there is always some loss when going through a duplexer

I was curious about making some adjustments while I was actually transmitting (into the dummy load), and found just making some tiny adjustments on the duplexer that I was able to get that output to 19.8 to 20.4 watts
Which leads to my question. Should a duplexer be tuned for maximum output, and is using this method ok, or just go by what the spectrum analyzer is saying is good? I really don't know enough about this stuff, but just enough to be dangerous. On the rx side, I just relied on what the spectrum analyzer was telling me

 

[prcguy]

You don't tune a flat pack notch duplexer for max output, you tune the notches for maximum attenuation at the desired frequencies. For that you need a two port analyzer or spectrum analyzer with tracking generator or service monitor with appropriate option. If you tweaked anything on your flat pack its tuning is ruined and you can't get it back, its impossible without proper test equipment.

The only kind of duplexer you might be able to tune for maximum output and best receive is a pass only type and even then you want the proper test equipment to do it right.

 

[Ubbe]

When fine tuning always do that at the site with the antenna connected. Use a T-connector on the antenna coax that has a 30-40dB attenuation to a signal generator and set the level to get a noisy signal at the receiver. Have a power meter connected in the antenna coax.

Then you can tune any filter to max power and max reception. Usually you can't get much better than 20W to the antenna from a 25W transmitter and sometimes have to settle for 15W to not ruin the reception.

You can do a coarse adjustment at home with just the filter. First set max signal thru RX-ant and max for TX-ant. Then set max attenuation for the TX frequency for the RX-ant part and max attenuation for the RX frequency in the TX-ant part of the filter. Then check back and forth between the first and second procedure. With a VNA type of device you can see the notch as you tune as well as how the bandpass tuning moves, and that's a big help if the filter isn't even close in its current tuning to the frequencies you are using.

Those GR type of Motorola repeaters use standard mobile radios, so isn't top of the line performing for repeater use, so that 15W to the antenna are probably what can be expected. It's a totally different quality if you use MTR or MSF or those kind of models that are designed for real repeater use.

/Ubbe