FYI,
What i have found that work great is to use your monitor and 1 if not two
receivers. I have found that the final tune has such a sharp drop that a radio
on the port and the monitor on high gen gets it right on. One word of caution
make sure all your cables are top notch and 100 % shielded. I can't tell you
how many hours i have spent chasing my tail because of a bad shield on a
connector. Also remember to terminate all ports during tuning.
Scott
I would like to expound upon this a little.
A while back a gentleman contacted me and warned about the wording on my
suggested duplexer tuning page at:
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So I reworded it to allow some caution, but here is the real skinny.
He suggested that the tuning rod made from Invar (a material that expands and
contracts at the same rate as aluminum) would be damaged, by the arcing, from
tuning the cavity under power and load.
I agree if the cavity is not in resonance, the arcing will be significant due
to the mismatch, however when a cavity is close to resonance, arcing is
minimal.
So...... My suggestion is to use little power if retuning a duplexer to a new
frequency that is more and a few kc's from where it is now tuned, to get is
close, then peak them either for lowest SWR or for maximum power which ever
you prefer with the power you intend to use.
I use a Yaesu FT-530 handheld and a Bird wattmeter with a 5 watt slug to get
the pass side close. I then use my service monitor (IFR 1200A) and the handie
to make the notch close. I then put the duplexer in line using the cabling I
intend to let at the site and tune the SYSTEM for maximum performance.
I tune for maximum power for solid state equipment, and minimum SWR in Tube
power.
The best way is to have Bird samplers that you can let in place so as not to
change cabling lengths, but I realize not everyone has the means of doing
that.
I have used my GE Mastr Pro / II 4EF5A1 330 watt 2 meter amp into a set of
Wacom WP-641 duplexers in one of my systems for years.
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I recheck tuning on the system every 6 months UNDER POWER. I have never had a
duplexer failure due to tuning under power.
If you use your head....and common sense.... there is no problem.
Kevin
Oh yes, One other thing.....
In duplex service.... Tubes are better than transistors.....less noise.
