On 2/2/2014 5:32 PM, qrv@kd4e.com wrote:
I bypassed the Murch because they are designed for 80-10m and use
roller/rotary inductors.
I run the legal limit and have used tuners with rotary inductors in all
but the early Dentrons. They did require periodic cleaning and before
the legal limit went from 1 KW DC input (600 out or about 1200PEP out)
to 1500 out, tuners only had about a third the work they do now. IIRC We
could only run a 100W on 160 So the high power, low impedance was not
what we see on 160 today.
Concern about the rotary inductor is valid, but at 1500 into the tuner,
IF and I emphasize the "if" components are appropriately sized, the coil
and contact are cleaned regularly there should be few problems.
I ran a pair of MFJ 989Cs for a number of years and other than the
occasional arc on 160 and keeping them clean, they did quite well. The
high voltage RF arcs did no visible damage, unlike an arc on the tuning
cap in a legal limit amp.
Were I running QRO as some would define, I'd reconsider.
I have the parts of a fixed vacuum cap from a several hundred KW
generator. That it had arced there is no doubt! <:-)) However I think
that cap would still have worked well even at QRO on steroids. Thing is,
it was big! and heavy! As a guess I'd say 10 to 15#, give or take and
about a foot long with a diameter of roughly 6 inches.
I said parts, as it had been dropped, losing both its vacuum and
structural integrity.
73
Roger (K8RI)
I have owned one in the past & it appeared to be well made.
One of the often overlooked Tuners are the Murch UT-1000 and UT-2000.
They have not been made in many years and sell for much less than their
more modern (and expensive) counterparts.
The UT-2000B will cover 160 - 10 and will load up the proverbial
bedspring.
They show up over on the "evil empire" from time to time.
73, Dick, W1KSZ
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