"Mike Knudsen" wrote in message
...
In article , "Scottm"

writes:
Wow, I hadn't realized that mech filters (and maybe even xtal lattices?)
can go
sour with age.

I'm wouldn't say its with age, specifically, but use and mositure migration
appear to be the culprit. I've opened bad ones up and found breaks in the
tiny spot welds that attach the wire to the disks. I assume that either a
good solid jolt (read UPS drop test) or the constant minute vibrations the
filter experiences could do this. I have also opened them up to find
moisture migration that has curroded or rusted the wire and disks. Any
change in the spacings of the disks will dramatically change the filter's
charactoristics.


Presumably this would happen in receivers as well -- now maybe I know why
some
of my BA RX sound better on SSB than others? Though all are more than
acceptable.

Given a transceiver, where the same filters are used in tx and rx, if most
received SSB signals sound good, cna you assume the tx side is good also?
Not
counting problems in the diver and final, of course.

Yes. But sometimes it really hindges on the ear of the critic as well as the
mic response. You can lose a couple hundred cycles on receive and still
think that it sounds OK. You can lose a couple hundred cycles on TX and it
will still transmit but not sound nearly as good as it should. This is
particularly true with the S lines that use a 2.1 KC filter. You lose 200
cycles on the lower side and now your bandwidth is only 1.9 KC and sounds
very tinny. Conversely, however, the opposite sideband sounds great because
it has widened its passband. Also, when you transmit you are being compared
against every other transmitter. When you receive, everyone is going to
sound equally broad or narrow to you unless you compare it directly to
another receiver.

One final point, shifting of the 455 IF crystals can cause a similar result.
If they drift off frequency, they will shift the IF. If they shift the
lower too low or the upper too high it will cut part of the response the
same way that a change in the filter will.

I have only one Collins set, a KWM-2, which makes any SSB signal sound
terrific. I've had goon on-air reports from it, so I guess its filter is
hanging in there.

The KWM-2 is a great radio. I have a RE 2A and love it.

73, Mike K.

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