[1000mp] MP Roofing filter

[Thomas Beltran]

Blake:

> However the roofing filter requires resetting the IF gain back to its
original (non-IF mod) position.  One would need to go into the "hidden" menu
and turn the IF gain up and down each time you switched between them (ugh).

Actually, it was not as much of a difference as it might seem, or at least
on my Mark V that was the case.  My Mark V IF gain was originially set for
12 from the factory.  I set it to 9, and later 10 with the front-end mod.
The amp on the First IF filter, provides enough gain that I have it set to
11 now (one step lower than factory).  With a switchable setup, I would use
the front-end mod for the weak ones, and using 11 for all settings wouldn't
matter much.  Having used both, I don't see the settings as being so
critical.  Going from 9 to 12 in steps was barely a perceptable difference
(although 9 - 12 was a difference), so whether the gain is set for 10 or 11,
in my radio, this would not be so significant that it would "require"
resetting.

Using the Elecraft XG-1 signal generator, set to 50 mv, 11 is S-9, and 10
and 12 just slightly blinks above and below S-9.  [there was a whole thread
earlier this year on setting the IF gain - which, according to the manual,
is set so the S-1 segment just blinks - I think]   Of course proper
equipment could make these steps seem absolutely significant, but to my ear,
not much difference. As I've said before, I have a Drake R-4C that I set up
with both the stock first IF filter, and the so-called GUF-1 with relay
switching.  The experts say that the GUF-1 will absolutely change the radio
for mediocre, to a fine performer - I could not tell the difference!  I sent
the radio to Rob Sherwood, because I thought I had done something wrong.
The verdict was that everything was correctly installed, and, there just
wasn't much difference.   Maybe someone could figure out a revolutionary mod
to include an IF gain control........like the internal pot on my 75A-4.
Also, if one gets in the habit of turning on the rig holding the proper
button sequence, it is then easy to slip into the hidden menu - late at
night on 20, I have turned the gain up quite a bit to get that weak one.
Tom W6EIJ