[1000mp] Roofing Filter Observations

[Tom Rohlfing]

Installed the roofing filter last night.  The Inrad Front End Mod was previously in place, so the installation was a cinch -- maybe a couple of hours, including making some before and after measurements.  The hardest part was disconnecting all the cables from the MP and all the other gear that was on top of it, and then connecting it all up again.

The IF gain (menu 9-1) before the mod was 10.  I left the IF gain just the same after the mod.  I generated a fairly weak ( a few dB over the noise floor) signal from a piece of gear in my shack, and measured the audio peak signal amplitude before/after using an audio spec an.  It seemed to be identical as far as gain is concerned.  But since it's a front panel control (OK, it's behind the menu), it's no big deal to change it down the road if need be.

I haven't operated it yet in any conditions where I would expect to hear the difference (crowded band), so don't know that result yet.  As a matter of fact, most of my problems lately have been that there is nobody around to talk to (CW ops are getting old and tired, I guess).  But maybe in the next contest it will prove its worth.

My only negative observation is the feeling I have that there is a little more of a "pop" when running QSK as the receiver comes back to life after each dit or dah.  It's not audible with 2.4 KHz. bw, but with 500 it becomes noticeable, and with 250 it is a bit annoying.  (In my case "500" is the stock Yaesu 500 with an Inrad 400.  And my "250" is a pair of Inrad 250s.)  I don't know if this is an AGC thing, or filter ringing, or what.  It's still fine, but I think the QSK was a little cleaner before.  That was surprising, because I read other accounts where people said they thought it helped the key click problem in their own RX somehow.  (I do have the W8JI key click mod installed.)

73,
Tom / W7GT 

CW is A1