[1000mp] Filters options

Thu, 3 Jan 2002 00:15:11 -0500

You have more than one issue at work here.

One is bandwidth preference by usage. What are you doing when you are using a particular bandwidth,
and what do you want to hear and what DON'T you want to hear.

In my case, 3 CW situations:

1) Casual tuning around, would rather hear more. Use the Collins 500 Hz mechanical filter in the sub
RX. That lets me hear 700-800 Hz passband. I WANT to hear a little of what is above and below.

2) Contesting: Sending CQ's. I want to hear as much as possible, EXCEPT I DON'T want to hear the
guys up and down 500 Hz from my frequency. Need for the skirts of the cascaded filters' combined
passband to go down as sharply as possible. INRAD 400 Hz in both IF's does this. Even with skirts as
sharp as this, just using the RX RIT to go up or down 50 Hz can dramatically increase the
interference from an adjacent strong station.

3) Contesting. Search and Pounce. 400 is too wide. Often get caught where the station I want is a
few hundred Hz off another station I can hear, but he can't hear. INRAD 250 Hz in both IF's gives me
a sharp knife to hear one and not the other. Others prefer the 125 Hz filter. I would use 125 for
some things if there was a slot for it.

I have a friend who uses a 1000 Hz filter for all three of the uses above and somehow manages to
separate it all in his head and only listen to what he wants to hear. I can't do that.

The other issue is a "satisfying" sound. The same friend can't stand to listen to the 250 Hz
constrained passband for long. Says after a while it sounds like someone blowing a flute in his ear.
In 1) above, I find that a "satisfying" sound for tuning around. In a contest, what is "satisfying"
changes to not hearing other stations that keep me from copying the station I want to hear.

With differences like that between operators, it is hard to recommend combinations to anyone.

The best advice is to hook up with local operators, including contest ops if contesting is one of
your pursuits, and LISTEN to how the different combinations sound on their MP's before buying.

If I had unlimited slots?

a) 6 KHz, 2nd & 3rd IF (listening in BC Band)
b) 2.8 KHz 2nd & 3rd IF  wide audio SSB QSO's
c) 2.4 2nd & 3rd IF  all other use except heavy QRM in contests
d) INRAD 1.8 2nd & 3rd IF  heavy QRM condx in contests
e)  Collins "500" Hz 3rd IF  general CW listening around.
f)  INRAD 400 Hz 2nd & 3rd IF   Contest CQ's
g)  INRAD 250 Hz 2nd & 3rd IF  Contest Search & Pounce
h)  INRAD 125 Hz 3rd IF  Weak signal, extreme QRM/N, etc, use with 125 Hz DSP

The clever among us will note that a good deal of that can be gotten by careful picking of a few
slots with dissimilar bandwidths in 2nd & 3rd IF's.

If using a pair of MP's, one radio is designated prime for each mode. The prime contains the run
frequency combination and a search & pounce combination for it's mode. The alternate contains one
leisure and one search & pounce setup for it's alternate mode. The 6K BW's can be doctored to get
the various leisure wide settings on one or the other MP.

Of course, the cheapest alternative is to be like my friend and be able to "just pick it out" in his
head. Wish he could put that in a bottle. Course that would put George out of business.

73, Guy.

----- Original Message -----
From: "f6ira" <[email protected]>
To: <[email protected]>
Sent: Wednesday, January 02, 2002 3:03 PM
Subject: [1000mp] Filters options

> Hi folks. I need the advice of the readers from this reflector about
> additional filters for my Mark V. Most previous messages told about INRAD
> filters. Have read this with great attention. According the bandwidth
> buttons NAR1 seem to will great at 500/455 hertz with 705C INRAD made
> filter. This transceiver will use often in contests i think that for NAR2 in
> 8.2 and 455 FI the 250 hertz filters will too narrow for this mode. My view
> for NAR2 should be installing the 701B ( 400 herts) in 8.2 FI and 712C ( 300
> hertz ) for 455. What you do think about this ??.
> HNY 2K2
>
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