[1000mp] On-Air test for Roofing Filter check ??

[Jim W7RY]

SNIP:

As I have stated here before, and my findings were echoed in the recent RSGB
article, I feel the Inrad instructions are not correct in suggesting that
the IF gain setting in menu 9-1 be reset to the factory default value, if
you have had the Inrad IF mod in your radio previously.

The overall gain of the two stage low noise amplifier is apparently higher
than stated by Inrad, perhaps as high as 8 DB.  This permits a reduction of
the gain setting by as much as two to three numbers in menu 9-1.  Therefore,
the filter's amplifier accomplishes the same IF hiss reduction at least as
does the earlier IF mod.  Then, since the filter is narrower, it lets in
less band noise altogether.  I believe the noise floor is indeed at least 10
DB lower after the mod!  This change should be able to be noted as well by
the casual operator.  THERE IS NO NEED FOR BOTH MODS IN THE MARK V.

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Agreed!!  I did not have the IF mod kit installed in my MK-V. I did lower 
setting 9-1 from 13 down to 9. A big decrease in overall noise heard.

I did make a noise floor measurement using the MDS level. (minimum 
discernable signal). I noticed about a 8-10 dB improvement. Do I need
that much sensitivity? Most likely not. Although I was able to hear DF2PY 
on 160 meters last night (at about the +1db above lip reading level) I feel 
that the lowered noise floor did
attribute to me being able to hear him.

The beverage matching transformers are on order! I hope to get something up 
before winters end.

73
Jim W7RY
SW Washington




At 07:10 AM 12/29/2004, Mike Schatzberg wrote:
>Hello Dennis:
>
>I can see how some confusion about some of the improvements of the narrow
>roofing filter may occur.  For the casual operator, who does not know what
>IMD sounds like on the air, in the midst of a contest or pile up, the
>difference on IMD reduction may not even be recognized.
>
>Such an operator should be able to recognize reduction from whiskering
>interference from nearby very strong signals, or perhaps reduction in
>desense when using the wide 6 khz 3rd IF filter, with no 2nd IF filter (menu
>5-0 8.2-455).  Just select this option in menu 5-0, and you will hear the
>vast difference, with narrower overall bandwidth with the new 4 khz roofing
>filter and the ceramic 6 khz 3rd IF filter.  Now the overall bandwidth is
>approximately 4.8 khz, and desense from nearby strong stations far less!  I
>use this setting as my ultra low noise set up for very weak stations on 20
>meters.  Added selectivity, also with low noise can be added by
>superimposing the DSP IF filter, IDBT button, onto the 2nd IF.  This
>combination works very well indeed.
>
>As I have stated here before, and my findings were echoed in the recent RSGB
>article, I feel the Inrad instructions are not correct in suggesting that
>the IF gain setting in menu 9-1 be reset to the factory default value, if
>you have had the Inrad IF mod in your radio previously.
>
>The overall gain of the two stage low noise amplifier is apparently higher
>than stated by Inrad, perhaps as high as 8 DB.  This permits a reduction of
>the gain setting by as much as two to three numbers in menu 9-1.  Therefore,
>the filter's amplifier accomplishes the same IF hiss reduction at least as
>does the earlier IF mod.  Then, since the filter is narrower, it lets in
>less band noise altogether.  I believe the noise floor is indeed at least 10
>DB lower after the mod!  This change should be able to be noted as well by
>the casual operator.  THERE IS NO NEED FOR BOTH MODS IN THE MARK V.
>
>Even the casual operator will notice how quiet the receiver is, particularly
>with the RF gain control set back to the 1 to 2 o'clock position to avoid
>overload and to provide best fidelity on stronger signals.
>
>Happy New Year and Happy DXing,
>
>73,
>
>Mike Schatzberg
>WB2AJI
>
>
>----- Original Message -----
>From: "roofus" <roofus at sbcglobal.net>
>To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
>Sent: Wednesday, December 29, 2004 8:52 AM
>Subject: Re: [1000mp] On-Air test for Roofing Filter check ??
>
>
> > How interesting, so many have posted how well their roofing filter works
>and
> > now 1 (one) post saying he is not sure he saw a difference (non contest)
>and
> > it's "NOT TO ENCOURAGING".  I guess it could be worse, it could have been
>a
> > new IC7800 he just bought.
> >
> > Dennis KI8U
> >
> >
> > _______________________________________________
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> > 1000mp at mailman.qth.net
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> >
>
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