[1000mp] Noise Blanker Mod results

[Tom Rohlfing]

Thanks to Jaakko for his hard work.  This looks like good info.  THis topic
is a little confusing because there are MP's, MarkV's, and Fields out there,
all being discussed in the same reflector group.  And I'm not sure if they
are all the same with respect to this issue or not.

Let me see if I have Jaakko's bottom line conclusions correctly.  This is
what I THINK he is saying.

1.  If you do NOT do the mod, and have the NB OFF, and have the NB level
knob turned fully CCW (or the equivalent MkV/Field menu etting), then it
does NOT hamper dynamic range.

2.  If you do NOT do the mod, your dynamic range will suffer if you turn the
knob clockwise by some unspecified amount, regardless whether the NB is ON
or OFF..

3.  WITH the mod, then when the NB is OFF, it does NOT hamper dynamic range,
regardless of the position of the level knob (or the equivalent menu
setting).

4.  Whether you do the mod or not, when you have the NB turned ON, and the
level knob turned clockwise, your dynamic range will be compromised.

So you're OK if you don't do the mod, and leave your NB level control fully
CCW when you're not using the NB.  It seems that the only advantage to doing
the mod is so that you don't have to remember to turn your NB level fully
CCW (or equivalent menu) when the NB isn't needed.

Is this an accurate summary?

Thanks and 73,
Tom / W7GT


----- Original Message -----
From: "Jaakko" <Jahla@mail.suomi.net>
To: <1000mp@mailman.qth.net>
Sent: Saturday, March 22, 2003 1:03 PM
Subject: [1000mp] Noise Blanker Mod results


> Hello
>
> I did the noise blanker mod to FT1000MpV as suggested in Tom's web-site.
> Here are the results as I promised:
> http://wnet.suomi.net/kotisivu/jahla/index.htm .
>
> There was an error in my original measurement so that the IMDR figures I
> posted were too low - sorry about that. With the help from George I get
now
> similar figures as he and Tom.
>
> However - my claim that you do not need to do the noise blanker mod to
> maintain high dynamics is still valid. You just need to keep nb OFF and
> value lower than B11/A11. Or keep nb ON all the time. My proposal is to
keep
> nb OFF and the setting low and switch nb ON only when there is an
> interference you want to suppress (makes sense...)
>
> If you do the noise blanker mod then nb value, switching it ON or OFF have
> no effect on receiver IMDR. I propose doing the mod -  it is easy to do
and
> the performance is very good.
>
> The results are based on two tone signal measurements - when you are
having
> e.g. pulse type of interference using the noise blanker will in practice
> decrease receiver dynamics more or less.
>
> Jaakko - OH8NJ
>
>
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