Re: scopeing filters for eventual diversity receive.

Posted by Brett Howard on Mar 28, 2010; 7:24pm
URL: http://elecraft.85.s1.nabble.com/scopeing-filters-for-eventual-diversity-receive-tp4810767p4814399.html

Why use the S-Meter for this?  Depending on where you are in that S-Unit
that can make you miss the center.  What you need is a relative dB
measurement.  Turns out that the only piece of test equipment that you
need is a K3.  

Center the signal in the passband.  Then hit disp and use VFO to get to
the AFV menu item.  Let it settle on a value and then turn clockwise one
more click.  You should then see 0dBV.  Then as you adjust things you
can go up and down until you find the -3.0dBV points of the filter.  Or
you can test to the two -6dBV points and then calculate the mean of your
two points.  Just as simple but less error prone.

~Brett (KC7OTG)

On Sun, 2010-03-28 at 16:10 +0100, Dave, G4AON wrote:

> Inject a clean signal to the K3, around S5 - S7 in level, go into the
> CONFIG menu, adjust the filter offset (FLx FRQ) by rotating the main
> tuning knob until the signal drops one S point then adjust it to the
> other side until it again drops one S point. Set the offset to the
> middle of the two extremes.
>
> My 400 Hz 8 pole filter appeared to have more insertion loss than my 250
> Hz 8 pole, setting the offset solved the apparent additional insertion
> loss. My settings are -0.07 for the 400 Hz and -0.05 for the 250 Hz.
>
> 73 Dave, G4AON
> K3/100 #80
> -----------------------
>
> How are you testing for offset? Sounds like I should check the offset on my
> 5 and 8 pole filters.
>
> 73,
> N2TK, Tony
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html