Re: Opposite side band rejection ubitx V6


barry halterman
 

I did some experimenting with my V6 Crystal filter to see what I could do to improve the opposite side band rejection, if anything.
I did the Crystal can grounding that Allison suggested. My biggest gain, for me, was to change the tuning capacitors from 68 pf to 150 pf as I had five in the same smd package and the same size as the originals. I mainly operate CW so loosing a little fidelity in ssb, if there is such a thing, was no concern. The original bandpass was 3.0 khz. With the new capacitors the bandpass went to 2.1 khz. More to my liking for CW. I readjusted the BFO and seem to have improved the sideband rejection. I think that with a more narrow filter the opposite sideband is not heard too far from zero beat and the signal attenuates faster as you move further away. 
My test station to listen to the opposite sideband was W1AW last evening on both 80 and 40. W1AW can be extremely strong but I did not get to make measurements. Hopefully I can do that this evening.
So far, I like what I hear.
K3bo

On Thu, Jun 18, 2020, 5:10 PM Dale Parfitt <PARINC1@...> wrote:

Thank you Gary,

My apologies for not doing my homework. Much appreciated.

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Gary Anderson
Sent: Thursday, June 18, 2020 3:57 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Opposite side band rejection ubitx V6

 

On Thu, Jun 18, 2020 at 11:38 AM, Dale Parfitt wrote:

Hi Allison et al,

What  is the design in/out impedance of the crystal filter?

Dale,
SSB filter is 200 ohms per the circuit description
https://www.hfsignals.com/index.php/ubitx-circuit-description/
Rgds,
Gary

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