Topics

Opposite side band rejection ubitx V6

barry halterman
 

May I ask what  the opposite side band rejection typically is on the ubitx? Does 35db seem about right?
Barry
K3bo

Evan Hand
 

It has been a while since I did the measurements, so I may be susceptible to a senior moment.  It does sound about right.  I believe I was adjusting the BFO to trade-off opposite sideband suppression with tonal quality.  I would up somewhere around that figure.  I was trying to hit 43db, but the tone quality was really bad.

FWIW
73
Evan
AC9TU

barry halterman
 

Evan, I played around with the BFO but that really did not help much and like you said the tone quality went down hill. I was just curious.
Thanks
K3bo

On Thu, Jun 18, 2020, 12:27 PM Evan Hand <elhandjr@...> wrote:
It has been a while since I did the measurements, so I may be susceptible to a senior moment.  It does sound about right.  I believe I was adjusting the BFO to trade-off opposite sideband suppression with tonal quality.  I would up somewhere around that figure.  I was trying to hit 43db, but the tone quality was really bad.

FWIW
73
Evan
AC9TU

ajparent1/kb1gmx <kb1gmx@...>
 

I got to play with a bunch of them last year and the result...

The filters vary enough that a good one can easily exceed 40db and the
average was 35db.  One I hand optimized the filter did hit 45dB.

Overall of the filters seems rather narrow and those I measured were
under 2.1KHz wide A wider 2.4 to 2.7 KHz woudl work and sound
better.  The other was soem the caps used to load/tune the fitler
were less than optimal in value.  In all grounding the cans helped
between 2-3 db in the overall shape and opposing sideband rejection.

My suggestion is unless you into building and tunign crystal fitlers 
and have the gear leave it be.  You can break it faster than improve it.

Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

barry halterman
 

Allison, as always, appreciate your input. I have noticed that between my V4 and V6 there seems to be a noticable difference. The V4 tends to be better. I might try the grounding of the cases or change the termination caps to 100pf in my V6.
Thanks
Barry
K3bo


On Thu, Jun 18, 2020, 1:24 PM ajparent1/kb1gmx <kb1gmx@...> wrote:
I got to play with a bunch of them last year and the result...

The filters vary enough that a good one can easily exceed 40db and the
average was 35db.  One I hand optimized the filter did hit 45dB.

Overall of the filters seems rather narrow and those I measured were
under 2.1KHz wide A wider 2.4 to 2.7 KHz woudl work and sound
better.  The other was soem the caps used to load/tune the fitler
were less than optimal in value.  In all grounding the cans helped
between 2-3 db in the overall shape and opposing sideband rejection.

My suggestion is unless you into building and tunign crystal fitlers 
and have the gear leave it be.  You can break it faster than improve it.

Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

Dale Parfitt
 

Hi Allison et al,

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

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of barry halterman
Sent: Thursday, June 18, 2020 2:29 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Opposite side band rejection ubitx V6

 

Allison, as always, appreciate your input. I have noticed that between my V4 and V6 there seems to be a noticable difference. The V4 tends to be better. I might try the grounding of the cases or change the termination caps to 100pf in my V6.

Thanks

Barry

K3bo

 

 

On Thu, Jun 18, 2020, 1:24 PM ajparent1/kb1gmx <kb1gmx@...> wrote:

I got to play with a bunch of them last year and the result...

The filters vary enough that a good one can easily exceed 40db and the
average was 35db.  One I hand optimized the filter did hit 45dB.

Overall of the filters seems rather narrow and those I measured were
under 2.1KHz wide A wider 2.4 to 2.7 KHz woudl work and sound
better.  The other was soem the caps used to load/tune the fitler
were less than optimal in value.  In all grounding the cans helped
between 2-3 db in the overall shape and opposing sideband rejection.

My suggestion is unless you into building and tunign crystal fitlers 
and have the gear leave it be.  You can break it faster than improve it.

Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

Gary Anderson
 

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

Dale Parfitt
 

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

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