OT: Softrock for K3 IF

[K2QI]

Where are you finding the Softrock kits containing a 32764 KHz crystal for
the K3's IF?  I've gone to KB9YIG's website, and haven't seen anything about
ordering customized kits??

 

Tnx es 73,

James K2QI

______________________________________________________________
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

[Don Wilhelm-4]

James,

Dunno.

I got my crystal from Tony (KB9YIG), but I recall he said mine was one
of the last of the 8.215 MHz SoftRock Lite kits.
I would suggest you email Tony and see if he has any left.  It is close
to the 40 meter SoftRock RX Lite V6.2, except R6 is 22.1k. L1 is 34
turns and the primary of T1 is 9 turns.

If you can find a 40 meter Softrock V6.2 and the 32.768 crystal, you too
can have an 8.215 kHz Softrock.  I use mine with the Clifton Labs Z10000
buffer amplifier to keep the Softrock oscillator from disturbing the K3.

73,
Don W3FPR

James Sarte wrote:
> Where are you finding the Softrock kits containing a 32764 KHz crystal for
> the K3's IF?  I've gone to KB9YIG's website, and haven't seen anything about
> ordering customized kits??
>
>  
>
______________________________________________________________
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

[K2QI]

Don et al,

Thank you all for your responses.

I got an email reply from Tony KB9YIG tonight.  He states: "I have at times
provided a Lite II kit with a center frequency of 8.191 MHz.  The Lite II
center frequency noise is thus away from the K3 IF center frequency.
Several have reported that it works well for them."

Since the center frequency is 8.191, I'm assuming I won't need the Z10000
buffer amp?

Anyway, I should be able to order one from him sometime mid-January.  He
goes on to say that he's quite busy filling other Softrock orders.

Tnx es vy 73,
James K2QI

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, January 07, 2010 7:51 PM
To: James Sarte
Cc: 'Elecraft'
Subject: Re: [Elecraft] OT: Softrock for K3 IF

James,

Dunno.

I got my crystal from Tony (KB9YIG), but I recall he said mine was one
of the last of the 8.215 MHz SoftRock Lite kits.
I would suggest you email Tony and see if he has any left.  It is close
to the 40 meter SoftRock RX Lite V6.2, except R6 is 22.1k. L1 is 34
turns and the primary of T1 is 9 turns.

If you can find a 40 meter Softrock V6.2 and the 32.768 crystal, you too
can have an 8.215 kHz Softrock.  I use mine with the Clifton Labs Z10000
buffer amplifier to keep the Softrock oscillator from disturbing the K3.

73,
Don W3FPR

______________________________________________________________
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

[Don Wilhelm-4]

James,

I would highly advise the buffer amplifier.  The lack of a buffer amp
will not hurt the Softrock, but the Softrock oscillator signal will be
injected back into the K3, and can degrade the K3 receiver performance.  
If you omit it, please do not complain about strange howls and birdies
nor decreased dynamic range performance on your K3.

The IF output port on the K3 is "wide open", and will respond to 8.191
kHz as well as 8.215 (only 24 kHz away), so if the signal is large
enough, even the Hardware AGC can be activated and de-sense the entire
K3 receiver.

See Jack Smith's writeup about the K3 with the Softrock.

73,
Don W3FPR.

James Sarte wrote:

> Don et al,
>
> Thank you all for your responses.
>
> I got an email reply from Tony KB9YIG tonight.  He states: "I have at times
> provided a Lite II kit with a center frequency of 8.191 MHz.  The Lite II
> center frequency noise is thus away from the K3 IF center frequency.
> Several have reported that it works well for them."
>
> Since the center frequency is 8.191, I'm assuming I won't need the Z10000
> buffer amp?
>
> Anyway, I should be able to order one from him sometime mid-January.  He
> goes on to say that he's quite busy filling other Softrock orders.
>
> Tnx es vy 73,
> James K2QI
>  
>

______________________________________________________________
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

[K2QI]

Understood Don.  I'll pick up a buffer amp to go with the SoftRock.

Thanks for the info.

Vy 73 de James K2QI

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, January 07, 2010 9:04 PM
To: James Sarte
Cc: 'Elecraft'
Subject: Re: [Elecraft] OT: Softrock for K3 IF

James,

I would highly advise the buffer amplifier.  The lack of a buffer amp
will not hurt the Softrock, but the Softrock oscillator signal will be
injected back into the K3, and can degrade the K3 receiver performance.  
If you omit it, please do not complain about strange howls and birdies
nor decreased dynamic range performance on your K3.

The IF output port on the K3 is "wide open", and will respond to 8.191
kHz as well as 8.215 (only 24 kHz away), so if the signal is large
enough, even the Hardware AGC can be activated and de-sense the entire
K3 receiver.

See Jack Smith's writeup about the K3 with the Softrock.

73,
Don W3FPR.


______________________________________________________________
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

[Julian, G4ILO]

It's worth asking around as there are a lot of unbuilt SoftRock kits around. I think people were either frightened off by the SMT parts or they just never got around to it. Building it is harder than doing a K3 mod.

I do wonder how many people have actually tried the SoftRock on a K3 without a buffer amp to see if it is really necessary? I believe the buffer amp was originally intended for use with the K2, which does not have a steep sided crystal filter to prevent the LO getting into the IF. Don makes a valid warning about the possibility of the LO activating the hardware AGC but has anyone actually validated if that is the case?

The SoftRock is meant to be a cheap solution so it seems a bit out of proportion to use a buffer amp that costs twice the price of a SoftRock kit. I found an article here http://www.kingsqueak.org/stuff/softrock_IF_tap.pdf that shows a buffer amp that can be built from parts most people probably already have, and that's what I intend to try once I finish building my SoftRock if I find that I need it.

[P.B. Christensen]

> I found an article here
> http://www.kingsqueak.org/stuff/softrock_IF_tap.pdf
> that shows a buffer amp that can be built from parts most people probably
> already have...

His buffer consists of a pair of cascaded FET source-followers.  It would be
a good idea to measure reverse isolation of the circuit for use with
Softrock and if necessary, use a shielded enclosure if circuit layout cannot
be optimized.   Also, typical A (gain) value for a source-follower is less
than 1.0 and is often in the area of 0.5, depending on the transconductance
(gm) of the FET and the source resistance.  The overall gain is set by the
product of the two source-follower A values:

A = A1 * A2

So, it's possible to easily end up with an A value circuit loss of ~ 0.25
which represents a combined voltage loss of 12 dB which may, or may not be a
problem with the desired display resolution through Softrock.

The source resistor in a source-follower is primarily responsible for
setting the output Z and is generally chosen to be close to the reciprocal
of the gm value.  In his circuit, that's about 1K.  I would prefer to see a
much lower output Z (i.e., 50 ohms), especially if high-capacitance cables
are used for RF sampling.  It would be better to find another way to achieve
a high degree of isolation and low driving Z without that much loss (e.g.,
the Z10000B amplifier or similar) and build it into the K3.

Paul, W9AC

______________________________________________________________
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

[P.B. Christensen]

A final note:  The author of that circuit created a pseudo low-Z output
through the use of a 20 dB resistive pad.  The 1K output Z of the final FET
is feeding the low Z pad.  Other than creating a lower final source Z at the
expense of further circuit loss, I cannot imagine why he was satisfied with
a total loss that may approach 32 dB into the Softrock -- except perhaps to
build in more reverse isolation through the use of the 20 dB pad.

Considering the parts count of his circuit, there's an even stronger case
for building a low-loss, low noise buffer amp using a high-grade isolation
amp with a low source Z.

Paul, W9AC



----- Original Message -----
From: "Paul Christensen" <[hidden email]>
To: <[hidden email]>
Sent: Friday, January 08, 2010 7:25 AM
Subject: Re: [Elecraft] OT: Softrock for K3 IF

>> I found an article here
>> http://www.kingsqueak.org/stuff/softrock_IF_tap.pdf
>> that shows a buffer amp that can be built from parts most people probably
>> already have...
>
> His buffer consists of a pair of cascaded FET source-followers.  It would
> be
> a good idea to measure reverse isolation of the circuit for use with
> Softrock and if necessary, use a shielded enclosure if circuit layout
> cannot
> be optimized.   Also, typical A (gain) value for a source-follower is less
> than 1.0 and is often in the area of 0.5, depending on the
> transconductance
> (gm) of the FET and the source resistance.  The overall gain is set by the
> product of the two source-follower A values:
>
> A = A1 * A2
>
> So, it's possible to easily end up with an A value circuit loss of ~ 0.25
> which represents a combined voltage loss of 12 dB which may, or may not be
> a
> problem with the desired display resolution through Softrock.
>
> The source resistor in a source-follower is primarily responsible for
> setting the output Z and is generally chosen to be close to the reciprocal
> of the gm value.  In his circuit, that's about 1K.  I would prefer to see
> a
> much lower output Z (i.e., 50 ohms), especially if high-capacitance cables
> are used for RF sampling.  It would be better to find another way to
> achieve
> a high degree of isolation and low driving Z without that much loss (e.g.,
> the Z10000B amplifier or similar) and build it into the K3.
>
> Paul, W9AC
>
> ______________________________________________________________
> 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