Softrock performance update - Si570 capacitor error

[Walter KD0NUZ]

I see that KB9YIG's site now has a big red notice about an error in the Softrock design that degrades performance.  I think the SR63-ng has this error as well - C116 on the schematic - http://vk2zbb.com/images/sr63ng/Schematics/clock-1.pdf

From fivedash.com - 

ATTENTION:An SMT capacitor on pin 1 of the Si570 needs to be removed to comply with the NO CONNECT for this pin for the Si570 supplied with the various kits. Having this capacitor mounted on the circuit board degrades the performance of the RXTX transceiver, especially the higher frequency builds of this kit. This capacitor has the following designation for the various kits: C55 for the RXTX Ensemble transceiver, C33 for the RX Ensemble III receiver, C33 for the 6m/4m/2m RX Ensemble receiver, and C33 for the RX Ensemble II receiver.

 

I'm going to try this modification on an RXTX and my SR63ng later today...

73

Walter

[Alan]

Original Message -----
Subject: [MOBOKITS] Softrock performance update - Si570 capacitor error

>I see that KB9YIG's site now has a big red notice about an error in the
> Softrock design that degrades performance. I think the SR63-ng has this
> error as well - C116 on the schematic -
> http://vk2zbb.com/images/sr63ng/Schematics/clock-1.pdf
>

Walter,

Just one person reported this.

Personally I have been unable to confirm his findings.
It involves 50/100Hz spurs seen each side of the Si570 signal.
I see these by looking with another SDR, a Funcube Dongle, they are more prominent at 10m operating frequencies. Si570 output
112MHz+

But removing the capacitor has made no difference in two of my Softrocks.
Playing around powering the Si570 components without USB connected does seem to affect this.
I'm not sure how this can be achieved in the Mobo, I have modified my Softrocks so USB may be disconnected after setting the
frequency.

It would be interesting if checks were made before and after this capacitor was removed.
The data sheet definitely says "NC" but does the capacitor actually affect anything for you?

73 Alan G4ZFQ

[David Jones - KB9GPM]

There was a big discussion thread about this in the yahoo softrock group.  I'll have to go back and look it up to make sure I remember right.  But I think it was against the manufacturers recommendation and in some cases/bands caused problems.

David 

   KB9GPM

[tom]

Anyone still out there monitoring this group?
I am attempting to move my mobo from one PC to another and have some
issues for those familiar with Christo's PSDR software and CFGSR.

Tom

[David Jones - KB9GPM]

Well I can try to help.  What kind of problems are you having?

David

[tom]

Thanks for the response David. It's like reinventing the wheel after 4
years. I had to relearn to use Loftur's MoboControl software. I couldn't
figure out why I didn't have a second serial port for transmit available
on the new pc (which does have serial capability) and looks like I need
virtual serial port software. Also could not find skins for PSDR version
1.19.xx though I should probably ask Chrsito for that information. My
output is presently a low 2 watts max. and that could be an RXTX 6.3
transistor issue. PSDR wouldn't tune without CFGSR running but I think I
didn't check I2C adapter option.

I'm glad someone is still monitoring this group...

Tom

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Tom

[David Jones - KB9GPM]

Sounds like you got your problems all lined out.  Don't feel bad.  I haven't played with mine for about a year.  Too many other projects and toys to mess with :)

David

[marc olanie]

Hi Tom

I'm away from home... hard to reproduce your situation.

I've never used any "direct serial" control, I can't help you a lot on this subject.

2W on the output is definitely not normal. But I doubt it could come from the 6.3 itself. If the softrock has any trouble after the QSE, (or "in" the QSE) you probably won't have any kind signal out, even 1 mW.

I would probably test the Bias control circuit and the state of the output of the first driver (2N3866).

Oh, and please check the "good health" of the various transformers in the TX RF path. A short between two turn could heavily impair the signal (particularly the transformer located after the 3866) . A bad connecter filtrer could have the same effect (by the way,do you have the same troule on every band ? ).

If a filter is broken or badly connected, you'll have trouble in RX too

Hope you'll quickly find the culprit

73'

Marc f6itu

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[tom]

Thanks Marc. I got it all running on my new PC. I will check out the
driver transistor first. I have a 20 watt amplifier at the output of the
Mobo that M0RZF built and I am able to get just about 20 watts out with
the 2 watts in, so not so bad...

Tom

On 4/18/2015 10:33 AM, marc olanie wrote:
> Hi Tom
> I'm away from home... hard to reproduce your situation.
>
> I've never used any "direct serial" control, I can't help you a lot on
> this subject.
>
> 2W on the output is definitely not normal. But I doubt it could come
> from the 6.3 itself. If the softrock has any trouble after the QSE, (or
> "in" the QSE) you probably won't have any kind signal out, even 1 mW.
>
> I would probably test the Bias control circuit and the state of the
> output of the first driver (2N3866).
>
> Oh, and please check the "good health" of the various transformers in
> the TX RF path. A short between two turn could heavily impair the signal
> (particularly the transformer located after the 3866) . A bad connecter
> filtrer could have the same effect (by the way,do you have the same
> troule on every band ? ).
> If a filter is broken or badly connected, you'll have trouble in RX too
>
>
> Hope you'll quickly find the culprit
>
> 73'
> Marc f6itu
>
> 2015-04-16 18:21 GMT+02:00 David Jones - KB9GPM <djon...@gmail.com

> <mailto:djon...@gmail.com>>:

> > For more options, visithttps://groups.google.com/d/optout.

[Sid Boyce]

The leads on the 2N3866 are very short.

I got low output and a distorted waveform. A guy suggested increasing
the distance between the 2N3866 and the ground plane.

I soldered extensions to the leads and that fixed the problem.
73 ... Sid.

Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Senior Staff Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks

[tom]

Thanks Sid, I'll check that out on mine.

Tom

Tom

[VK5ZAG]

I do Check this site periodically. It seems there is less interest now in IQ stuff. Same with PSDR IQ
My own MoBo has been used faultlessly for 3 years or more and is my primary rig with 400W P.A. 160-10m with PSDR IQ and USBSDR and win7 64
PMs will be answered.

[David Jones - KB9GPM]

I started building my a couple years ago and got side tracked with family and other things.  I really need to finish it.  It had the finals, filters, and the power/swr sense board to go.  Maybe this summer I'll get a chance to catch up on things.

[Dave Matthews]

I am in pretty much the same place with mine. It is complete and
ready to mount to something. We bought a different house last year
and I haven't even started to set up a station yet.

Dave
W2IJL

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