----- Original Message -----

From: kd5nwa

To: softrock40@...

Sent: Wednesday, September 21, 2005 6:18 AM

Subject: Re: [softrock40] Re: DSP Image Rejection problem and some thoughts

Possible ground loops? Feed the power to the device from an
independent floating power supply and see if the gunk in the center
of the band goes down. Should not be too hard to try out, I would do
it myself but I have not received my order yet. Better yet supply the
power from a set of batteries.

>Ahh the small board -- good question as to why is it so dang small -- I
>think one of Tony's original goals for the gizmo was more of a
>demonstration vehicle than an experimenter vehicle.?? I for one wish it had
>more working room, but I will say the experience has vastly improved my
>soldering and rework in small places.
>
>The central hump you're seeing around 7.056 is normal.? The gunk you're
>seeing around this is a consequence of the software architecture.? What is
>happening is that the hardware takes the swath of RF centered and 7.056 and
>downconverts? it such that 7.056 is essentially at DC.? Also down there
>near DC is noise and 60 hz (and its harmonics) hum.? When one tries to tune
>down near 7.056, the local software oscillator will be down in the 100's of
>hz's.? The output of this will be Software LO +/- 60 Hz (and
>harmonics).???? Things will always be a bit messy near the center frequency
>-- quieter less hummy sound cards can help, but I don't believe there's any
>practical way to get rid of all the gunk in the middle.
>
>If you want to check out the hardware sans computer, and have a signal
>generator and a scope you can put in a -30 dbm signal at 7.050 or so into
>the antenna.? Look at the audio output on the I and Q channels -- it should
>be about 6 khz (7.056 - 7.060) and on the order of about 0.8 Vpp or so
>(don't take my nums as precision numbers, they are all from memory).? The
>thing to look at is if both the I and Q channels are comparable in
>magnitude -- if one is half the other something is not quite right in the
>hardware.? You can also take a look at the phase relationship -- it should
>be about 90 degrees between teh two channels.? While you've got the scope
>out check the clocking signals to the FST3126.? If you've got a generator
>and no scope, you might be able to compare the two channels with a good RMS
>voltmeter.
>
>One last thing to check -- make sure you're using a sound card with a
>stereo input.???? Using a mono mic in input would give the symptom of not
>being able to null the image.
>
>Hope this helps.
>
>Regards,
>
>Bill (kd5tfd)
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>


--
Cecil
KD5NWA


I fail to see why doing the same thing over and over and getting the
same results every time is insanity: I've almost proved it isn't;
only a few more tests now and I'm sure results will differ this time
...

Ahh the small board -- good question as to why is it so dang small -- I
think one of Tony's original goals for the gizmo was more of a
demonstration vehicle than an experimenter vehicle. I for one wish it had
more working room, but I will say the experience has vastly improved my
soldering and rework in small places.

The central hump you're seeing around 7.056 is normal. The gunk you're
seeing around this is a consequence of the software architecture. What is
happening is that the hardware takes the swath of RF centered and 7.056 and
downconverts it such that 7.056 is essentially at DC. Also down there
near DC is noise and 60 hz (and its harmonics) hum. When one tries to tune
down near 7.056, the local software oscillator will be down in the 100's of
hz's. The output of this will be Software LO +/- 60 Hz (and
harmonics). Things will always be a bit messy near the center frequency
-- quieter less hummy sound cards can help, but I don't believe there's any
practical way to get rid of all the gunk in the middle.

If you want to check out the hardware sans computer, and have a signal
generator and a scope you can put in a -30 dbm signal at 7.050 or so into
the antenna. Look at the audio output on the I and Q channels -- it should
be about 6 khz (7.056 - 7.060) and on the order of about 0.8 Vpp or so
(don't take my nums as precision numbers, they are all from memory). The
thing to look at is if both the I and Q channels are comparable in
magnitude -- if one is half the other something is not quite right in the
hardware. You can also take a look at the phase relationship -- it should
be about 90 degrees between teh two channels. While you've got the scope
out check the clocking signals to the FST3126. If you've got a generator
and no scope, you might be able to compare the two channels with a good RMS
voltmeter.

One last thing to check -- make sure you're using a sound card with a
stereo input. Using a mono mic in input would give the symptom of not
being able to null the image.

Hope this helps.

Regards,

Bill (kd5tfd)






Yahoo! Groups Links

Yesterday I asked for help with the following: Has anyone else had a problem getting PowerSDR to run? When I start PowerSDR the logo comes up but when it says it's initializing DSP it hangs and never does anything else.

Bill Tracey got it on the first try when he said: After initializing the DSP the code initializes the parallel port and then PortAudio -- any chance some other app is using the parallel port?

Turns out my parallel port is not working. Nothing is connected to it so I hadn't noticed. Don't have it fixed yet but I'm hopeful. Thanks Bill.

73,
Nick Brown AB0WE

The radio went together fairly easily, though I'm at
a loss to figure out why an experimenter's radio is
jammed onto such a small board. This might be OK for
a production rig, but some room would be nice to
experiment.

That said, the radio works except there is no image
rejection and the DSP image rejection controls do
nothing. The instructions say, "If the image cannot
be nulled at least 50 db, then a problem exists..."
Well, some guidance would have been helpful.
Especially, given my opening criticism.

I am reluctant to tear into this think quite yet as
there is not a lot of room to work. I originally
thought it may be a transformer mis-wiring on my part.

Again, we're talking an experimenter's radio on 40
meters where things are relatively less critical than
other bands, so a little larger toroid with more room
to make changes would make it a lot easier.

I'm hoping when I fix the image problem that all
that 7.056 +/- 5 khz energy is going to at least be
diminished. 7.056 is S5. 7.051/7.061 are S3.

Anyway, I have no doubt the problem is my error. I
just want a little direction so that I can minimize
stress on the board.

Eric
KE6US
www.ke6us.com

The radio went together fairly easily, though I'm at
a loss to figure out why an experimenter's radio is
jammed onto such a small board. This might be OK for
a production rig, but some room would be nice to
experiment.

That said, the radio works except there is no image
rejection and the DSP image rejection controls do
nothing. The instructions say, "If the image cannot
be nulled at least 50 db, then a problem exists..."
Well, some guidance would have been helpful.
Especially, given my opening criticism.

I am reluctant to tear into this think quite yet as
there is not a lot of room to work. I originally
thought it may be a transformer mis-wiring on my part.

Again, we're talking an experimenter's radio on 40
meters where things are relatively less critical than
other bands, so a little larger toroid with more room
to make changes would make it a lot easier.

I'm hoping when I fix the image problem that all
that 7.056 +/- 5 khz energy is going to at least be
diminished. 7.056 is S5. 7.051/7.061 are S3.

Anyway, I have no doubt the problem is my error. I
just want a little direction so that I can minimize
stress on the board.

Eric
KE6US
www.ke6us.com






Yahoo! Groups Links

-----Original Message-----
From: softrock40@... [mailto:softrock40@...] On Behalf Of Bruce Beford
Sent: Tuesday, September 20, 2005 6:56 PM
To: softrock40@...; qrp-l@...; QRP-Z@...
Subject: [softrock40] SoftRock: Update on 30M Xtals

I have received the 40.5Mhz crystals I ordered for use in the SoftRock to
allow operation on 30M. It is not going to be strictly plug and play. I
built my first Softrock with a socket for the crystal, and have been able to
get it to run with several crystals that run at less than the "stock" 28.224
Mhz. Was listening to 80M last night with a 14.318 Mhz xtal in there (Rx
center freq abt 3.58 Mhz) signals were slightly down due to the front end
filter, but it worked pretty well- Except for some 40M SWBC images.

I cannot get the 40.5Mhz crystals to fire in an unmodified SR40. I
breadboarded the oscillator cicuit from the SR40, and WAS able to get the
crystals to work if I removed C6 and C7 (100pf). When I replaced them with
33pf caps, I could get both the original crystal, and the 40.5Mhz crystal to
fire up fine. However, I could not repeat this by replacing C6 and C7 on a
SR40 circuit board. I'm not sure yet what the difference is (between my
breadboard lash-up and the PC board, maybe other stray capacitances) I do
plan to do some additional experimenting. Possibly my stock of 2n3904s are
better(?) The ones supplied should work at this freq ok, so I'm not sure.

In any event, I am now sure these crystals work on the fundamental freq of
40.5Mhz. It looks like some mods will need to be done to a board to allow
operation at that high a freq.

I'll keep ya all posted.

73,
Bruce N1RX

-----Original Message-----
From: softrock40@... [mailto:softrock40@...] On Behalf Of EricJ
Sent: Tuesday, September 20, 2005 1:05 AM
To: softrock40@...
Subject: Re: [softrock40] Griffin PowerMate

Today was like Christmas. The two SR-40s and a Griffin
PowerMate showed up today. No time to build
today...that will be for tomorrow, but I did have a
chance to set up the PowerMate with the PowerSDR
software. Very easy setup using the instructions at
www.flex-radio.com under Downloads. In fact all their
manuals seem to be first rate so far.

I set mine up a little different than the instructions
for selecting VFO Step.

When you turn the knob, it tunes the VFO.
When you click and turn the knob, it changes the VFO
step size.

Let up and you are back to tuning the VFO at the new
step size. A VERY natural feeling action made even
better by the very high quality "feel" of the PM.

I played with the PowerMate using the *.wav files that
Bill made available earlier. It doesn't do anything
you can't already do with a wheel mouse. But it SURE
does it smoother. What a beautiful piece of equipment.
Tuning is like a REAL receiver now. hi. Can't wait to
get one of the sr-40s going tomorrow.

Eric
KE6US
www.ke6us.com


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