Re: Re : is there a computer doctor in the house ?
- Hi Daithi
thanks for mentioning use of lock
and RIT - must remember these.
By the way, when I worked you a few
days ago and mentioned your visible sidebands
I probably had too much rf gain.
I've been doing lots of experimenting
measuring my IMD etc etc + reading up on psk31
lots yet to learn.
This is a brill mode and 30m rules ok hi!
73 Rob G3RCE 30MDG#0852
- Hello Ed and Andy,
Thankyou for your responses. Andy,your query "is the net control on"?
Well I have Digipan, and what the equivilant name is I can't
remember, but it used to be on, so I'll do a check tomorrow. The
reason I say this is because strange things happen, for example
sometimes the signal indicator in the right corner of the screen
appears, and sometimes it doesn't ! Why, simple answer, I dunno !
Also I have another little problem which I could never solve on this
computer. A couple of years ago I had a fuse blow in the rig PSU
which caused all sorts of problems for me and among them was strange
happenings on Digipan, it opened on PSK63, but would not decode it. I
decided to download a new copy, deleted all I could find of the
unwanted software and downloaded a new copy and bless my soul if the
new copy didn't have the same problem, I couldn't believe it !
So I downloaded again, and again, and the third copy still had the
same problem,so I have to squirt a bit of RF on the waterfall to get
it to change from fat lines to thin lines and decode PSK 31. Again
why does it do this, I dunno ! The PC which doesn't seem to be able
to TX/RX on the same frequency has an otherwise perfect Digipan copy
which opens as it should. I've since been told that there is
something amiss in the registry and to find "something" (I've since
forgotten)but when I checked the registry I couldn't find it anyway.
Hello Ed, now about this sound card calibration. I know nothing about
this, so how do I go about adjusting the RX sampling frequency to
compensate ? Would you be kind and give me some instructions, if you
wish to do it off here post it to Mel gzerogqk@...
OK, that seems to be it for the moment, as the BBC used to tell us
when the TV service went belly up, Normal service will resume as soon
Kind regards to all, Mel G0GQK
- To be absolutely honest, I found that calibrating the sound card wound up being a waste of time.The reason is simple - your Tx and Rx frequencies are slightly offset, so you spend ages aligning them.Then you go on the air, send a CQ - and lo and behold - the incoming signal can be anything up to 25 Hz or more away from your carefully aligned frequencies - because the other guy isn't quite matching your exact spot.remember - the average rig can be anything up to 4 parts per million inaccurate - and on 30 metres, that works out at 40 Hz (which is almost the width of your signal)73 de Daithi GI7OMY
> Hello Ed and Andy,Andy,your query "is the net control on"?
> Thankyou for your responses.
> Well I have Digipan, and whatthe equivilant name is I
> can'tso I'll do a check tomorrow. The
> remember, but it used to be on,
> reason I say this is because strangethings happen, for example
> sometimes the signal indicator in the rightcorner of the screen
> appears, and sometimes itsimple answer, I dunno !
> doesn't ! Why,
>which I could never solve on this
> Also I have another little problem
> computer. A couple of years ago I hada fuse blow in the rig PSU
> which caused all sorts of problems for me andamong them was strange
> happenings on Digipan, it opened on PSK63, butwould not decode it. I
> decided to download a new copy, deleted all Icould find of the
> unwanted software and downloaded a new copy and blessmy soul if the
> new copy didn'tcouldn't believe it !
> have the same problem, I
>third copy still had the
> So I downloaded again, and again, and the
> same problem,so I have to squirt a bit of RF onthe waterfall to get
> it to change from fat lines to thin lines anddecode PSK 31. Again
> why does it do this, I dunno !
- --- In 30meterPSKGroup@yahoogroups.com, "Mel" <Gzerogqk@...> wrote:
> Hello Ed and Andy,
> Thankyou for your responses. Andy,your query "is the net control
> Well I have Digipan, and what the equivilant name is I can't[...]
> remember, but it used to be on, so I'll do a check tomorrow. The
> reason I say this is because strange things happen, for example
> sometimes the signal indicator in the right corner of the screen
> appears, and sometimes it doesn't ! Why, simple answer, I dunno !
> Hello Ed, now about this sound card calibration. I know nothingabout
> this, so how do I go about adjusting the RX sampling frequency toyou
> compensate ? Would you be kind and give me some instructions, if
> wish to do it off here post it to Mel gzerogqk@...soon
> OK, that seems to be it for the moment, as the BBC used to tell us
> when the TV service went belly up, Normal service will resume as
> as possible.Mel,
> Kind regards to all, Mel G0GQK
The term 'net' control is used in MultiPSK only I think. On other
programs such as Digipan the term 'Tx lock' is used. As long as the
Tx frequency is not locked it should track the Rx frequency.
MultiPSK has a built-in calibration procedure that determines the
correct Rx and Tx sampling frequencies. With other programs you can
estimate the offset between Rx and Tx by locking the Tx frequency and
noting the difference between Tx and Rx frequencies. Make sure that
the other station does not have not have the Tx frequency locked.
Since each station may have some offset error, the data should be
collected for many QSOs so these errors would be averaged out.
If you collect this data for many QSOs at different frequencies
across the audio spectrum and plot the pairs of frequencies, you
should be able to determine if there is a fixed offset independent of
the audio frequency or if the offset is proportional to the audio
A fixed offset would indicate an offset in the radio. An offset
proportional to the audio frequency would indicate a difference in
the Rx and Tx sampling frequencies. If you find that there is a
difference in the Rx/Tx sampling frequencies, compute the ratio of
the sampling frequencies and apply this correction to one of the
frequencies. Digipan and MixW both have options for applying
corrections to each sampling frequency.
If you are confident that the station your are working has no offset
between Rx and Tx frequencies, you can perform this test by tuning
your radio and checking the offset across the audio spectrum. If the
other station does have an offset, you will still be able to
determine if you have an offset that is proportional to the audio
I hope this helps. If you would like to collect some data and send
it to me, I would be happy to analyze it.
- Hello everyone,
Thanks to everyone who have replied and especially Ed. All I can say
is Phew !!! I hadn't realised it was going to be so complicated ! I
have made notes on the descriptive information you sent and I'll go
down the shack tomorrow and see what transpires. You mentioned that
Digipan has options for applying corrections to each sampling
frequency. I spent some time having a good look at Digipan but I was
unable to see anything like this.
Something I have observed is that the AFC " pulling power" on the one
version of Digipan on computer A, my normal one, seems to be better
than on computer B, which is the one which seems not to be tracking
signals as well and is off with RX/TX. Going back to 2001, at that
time I was using a TS430 for my first attempts with PSK, and I
believed at the time that it was perhaps the 430 which was the
problem which a station told me about the RX/TX being off.
I will try Daithi's suggestion by locking the TX frequency and see
how well the AFC will pull into the signal, but as mentioned earlier
it doesn't seem to react as well as computer A.
I did think about Jean's idea of using the RIT on the rig but as
there is no way to measure an offset it was a bit "iffy", perhaps I
should say, impossible to calibrate.
Referring to Daithi's comment about the AFC I put out a CQ call the
other day and a station replied parallel to my frequency. Thinking
he's a bit close I'll move a bit,I put out another CQ, and it
happened again, so I thought he must be responding to me. So to check
it out I sent a message "please reply on my frequency" He called
again off frequency and then went QRT. The next contact responded
exactly on my frequency, its a mystery. The only way to find out is
to have a local contact but there's nobody local who is using PSK.
Anyway,where are my pills ? I think I'll go and have a lie down in a
darkened room !
Kind regards to all, Mel G0GQK