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From: N1BUG <paul@n1bug.com>
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Message-ID: <09f31f89-e183-d304-e9f6-103a516748c9@n1bug.com>
Date: Fri, 16 Nov 2018 10:03:46 -0500
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Subject: Re: LF: Methods to transmit DFCW
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Reply-To: rsgb_lf_group@blacksheep.org

Hi Markus,

Mine too! I would strongly prefer that every exciter and amplifier
be linear but sadly that is not the case in my station. The other
monster in the chase is frequency stability. ;-)

I do have a SSB HF transceiver and a home built downconverter for LF
transmitting. I used this for some CW and JT9-1 QSOs. Unfortunately
it is of no use for slow modes. The converter has a 10 MHz OCXO
which is very stable but the HF transceiver operating at 10.136 MHz
has a cyclic thermal drift of about 6 or 7 Hz every time my furnace
comes on and changes the room temperature! Transmitting, even at low
power will also cause problems with heat. This is no good at all. I
could try to put some kind of heater (like a crystal oven) on the
transceiver's TCXO and try to add some insulation around it. This
would not be easy due to its location on a large PCB and limited
space. I doubt I could make it good enough.

Better of course (and very interesting!) would be to replace the
TCXO with an external GPS locked oscillator but I do not know if I
am up to this challenge. It would require some very delicate surgery
I guess.

In an ideal world the HF transceiver TCXO would be replaced by a
GPSDO, the 10 MHz OCXO in the downcoverter replaced by a GPSDO, the
downconverter rebuilt to be linear, the amplifier replaced with one
that is linear, and the LO in the SDR receiver replaced by a GPSDO.
Unfortunately we do not live in an ideal world and probably none of
that is going to happen. :-)

73,
Paul


On 11/16/18 9:18 AM, Markus Vester wrote:
> Hi Paul,
> 
> guess my preferred method is a linear SSB exciter which can do
> all sorts of modes, including specialties like chirped Hell and
> picture transmissions, or 1-dB stepped power tests. On the other
> hand with one sitting here this is easily said ;-)
> 
> Stefan and Tom have successfully employed a Raspberry Pi, which
> can produce modulated RF directly on one of it's digital output
> pins. This has been used for WSPR but I guess it could also make
> DFCW.
> 
> Best 73, Markus (DF6NM)
> 
> 
> -----Ursprüngliche Mitteilung----- Von: N1BUG <paul@n1bug.com> 
> An: rsgb_lf_group <rsgb_lf_group@blacksheep.org> Cc: lowfer
> <lowfer@mailman.qth.net> Verschickt: Fr, 16. Nov. 2018 12:34 
> Betreff: Re: LF: Methods to transmit DFCW
> 
> Thanks Andy. I have no proficiency at all in PIC or Arduino 
> programming. In my younger days I wrote some reasonably complex
> DOS programs but a lot has happened since then an the old brain
> isn't what it used to be I'm afraid.
> 
> I am not against *trying* to learn but will consider this a last 
> resort if no more complete or operator friendly system can be
> found.
> 
> 73, Paul
> 
> 
> On 11/14/18 10:42 AM, Andy Talbot wrote:
>> Depends how proficient you are with PIC or Arduino or Whatever
>> programming. There are still AD9850 moduiles to be found on
>> Ebay - that are not completely obsolete or sold-out yet.
>> 
>> Write your controller code to switch between two or three (for
>> DFCWi) frequencies under control of the ON7YD software,
>> toggling RTS / DTR on a COM port interface (use an FTDI USB one
>> if necessary)
>> 
>> 
>> www.g4jnt.com
>> 
>> 
>> 
>> On Wed, 14 Nov 2018 at 11:50, N1BUG <paul@n1bug.com> wrote:
>> 
>>> I am looking for a better method to transmit DFCW for 2200
>>> meter QSOs. For my QSO with 2E0ILY I used a QRP Labs U3S for
>>> the transmitter. This worked very well for DFCW60 when I was 
>>> transmitting every other night. For any QSO attempts
>>> involving quick change from RX to TX it would be difficult
>>> because of the time required to program a new message!
>>> 
>>> One possibility would be to modify this method used by N1VF
>>> for JT9 QSOs with a U3S:
>>> 
>>> https://bgelb.github.io/u3s-qso.html
>>> 
>>> I am a little concerned about messing up my trusty U3S but I
>>> may try that.
>>> 
>>> It looks like the easy way is the old QRS software by ON7YD.
>>> This is very interesting but I don't have a suitable
>>> transmitter. Are there any published designs for DFCW
>>> transmitters which could be controlled in this way? I wonder
>>> if parts would still be available? I am guessing these used
>>> synthesizers which are not current generation any more. :-)
>>> 
>>> Any other suggestions?
>>> 
>>> 73, Paul N1BUG