Subject: Re: LF: Methods to transmit DFCW
To: rsgb_lf_group@blacksheep.org
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Message-ID: <ce92cf54-2d0d-1394-9f48-259027e1827b@n1bug.com>
Date: Fri, 16 Nov 2018 14:23:25 -0500
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Andy,

The FDM-DUO looks good. For me it's the same issue as fixing the
stuff I have... a purchase of that magnitude requires 2 years of
budgeting. It is definitely worth considering, as it would be a lot
easier and not much more money than correcting drift issues with the
kludge of stuff I have now! I would be using it only for LF and MF.

I don't think Stefan would agree it goes anywhere near DC ;-)

73,
Paul


On 11/16/18 10:17 AM, Andy Talbot wrote:
> The Elad FDM-DUO  will Tx down to DC (well, 10kHz really),  0dBm  from a
> low power port and has its own internal soundcard so Tx level is always
> matched perfectly when using digi-modes.  You just need to add a PA.
> 
> It is certainly not a cheap rig, but is a lovely bit of kit as a modern SDR
> transceiver.   And of course can be locked to a 10MHz reference input.
> > 
> 
> 
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>
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> The low power output will work up to 165MHz, so useful for 70 and 144MHz
> bands.   The Rx will work there, provided you bandpass filter out aliases.
> Tx does not have alias problems as it uses a higher sampling rate than the
> Rx
> 
> Andy
> www.g4jnt.com
> 
> On Fri, 16 Nov 2018 at 15:11, N1BUG <paul@n1bug.com> wrote:
> 
>> 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