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Author Topic: 20 metre transmitter kit suitable for data  (Read 1241 times)
EI4HQ
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« on: May 05, 2013, 09:33:53 AM »

Hi,

I'm getting stuck into a new project that will involve a 20 or 40 metre QRP transmitter (a few watts is sufficient) capable of transmitting DominoEX.
 
I do a fair bit of construction but I haven't gone down the homebrew transmitter route before so the space is entirely unknown to me; I'd appreciate a steer from anyone to either a good transmitter design or (even better) a suitable kit.

Thanks in advance
Cormac, EI4HQ
[Cobh, IO51uu / UTC+1] NNNN++++
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WB6BYU
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« Reply #1 on: May 07, 2013, 12:19:28 PM »

I'm not familiar with the modulation type of Domino, but unless it is a keyed carrier mode
such as Hellschriber then it will require a linear transmitter chain.  If it is designed to be
fed into the mic circuit of a rig, then any transmitter designed for SSB should be adequate
for the purpose.  (The main issue will be VFO stability.)
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EI4HQ
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« Reply #2 on: May 10, 2013, 10:28:22 AM »

Noted with thanks - it is as you describe so I'll add VFO stability and linear requirements to the list...
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WB6BYU
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« Reply #3 on: May 10, 2013, 10:57:31 AM »

If you are only operating over a narrow frequency range, using a crystal oscillator in place
of a VFO may be adequate.  (Some digital modes are much more critical for frequency
stability than others.)

The BITX design may be a good starting point.

I'm not that familiar with the kit offerings currently available, but here are a few
designs to consider.  Just about any SSB transmitter strip using a CB output transistor
is probably going to work, then question then becomes the VFO/XTAL oscillator.

http://www.intio.or.jp/jf10zl/14mssb10w.htm
http://www.qrp.pops.net/willy.asp
http://www.vanyi.net/homemade/homebrew-hf-ssb-transceivers/
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WB6BYU
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« Reply #4 on: May 10, 2013, 12:43:32 PM »

And here is another link - there are a number of circuits of interest in both the 40m
and 20m sections;

http://www.pg1n.nl/articles.php?lng=nl&pg=123

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