[GreenKeys] Demod Bds & some help

[epvgk at limpoc.com]

On Sat, Sep 03, 2011 at 02:39:59AM -0400, WA5CAB at cs.com wrote:
> Eric,
> 
> Teletype machines are asynchronous.  Unless you are trying to simulate one 
> of the Crypto systems, there is no requirement to keep receivers synced.  
> And almost all HF radio sets since AN/GRC-19 either come with built-in FSK 
> transmit capability or have outboard modulators available.

I think the idea is/was to not potentially miss a character after a period
of idling that's not an even multiple of a character time (ie, 7.42 bit times
at 60wpm) I personally don't see the point as i always send a LTRS or two 
before transmitting anyway, but this is apparently the rationalization for why
all the software RTTY programs do that. I find it annoying because the 
machine is almost as loud "printing" nulls as it is with an open loop. 

eric


> 
> In a message dated 09/03/2011 01:04:29 AM Central Daylight Time, 
> epvgk at limpoc.com writes: 
> > On Fri, Sep 02, 2011 at 10:23:42PM -0700, Norm wrote:
> > >Hi
> > >I just received two of Eric Volpe's demod boards, anxious to wire them up 
> > and try them. they really look professional.  I have a demod ckt now, is 
> > there anybody out there wanting to tackle a mod board, or has someone built 
> > some already?  I would be interested in one or two.  Could someone help me 
> > out on this, someone awhile back a month or two, mentioned he had some 
> > rectifiers for sale.  It sounded like they were on boards also.  I must have 
> > deleted that message ,because I don't have it in my files.  Thanks Eric you 
> > done yourself proud.
> > >
> > >Norm
> > >WB7WEQ 
> > 
> > A mod board is not impossible... Would this be for radio use, or something
> > else? It seems like it's a little more complex than the demodulator. 
> > 
> > I had a couple of ideas on how to do it cheaply but I'm curious what 
> > people 
> > would be after in terms of features - I suppose we'd need adjustable 
> > center 
> > frequency, split, output level, mark/space swap? Anything else? I suppose 
> > also it would have to be able to adapt to whatever loop voltage/current 
> > you 
> > threw at it, as well, and put out a nice clean sine wave. 
> > What about more fancy features like sending nulls when there's no data 
> 
> > coming, to keep receiver in sync? That would of course require receiving, 
> > retiming and retransmitting the signal. 
> > 
> > eric
> 
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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