[NLRS] Moderately priced transverters and digital modes?

[Dr. Gerald N. Johnson]

There are also many solutions to DEMI stability. First thing is 
minimizing the heat dissipated in the transverter case by setting it up 
for 0.1 watt or less IF drive, not 10 watts. The actual mixer only needs 
-10dBm. Second is surrounding the crystal with good insulation foam, 
like Dow Blue Board. Then its handy to add heat to the crystal with a 
positive temperature coefficient thermistor usually one that switches at 
about 40C.

Its possible to convert to use an external oscillator such as a 
frequency standard to either discipline the internal oscillator or 
replace it with a direct frequency synthesis (multiplier and mixer board 
ofen by G4HUP). Some discipline the 10 MHz standard with GPS signals or 
a rubidium reference. Those allow better stability in the transverter 
than in the tunable IF rig.

Now DEMI sells many LO's with a PLL board called Apollo that with an 
good external reference gets the frequency well under control, at some 
cost in phase noise effecting receiving ultimate sensitivity (a 
controversial topic).

Fact is the propagation mode may not be stable enough for HF digital 
modes that demand strict frequency stability with propagation 
enhancements coming from passing aircraft and birds and bees to say 
nothing about air in motion.

73, Jerry, K0CQ

On 3/9/2012 9:50 PM, Louis Sica, Jr. wrote:
>
>
> Hello Group
>
> The newbie again :)
>
> Ive seen several posts around the web saying both the DEMI and Elecraft transverters just aren't stable enough for digital modes, especially the MS "ping" modes. Is this true? Would I have to get one of those kilobuck European units or a stand alone multimode rig?
>
> Thanks to all for their help with this.
>
> -----
> Lou Sica AC0X
>
>