[R-390] R-390A (digital readout)

[chuck.rippel at cox.net]

Interesting subject...

If the PTO end points are set up correctly so the mixing scheme and 
tracking pre-selector matches the cam profiles, calibrated to the 
nearest 100kc, the mechanical counter is very accurate.  I've seem some 
accurate to < 100 cycles.
Frequency errors usualy mainfest themselves across band to band changes. 
That is, if a receiver is calibrated to 8.2 mhz and you rotate the MC 
control up to the next band, most receivers will not "land" on 9.2 mhz. 
They will have to be re-calibrated.

The crystals in the oscillator drift a bit over time.  Remember also, 
most are hetrodyned twice, some 3 times where the fundamental error may 
be multiplied.  One could put a counter on the output but still not 
capture the error caused by the crystals in the 1st oscillator.

While its not made for the R390A, perhaps something like this, 
programmed to accommodate the mixing scheme of the R390A might be very 
helpful to some.

 
http://www.ebay.com/itm/190579917545?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649  
<http://www.ebay.com/itm/190579917545?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649>

Chuck Rippel

On Wed, Mar 14, 2012 at 12:46 PM, Tisha Hayes wrote:

> "R-9XX The R-9xx is alleged to have contained a small LED digital 
> readout where the veeder root counter exists in the center of the 
> R-390A. No documentation or photographs of this model have surfaced 
> yet."
> 
> ------------------------------------------------------------------------------------------ 
> I could see where something could be cobbled together with a tiny 
> optical encoder, some digital logic and a display. Going into that 
> sort of effort would just show you the desired receive frequency and 
> not the actual frequency. If someone was going to go that far they 
> might as well replace it with a R-390A version of a digital dial where 
> you actually are reading the frequency of the radio. That way you 
> could get around the slightly non-linear performance of a PTO that is 
> not exactly dialed in to the Hz.
> Otherwise all you are doing is replacing a mechanical odometer type of 
> display with LED's that are reading the same shaft movements.
> It is a marvel in itself to keep all of the knobs, odometer display, 
> cams, PTO, stops and gears all dancing together in synchronicity. That 
> is one of the things that initially attracted me to the R-390A, that 
> is is essentially an 80 pound watch with a really good receiver glued 
> onto the backside (lol).
> -- 
> Ms. Tisha Hayes/ AA4HA - "Life isn't about how to survive the storm, 
> but how to dance in the rain"