[NLRS] Band Decoder/ Antenna Selector

[John P. Toscano]

Eric Shook wrote:

> I remember a conversation that I had at breakfast
> about building a setup that would switch everything as
> the bands were switched on the radio.  I came across
> this and was wondering what people thought about it
> for VHF/Transverter use.
> 
> http://www.qth.com/w9xt/decoder.html

Hi, Eric.

Their web site omits an important piece of information, namely what 
radios have the 4-bit band output port that their device plugs into. 
Certainly, none of my radios have it.

They *DO* point out one other thing that is probably pertinent.  It is 
designed for "all" bands, but to them, "all" means "all below 50 MHz". 
They imply that there might be some radios that put out a unique signal 
for higher bands, since they mention that there are some "undefined" bit 
combinations -- only 9 HF bands, and 2^4 = 16.

Other than those two little problems, it looks like a nifty little 
device.  If you have a radio that has this 4-bit band output, especially 
if it uses the undefined output combinations for 6M, 2M, 70cm, etc., 
then I'd say to go for it.  The other issue is that you still don't have 
what is needed to pick one of multiple transverters, unless every one of 
them uses a unique IF band.

The IC-706 MkII has an analog output that could be used for decoding the 
band with a set of window comparators built out of op-amps and a few 
resistors, but unfortunately, the IC-706 MkIIg does not put out a 
perceptibly different voltage on this pin when switching between 2 
meters and 70 cm.  What a bummer!

It might end up being easier to do the control the other way.  Build a 
box with a PIC or other small microprocessor and a serial port to the 
radio's computer interface port.  Pick the band on the new box and it 
would (a) switch any necessary relays (b) enable the proper transverter, 
(c) tune the IF radio to the proper frequency, and maybe even (d) 
continuously display on an LCD or LED front panel the converted 
frequency by doing the math on the IF radio's tuned frequency (read back 
from the computer interface port) as you twirl the tuning knob.

73 de W0JT