Automatic Band Decoder - a gadget with many uses
On the back of my FT-450D theres a "LINEAR" output socket which interfaces with a
linear amplifier. This socket provides alot of info from the radio, one thing being
4-bit BCD output which will indicate what band is currently selected.
A similar output can be found on most semi modern trancievers today
so check your manual if you want to make use of this circuit.
Here's how it looks on my FT-450D.
This can be used for a lot of different things, like selecting the right bandpass filter
in your amp, or selecting the right antenne for the currently selected band. This could
be engineered to take place in fully automatic mode.
I have a homebrew wireless antenna switch with 4 inputs. i could let this band decoder
trigger any of the 4 channels on the transmitter, and selecting between 4 antennas
for operating on any of the 9 HF bands the decoder handles.
simple 9 band decoder schematic.
here's the board in prototyping.
This time however, i have chosen to build the decoder into a nice enclosure with LED
indicators for the chosen band. In this box i will also mount the indicator panel for
my wireless antenna switch. This will tell me which antenna i have selected and on
what band i am currently operating it.
My original front Photoshop design, with a couple of LED's turned on.
The actual front for the decoder/antenna switch indicator.
printed in photoshop, laminated, glued in place and drilled.
the pieces are coming together nicely, and it works. so far so good
front view
In time this board will be used in a homebrew amplifier for auto selecting
the proper bandpass filters when im changing bands on the radio.
And here it is, connected to my radio and running. it works like a charm.
