On Thu, 2009-06-18 at 14:46 -0400, Eric Rosenberg wrote:
> TT says they don't have a schematic for the 311, which apparently isn't
> really a Band Data Decoder, but rather an inverter.
> Have any of you opened up the box and looked at it.. or reverse engineered
> it? I'd like to control my Herc II with something other than my Orion, but
> am not sure how to wire it up.
> Eric W3DQ
> Washington, DC
I've downloaded the 565, 566, and 420 manuals plus the data sheet for a
UDN2982A and read the band connector data in the Tentec manuals.
The outputs of the Orions is a low, one wire per band. Its open
collector, good for a maximum of 250 milliamps which could run a small
relay as illustrated in the manuals. E.g. its essentially a contact
closure to ground.
The input of the 420 is the same except it needs one wire raised above
2.4 volts to indicate the band. There 10 and 12 share a wire, 15 and 17
share a wire and 30 and 40 share a wire. The maximum input voltage to
the interface chip is about 20 volts. If it wasn't for the shared lines
a couple CD4009 Hex inverter chips would do the job, with a gaggle of
pull up resistors on their inputs (10K input to +supply and there's 13.5
volts on the Orion band connector). The necessary sharing could come
from a three gates in a CD4072 quad OR gate, or a half dozen diodes. Or
those that stay one wire to one wire could be inverted with a CD4009 and
those with two wires to one could use three gates of a CD4011 NAND gate.
Tie the unused gate inputs to ground or supply. Adding LEDS for band
indicators is an option.
Alternative, and apparently what the 311 does is to use 11 PNP
transistors as I described already, tying their collectors in parallel
when the bands are shared.
To run from a radio with BCD output, I'd probably use a CD4514 that
takes in 4 wires binary and puts out 1 of 16 high. It works from 5 volt
to 15 volt logic and supply. I know the FT-857 and 897 have that BCD
The rest of the details are in the Tentec manuals.
But a simple cable between an Orion and the 420 is out.
73, Jerry, K0CQ
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