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Copyright 1995 - 2008   John Tait   All rights reserved.

Automatic Band Decoders

The next step in our search for luxurious operating is to replace the manual selector switch with an automatic one. Again, these are available commercially, and yet again my Scottish ancestors whisper.. "Nay laddie..! Keep yer brass in yer pocket, an build one yersel'... "

Commercial units can be found at ON4AOI, MicroHAM  Array Solutions, Top Ten Devices , Dunestar Systems , and probably others that I'm not aware of.

To build a Band Decoder to drive our remote relays, we need to supply the band information from the rig to the decoder. Problems now arise, in that Kenwood don't have this facility at all, ICOM provide this data in the form of a set voltage value for each band, and YAESU provide the data in the form of a Binary Coded Decimal (BCD) output to a socket on the back of the rig. Interfaces can be built for the ICOM and YAESU rigs, But how about KENWOOD??. Fear not...fellow convicts...Help is at hand..!!!

Extremely clever people, who write nice logging software for us dimwits have come up with a solution... In their wisdom, they have decided that YAESU have the best system, so they have written their software to emulate a YAESU rig. In other words, if you connect any brand of rig to your computer, this software can put the BCD band information out to the printer port of your PC, in exactly the same format as it appears on the back of a YAESU rig....Devilishly cunning eh..??

Two logging programs that I know have this facility are CT (K1EA) and DX4WIN. There are probably many others that I'm not aware of.

 

( almost complete ON4AOI pcb)

 

 

Thanks to the generosity of people like Bob K6XX and Guy ON4AOI I didn't have to design one for myself, as they had done all the clever stuff for me... The K6XX decoder is extremely simple, just using a TTL chip, and a handfull of discrete components.  Bob has a lot of nice usefull things that you can homebrew.  I incorporated his PTT amplifier on my own Band decoder PCB, which tidies things up nicely. I used  good "beefy" switching transistors, and it'll probably key the national grid...!! 

 The ON4AOI decoder has now gone commercial. I built an early design of Guy's. He originally gave all the details on his webpage. He has now updated the design, and is selling it commercially. It is a very comprehensive design with ten outputs. It uses buffering of the input, and opto-isolators on the output, so it is a very safe unit.  By "safe"...I mean that your rig is protected from any "nasties" coming back to the rig from the outside World...It can control a bandpass filter unit (such as the Dunestar) as well as the antenna switch. You can also arrange the switch to control combinations of bands.. For instance, if you are using a tribander, the decoder can be programmed to select the same antenna for the three bands.  As with all the good decoders, it'll happily work with Yaesu or Icom rigs and the usual logging programs that can output band data to the LPT port.. Writelog, DX4WIN, CT, Trlog etc. Guy supplies the decoder in various combinations, from a bare PCB, to a fully boxed unit with all the "add-ons".

 

     Amongst the goodies on W9XT's site, I found another band decoder. It is a complete PCB, and can control 10 antennae. I recently bought one of these, and on examination of the PCB, I see that Gary also uses opto-isolators in his design. This appears to be a  nice inexpensive option for the guy who wants to supply his own box, or incorporate it into his own station control box, SO2R or whatever.

  Steve Wilson G3VMW has done just that, using the W9XT board, to which he has added his own source drivers, using BD140 transistors. We both reckon that this approach is safer than using current sink drivers.

 

Steve's Homebrew Decoder. W9XT board top RHS, PSU on LHS, Source drivers in centre.

  

Front view of Steve's decoder... Sexy artwork!   On top of the Switch box is his homebrew Antenna Switch Box using the Far Circuits PCB for the KO4NR Antenna Switch published in the April 2005 QST.

 

( Pic of my completed band decoder. It uses the ON4AOI pcb)

 

 

I built Guy ON4AOI's original design. It worked first go, with no problems. I cased it in an old external modem case, which had a 12/24Volt DC power supply already in it. I just stripped out the old modem PCB and made a new front panel to hold the LEDs, rotary switch etc. It has a DB9 socket on the back to take the input from my FT1000MP, or from a PC printer port, and a pair of DB25 sockets to drive the remote relay box, and a DUNESTAR Band Pass Filter unit (at the same time). I resprayed the box, and I think it looks quite sexy...!!

 

 

Here's another beautifully finished unit, made by Akira JA1EOD

 

 

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