R.L. Drake

Drake Mods - AUX7

Authored by VE3EFJ

13.0 AUX7

    You can make the all band transmit mod by just cutting one trace for the TX band inhibit line. The other, official way of getting additional bands is through the AUX7. This was an option board on the TR7 series that allowed one to operate the TR7 either crystal controlled or allow one to buy program modules for any .5 MHz segment. Special program modules were ordered for transmit. Use of an AUX7 is a nice touch, for by just rotating 2 switches, you can get to any band you want without modifying the transceiver. The option modules were all the same - you 'programmed' the modules by cutting off the appropriate pins from a chart.

    Drake no longer provides the AUX7 optional band modules, but you can make your own from a 14 pin DIP header and a batch of 1N4148 diodes. Each of these modules will consume less than 13 diodes, depending upon the frequency. Yes, its a lot of diodes. Typically, you'll need 7 or 8 diodes per module. You must use the diodes, for the band modules are matrixed.

    The AUX7 is not easy to install or gain access to for it involves opening the TR7. The front panel will flip down, but to do this, you need to extract the band switch shaft. If you are not careful, you can rip the wafer rotors out when you extract or reinsert the shaft. This will cause REAL trouble and given the age of the unit and replacement parts availability (don't count on it!),

    The AUX7 band module has a separate pin for TX enable. Obviously, this pin must be enabled for any of the WARC amateur bands you need or want to enable. The band switch must be set to the appropriate filter range. If it is set to a range that does not match the module programming, the SETBAND light will come on.

    When you set up the DIP header with the 1N4148 diodes, use the following programming chart. The pin numbers are as if it were an IC. Make sure you do not wire it backwards! This is a very common mistake:

         PIN  USE                       PIN  USE
         ===  ==========         ===  ==========
           1  Select 5V                   8  Range B2
           2  Range A0                  9  Range B3
           3  Range A1                 10  TX enable
           4  Range A2                 11  Band A
           5  Range A3                 12  Band B
           6  Range B0                 13  Band C
           7  Range B1                 14  Band D

    Essentially the AUX7 programming is divided into 2 halves - BAND and RANGE. BAND sets the band as if it were coming from the band switch. RANGE sets the .5 MHz offset as if you were to hit the UP/DOWN buttons on the front panel. The BAND programming is compared against the BCD band switch wafer. If there is no match against these two, the SETBAND light comes on. This is used to tell the operator that the band switch setting does not correspond to the programming and the band switch should be rotated until the light extinguishes.

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