2600/2510 conversion

Unlock the RIT on the HR-2600

    One of the finest 10 meter mobile radios I've ever used was the Uniden 
HR-2600.  It's full of capabilities, such as CW, SSB, AM, FM and even repeater 
splits.  As nice as it is, it's still missing the ability to exactly tune onto
the other station.  It's possible to be as much as 50 cycles off frequency 
because of the built in one hundred cycle tuning.  You can, of course, tune 
the receiver exactly to the other station by using the RIT (Receiver 
Incremental Tuning) on the radio, but this does not move your transmit signal, 
only the receive frequency "SLIDES".  What the radio needs is an XIT control 
to allow you to move the transmit frequency.  If we can modify the existing 
RIT to move the transmit frequency at the same pace as the receive frequency, 
the new control would be a combination RIT/XIT control in one, and this is a 
powerful feature.  It didn't take me long to decide that I had to "XIT-IT".

Parts:

    To perform this modification, you will need a soldering iron, electrical 
tape, pliers and a screwdriver.  You will also need two 8 inch pieces of wire,
these will be referred to as WIRE 1 and WIRE 2.  Regular hook-up wire or
speaker wire will work fine.  As a control to fine tune the frequency of 
the new RIT/XIT you will need a 10,000 ohm variable resistor (10k pot).
Both the thumb-wheel style and the pc mount versions are fine choices.

Preparing The Radio:
    Start by placing the radio with the speaker side down.  Disconnect the 
antenna coax and power, remove the top 4 cover screws and place the top cover 
to the side.  Turn the radio around so the back is facing you.

The Conversion:

There are two small vertical square green boards mounted to the inside front
of the radio, one on each side.  Locate the one on your left first.  Notice
that on the top right corner of this board, there are 3 vertical soldered pins.
Solder one end of WIRE 1 to the 3rd pin down from the top.  This point is
common to the radio's original transmit and receive control voltages.



    Next, locate the right vertical square green board. There are 7 vertical 
soldered points on the left side of this board.  Pins 6 and 7 are actually 
connected together on the board.  Also, one of the 2 white leads from the 
radio's lamp light is attached here.  Solder one end of WIRE 2 to this point. 
This will supply the voltage for our new RIT/XIT control.  



    Now turn the radio so the front is towards you and locate VR11.  It is
in the front right section (end closest to you) of the radio.  It is also the 
right most of 3 white variable resistors with crosses on their tops. This 
control allows you to adjust the voltage which sets the radio's transmit 
frequency.  Notice diode 43 (D43) just in front of VR11.  Cut the cathode side 
of the diode wire near the circuit board.  The cathode side is the side 
closest to you and is marked with a yellow band.  Gently straighten the diode 
so it stands vertical, this will keep it away from the cut you just made.
    


    Next find the 5 wire white jumper plug located just left of center on 
the radio's large circuit board.  Cut the center wire (orange) about 1 inch 
above the white plug.  This wire provided voltage which determined the 
receiver frequency.  Tape the top wire of your cut to insulate it from other
wires.



    Solder the 2 free ends of WIRE 1 and WIRE 2 as follows.  Solder WIRE 2 to 
the center tap of the 10k variable resistor.  Solder WIRE 1 to either of the 
two remaining leads of the pot.  Position and tape the resistor to any 
convenient spot (to some other wire works well) that you can still access, yet 
so it can't short out to any other component.


Testing Your Work:

    Connect the antenna and power but do not replace the cover yet.  Now you 
have to calibrate the frequency display.  Since a single source is now 
supplying the voltage to control both the transmit and received frequency, you 
can place the radio back on frequency simply by tuning to a local ham on a 
known frequency.  Set the RIT (now RIT/XIT) to the center OFF position and 
adjust the new 10k pot to set the radio on the correct frequency.



    If you want to get fancy, you may also want to consider adding an external 
switch to allow you to toggle between the RIT/XIT and the original RIT.  I 
haven't had a need for this to date, so I'll leave this mod up to you.



    That's it!!  With the new RIT/XIT on, you should be able to track about 
1 1/2 to 2 kHz on each side of the center frequency.  The display does not 
change frequency as you tune, so watch the band edges!