Unlock the RIT on the HR-2600
"XIT-IT"
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!
Copyright © 1996-2006 Ed Oros and Bob Cocco All Rights Reserved.
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