Unlock the RIT on the HTX-100
"XIT-IT"
I've had a lot of fun working DX from my car with this rig. It is
one of the easiest to modify, if you want to unlock the RIT. One of the major
drawbacks with a rig of this class (HR-2510,HR-2600, HTX-100) is the tuning.
There are usually 4 step sizes used when tuning to the desired frequency. (500
kHz, 10 kHz, 1 kHz and 100 cycles). The 500 kHz step is rarely used. Its main
purpose is to move you from one part of 10 meters to another. For example, if
you are in the CW portion of the band and want to move to the SSB end, this
switch is handy. The 10 kHz step tuning can be used when looking for contacts
but you skip over most of the band. The 1 kHz step isn't too bad, but if the
other station is 1/2 kHz off frequency, you'll have to switch over to the 1
hundred cycle tuning. Even then, the station may be 50 cycles off from you. I
always found myself using the 10kHz step to find a section of the band with
activity, then switching to the 1kHz step to pick out a 'loud one' then
switching again to the 100 cycle tuning to fine tune the person in. Often times
I still could not get the station in just right, and there just isn't any other
way to get any closer to their frequency! Sure, you can use the rig's RIT contol
to tune your receiver right on, but then your transmit frequency is still off a
bit since it doesn't move with the RIT control!
What's the answer? A simple modification to allow the transmit frequency to move
in sync with the receiver frequency when using the RIT control. This mod takes
only a few minutes, is reversable (in case you change your mind later) and
really makes the radio a pleasure to use afterwards.
Parts:
There are
only 2 parts to this conversion. You'll need a 6 inch piece of wire and a 10k
variable resistor. Any 10k pot should work fine.
Preparing The Radio:
To begin the conversion, first place the radio on a flat SOFT
surface (the cases of these rigs seem to scratch easily) with the speaker side
down, and place the rig so the front is facing you. Remove the top 4 cover
screws and the top cover. Locate the radio's lamp light, and follow the white
leads down to the green circuit board. Notice that one of the lamp's leads is
connected to a point on the board marked as +8. Now look on the circuit board to
the right of the +8 point. You should see a white jumper plug. In front of this
and slightly to the left is a printed circuit board trace line. It is a straight
line with a solder point on each end. If you have a volt meter take a voltage
reading from this trace against the chassis ground. It should read near 7 volts.
Mark down this number.
The
Conversion:
Next, disconnect the power from the radio. Take
the 10k variable resistor and solder the center tap lead of the resistor to the
board at the +8 solder point. Next take the 6 inch wire and solder it to either
of the two remaining leads of the variable resistor. Use a sharp tool to break
the straight line trace that you had just found. Cut it in the middle of the
line if possible. Then solder the free end of the 6 inch wire to the end of the
trace closest to the front of the radio. The existing end solder point works
nicely for this. This trace line originally provided voltage only during
receive. Since the 8 volt source that we are now tapped into is there during
both receive and transmit, the control will change frequency in both cases now.
Testing Your Work:
Connect the antenna and power but do not replace the cover yet.
Now you have to reset the radio back on frequency. To do this, you can use a
frequency counter, or a local ham. Set the RIT (now RIT/XIT) to the center OFF
position and adjust the 10k resistor to set the radio on the correct frequency.
Have your ham friend transmit on a pre-determined frequency while you set the
resistor to tune them in. Another method would be to use the voltage reading
that you took earlier, you can just check the center tap of the resistor now and
set the pot to the original voltage and you will be close to the correct
frequency. Once back on frequency replace the cover, screws, antenna and power.
At this point, let me inject a word of warning, your frequency display WILL NOT
CHANGE as you use this new RIT/XIT. So be careful around the band edges, don't
get too close or you may actually be out of band!
Now You're ready to see how much easier the rig is to operate. With the RIT
unlocked, I generally just leave the step size set to the 1kHz position, tune
close to a "loud one'" and then just use the RIT/XIT for the final touch up. You
get about 1 1/2 kHzs on each side of the control's center. It's great! Have fun
and I'll see you on 10 meters!
Copyright © 1996-2006 Ed Oros and Bob Cocco All Rights Reserved.
All trademarks belong to there respective owner.
The Content of this page is provided as is, and should be accepted and used without expecting any particular fitness for any particular purpose.
No liability is assumed with respect to the use of this information.