Sirius Sat Radio Antenna Hack / Mod

Sirius XACT XTR3 Tuner.

This will mod improve the FM radio signal on your unit.
Open the unit up by removing the 2 screws on the bottom, using a Hex screwdriver.
Remove the top cover.

The large copper wire circle is the FM broadcast antenna that sends the signal to your radio.







There are 2 ways to improve your signal.

#1. Find the top part of the loop wire, and CUT it at the connection point to the board. Cut it in 2 places, about 1mm apart, so that it cant touch anymore. This goes back to ground and decreases the range.






#2. Do the #1 mod, but also solder a 31" piece of thin wire (24-18gauge) to the BOTTOM connection point.






This will now be a full length wire antenna.
This wire will be tuned to the 89 MHZ portion of the radio band, which is where most Sat Radios are tuned to, due to empty radio stations in that range.
Try to keep the wire straight, and not bunched or coiled up.

Radio Shack HTX-242 COS / COR Mod

This is a mod for the Radio Shack HTX 242 radio.


It allows this 2 Meter Ham Radio mobile to allow COS /COR sense to be used for a repeater RX or other use requiring squelch or signal sense.

Open the bottom cover on the radio by removing the 4 screws.





On the radio's front right, find the 3 transistors about 1 inch in from both the front and right side.
There is a resistor with a "473" printed on it, just below the top transistor. Tap off the RIGHT side of this resistor.






This will provide ~ +3VDC when no signal is present, and will drop to 0v when there is a signal.
This is a High to Low signal point. Most repeater controllers can be switched to select the correct setting. If not, you can make a small signal transistor switching circuit.

XM Radio Mod / Hack - Pioneer GEX-FM903XM

This is the mod /hack for the Pioneer GEX-FM903XM tuner.

Open the case with the 4 screws.
Remove the screw for the heat sink for the Voltage Regulator transistors.
Remove the screw in the center of the board.
Twist the metal pieces along the edge of the board that are used as hold downs.


You can tap the audio in 2 different places.

#1. Tap near the 8pin IC near the center of the board, on the top.
There are 2 surface mount resistors, one above and one below the IC. They are both Grey in color . Tap the left side of each.




This will give you your Left and Right channel + audio.
You can get ground - from one of many place. You can use the center screw in the middle of the board, or one of the metal lids over the DIGITAL or ANTENNA modules.



#2 spot is on the bottom of the board.
There are some test points on the top left of the board.
Locate the 3 test points labeled:
RCH AGND LCH




These are the Right Channel, Audio Ground and Left Channel.
Simply tap all 3 of these for audio.


That is all there is to it, for getting RCA audio out of the Pioneer GEX FM 903 XM tuner.

Selectone ST-907 Programmer Board

I had a request by E-Mail to help a fellow HAM operator get info or a schematic on the no longer supported Selecton Model ST-907 programmer board for DTMF and ANI Tone Encoder boards. Selectone no longer has any info on it, so I made up a schematic.






Parts List, From Left to Right.
36 Pin Parallel Printer Connector
9v Battery Clip
13 Pin programming connector for Selectone boards
Zenier Diode
10K 5% 1/4w Resistor
10K 5% 1/4w Resistor
100K 5% 1/4w Resistor
Zenier Diode
47K 5% 1/4w Resistor
47K 5% 1/4w Resistor
2N4401 Transistor
47K 5% 1/4w Resistor
10K 5% 1/4w Resistor
2N3906 Transistor
10K 5% 1/4w Resistor



All the pins #19-36 are connected to ground/neg.
12 holes are provided on the bottom of board for prototyping, testing or direct wiring.

My schematic isnt 100% exactly the same on the trace locations, and its not to scale, but the original board used a double sided traces, so I had to modify it a little bit for one sided viewing, so it wouldnt get confused, as some traces were too close or overlapped on top and bottom. I did try to get it as close as possible tho.


Software for the ST-907 board can still be found on the Selectone website.
http://www.com-spec.com/selectone/download/st_confg.zip


I made the schematic using a cool program called ExpressSCH. You can built schematics and have a company make PCB boards for you for a reasonable price, if you wish.
The software can be found below for FREE!
http://www.expresspcb.com/ExpressPCBHtm/Free_schematic_software.htm

Here is my file for the Selectone ST-907 Board.
http://www.mark-rodgers.com/Project%20Pics/Selectone%20ST-907.sch

Please let me know if you have trouble downloading the file.