The GRC-106 Radio and Acc

Radio set AN/GRC-106 is a high frequency (HF), single-sideband (SSB), radio receiving-transmitting set. This set operates over a frequency range of 2.0 to 29.999 MHz. Radio set GRC-106 operates on any one of 28,000 selectively tuned operating frequencies, spaced in 1-kilohertz increments. The additional feature of vernier tuning (+or- 600 Hertz about any 1-khz increment) allows reception on any frequency in the operating range. The selectivity insures compatibility with existing amplitude-modulated and radio-teletypewriter equipment that does not have the same accuracy and stability as the GRC-106.

The GRC-106 is used for receiving and transmitting USB voice, USB compatible amplitude-modulated AM, and CW signals in a simplex operation, over a 50 mile range. Conventional AM signals can be received but not transmitted. FSK and narrow FSK signals can be received and transimitted, using the appropriate ancillary radio-teletypewriter terminal equipment and primary power source (high capacity vehicular generating system). The GRC-106 is primarily intended for use as a mobile radio link in a communications network; however, it may be used in a fixed mobile station. It is usually vehicular mounted, using an appropriate vehicle mounting kit. The fixed mobile station application is the same as the mobile application, except that a dipole antenna is used in place of the whip antenna to increase circuit path reliability and extend the range of operations.

The first paragraph of tells you about the radio from the Military viewpoint as It was taken from the operators manual.

Now from my view point.

When I got my GRC-106, Its operating condition was unknown. I borrowed a manual from a good friend of mine Al W6GER and started trouble shooting the radio. I found some small problems and got them taken care of and had the 106 up and running in about 3 hours. I was quite happy about this and also about the fact the MD-522 RTTY modem was working. I put the rig on Clatternet (10.137 USB 850 Shift at 9:30 AM PST) the next Saturday and was quite happy about how things were working.

After using the radio for a while I have noticed some things that makes a difference to use it on the Ham Bands. The SSB filter has a lot of ringing in it and the receiver in general is quite noisy. I also found out the hard way that you Do Not Want to have the MD-522 hooked up to the radio if you want to use CW! I did and this is what happens, when you go to the CW mode and go to transmit the 3349 Amp does not turn on all the way and it Blows the switching transistors in the Amp! I got real lucky and was able to buy another front panel from Fair Radio . I replaced the original one with the one from Fair Radio and I was back on the air. I also have found that this radio is like the rest of my Military Radios that use Carbon Mics, that Motorola Carbon Mics have more drive and sound a lot better than M-29 Military Mics.

The radio is of course quite noisy due to it fans running, but with a set of headphones on it is very usable. As you can see in the main photo that I have had it setup in my Ford truck using its 15 foot whip. It did quite a good job on 40 and 20 meters.

June 30 2004

I just got back from Field Day and trying out a better radio bench ( heavier built) and leaving the GRC-106 and MD-522 setup in the back of my Ford Truck. The new bench is heavy enough to support the weight of all the radios that I had mounted on it. They included the following: the 106 and its amp, the MD-522 and a RT-524. I tried out several antennas on this trip to see how the GRC-106 would handle the different types. They included the following: A Tape dipole setup on 40 meters, The 15 foot whip mounted on the truck, and a 150 foot long wire that was about 45 feet up between a couple of Fir Trees. The 106 had no problems matching the tape dipole on 40 meters, this was expected. The 106 had no problems with matching the truck mounted 15 foot whip on 40 meters and above, but it could not match the whip to the radio on 80 meters. The 150 long wire was a pleasent surprise! The 106 had no trouble matching the antenna on any frequency that we tried that weekend. I have added a couple of photos of the new radio bench in the back of my Ford Truck.

April 22 2005

I have added a new info page for the GRC-106

This for general interest and to help the fellows mantain their radios. This info came from both the Armyradios list and the Milsurplus list. Mike

Info Page

April 18 2007

I have just added a manual page to the site and you now can download the manuals for the GRC-106 and the MD-522A.

GRC-106 Manuals

This info was sent to me by Bob Spiteri

Those radio sets sure brought back some memories of my early years as an RTTY Operator. Both the AN/GRC-122(*) and the AN/GRC-142(*) had the MD-522(*) modem. The difference was the AN/GRC-122(*) was duplex with two Reciever/Transmitters RT-834(*) or RT-662(*), one MD-522(*) modem and one AM-3349(*) Amplifier. The AN/GRC-122(*) also had two TT-98 Teletypes and a TT-76 with Tape Device in addition to seperate cryptological systems for the transmitting TTY set and the receiving TTY set. The Receive only RT was mounted on top of the modem. The AN/GRC-142(*) was simplex with only one Reciever/Transmitter RT-834(*) or RT-662(*), one MD-522(*) modem and one AM-3349(*) Amplifier. The AN/GRC-142(*) also had only one TT-98 Teletype and a TT-76 with Tape Device with a cryptological system for TTY. A spare RT could be mounted on top of the modem if your unit was allocated running spares.

The AN/GRC-142/122 Nomenclature applies only to Simplex/Duplex Radio Teletype Configurations using the AN/GRC-106(*) radio set inside a shelter (S-250, S-318, etc.) which was usually mounted on a pick-up or Gama Goat which could operate AC/DC and fixed or mobile.

The same configuration in a fixed station or dismounted (set up in a tent or building) was called the VSC-1. The same configuration on a M-151 Jeep was known as a VSC-2. The same configuration in an M-577 Command APC using the AN/VIC-1 Intercommunications set was called the VSC-3.

The Radio Set AN/GRC/106 Nomenclature applies only to the Reciever/Transmitter RT-834(*) or RT-662(*) and one AM-3349(*) Amplifier, mounts, brackets, power and interconnect (dog-bone) cables, whip antenna lead and insulated off-set tube Loudspeaker, Microphone, headset, CW-key & cable,1/4 Wave 15 foot whip and AN/GRA-50 Half-wave (Doublet) antenna.

Also, that 'Receiver In' binding post on the RT can be used to increase your RF Gain/Signal when you are operating stationary. It is especially helpfull when you are using the Cobra Head/Doublet antenna on the higher HF freqs which require a shorter antenna cut to frequency. You can use a double strand of insulated wire of any length (100 fett should do nicely). Strip and twist together one end of both wires and attach to the binding post. run the wire outside your rigg and tie a knot or small loop in the wires at about 15 feet away from the rigg. sepearte the two conducters and run them to form a ' T ' and orient as you would the doublet antenna broadside to the distant station. This 'Receive Only' antenna can be used to enhance the receive signal strength on one or both receivers however it is important that you keep the antenna as far away as possible from the transmitting antenna and avoid handing the antenna when a nearby transmitter is operating (unless you don't mind RF burns).

Also, the two RF cables, which connect the RT/AMP RF Drive connectors and the 'RT RF In' to the 'Rec Ant' connectors should be about six inches long (just long enough to make the trip from one connector to the other). You have a great page. Thanks for the memories. Bob Spiteri, U.S. Army Signal Corps Retired

These photos were sent to me by Carlo Fontanelli in Italy. He has a very nice collection of GRC-106 Radios.
These photos are clickable so that you can see the full size photo of each radio. The radios are as follows: The first one is a General Dynamics, the second one is a Magnavox, the third one is a Cincinnati, the fourth on is a restored Bundeswher 106A that Carlo has just finished up, the fifth is a nice pair of 106's! The last photo is of a German made GRC-106G4.

Updated 06-01-08