Military Radio - Computer Interface

I'm trying to figure out a good way to pass along audio from a computer to a military radio, and vice-versa. I've bought this General Dynamics USB Audio Adapter that I'm going to try out: http://www.ebay.com/itm/General-Dyn...6413625?hash=item2cb6dbb739:g:ldEAAOSwImRYJNp~

Unfortunately, I haven't found any documentation for it, plus I have a pretty strong hunch that it's not going to be happy with the audio levels from the radio since it's intended to work with a headset...anybody have any documentation on what those levels would be? For physical hookup, I'm hoping that these cables (A3013735- will do the trick: http://www.ebay.com/itm/Military-10...530732?hash=item1c8da5b1ec:g:ZGAAAOSwIgNXvzTR

I know one alternative that should work would be making use of that neat VIC-3 adapter for sale on here, plus adding a USB sound card and standard 3.5mm cable. Are there other alternatives out there?

Update on the General Dynamics device. It came in on Thursday and I've been playing with it off and on. First off, it's beautifully plug-and-play. I just grabbed the typical USB B cable and plugged it into a Windows 7 machine...in about 10 seconds, it had self installed and was ready for use as "UAA_1". Funny enough, it shows up as both a mouse and an audio device... The reasoning for this is it treats the PTT button as a middle-mouse click. I'm sure this was done for a specific application General Dynamics developed, and may be able to be captured by another program and replace it with another output. The handset operates in full duplex, so pressing the PTT does not cut off received audio, but you can only transmit audio while holding the PTT, as you would expect. The switch on the front of the device indicates "OP1" and "OP2." I haven't been able to identify a functional difference; however, I can say that when you switch it to OP2, the device will reinstall as "UAA_2." Lastly, there's the ANR power socket on the rear that appear to be accept a typical barrel coaxial connector, and displays a polarity diagram on the rear, but doesn't specify what voltage/amperage the box is expecting.

As for the audio quality, it's excellent with no sort of static or breaks that I can detect. You do clearly hear noise from the engagement/disengagement of the PTT switch, but it's not an overly loud spike. The microphone comes in very loud to the computer, but still is within the adjustment range in the Windows mixer. As well, the speaker output isn't as high as I like-at max volume, it's only loud, but not deafening like you'd have for any actual military radio (so...don't go using this in a high noise environment if your life depends on it). So far I've tried it with an H-250, a Harris modified H-250, and an RF-3020-HS002. Although it should be said that the RF-3020-HS002 behaved differently, being in full duplex without using the PTT, yet the PTT still functioned as that middle-mouse click.

I also just received a jumper cable today, but I can't seem to get it to actually connect. Both connectors on it are A-3167702-2, which seem to not want to fully seat into the U-283 panel jack of either the General Dynamics box or my PRC-138... What's different about this cable is the plastic insert is red instead of blue, plus rather then having the pins stick up from the plastic, they seem to be near-flush mounted. It seems like the red plastic is hitting the edge of the metal shell of the U-283 and preventing a full seating.

EDIT: I almost forgot one of the cooler discoveries about this! I connected the General Dynamic box to an Android phone with USB On-the-Go and it was fully functional! I had some fun making a phone call from my cell phone with an H-250. This opens up some really neat possibilities with a few android radio apps that are out there.

I don't think I understand a tenth of what you are talking about, but -

this sounds like it has some very cool possible applications for creating "radio chatter" during a static display?


I have a program on my computer that converts typed text to Morse code. I am just trying to figure out some way to use it on static displays.

Doghead will be blasting you soon for the link to an auction site. I inadvertently posted a link and got a warning the other day. Don't understand the reasoning behind that rule but whatever. Looks interesting.

WOW, so with your tech license you could use it in conjunction with your radio and Ham set up, what did it set you back ?

1 Patriot-of-many said:

Doghead will be blasting you soon for the link to an auction site. I inadvertently posted a link and got a warning the other day. Don't understand the reasoning behind that rule but whatever. Looks interesting.

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I hear you. There's really no other source of information for this piece of hardware at this time, so I hope they'll let it stand so everyone can see what I'm talking about until myself or someone else can document it elsewhere.

Jericho said:

WOW, so with your tech license you could use it in conjunction with your radio and Ham set up, what did it set you back ?

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The interface hardware? I spent $26 for the USB interface box, $15 for an interconnect cable, plus I already have several H250 handsets and USB-B cables around.

If you mean my radio equipment, then that answer is far too much. It's in the thousands with few signs of ever returning the investment except in what I learn from it.

My goal here is to use the USB audio interface to be able to use my computer as a modem for my PRC-138 (for modes other than what's built in) and to also offer an Internet gateway so that my PRC-138 can be a node if ever needed. I can't really do much on HF right now on just my tech license (I can basically do CW on HF and use the 6M band full function). I'll actually be taking my test for the general upgrade this Thursday, so we'll see if I learned enough to pass!

Sorry, almost missed your message. I have more practical functionality in mind, but you absolutely could use this for a static display. As a matter-of-fact, I've already unintentionally done that. I wanted some interesting chatter to listen to when first testing, so I pulled up YouTube videos that had long strings of radio chatter and played it out on my military handset. Plus as I already mentioned, I successfully had a phone call with this device as the audio sorce. With a little creativity and a gutted radio chassis, you could easily make a pretend radio.

...Then again, if we're being technical, you'd be installing an extremely compact, lightweight, multi band data/voice radio into a ruggedized case and giving it a U-283 interface. I think we often forget how absolutely incredible the cell phones we carry around daily really are. ..

If you studied you will do fine. It's not really that bad good luck !

Another small update... I forgot that I had a GRA-39 unit around that has a U-229 plug to output and receive audio levels appropriate for operating a radio. With it, I can hear audio played out clearly from my PC to H-250 handsets at both sides of the GRA-39 and the loudspeaker on the local side. Handset transmission is unfortunately a problem. From the remote unit, I get stupid-loud audio fed to my PC for just a few moments before it cuts out and won't send more audio until I release and reapply the PTT. On the local unit, there is no problem, I can send audio at perfectly acceptable levels and there are no cutoff issues. One consistent issue is all audio being played from the PC side-tones back to the PC at a low audio level. I'm not sure if this is by design of the GRA-39, or if I have a malfunctioning unit.

Seems that this saga must continue once I have a separate interconnect jumper cable come in. that actually wants to connect to my terminals. ...if that works out, then step two will be hitting the repair manual for my GRA-39 to see what's up with it...

papakb said:

Wirefox, Did you cellphone provide power to the USB box or did you power it externally? I have 4 of them and haven't used them for anything at this point. My plan was to use them with some of the mil computers I have but your comment on using them with an andriod phone have me interested. I've contacted several different groups at GD and no one seems to know (or won't tell) what group was the primary proponent for this product.

Something I've learned dealing with defense contractors over the years. After a product is more than a few years old they never heard of it and even though there are hundreds of them out in the public they still seem top think they are top secret national defense products! I guess it's just a carryover of the DOD CYA at all costs mentality. LOL

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The cellphone actually provided all the power for the test, but if you have an interest in saving battery life, this adapter (what I used) also allows you to inject external power: https://www.monoprice.com/product?c_id=116&cp_id=11602&cs_id=1160202&p_id=11595&seq=1&format=2 I can't guarantee that all phones will push out enough amperage to power the UAA, as I have no idea what the power draw requirement is.

Alright, new cables came in and they have physical fit, but no function. Computer can send audio out and its received fine, but I can't seem to accurately get anything from radio to PC: I can hear audio at the PC that changes tone and static patterns based on what frequency and operating mode I'm in, but absolutely nothing is intelligible...on my handset, I could hear clear but faint signals (was testing indoors, so no good antenna away from interference), but those same signals were not heard through the computer interface. I'm going to conclude that this is really not meant to directly operate a radio connected to it, but only handsets/headsets. It can be tricked into working by using a GRA-39, but that's horrendously inefficient, bulky, and it's narrowband. I've seen a couple of simple PC interface circuits that I'll have to try and and just make due with those.

If you are OK with using civilian market ham radio interface hardware, then I think that a SignaLink USB interface by Tigertronics should work well. I've been using one for years with my civilian HF ham radio gear, and I plan to try interfacing one to my green radios (particularly my AN/PRC-70) soon, too. You would need to build your own interface cable. I have the model that's bundled with an unterminated radio cable on order, and I'll mount an M55116/4 connector that I already have on the cable.

nf6x was talking about mil/civ interface and the comments on the video had pin out information I thought may be helpful.

papakb said:

Wirefox, have you tried the GD USB box with the original single earpiece David Clark headset that came with them?

M38in maine, just curious why this video got posted in this topic?

Kurt KG6KMJ

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No I haven't. I don't own one of those. I'd be happy to bring the USB interface and a laptop to Findlay if anyone wanted to try it out.

1 Patriot-of-many said:

Doghead will be blasting you soon for the link to an auction site. I inadvertently posted a link and got a warning the other day. Don't understand the reasoning behind that rule but whatever. Looks interesting.

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People link to them and then they rot out in a couple of weeks and nobody who finds the post months or years later can see what they were talking about.

OP - The GD UAA you bought is not intended to interface with radios. It's intended to interface headsets with PCs for operations stationed at terminals - like say, for example, drone operators, or whatever. If you are going to jumper it to a radio to use it like a signal link or rigblaster you may have a couple of problems. Besides the audio levels being wrong, I don't think the UAA will trip PTT on the radio properly - PTT pulls the pin to ground and in the intended setup it's the headset that does that, not the UAA, so I don't know why it would have the circuitry. The rigblaster and signallink consumer products do though.

Try checking the mic levels though - it sounds like from what you describe they are maxed out, so maybe you can adjust them in the windows mixing console (it's hard to find) and if that doesn't work, make a cable to pad the mic input to the UAA. I deal with this all the time with ham radios.

And yes those jumper cables work on radios which support being ganged together as a repeater, mic to speaker and speaker to mic, but those radios have special provisions when they operate in that scenario.

aleigh said:

People link to them and then they rot out in a couple of weeks and nobody who finds the post months or years later can see what they were talking about.

OP - The GD UAA you bought is not intended to interface with radios. It's intended to interface headsets with PCs for operations stationed at terminals - like say, for example, drone operators, or whatever. If you are going to jumper it to a radio to use it like a signal link or rigblaster you may have a couple of problems. Besides the audio levels being wrong, I don't think the UAA will trip PTT on the radio properly - PTT pulls the pin to ground and in the intended setup it's the headset that does that, not the UAA, so I don't know why it would have the circuitry. The rigblaster and signallink consumer products do though.

Try checking the mic levels though - it sounds like from what you describe they are maxed out, so maybe you can adjust them in the windows mixing console (it's hard to find) and if that doesn't work, make a cable to pad the mic input to the UAA. I deal with this all the time with ham radios.

And yes those jumper cables work on radios which support being ganged together as a repeater, mic to speaker and speaker to mic, but those radios have special provisions when they operate in that scenario.

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Thanks aleigh. That's the same conclusion I've formed about the UAA. I've already played with the mixer settings quite a bit and that's how I got it to be vaguely useable. It works very well with what it's intended to do (PC, headset interface) but doesn't handle the role of radio, pc interface in a usable manner, due to improper triggers and audio levels so far out of whack that they can barely be made useable. A custom cable setup on a Signalink really is the better solution here, but it was a fun experiment none-the-less, plus I have some audio recording guys very interested in being able to direct-record that unique, military sound via this UAA. Definitely a fun gadget to have around.

mic pads (attenuators) are widely available and cheap to DIY. For that mater all you really need is an audio-grade log pot inline. But you still have the PTT problem. It is a cool toy though. Be neat if you play video games, you know, sit there and scream on vent with your military headset.