Racal Headsets

[papakb]

The CX13479 bailout cords are getting a bit hard to find but here's another solution. This cable is made by Racal specifically to replace the long bailout cords with a shorter version. They can be purchased from Racal as pn#437936 but they're $200. Better to find them online if you can.

We tried this cable with several radios and headsets and could not get it to work.

 

[Hpwr]

Steve, if the 174 is powering pin E of the U229 connector then all you'll need to do to get the ANR working is wire it to pin F of the U329 connector on the headset. The high gain issue on the mic could be fixed with a resistor inline but just moving the mic away from your mouth might also do it. I never cared for the mic being that close anyway.

Kurt, per my post I have it working and powered from the 174, just moved the power wire from pin F to Pin E in the U329, and dont use pin F, which the 174 doesn't have anyway. Many CX-13479 cables still on Ebay....although cost as much as the RA5000 it self.

Thanks Again,
Steve
KM4V

 

[papakb]

Here's a picture of V3 of the adapter box. I had a bad connection in the U229 plug that I needed to fix and on your note I've epoxied a 20K trimpot to the inside of the adapter box to make the mic gain adjustable. I used a Hammond 1590A box for the project and everything fits into it well.

The secondary purposes of the adapter box was to create an access point to apply ANR voltage to the headset when they're being used with older equipment that doesn't supply power from the audio connector like the PRC series radios and the VRC-12s.

When I vary the voltage applied to the red and black wires over 9 volts I can hear the ANR circuit turning on and off. Now all I need to do is find a convenient voltage source in the HMMWV.

 

[Hpwr]

Kurt,

Thanks that would be great, looking forward to the pics. Some years ago I built a Clansman (PRC320, etc) audio breakout / test box, and while building it I also set it up to be able to use Clansman's audio gear on US radios and Us audio gear on Clansman. The Clansman audio use balanced mics so in this box I transformer isolated the balanced to US unbalanced audio. Anyway turned out pretty well and has been a handy test / adapter device. PS also added a PTT switch (momentary or latched on) for using it as a test box.

Steve
KM4V

 

[papakb]

The latest update on the Racal headset project. The adapter box works exactly as intended and wired as explained above. The pot that was added for reducing mic gain did nothing with the 8 headsets we tried it with and was removed. The ANR circuit kicks in when anything over 9 volts is applied to pin F of the U329 connector and dramatically increases the amplification and quality of both the transmit and received audio signals so I highly recommend incorporation it into the box. These tests were done between a PRC-126 and a PRC-77 with the headsets connected alternately to both radios so it should work with any of the PRC or VRC family of radios. Since the U229 plug is the one attaching to the RT it doesn't mess with the fill pin (F) if the radio has one.

Some further testing of the headsets shows that the headset draws about 50mA when connected to the adapter box. Using an online battery calculator a 9 volt battery should last at least 300 days with the headset connected to it. If the headset is only connected when used the battery will literally last for years so the solution is to install it in the Hammond 1590A project box and call it a day!

 

[papakb]

We had this box out this past weekend and it worked perfectly with an RT-524 in a friends M151A2. I've put together a couple of them now for people and all the feedback is positive.

 

[Wire Fox]

I can report in: the RACAL 5000 headsets work directly on a PRC-138 with no adapter. Only issue was as others have noted: the mic gain is very hot. Just keying up showed almost full power TX on my radio. These really need to be stepped down to work correctly...

Sent from my Nokia 6.1 using Tapatalk

 

[Wire Fox]

Another odd comment... I haven't yet tried to see what happens when my headsets are connected to a power source to activate the intercom-powered ANR as I don't yet have a functional intercom system assembled, but I did notice this:

I bought two Racal 5000/1/6400 headsets from different sources. Both are new. The older one (by serial number) is only MOD 1. The newer one has MOD 1 & 2 checked. With battery powered talk-through enabled, the MOD 1-only headset faintly passes sound through. Basically, it's enough that if someone is directly talking to you, you'll understand them clearly. As well, you can identify where mid-volume sounds are coming from. Anything at a whisper or a light tap will be muffled out. With the MOD 2 headset, everything is loudly amplified on battery only. I can hear every faint sound in the room, voices come in crystal clear from anywhere around me. I have very full situational awareness while wearing the headset.

The MOD 1 headset did also have a connection problem...the left ear kept cutting in and out, so I had to disassembled the headset and reassembled it to improve the connection of the internal contacts (it uses spring-loaded pins). So, I can't be 100% sure that the lower audio volume on the 1st headset isn't in-part due to further electrical issues. It does seems like it was reliably working after I reassembled it, so I'm more inclined to believe that the difference in performance is due to the different MODs the headset was manufactured with. If anybody wants to comment about what MODs are punched on their headset and how they perform, they may help to confirm or deny this hypothesis...

 

[hrbergeron]

I use racals in my LMTV through an intercom and to a PRC-77. The intercom main box connects to the MT-1029 and the individual control boxes set the listen and work radios. For the price of ~$50 on eBay, they're pretty nice units. You can also shoot with them too because they have automatic noise cancellation and in my opinion they work better than my Howard Leights.