Robin Rumbolt is a free lance writer and an electronics engineer now working a temporary contract job for Philips Consumer Electronics. He lives in Knoxville - eastern Tennessee. He is 53. Married, with 3 children, two in college and one in high school, Robin has been an amateur radio operator (WA4TEM) for 38 years and a private pilot for about 30 years.Robin recently took up the PPG sport and enjoys the flying!
He owns a SkyCruiser and an ITV Opale wing.
Along with my first paramotor and wing I purchased the KIWI/NAC 2000 Radio Helmet supplied by Ohio Powered Paragliding (www.flyohio.com)
I like the headset. The helmet fits well. The earphones are very comfortable and seal so well over the ears that engine noise is not a problem. The microphone seems to pick up my voice with very little motor noise. The intercom function is nice. Having the pigtail connector outside of the helmet makes it easy to interface various kinds of radios.
I am right-handed. So when I bought my paramotor, I specified that it be rigged for a left-handed throttle. This leaves my right hand available for playing with GPS, radio, etc. Unfortunately, my radio helmet came rigged with a PTT button on the LEFT earphone. Using the radio then became like a weird sobriety test with my right hand reaching over my helmet to my left earphone. Clearly, this had to change.
The first thing I did, was to sketch out the NAC-2000 intercom circuit. The diagram, for you electronics buffs, is shown in figure 1. While the actual electronics were sealed in a potted module, the connections were easy to figure out. The PTT switch merely applies power from the 9v battery in the left earphone to the circuit in the right earphone. But the power first goes through a jumper in the radio side connector. Did you ever notice that nothing works when the radio side cable is not plugged into the helmet cable? Well, that jumper is why. No jumper, no power. It was then apparent that an external switch would take very little effort to add.
Where would be the best place to put a PTT switch? My first thought was to put it on my throttle handle somewhere. But I worried about noise pickup from the engine via the kill switch wiring. I was also concerned about having another long wire for the prop to eat, or for me to get tangled in. My solution was to attach the switch to the headphone cable, just below the headset pigtail connector.
This mod requires use of a small tipped soldering iron, a very small Philips screwdriver, and a magnifying lens to see what your doing. Parts needed include a new PTT switch (Radio Shack #275-646), a 2 inch length of 5/8 inch OD PVC pipe (spray-painted black), and a 12 inch piece of 2 conductor wire.
First, disconnect the radio side of the cable from the headset pigtail by separating the connectors. (Fig. 2)
Then pop open left earphone of the headset by prying it open with your thumb or finger. (Fig. 3)
Remove the foam padding and you will see the battery and the PTT switch. (Fig. 4)
Using the soldering iron and a small piece of wire, solder a jumper across the internal PTT switch. (Fig. 5).
Then carefully reassemble the earphone. Set the headset aside. It's done. Next, using the small Philips screwdriver, remove the three screws holding the radio side connector together (Fig. 6).
Push the cable thru the back of the connector shell. The front of the connector should then pop out. There will be some plastic wrap around the pins. Either push it back or cut it out of the way. When that's done, you should see pins two and three jumpered together with a solder bridge. (Fig. 7)
Unsolder it. Thread the two-conductor wire through the back of the connector shell.
Solder one wire to pin 2, and the other to pin 3. (Fig. 8)
Check your connections to make sure that nothing is shorted, and that there are no sharp solder "points" sticking out to short to the connector shell. If you haven't cut it loose, now put the plastic wrap back around the pins. Reassemble the connector, and install the screws,
Remove the plastic nut from the switch body & discard.
Run the other end of your two-conductor cable through the piece of PVC pipe and solder the two wires to the two switch terminals (Fig. 9)
It doesn't matter which wire goes to which terminal.
I found that by filing down the threads on the switch body, the switch made a nice, tight friction fit into the PVC pipe section. Push it into the pipe. Use a little glue if you need to. It will look like Fig. 10.
Press the button a couple of times to make sure that it pops back out every time. The first time I fit the switch into the pipe, the fit was SO tight that the switch body was compressed enough to prevent the button from popping back out.
Re-attach the radio side connector to the helmet side connector. Then press the new button. You should hear the intercom click if all is properly installed.
In my installation, I wanted the button always facing up. So I attached the pipe/button assembly to the radio cable by wrapping it with several turns of black electrical tape. The final cable assembly is shown in Figures 11 & 12.
That's it! Now I can reach the PTT switch with either hand with no worries!
Good flying & communicating!
Robin Rumbolt WA4TEM