THis is not an ICE question but I am at a loss as to where it should go. I am trying to set up a Bike to Bike Intercom using PMR446 Radio's. I am using noise cancelling, low impedance electret mics in the headsets to reduce the wind and engine noise. The only problem is that I am trying to get it to operate on VOX mode and the mic is tripping at noise levels which are just too low. I need to attenuate the mics so they don't hold the TX open all the time. I tried to put in a pot in line to reduce the voltage, but it doesn't desensitise the gain on the mic enough. I have been told also that if you reduce the voltage by too much, it will destabilise the circuit. I am not really up on this and could use some help.

Cheers Ash

[Edited by DRUNKNORGY - 12/18/2002 9:43:53 AM]

Try uk.rec.motorcycles, they are an absolute mine of information, and not just about motorbikes. It's a robust group though, so you'll need to top-post and stuff to avoid a serious flaming :)

Steve.

Ash,

Mail me offlist?

S(imon)

Try EARS

Ask for Mick. He's a biker & used to dealing with couriers etc. Top notch radio engineers too!

This won't be much help but the way the Autocom does it is it has two mikes. One facing forward (towards the road) and one rearwards (towards you).

Phase cancellation is used to remove the signal taken from the front mike from the signal coming from the rear mike. What is left is just your voice. It works really well my bike mates and I often enjoy bike to bike converstaions at over a ton. The Autcom unit and headset is guaranteed to work up to 160 but I doubt you'd be able to hear it at much above 120 TBH!

I also have had some friends who have tried everything they could think of to put together a home made solution such as you are doing and they have all eventually admitted defeat, and gone with the Autocom. It's expensive but it works really well. Most of my bike mates now have one and I also plug my phone into it also so I can chat to my fellow bikers and keep my wife informed of what time dinner needs to be ready for when I get back ;);):):):D:D

Having a three way conversation with someone on the phone and my wife riding pillion is also good fun :D:D

Matt :)

P.S. Using the Autocom, people on the phone/other end of the radio can't tell I'm even riding my bike. They say it just sounds like I'm at home - even when I'm on the motorway or on the continent going for the land speed record ;):):D

Have to agree with regards the Autocom system. It really is fantastic, and its definately one of my 'best buys'. People who have never used an intercom would say you dont need one, but people who have would never go back to not having one.

Ricky !

Thanks for the Advice, I have been looking at the autocom system and gave the rep a good grilling at the NEC last month. The only problem is its just so expensive (i'd rather spend the money on track days:D) I have a mate who's just as keen to get the intercom system running as myself (he's also an electronics engineer). He said that the electronic noise cancelling is the best way to go as you described but I am trying with these noise cancelling mics first. I had some success last weekend with a plantronics headset and tested it up to an indicated ton (and he could still understand me)These mics use a clever porting arrangement in the back of them and are more successful that anything else to date.

Ash

If you're keen to do it yourself, have a look for a throat mic.
They strap onto your neck, I have seen them both as a complete strap fitting and also with a very small headphone style fixing, (like a thin metal sprung band).

I've used them on military radios and they are very good.

Not sure where you can get some but a quick web search will probably turn some up?


Mike
Scooby Mania