interference with mustering radios

[Tim]

Having problems with these mongrel mustering radios, just wondering if anyone has beaten them yet. Am flying a side by side open cockpit Ross Symes machine, 912, Micro Avionics headset with a GME TX 3500 80 Channel UHF, There is a constant loud background noise to the mustering bikes on the ground when I"m transmitting at cruise speed, the noise disappears with power off. Its not electrical and there is no background noise when talking on intercom with a passenger at cruise. Seems to be prop noise? maybe. I"ve almost resorted to throwing hand written notes to the blokes on the ground!! Any ideas??

[aussie_paul]

Having problems with these mongrel mustering radios, just wondering if anyone has beaten them yet. Am flying a side by side open cockpit Ross Symes machine, 912, Micro Avionics headset with a GME TX 3500 80 Channel UHF, There is a constant loud background noise to the mustering bikes on the ground when I"m transmitting at cruise speed, the noise disappears with power off. Its not electrical and there is no background noise when talking on intercom with a passenger at cruise. Seems to be prop noise? maybe. I"ve almost resorted to throwing hand written notes to the blokes on the ground!! Any ideas??Tim, I had that trouble many years ago(1984) while using the hand microphone to talk back to home. I needed a resister in the line to get rid of the background noise and just let my voice through. I put a variable resister in the mike housing and kept adjusting and testing. I got my wife to record the tests as her quite good was very different to my quite good!!!!There could be a microphone gain, (micgain) adjustable trim pot in the circuit that may be adjustable.Try doubling/trebling the foam around the mic and talking louder as an initial test.Aussie Paul.

[Brian]

PB is on the money, you need a resistor[ 5 ohm I think] Ask Rosco. Wonder he didnt put one in when he set everything up. Makes all the difference !!!

[MilesW]

I assume you are using the Micro Avionics blackbox? If set up properly should be as good as you"ll hear on any rotary wing. Inside there is a set of dip switches for mic gain. Usually have to be adjusted for each different brand of radio. Do you have the instructions? I can scan a set and email them to you if you need them. Miles

[Tim]

Thanks you blokes, Miles it is a Microavionics black box, and I don"t have the instructions, a copy would be great. Adrian has given me different settings for the box, but made no difference, so I put it back to default. Will try a resistor as well. This is also the first time I"ve used the new 80 Channel UHF, the old 40 channel with the 582 engine, (more engine noise?), didn"t have a problem.

[birdy]

Having problems with these mongrel mustering radios...........Only problems iv ever had with the rosco setup is the bastereds one the ground wont shutup. [ if theres anyone down there.]

[Brian]

The new 80 channel UHF"s are causing no end of problems from what I hear.

[chook]

Tim as you are aware our little jaunt up your way has been cancelled until next year. I had anticipated a complete rewire of your machine when we visited anyway. Fr the rest of you, Tim lives and operates. About 50m from the coast so salt is a major problem, so effectively it"s quicker and easier to junk everything except the sealed electronics about every couple of years.Tim when are you back in town? Are you currently mustering? And it sound as if you have changed the UHF anyway which will require marrying into your existing system again.I am currently in Hobart and won"t be back in town for another week.Regards..........Chook

[bishoff7]

Tim Have you cured yor problem with the background noise as yetI am really interested to know what you foundRegards Bish

[chook]

Bish I have just revisited this thread.The answer was a faulty connection on a antenna lead conversion cable. Not a standard connector.Effectively when the rotax reached 3000 rpm it was the vibration frequency which caused the centre pin in the connector to vibrate and cause an intermittent connection when transmitting (and receiving but it was not as pronounced).Tricky one to locate.It is the silver connector at the bottom left hand side of the black box (GME 3500)