Speedo
FOUNDER
TN
One of the nicer planes at work has an annoying tone in the intercom, and our mechanics have tried but have not been able to fix it. We have few avionics guys available to us, so I'm hoping someone here can give me a few tips that I can pass along to the mechanics.
The plane's audio panel is set up for the following com radios: HF, Com 1, and Com 2. It also has buttons for Nav 1 and 2, ADF, etc, but I don't think the problem lies there.
The radio stack includes a marine band VHF controlled by the HF button on the audio panel, a Garmin 430 controlled by the Com 1 button, and a KX 155 controlled by Com 2. I need to be able to monitor the VHF marine band radio all the time and simultaneously Com 1 or Com 2. However, whenever I select the marine band radio when I've also got Com 1 or Com 2 selected I get a loud and annoying dentist drill sort of noise. I can bear it for only about ten minutes, and then must deselect the marine band radio (by pressing the HF button on the audio panel).
The noise is only heard when I have the marine band radio and either of the com radios selected on the audio panel. If I select only the marine band radio I do not hear the noise. I do not hear the noise when the marine band radio is not selected and either or both of the other two com radios are selected.
The noise goes up in volume and frequency with increasing RPMs. As I turn off the Nav lights, the beacon, and the LED landing and taxi lights the volume of the noise drops as each switch is opened. However, the noise is still there.
Today I flew a different plane and it did not have the same noise problem. It was equipped with a marine band radio, Com 1 was a KX155, and Com 2 was an Apollo GX60. On this plane I could select all three radios simultaneously and there was no noise at all.
Are there any radio gurus out there who have encountered this problem themselves, and if so, how did you cure it?
[Oh, and by the way, this morning I flew from St. Mary's to Anvik, and then ten miles up the mighty Yukon to Grayling, and then back to St. Mary's. It was a beautiful, cold, clear morning. Most of the moose were still lying down (tough buggers), the inversion layer was creating "fairy castles" out of the hills near Marshall and along the Andrefsky River, and the air was smooth as silk. It was cold, cold, cold down low, but climbing to 2,000' put me above the inversion layer and it was much warmer there.
On cold mornings like this the engine develops loads of power, and an empty plane is often airborne before the engine reaches 24 inches of manifold pressure; quite a contrast to summer, when I might need to use 26 or 27 inches even when empty.]
Thanks in advance for all tips and suggestions.
The plane's audio panel is set up for the following com radios: HF, Com 1, and Com 2. It also has buttons for Nav 1 and 2, ADF, etc, but I don't think the problem lies there.
The radio stack includes a marine band VHF controlled by the HF button on the audio panel, a Garmin 430 controlled by the Com 1 button, and a KX 155 controlled by Com 2. I need to be able to monitor the VHF marine band radio all the time and simultaneously Com 1 or Com 2. However, whenever I select the marine band radio when I've also got Com 1 or Com 2 selected I get a loud and annoying dentist drill sort of noise. I can bear it for only about ten minutes, and then must deselect the marine band radio (by pressing the HF button on the audio panel).
The noise is only heard when I have the marine band radio and either of the com radios selected on the audio panel. If I select only the marine band radio I do not hear the noise. I do not hear the noise when the marine band radio is not selected and either or both of the other two com radios are selected.
The noise goes up in volume and frequency with increasing RPMs. As I turn off the Nav lights, the beacon, and the LED landing and taxi lights the volume of the noise drops as each switch is opened. However, the noise is still there.
Today I flew a different plane and it did not have the same noise problem. It was equipped with a marine band radio, Com 1 was a KX155, and Com 2 was an Apollo GX60. On this plane I could select all three radios simultaneously and there was no noise at all.
Are there any radio gurus out there who have encountered this problem themselves, and if so, how did you cure it?
[Oh, and by the way, this morning I flew from St. Mary's to Anvik, and then ten miles up the mighty Yukon to Grayling, and then back to St. Mary's. It was a beautiful, cold, clear morning. Most of the moose were still lying down (tough buggers), the inversion layer was creating "fairy castles" out of the hills near Marshall and along the Andrefsky River, and the air was smooth as silk. It was cold, cold, cold down low, but climbing to 2,000' put me above the inversion layer and it was much warmer there.
On cold mornings like this the engine develops loads of power, and an empty plane is often airborne before the engine reaches 24 inches of manifold pressure; quite a contrast to summer, when I might need to use 26 or 27 inches even when empty.]
Thanks in advance for all tips and suggestions.
