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#1
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radio squeal question.
radio is an icom a200 headset is a clone of a dave clark, an australian altronics C9073 when taxying and early into the flight when I press the ptt the radio squeals in the headset. after a while in the air the squeal vanishes and the radio setup works just fine. I changed headsets today while taxying out and discovered that the squeal vanished with the headset. The new/different headset worked fine. I thought it might have been moisture/condensation and have wd40'd the connectors without changing the problem one iota. anyone an idea as to what would cause this problem? all equipment appears to be in sound working order with no damage. Stealth Pilot |
#2
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radio squeal question.
My best guess is that the "cloners" didn't take into account RF pickup by
the headset leads and you are getting RF into the mic circuit, which rectifies in the first transistor junction it comes to, becomes an audio signal, feeds itself into the transmitter modulator, gets on the output, feeds itself into the headset leads, and round and round we go. Jim "Stealth Pilot" wrote in message ... radio is an icom a200 headset is a clone of a dave clark |
#3
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radio squeal question.
RST Engineering wrote:
My best guess is that the "cloners" didn't take into account RF pickup by the headset leads and you are getting RF into the mic circuit, which rectifies in the first transistor junction it comes to, becomes an audio signal, feeds itself into the transmitter modulator, gets on the output, feeds itself into the headset leads, and round and round we go. Jim "Stealth Pilot" wrote in message ... radio is an icom a200 headset is a clone of a dave clark Ahh Jim You are correct... a lot of problems with Altronic headsets due shielding etc.... Some of our customers have fitted ferrite beads on the headset line and that seems to work well. Australian or otherwise, they are NOT a David Clarke !! and fall well short as a clone. Regards Michael @ XCOM |
#4
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radio squeal question.
On Mon, 06 Nov 2006 02:26:25 GMT, USER wrote:
RST Engineering wrote: My best guess is that the "cloners" didn't take into account RF pickup by the headset leads and you are getting RF into the mic circuit, which rectifies in the first transistor junction it comes to, becomes an audio signal, feeds itself into the transmitter modulator, gets on the output, feeds itself into the headset leads, and round and round we go. Jim thanks jim. it hasnt been evident for 6 years. I wonder why it clears after some flying time. hmmm.....whats about to fail.... "Stealth Pilot" wrote in message ... radio is an icom a200 headset is a clone of a dave clark Ahh Jim You are correct... a lot of problems with Altronic headsets due shielding etc.... Some of our customers have fitted ferrite beads on the headset line and that seems to work well. Australian or otherwise, they are NOT a David Clarke !! and fall well short as a clone. Regards Michael @ XCOM interesting comments. they have been in use in the aircraft for 6 years without problem up until recently so i suspect that your comments are not quite correct. a friend and I have flown in his thorp and swapped the dave clarks and the altronics for 15 minutes about. neither of us could tell the difference. we dont believe that they fall short as a clone. the latest dave clarks at $aus1,350 or so a headset are more expensive than gold for the weight if my calc was correct. Stealth Pilot |
#5
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radio squeal question.
The latest David Clarks don't compare to the Altronics... the DC 13.4's
do and they are only $480 AU$... the latest DC's have all the bells and whistles (and the price tag). All i can do is speak from experience having 1200 XCOM customers, many in AU with Altronics headsets and a vast majority cause problems..... Simple test, press the PTT button with one set of headsets only plugged in and move around the cockpit, does the squealing sound change ?? turn your head in all sorts of directions and listen to the squeal change, this is RF feedback getting into the headsets. If it was the wiring in the aircraft it doesn't move and the squeal would be more or less the same. Please try the test. Now why after 6 years is this suddenly happening ?? It could be the shielding has finally let go from pulling the plugs out by the cords, it could be tarnishing on the plugs it could be a heap of things... even corrosion on your aerial. Send me an email through XCOM for some more ideas or call me on 0418 168 665 if you need any other help. Regards Michael @ XCOM Stealth Pilot wrote: On Mon, 06 Nov 2006 02:26:25 GMT, USER wrote: RST Engineering wrote: My best guess is that the "cloners" didn't take into account RF pickup by the headset leads and you are getting RF into the mic circuit, which rectifies in the first transistor junction it comes to, becomes an audio signal, feeds itself into the transmitter modulator, gets on the output, feeds itself into the headset leads, and round and round we go. Jim thanks jim. it hasnt been evident for 6 years. I wonder why it clears after some flying time. hmmm.....whats about to fail.... "Stealth Pilot" wrote in message ... radio is an icom a200 headset is a clone of a dave clark Ahh Jim You are correct... a lot of problems with Altronic headsets due shielding etc.... Some of our customers have fitted ferrite beads on the headset line and that seems to work well. Australian or otherwise, they are NOT a David Clarke !! and fall well short as a clone. Regards Michael @ XCOM interesting comments. they have been in use in the aircraft for 6 years without problem up until recently so i suspect that your comments are not quite correct. a friend and I have flown in his thorp and swapped the dave clarks and the altronics for 15 minutes about. neither of us could tell the difference. we dont believe that they fall short as a clone. the latest dave clarks at $aus1,350 or so a headset are more expensive than gold for the weight if my calc was correct. Stealth Pilot |
#6
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radio squeal question.
Stealth Pilot wrote: radio is an icom a200 headset is a clone of a dave clark, an australian altronics C9073 when taxying and early into the flight when I press the ptt the radio squeals in the headset. after a while in the air the squeal vanishes and the radio setup works just fine. I changed headsets today while taxying out and discovered that the squeal vanished with the headset. The new/different headset worked fine. I thought it might have been moisture/condensation and have wd40'd the connectors without changing the problem one iota. anyone an idea as to what would cause this problem? all equipment appears to be in sound working order with no damage. When you are on the ground the antenna pattern is modified by the nearby ground, allowing more of the RF field to be incident on your headset and wiring. Sometimes, also, if your antenna is on the bottom, the nearby ground can change your antenna's SWR, which may result in antenna currents flowing on the outside of the coax. You might try ferrite beads on your mic leads close to where they enter the radio, and also a large clamp-on ferrite on your antenna's coax near the antenna connection. Stealth Pilot |
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