If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
where exactly to put the noise filter
Hi There,
We have a 1966 mooney m20e. We're just in the process of putting in a noise filter so that it will hopefully reduce some of the static on the radio. I'm wondering if the filter goes between the generator and the voltage regulator.... or if the filter goes between the voltage regulator and the buss. Any help would be appreciated, Thanks... -Dico |
#2
|
|||
|
|||
Dico,
What problem are you trying to cure? If you have "popping" type of static in your Com/Nav receiver, then you have a bad shield on a spark plug, or poor shielding on your P-leads where they run from the mag to the mag switch. Noise filter on the alternator wont do anything for this... If you have audible strobe squeal which goes away if you turn off the strobes, ditto... This requires work in the audio wiring and possibly in the strobe cabling . If you have alternator howl or whine which varies with engine speed, and goes away if you turn off the ALT field, then a noise filter installed on the alternator is unlikely to do much, either... This means that your audio wiring (audio panel, intercom, mic/headphone jacks) need attention. If you have "hash" type noise on the Com/Nav receiver, then see if it goes away when the engine is stopped (on the ground). If it does, then it is likely induced by mechanical vibration. Bad antennas, bad coax fittings, radios not properly seated in the rack can cause this. About the only symptom which installing a filter on the alternator is likely to cure is if you have "hash" type noise when listening to 200-400Khz on your ADF receiver. MikeM Skylane '1MM Pacer '00Z Dico Reyers wrote: Hi There, We have a 1966 mooney m20e. We're just in the process of putting in a noise filter so that it will hopefully reduce some of the static on the radio. I'm wondering if the filter goes between the generator and the voltage regulator.... or if the filter goes between the voltage regulator and the buss. Any help would be appreciated, Thanks... -Dico |
#3
|
|||
|
|||
Hey Mike,
What's the cure for "bleed through" from one com radio to the other? We usually keep "Com 2" tuned to our local AWOS frequency. When we're near Iowa City, we can faintly hear it in the background through our headphones -- even when "Com 2" or "Both" aren't selected on our audio panel. Of course, this isn't an issue without ANR headsets (couldn't hear it), or when we're far enough away from the strong signal -- but it's one of those little annoyances that always bugs us. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#4
|
|||
|
|||
Jay Honeck wrote: Hey Mike, What's the cure for "bleed through" from one com radio to the other? Usually "bleed through" refers to the effects of RF overload on Com2 while transmitting on Com1, or vice versa. Most audio panels contain automatic muting circuits which completely block the audio from opposite com reciever while the other's transmitter is keyed. We usually keep "Com 2" tuned to our local AWOS frequency. When we're near Iowa City, we can faintly hear it in the background through our headphones -- even when "Com 2" or "Both" aren't selected on our audio panel. This sounds like inadequate isolation in the audio source switching of the audio panel. Most of modern audio panels (King, PSE, RST) do not intrisically have this problem. I think you have a PSE, which shouldn't do this. It is likely that your installer did something funky with the audio wiring between Com1/Com2 and the audio panel to induce this. Could be that the Speaker outputs of the Com radios are wired to 8 Ohm dummy load resistors inside the audio panel. If the installer took a shortcut and shared the ground connection from speaker-low output on the Com(s) to the audio ground on the audio panel, it created a classic ground loop between the speaker audio loop and the headphone output loop, thereby creating the crosstalk. Better wiring technique might have prevented this. Most modern Com radios dont care if the speaker outputs are terminated into a dummy load resistor when not connected to the overhead speaker, so it isn't even necessary to utilize those loads built into the audio panel. Of course, this isn't an issue without ANR headsets (couldn't hear it), or when we're far enough away from the strong signal -- but it's one of those little annoyances that always bugs us. For further diagnosis, I'll bet that if you turn the volume control of the non-selected comm radio down, then the bleedthrough will go away. Also try switching the non-selected com receiver to the overhead speaker while listening to the primary com on the ANR headsets, and report back. MikeM Skylane \1MM Pacer \00Z |
#5
|
|||
|
|||
On Fri, 20 Feb 2004 17:57:10 GMT, "Jay Honeck"
wrote: Hey Mike, What's the cure for "bleed through" from one com radio to the other? We usually keep "Com 2" tuned to our local AWOS frequency. When we're near Iowa City, we can faintly hear it in the background through our headphones -- even when "Com 2" or "Both" aren't selected on our audio panel. Of course, this isn't an issue without ANR headsets (couldn't hear it), or when we're far enough away from the strong signal -- but it's one of those little annoyances that always bugs us. Jay - what make/model are the COM radios in your plane? -nathan |
#6
|
|||
|
|||
This sounds like inadequate isolation in the audio source switching of
the audio panel. Most of modern audio panels (King, PSE, RST) do not intrisically have this problem. I think you have a PSE, which shouldn't do this. Actually, I have a Narco CP-136 audio panel. (See a picture of this model at http://www.ronhahn.com/Hawk-XP/CP136.html ) For further diagnosis, I'll bet that if you turn the volume control of the non-selected comm radio down, then the bleedthrough will go away. Yep, I believe it does. So this means the audio panel is wired incorrectly? Also try switching the non-selected com receiver to the overhead speaker while listening to the primary com on the ANR headsets, and report back. Okay, will do. I should expect to hear the AWOS broadcasting quietly on the speaker, I presume, same as I hear in my headset? -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#7
|
|||
|
|||
Jay - what make/model are the COM radios in your plane?
Com 1 is a brand new Narco 810-R, digital. (It's the slide-in replacement for the Com 120) Com 2 is an old-but-perfect Narco 120. Both work flawlessly. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#8
|
|||
|
|||
On Fri, 20 Feb 2004 23:11:27 GMT, "Jay Honeck"
wrote: Jay - what make/model are the COM radios in your plane? Com 1 is a brand new Narco 810-R, digital. (It's the slide-in replacement for the Com 120) Com 2 is an old-but-perfect Narco 120. Hi Jay, Take this with a caveat as I am a digital engineer who likes to learn about RF stuff. I could be in left field here... I asked because I was trying to determine if the radios utilized the same IF frequency (which they would if it is the same radio). I don't know enough about the Narco 810 or 120 to determine if they share the same IF. Where I was going with this... The bleedthrough might be leakage from the IF section of one radio coupling into the IF of the other radio. That would explain why the audio is only noticeable as you are near the AWOS transmitter, where the energy entering the IF stage on COM2 would be strongest. An interesting test would be: 1. Shut off COM2 on the audio panel 2. Fly to a distant location where you can't hear the bleedthrough. 3. Turn on the audio for COM2 4. Can you hear the AWOS over the audio panel? If you can hear the audio, then I suspect the audio problem is related to the radio and not the audio panel (or audio wiring). -Nathan |
#9
|
|||
|
|||
Jay Honeck wrote:
This sounds like inadequate isolation in the audio source switching of the audio panel. Most of modern audio panels (King, PSE, RST) do not intrisically have this problem. I think you have a PSE, which shouldn't do this. Actually, I have a Narco CP-136 audio panel. I do not have any experience with these, so the lack of isolation could be a shortcoming of the design. (See a picture of this model at http://www.ronhahn.com/Hawk-XP/CP136.html ) For further diagnosis, I'll bet that if you turn the volume control of the non-selected comm radio down, then the bleedthrough will go away. Yep, I believe it does. So this means the audio panel is wired incorrectly? It just means that the bleed-through is happening at audio frequencies; not by one IF coupling to the other IF as another poster postulated. Also try switching the non-selected com receiver to the overhead speaker while listening to the primary com on the ANR headsets, and report back. Okay, will do. I should expect to hear the AWOS broadcasting quietly on the speaker, I presume, same as I hear in my headset? Yes, but try to determine if the faint feedthrough you hear in your headphones is reduced by routing com2 to the speaker. It will be a subtle difference, because the speaker audio will leak into your headphones accoustically. If the feedthrough is reduced, then my speculation about the dummy load resistors would warrant more investigation. MikeM Skylane '1MM Pacer '00Z |
#10
|
|||
|
|||
An interesting test would be:
1. Shut off COM2 on the audio panel 2. Fly to a distant location where you can't hear the bleedthrough. 3. Turn on the audio for COM2 4. Can you hear the AWOS over the audio panel? If you can hear the audio, then I suspect the audio problem is related to the radio and not the audio panel (or audio wiring). I don't think I've got enough information here. What position would I have the audio panel in for this test? Com 1, Com 2, or Both? And, assuming Both, what do you mean when you say "Can I hear the AWOS over the audio panel?" Do you mean on the speaker? Or in my headphones? -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Small plane noise is destroying my life | Robert Morien | General Aviation | 5 | December 1st 04 06:01 PM |
K&N Performance Gold Oil Filter? | MikeremlaP | Home Built | 0 | September 3rd 04 05:58 PM |
Plasma Reduces Jet Noise (Turbines?) | sanman | Home Built | 1 | June 27th 04 12:45 AM |
Aviation Conspiracy: Bush Backs Down On Tower Privatization Issue!!! | Bill Mulcahy | General Aviation | 3 | October 1st 03 05:39 AM |
Airwolf oil filter system | kevin | Owning | 3 | August 7th 03 04:24 PM |