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Difficult radio static problem...Please help!

Hobbit44

Member
My first post on Van's and I know this is a common problem, but I've exhausted ideas and read and rewired for two weeks. Could really use some insight!

Zenith 701, just doing Phase I test flights.
Radio is a Becker AR 3201 with built-in intercom.

Wiring diagram followed closely and assistance from hangar mate and other EAA guys. (hangar mate is an engineer with an RV-10 he built)

Antenna on belly of aluminum plane, isolated carefully. Coax connected well and shielding grounded at antenna base.

Radio clear, transmits well, intercom works well, everything working great....until take-off. A few feet off the ground, static begins. Loud static. Not a whine from alternator, but does seem to vary with RPM sometimes. Can hear faint "clicks" in headset when elevator trim tab button is actuated. Hard to hear others transmitting, due to constant static, but they report they hear me 5x5. If receiving a powerful transmission from another radio, it is clear. Most received signals are not strong enough to suppress all the static. On landing, radio clear again. No static. With full-power run-up on ground, no significant static.

Initially headset jack grounds and mic jack grounds were combined to one ground wire (shielded), which went to grounding block near radio.

Rewired, as we noted that wiring diagram showed these grounds to have pin positions into radio.
Fixed:
Headset and Mic jacks have grounds which terminate in pins into radio. PTT ground (shielded) goes to grounding block near radio. Headset and mic and PTT wires are shielded. Headset jack grounds connect with shielding and shielding goes to headset ground pin for radio. Mic grounds use conductor wire (shielded) to go to mic ground pin in radio.

Tried: (without benefit)

disconnecting intercomm.

adjusting squelch, intercomm level, single-sideband level (3 philips screw adjustments on side of radio case)

rechecking and further insulating antenna from aluminum skin.

took grounding connection off of coax shielding at antenna...leaving coax shielding not grounded. At this point, others could not hear my transmissions well at all. Transmission clarity was terrible.

reconnected shielding at antenna (angled whip antenna with design to have shielding grounded at antenna base) and moved antenna further back in aircraft (to get farther from generator -- Rotax 912ULS with proper resistor plugs and generator at firewall-side of engine--electronic ignition). My transmissions are clear again.

Connected hand-held rubber-ducky antenna to back of radio. Still same static.

connected radio to ELT antenna (coax), which sits on top of aircraft, behind cockpit.--THIS SEEMED TO CLEAR ALMOST ALL STATIC. Thus, I moved the radio antenna (under the belly) another two feet back from firewall (should be plenty far away from engine, ignition, and generator, at this location).

Still static.

I'm perplexed. The static is not characteristic of alternator "whine". Hearing the faint clicks of the trim switch being activated, makes me think there is something feeding radio signal from the airframe to the radio...but why fine on the ground?

If anyone has any insight into this, I'd be most grateful. My friend with the RV-10 suggested I try this forum, even though I have a Zenith :)

I suppose, if nothing else, I'll try again connecting to the ELT antenna and see if that really does clear it up. If so, I suppose I may try moving the antenna again, but several guys with more grey hair than me don't think it should have to be moved from where it is.

Thanks again for reading and any thoughts or ideas!
 
That is weird.

What else is different from run up to take off? By chance are you turning on any LED nav lights or strobes? How about a USB charger?

Is your buss voltage changing a lot from run up to flying? Perhaps your radio or something else is voltage sensitive.

If nothing else I’d pull the breakers on everything, one at a time when in the air to see if you can change the noise level. This would include the alternator. If so, then work from there.

Carl
 
That is weird.

What else is different from run up to take off? By chance are you turning on any LED nav lights or strobes? How about a USB charger?

Is your buss voltage changing a lot from run up to flying? Perhaps your radio or something else is voltage sensitive.

If nothing else I’d pull the breakers on everything, one at a time when in the air to see if you can change the noise level. This would include the alternator. If so, then work from there.

Carl

Hi. Thank you for the thoughts on this. It's a very simple panel. Master goes on, then start, then avionics. No other electronics are changed, turned on or off, nothing plugged in, etc, etc. Have had strobes on / off without any changes during all phases. Bus voltage reads steady at 14v throughout.
 
Do you have anything plugged in to a portable battery, perhaps your phone or tablet? I had a similar problem with radio static that occurred when I plugged my iPad into a portable battery using a USB cable. As soon as I unplugged it, the static went away. (Mine didn't occur only when airborne, but any time the portable battery was in use.)

My other thought is your statement that you "further insulating antenna from aluminum skin". Typically the antennas I am familiar with do not want the mounting to be insulated from the aluminum skin, but instead used the installation screws to bond the antenna base to the skin so that the skin acts as a ground plane. A crazy idea, but if you do have the antenna base isolated from the aircraft skin, perhaps there is some type of static build-up between the antenna and the skin due to airflow across/between the skin and the antenna? Just a wild thought.

Good luck with your trouble shooting.
 
If you have not checked the antenna using a SWR meter, you should.
The SWR should be 2 or less on all frequencies. Ask around, someone might
have a SWR meter that you can use. If not, eBay and Amazon have them.
In addition to the meter, you will need male or female adapters to convert
from "N" to BNC. A cable will also be needed to connect the radio to the meter.
Even though the antenna should work equally well mounted on either top or
bottom of the fuselage, you can not argue with success.
Move it to the top if it works better there.
 
Via settings or some other menu (I don't know how the Becker works), would you be able to turn down or turn off the built-in intercom volume as an experiment to isolate if the static is coming from the intercom circuit. Also, maybe at the same time, if programmable, turn intercom squelch all the way up, again just to isolate.

I had the same problem that you describe with a Trig TY91, in a very noisy airplane. On the ground, all was good, not enough noise to break the squelch on the built in intercom. Once I was under power and on the go, loud static.

It turned out that via the menu settings I had to dial up the intercom squelch quite a bit to get it to settle down.
 
Not all antennae are grounded. Delta Pop makes com antenna that are not. Thought I had a bad one until I called them.
 
Antenna on belly of aluminum plane, isolated carefully. Coax connected well and shielding grounded at antenna base.

1. What kind of antenna?
2. Why is it isolated? The base needs to be connected to the ground plane.

FWIW two weeks ago I did a flight review with a gent in an old Bonanza. Both radios had static when receiving that sounded like bacon frying. I advised him to remove the antennas, clean the bases up well, and reattach. He reports that fixed the problem.
 
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You have a crappy antenna or an improper antenna installation.

At least tie the aluminum ground plane to the airframe as a first step, unless I read that wrong.

More specifically, a good antenna will be dc grounded. The RF is inductively isolated from ground. You are probably getting static buildup and discharge on the antenna as soon as you get airflow. The dc connection allows this charge to bleed off.
 
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+1 on checking your USB chargers.

I had a similar problem when I used some USB chargers from the Aviation Department at Amazon. But it was intermittent and generally only happened while on the ground.

Also, would like to echo the isolated antenna question - I'm curious if there's a reasoning
 
If you have not checked the antenna using a SWR meter, you should.
The SWR should be 2 or less on all frequencies. Ask around, someone might
have a SWR meter that you can use. If not, eBay and Amazon have them.
In addition to the meter, you will need male or female adapters to convert
from "N" to BNC. A cable will also be needed to connect the radio to the meter.
Even though the antenna should work equally well mounted on either top or
bottom of the fuselage, you can not argue with success.
Move it to the top if it works better there.

Great idea. I'll definitely check if I can find someone with an SWR meter. As someone else posted...perhaps it is just a crummy antenna. It's very, very old, left over, sitting in the corner of a hangar for many years. So that could be it! Antennas are a few bucks, so I hesitated to try replacing it without knowing what's going on, but an SWR meter will give me a good idea. THanks!
 
You have a crappy antenna or an improper antenna installation.

At least tie the aluminum ground plane to the airframe as a first step, unless I read that wrong.

More specifically, a good antenna will be dc grounded. The RF is inductively isolated from ground. You are probably getting static buildup and discharge on the antenna as soon as you get airflow. The dc connection allows this charge to bleed off.

Ahhh. So, as I have it now: Antenna is connected to center conductor of coax. Coax shielding is grounded to airframe (aluminum skin, which is also the ground-plane of the antenna), but Antenna itself is not grounded. Does this mean just grounding the metal part of the antenna to the aluminum skin of the airframe? Wouldn't that negate the insulating pieces of the mount, that are designed to keep the antenna from touching the airframe? It appears the mount is made out of a fiberglass material and makes a very solid separation from the skin of the aircraft to the antenna. I think the antenna itself is supposed to only connect with the center conductor of the coax. (could be wrong....have read a lot of posts about 'grounding' the antenna...seems like someone solved exactly my problem by doing this...but seeing as the mount is designed to prevent this....???)
 
+1 on checking your USB chargers.

I had a similar problem when I used some USB chargers from the Aviation Department at Amazon. But it was intermittent and generally only happened while on the ground.

Also, would like to echo the isolated antenna question - I'm curious if there's a reasoning

No USB Chargers, nothing plugged into anything. Steam guages. Only electrical components are a Hobbs meter, digital tach (cheap one that has wire wrapped around one spark plug wire...but that wire doesn't run anywhere the antenna coax runs), and the trim tab adjustment button (other side of the panel from the radio).
 
You have a crappy antenna or an improper antenna installation.

At least tie the aluminum ground plane to the airframe as a first step, unless I read that wrong.

More specifically, a good antenna will be dc grounded. The RF is inductively isolated from ground. You are probably getting static buildup and discharge on the antenna as soon as you get airflow. The dc connection allows this charge to bleed off.

This sounds most likely. I'll try grounding the antenna itself to the airframe (which is all aluminum and connected to negative battery terminal and negative from generator). Static of airflow seems a good possibility I hadn't really thought of. We'll see. Could be the easiest fix to try first, but old, crappy antenna is a very high probability also. (very old...was sitting in hangar rif-raff for years and years...but hey, the price was good!)

Really appreciate you guys! So great to have input and more than just my limited expertise weighing in. Gives me a place to focus and a couple of things to try! I'll let you guys know after the weekend.
 
The center of the coax is connected to the antenna through the center pin of
the BNC connector. The shield of the coax is connected to the antenna base.
The antenna base MUST be electrically connected to a ground plane. Usually
that connection is via the antenna mounting screws. The rubber gasket that
comes with an antenna is NOT designed to electrically insulate the antenna
base. The purpose of the gasket is to protect painted surfaces. The antenna
mounting screws must electrically connect the antenna base to the ground
plane. Each end of the screws should be touching bare metal.
Another possibility for static only while airborne is wind blowing on microphones.
 
The center of the coax is connected to the antenna through the center pin of
the BNC connector. The shield of the coax is connected to the antenna base.
The antenna base MUST be electrically connected to a ground plane. Usually
that connection is via the antenna mounting screws. The rubber gasket that
comes with an antenna is NOT designed to electrically insulate the antenna
base. The purpose of the gasket is to protect painted surfaces. The antenna
mounting screws must electrically connect the antenna base to the ground
plane. Each end of the screws should be touching bare metal.
Another possibility for static only while airborne is wind blowing on microphones.

Thanks much! Yeah. From other places, a guy with the exact same problem grounded the antenna and it fixed the problem. I need to ground the antenna to the ground plane (flat aluminum belly where antenna is mounted). The antenna mount has no screws as it's just a simple bent-whip metal antenna. Decided I'm going to need really good comms anyway and quality of sound is paramount for the operations I'll be doing (all very close to airport with traffic, going up and down a lot and in and out of pattern a lot). This led me to: I need to ground antenna...but while I'm at it, I may as well just have a good, new antenna. The new one is a RAMI AV-10 straight antenna (fiberglass) with an oval base with the 4 mounting bolts. Once I mount this one, and connect it well, I believe I'll have good, clear comms.

VSWR 2.0-1

Finally realized messing around with an old, angled antenna (VSWR 3.5-1)
is probably part of the problem...and just buying a brand-new, higher performance antenna will likely make things more clear anyway. Agonized over the RG58 cable vs. the RG400 and stuck with the RG58. Probably have about a 4 ft run or less of cable, so I don't think that will make a difference, but will switch it, if you guys think it's worth going with RG400.
 
A simple cheap antenna will perform just as good as an expensive one if it is
installed properly. The antenna rod is NOT grounded whatsoever. The coax
shield is what is connected to the ground plane, usually via the antenna base
which is insulated from the antenna rod. If all you have is a rod, it is mounted
to an insulator and connected to the coax center conductor. The coax shield is
connected to the ground plane. Some homemade antennas do NOT use BNC
connectors. Instead the Coax is connected with screws and nuts.
RG-58 is good enough. No need to use RG400
 
Try one of these. I had a noisy situation that I couldn’t “fix”. I installed one of these and the problem is gone. Good price, and good performance. Use a doubler on your belly skin, riveted, and use toothed lock washers under the mounting nuts, even with nylon lock nuts. The teeth in the washers bite into the base providing excellent grounding for your BNC connected coax shield.

http://www.deltapopaviation.com/VHF_Com_Antennas.html
 
A simple cheap antenna will perform just as good as an expensive one if it is
installed properly. The antenna rod is NOT grounded whatsoever. The coax
shield is what is connected to the ground plane, usually via the antenna base
which is insulated from the antenna rod. If all you have is a rod, it is mounted
to an insulator and connected to the coax center conductor. The coax shield is
connected to the ground plane. Some homemade antennas do NOT use BNC
connectors. Instead the Coax is connected with screws and nuts.
RG-58 is good enough. No need to use RG400

Thank you Joe. You've confirmed exactly the setup I have and the way the antenna is connected. I may end up returning the new antenna if this old one works fine, once I do some more trouble-shooting. Just not sure where to go with it. I did try grounding the antenna (not just the shielding to the ground plane at the mount, but tried grounding the antenna itself, with a wire wrapped onto the mounting stalk, connected to the airframe) previously...now I recall...and it didn't help. You also confirmed why I didn't go and replace the antenna when that was suggested as an option by guys at my airport. I figured it should work fine. Dang. Just not sure where to go with troubleshooting at this point. I'm certain the antenna is connected properly (has the ring soldered to the shielding at the mount, well seated to the airframe, and the center conductor of the coax is well connected with a ring between two of the mounting bolts. Coax not running parallel to anything that might cause interference. I'm going to take a handheld up and connect it to the antenna coax and see if the antenna works fine with a handheld. That'll eliminate the problem being the antenna, I think. Appreciate your input.
 
Try one of these. I had a noisy situation that I couldn’t “fix”. I installed one of these and the problem is gone. Good price, and good performance. Use a doubler on your belly skin, riveted, and use toothed lock washers under the mounting nuts, even with nylon lock nuts. The teeth in the washers bite into the base providing excellent grounding for your BNC connected coax shield.

http://www.deltapopaviation.com/VHF_Com_Antennas.html

Thanks Scott. I have a RAMI AV-10 on the way. Very similar design to what you sent. Perhaps that will solve the problem! Appreciate you sharing your experience.
 
A simple cheap antenna will perform just as good as an expensive one if it is
installed properly. The antenna rod is NOT grounded whatsoever. .....

Please take a look at the second FAQ on the DeltaPop webpage. Inductive reactance is a handy thing in the RF domain and antenna design.
 
What happens if you completely disconnect the coax from the radio and go flying?
Does the static go away? If so, that test confirms the static is coming from the antenna.
Do not transmit with the coax disconnected. It is not good for the radio.
 
When you try the handheld also connect the handheld antenna to your aircraft antenna coax and see if that works.
 
What happens if you completely disconnect the coax from the radio and go flying?
Does the static go away? If so, that test confirms the static is coming from the antenna.
Do not transmit with the coax disconnected. It is not good for the radio.

Understood and appreciate the warning about transmitting w/o antenna. Great idea for diagnosis. Thank you.
 
A simple cheap antenna will perform just as good as an expensive one if it is
installed properly. The antenna rod is NOT grounded whatsoever. The coax
shield is what is connected to the ground plane, usually via the antenna base
which is insulated from the antenna rod. If all you have is a rod, it is mounted
to an insulator and connected to the coax center conductor. The coax shield is
connected to the ground plane. Some homemade antennas do NOT use BNC
connectors. Instead the Coax is connected with screws and nuts.
RG-58 is good enough. No need to use RG400

Looks like this was spot-on. I did go ahead and buy a new, fiberglass, straight RAMI antenna. It's a nice antenna and should perform a bit better than the old one, but now have confirmed the old one was fine, as you suggested, and was properly installed with the rod of the antenna connected to the coax center conductor, and the ground plane connected to the coax Shielding. This setup was proper and everyone could hear me transmit 5x5.

I'm ok with having a slightly better antenna, and won't return it now that I've spent all the time and energy installing it. It will no doubt have a bit better performance than the previous bent antenna.

This new RAMI antenna was installed absolutely properly, with good grounding of the base to the flat, aluminum belly of the Zenith. It connects with a BNC connector, so there's no confusion of what connects to what. I even tried two separate cables with BNC on each end, to make sure the cable wasn't a problem.

New data points: New antenna didn't do anything for constant noise, on all frequencies, just after take-off. There is a small amount of constant mic-noise, I was able to quiet with covering the mic aggressively (front and back). But this was nothing compared to the overwhelming static still persisting. So I started disconnecting grounds, one by one, at the grounding block. First headset jacks' ground...no effect. Everything worked the same! Then I disconnected the PTT ground. Everything the same except PTT no longer working. Then I disconnected the radio ground...no effect! (surprised me).

Two different headsets, same deal.

So I hooked up a handheld to the new antenna...same problem and even worse! (used a headset jack adapter to the handheld).

There are no adapters, no other equipment installed, no USB ports, just a cigarette-lighter plug with nothing in it. (I'll certainly try pulling the fuse on that next time).

Sum total: I'm convinced that I've got radio frequency pollution from the ignition system. When I checked, the plugs were the recommended ones for Rotax 912-ULS, but I can't be certain about the wires. It may be that the plug wires are not shielded? This would go along with changes with RPM and such.

Anyway. I really appreciate you guys giving me so much input. I think I've effectively ruled out a problem with the antenna and radio (since handheld has the same issue...and, I'm pretty sure...even with the rubber-ducky antenna). So if the handheld has the same static with a rubber-ducky antenna, and everyone can hear me crystal clear when I transmit, I'm guessing it's something from the ignition of the engine.

Will look into that next time I'm back out there. Try to identify what kind of wires are on there.
 
How are the ignition switches wired? The shield of the ignition coax cable
should not be continuous from end to end. On my plane,
the magneto shield is grounded at both ends, however the shield is not continuous
from end to end, being separated in the center on the forward side of the firewall.
 
How are the ignition switches wired? The shield of the ignition coax cable
should not be continuous from end to end. On my plane,
the magneto shield is grounded at both ends, however the shield is not continuous
from end to end, being separated in the center on the forward side of the firewall.

I have no idea about this. Do you mean the ignition switch from the panel? Which takes the key? I don't think you mean that. I think you mean the switches elsewhere, but on a Rotax, there are electronic ignition modules on top of the engine, with big mulit-connector plugs. These the feed out to the spark plugs with spark plug wires.

I'll have to talk with Rotax, most likely to find out if the ignition modules or wires are wrong or something with the wiring of the generator (on the firewall side of the engine). But yeah, I think it's something with the ignition system, because I'm pretty sure a handheld with the rubber-ducky had the same issue.

Thanks!
 
Disconnect mic

This may be a bit left field, but is easy enough to test. If the headphone jack for the microphone cord is left unplugged, does it have any effect? This would show if the microphone is perhaps picking up interference. It sounds like you have checked pretty much everything else.
 
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On my RV-12, there are two ignition switches that are used for mag check and
for shutting off the engine. There is coaxial cable running between those switches
and the ignition modules. Like I said, the coax shield is separated in the middle.
 
On my RV-12, there are two ignition switches that are used for mag check and
for shutting off the engine. There is coaxial cable running between those switches
and the ignition modules. Like I said, the coax shield is separated in the middle.

That would sure be an easy fix! I do have an ignition switch, and can check top and bottom ignition systems, likewise, so maybe there's coax behind that ignition switch. If so, hopefully there is no break mid-way, in which case I'll make one and see what happens. Thanks.
 
Thought I would throw out a couple of thoughts that, thus far, have not been addressed.

Is there filtering on the output of the voltage regulator's R lead? The RV-12 has a 22,000 MFD filter capacitor used with the standard Ducati regulator. Silent Hektik suggests a 33,000 MFD filter capacitor for their regulator. If you don't have a filter capacitor installed now, you may want to consider adding a 33,000 or 22,000 MFD capacitor between the output of your voltage regulator (the R lead) and your air-frame, or better yet, the negative terminal of your battery or common ground point if you have one. If you do have a filter capacitor installed, carefully check the crimp connections and make sure that the capacitor is well grounded.

If the filter capacitor ends up being installed firewall forward, would also suggest you choose a capacitor that has an automotive rating because they tend to be rated for higher temperatures than the standard electrolytic capacitors which are typically around 85°C (185°F). I chose one rated at 150°C (302°F) when I upgraded my electrical system to a Silent Hektik regulator. Easy to find at Mouser.

Consider grounding the engine with a separate ground wire. On my 912ULS engine, I installed a separate ground wire (12 gauge I think) between my common ground point and the engine. There is a convenient unused threaded screw hole on the #3 cylinder head in the vicinity of the water temperature probe.
 
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Thought I would throw out a couple of thoughts that, thus far, have not been addressed.

Is there filtering on the output of the voltage regulator's R lead? The RV-12 has a 22,000 MFD filter capacitor used with the standard Ducati regulator. Silent Hektik suggests a 33,000 MFD filter capacitor for their regulator. If you don't have a filter capacitor installed now, you may want to consider adding a 33,000 or 22,000 MFD capacitor between the output of your voltage regulator (the R lead) and your air-frame, or better yet, the negative terminal of your battery or common ground point if you have one. If you do have a filter capacitor installed, carefully check the crimp connections and make sure that the capacitor is well grounded.

If the filter capacitor ends up being installed firewall forward, would also suggest you choose a capacitor that has an automotive rating because they tend to be rated for higher temperatures than the standard electrolytic capacitors which are typically around 85°C (185°F). I chose one rated at 150°C (302°F) when I upgraded my electrical system to a Silent Hektik regulator. Easy to find at Mouser.

Consider grounding the engine with a separate ground wire. On my 912ULS engine, I installed a separate ground wire (12 gauge I think) between my common ground point and the engine. There is a convenient unused threaded screw hole on the #3 cylinder head in the vicinity of the water temperature probe.

Going to definitely look into this! THanks!
 
How are the ignition switches wired? The shield of the ignition coax cable
should not be continuous from end to end. On my plane,
the magneto shield is grounded at both ends, however the shield is not continuous
from end to end, being separated in the center on the forward side of the firewall.

Checked this out. Didn't ever know there was coax from the ignition switch. Luckily, there was an easy place to access these two coax cables just on the front side of the firewall. Neither had any break in the cable anywhere, so I stripped off the covering and separated the shielding and wrapped them well. Break made! This may be the answer, but I still suspect I'm going to need an RF filter after the Voltage regulator because there's just a thick, red wire from the R lead of the Voltage Regulator running straight to a 25amp fuse for the power supply for the panel. I suspect this wire is emitting a lot of RF and an RF filter (as suggested somewhere) will help. Now I just need to know what type of RF filter do I need? Anyone?
 
Thought I would throw out a couple of thoughts that, thus far, have not been addressed.

Is there filtering on the output of the voltage regulator's R lead? The RV-12 has a 22,000 MFD filter capacitor used with the standard Ducati regulator. Silent Hektik suggests a 33,000 MFD filter capacitor for their regulator. If you don't have a filter capacitor installed now, you may want to consider adding a 33,000 or 22,000 MFD capacitor between the output of your voltage regulator (the R lead) and your air-frame, or better yet, the negative terminal of your battery or common ground point if you have one. If you do have a filter capacitor installed, carefully check the crimp connections and make sure that the capacitor is well grounded.

If the filter capacitor ends up being installed firewall forward, would also suggest you choose a capacitor that has an automotive rating because they tend to be rated for higher temperatures than the standard electrolytic capacitors which are typically around 85°C (185°F). I chose one rated at 150°C (302°F) when I upgraded my electrical system to a Silent Hektik regulator. Easy to find at Mouser.

Consider grounding the engine with a separate ground wire. On my 912ULS engine, I installed a separate ground wire (12 gauge I think) between my common ground point and the engine. There is a convenient unused threaded screw hole on the #3 cylinder head in the vicinity of the water temperature probe.


I do have this type of capacitor, but it's not between the R-lead of the voltage regulator and the panel (where the R-lead runs to power the panel). I suspect this could be a problem. Do I need a second 22000uF capacitor? Or is this one just not wired in the right position? It's hard to see in the photos, but the R-lead from the voltage regulator goes straight back, through the firewall, and straight to the 25amp fuse which feeds the electrical busses for the panel. Is this possibly putting out a lot of RF? Could I put some sort of filter on it? Thanks guys!
 

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Radio noise

I had radio static in my Microair radio in the lower frequency range ; after placing magnet filters on the aireal, radio power supply and the power wire into the bus. : problem solved.
Steve
Rv3b
 
Have you tried shutting off one ignition at a time while flying to see if doing that has any affect on the noise?
 
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