Radio noise

[M Towsley]

Re: Radio noise

Just took some today. I really need to get the plane in natural light rather than using the flash. If tomorrow is good the wife and I will take a little trip and hopefully I can get some shots outside.

[woodmw]

Re: Radio noise

Marty,

When do we get to see pictures of and particulars about the new interior/panel?

Darryl,

After doing the cans and the shielded wires and lower shielded plugs the popping could be squelched out. I recently redid my instrument panel and interior and once I got a good look at the old P-Leads I knew I needed to make new ones. Using new shielded wire, (the white shielded aircraft wire), and grounding them at the mag only I no longer have any popping. I even lowered the squelch and still nothing. There is some debate regarding grounding at the mag only or mag and magneto switch, but after doing some research I decided to ground the shielding at the mag only. The other thing I did was to use a magneto 'can' at the magneto switch, which also is grounded. I had a picture of it, I will try and find it and post it. The can was purchased off of Ebay. One shows up now and then.

[flyguy]

Re: Radio noise

My lower ignition system is quiet, my upper one is very noisy.

The only thing different about my upper ignition system and my lower one is cans vs resistive, shielded plugs. Therefore the problem is: the cans (with C26 non-resistive plugs) do nothing to kill the high frequency part of the spark.

If you kill the high frequency part of the spark at the source (the plug gap) then you don't have to be concerned with where it will be conducted or radiated--it isn't there to start with. That is what the resistor part of the shielded plug does.

Eliminate the high frequency part of the spark at the source and you don't have to worry about isolating leads, shorting things to ground, locating your antenna more remotely, or using a radio with a (suppression feature?).

To back up my statements I give, as a simple example, the automotive ignition systems that do not use shielded plugs or wires. They just get rid of the problem with resistance only, and are very quiet.

Like most problems the best resolution comes by reducing to basics and clobbering the basic part.

My problem is that I just hate cutting holes in my top cowling to install resistive plugs, but that is still the best-don't fiddle with it, just fix it- solution.

DC

[M Towsley]

Re: Radio noise

Hank,

I did a lot of research on this. The general consensus was that both ends of the P leads shield did not need to be grounded. When I made the new wires I did not make a shield ground lead off of the magneto switch end of the P leads. The switch 'can' is grounded to the magneto switch ground and, of course, the magneto switch ground is then grounded to the aircraft. At the mag side the P leads are mounted to the bolt and the shield part of the P leads is grounded to the ground screw located on the magneto. After yesterdays test I found good results.

It would not be difficult to go ahead and make ground leads for the shield and then attach them to ground at the switch when originally making the leads.

Here is a link to a website that shows you how to make P leads and how to ground the shielding. I chose to not make the P lead portion un-shielded as long as is shown on the attached link as I wanted to keep the shield around the wire as much as possible. http://www.verticalpower.com/forums/...ing-to-magneto

[Hank Jarrett]

Re: Radio noise

Marty,
Interesting about shielding one end of the P leads. Did you ever try connecting a short between the Mag can and the P lead to see if anything changed?
Hank

[M Towsley]

Re: Radio noise

This is a link to Barnstormers showing an A7 switch with the shielding can.

http://www.barnstormers.com/classified_651787_AAF+TYPE+A7+Magneto+Switch.html

[M Towsley]

Re: Radio noise

Darryl,

After doing the cans and the shielded wires and lower shielded plugs the popping could be squelched out. I recently redid my instrument panel and interior and once I got a good look at the old P-Leads I knew I needed to make new ones. Using new shielded wire, (the white shielded aircraft wire), and grounding them at the mag only I no longer have any popping. I even lowered the squelch and still nothing. There is some debate regarding grounding at the mag only or mag and magneto switch, but after doing some research I decided to ground the shielding at the mag only. The other thing I did was to use a magneto 'can' at the magneto switch, which also is grounded. I had a picture of it, I will try and find it and post it. The can was purchased off of Ebay. One shows up now and then.

[flyguy]

Re: Radio noise

Yep, I have 4 of the "normal" C-26's in cans on top.

Marty, Fresno is just a reasonable cruise over in the Tcraft from here. I drop in there once in a while. They really helped me out when I was rebuilding my Eisemann mags.

Eventually it will be "bumps" I suppose.

DC

Edit/added. Inspiration in reference to comment of noise suppressing receiver: Think I will set up a test with my scope to check the frequency of the ignition snaps on the receiver audio signal. Maybe they would be out of the pass band for normal voice communication. Build a low pass filter to go in the headphone line ala an extension cord?
Probably would not work with someone with a squeaky voice, LOL, or an irritated female controller.

Darryl

[waltermrich]

Re: Radio noise

I miss quoted the S62 plugs are the shorter plug, and they are under my cowl, so sorry about that I do not think there are any plugs for an A65 shorter than the S62, the s in C26s probably stands for shieled , and i think you are correct that there is an old unshielded champion C26 plug

[M Towsley]

Re: Radio noise

DC,

Do some measuring first before you go down there. Everyone's cowl is a bit different. I think if a short shielded plug was available, and fit under the cowl, a lot of people on the forum would be using it. I would like to see a picture of one installed, preferably on the top front cylinders with the lead installed.

[flyguy]

Re: Radio noise

Well you have me on the C-26-S SH as listed by Fresno. So these are a metal enclosed plug that is shorter than say a REM 38 or 40? Didn't know such a thing existed, (as a C-26 I mean.) Guess I need to take a trip down there and check their stock for short shielded plugs. Love to get rid of the cans and the noise.

I can only guess from some of the reports similar to Mike's above that there are receivers that have some kind of noise suppression built in. Mine sure doesn't. Can't imagine how they would do that without killing the normal signal though.

DC

[waltermrich]

Re: Radio noise

C 26-S spark plugs are shielded, they are a single electrode plug like an auto plug I have the box right next to me I would send a photo if I knew how to, Look at the Fresno Airparts ad in Trade a Plane they are listed as a shielded plug for $10.75

[1938BF50]

Re: Radio noise

I am confused. Champion C-26's are NOT shielded plugs. Champion S-62's ARE shielded plugs and it is my understanding that they are the shielded version of the C-26?

FYI....I run the C-26's in the top and have no known issues with my Icom A6 either transmitting or receiving.

[waltermrich]

Re: Radio noise

The mags i quoted are S4RN-21 not SR4N-21 and the plugs in question are the old new surplus Champion C-26 and S-62 both are radio shielded plugs, I think the way to find out if it is the plugs making the noise is to put one of the plugs in question on the left mag which runs perfectly and is quite now and see if it makes noise, if not then I will know its in the P lead or some where else.

[swoeric]

Re: Radio noise

i dont know if it is receive or transmit...but if it silent on the radio and somebody hits the transmit button or you hit it you can hear the difference...well that is what is happening hear it sounds as if my plane or somebody elses plane keeps hitting the mike buttton and the red light for transmit on my radio comes on correspondingly