Announcement

**Robert Lees** · 08-24-2020, 11:49

Steve,
I operate my 1946 Taylorcraft here in the UK with Eisemann mags, unshielded plugs (Champion M41E) same as you and we don't have that problem. We used to operate with an Icom IC-A22 hand-held, and now use Icom IC-6AE hand-held (for 8.33 compliance) and we still don't have a problem. Does your Icom IC-A23 radio that you are using have an "ANL" button (Active Noise Level, I think)? like the IC-A22?

Is your external antenna grounded to the fuselage frame? (that helps!) We use a whip antenna (like an ELT) instead of a tapered white thing...what kind of antenna do you have?

The fact that you have an A-75 is a non-issue...it's the same as an A-65 and a C-85 in terms of ignition.

Rob

**PA1195** · 08-24-2020, 20:04

Rob's suggestions are excellent. The A23 has an ANL (auto noise limiter) that can help. It's the #3 from the bottom lower right on the face. It will reduce certain harmful interference but may not eliminate all. The suggestion to make sure the antenna base is grounded or connected to the nearby airframe is good. That's also particularly the coaxial cable external shield under the overlying plastic coating - it's a shared and direct electrical connection with the antenna base and radio cabinet. The connection should ideally be a short piece of flat wire braid with good conductivity (bare metal) between the antenna base and its metal support and airframe. Flat wire braid can be made from woven stranded coaxial cable shielding, but a common wire may also work. Keep the radio, coaxial feed line, and antenna away from any other wiring as all of them can receive static from nearby wire sources like P-leads and power wires as well as the engine.

ANLs work by detecting static noise or pulsed signal spikes in the receiver. They then either level them off some via filters so they are reduced in amplitude or simply blank them out further down the receiving network (called a noise blanker).

Gary

**PA1195** · 08-24-2020, 20:15

I'll add another thought. Make sure all electrical connections tfrom the magneto to the spark plugs are clean and tight. If the current can arc across a poor connection it can make pulse static. P-lead filters can reduce static from the magnetos, but normally the p-leads are formed from a two layer shielded wiring the covering shield of which is grounded at the magneto. Some advocate also grounding the shield at the magneto switch. That may help but also can cause ground loops which make noise. Trial and error with that shield grounding at the switch will inform.

Edit: The engine should also be grounded to the airframe even if it's not starter/generator equipped if a radio is used. Grounding or component bonding helps level static energy and reduce transmitted static between the aircraft's parts including a hand held radio.

Gary

**astjp2** · 08-26-2020, 12:05

I tried to shield a set of those wires, I kept getting weird intermittent rough running, found the spark was jumping the gap from inside the AN clip that goes on the plug to the shielding that I heat shrink'd to the wire, which was about 1.25" it was a shocking experience...

**PA1195** · 08-26-2020, 12:26

The plug wires in pic #1 above are lying on or near the cylinder. If wet or contaminated with conductive debris some surface current could occur between the cap and grounded metal.

One way to test for static is use a common AM portable radio to locate the source(s). Earphones help. Run the equipment and move the radio around (carefully) near suspected areas and parts. Wiring, switches, control cables to and from the engine, and wiring/mags on the engine. If the radio has an external antenna input use that with a wire to the radio port fixed to a stick to get close to static making parts.

We're waiting to see if Rob's ANL switch has been activated.

Gary

**steve canyon** · 08-26-2020, 16:31

Thanks for the suggestions I will try them and let you guys know what works . There is an ANL on my IC-A23 and I turn it on and it doesn't make much difference .

**PA1195** · 08-26-2020, 16:50

Typical ANLs reduce but don't eliminate all general static, or in other words "steady buzz and crackle". If the noise you're hearing is a series of separate but closely spaced "rapid pops" caused by engine ignition then it takes a noise blanker to reduce them. Noise blankers are different than noise limiters in how they work.

If it's "pops" try to find the source. Like is it one mag or the other...or is it one plug or more on one mag...or is it all plugs and both mags. Try first at idle to slow the rate of "pops" and switch mags to see if one (and its plugs and wiring) is worse than the other. Disconnect plug wires from the plugs one at a time (let the wire end float away from the engine) to isolate the worse offenders. Use the AM radio or handheld aircraft radio with its own rubber antenna near the wiring to seek sources. If all are noise makers make sure the aircraft antenna base is grounded to the frame. I also like to ground the radio with a wire to the frame by slipping a large crimp on electrical ring terminal between the BNC coax connection and radio then a wire from it to ground.

Gary

**Mark Bowden** · 08-28-2020, 05:39

Hi Gary, would you please post a picture of your ring terminal solution for the radio?
Thanks

**Mark Bowden** · 08-28-2020, 05:45

Steve, one thing you didn't mention was if you are using an intercom box. If so they can have noise issues too.

One caution for everyone I am going to have to fix is.... I had a Sigtronics intercom worked great until an overnight storm got some water into it. I replaced it with an AvComm. The AvComm female RCA plugs do not match Bose headset male RCA plugs which is a source of static. I had to disassemble it and bend the contacts into a better position.

**PA1195** · 08-28-2020, 09:14

Originally posted by Mark Bowden View Post

Hi Gary, would you please post a picture of your ring terminal solution for the radio?
Thanks

Sure Mark. Here's a couple examples using the antenna's twist-on BNC connector. The added ring terminal and wire can be used as either a counterpoise or also ground depending on choice. Tuned properly to 1/4 electrical wavelength the wire does enhance radio performance if only the small antenna supplied with it is used (no external antenna on the plane). If using an external mounted aircraft antenna simply ground the open wire end to the aircraft's metal frame - same type connection (wire and coax BNC fitting) can be used at the external antenna if it's ungrounded already.

Edit: for aircraft use try 234/121.5 Mhz = 1.9 ft. x 12" = 23" long wire. Or pick the frequency of use instead of 121.5 Mhz and divide it into 234.

HT Antenna Improvement

https://newhams.info/2018/12/11/ht-antenna-improvement/

https://hackaday.com/2014/02/08/impr...-antenna-wire/

Gary NL7Y