Strobe noise

algrajek · #1 12-13-2010, 08:14 AM

I have searched for this particular problem but still looking for an answer.
When I turn on my strobes on the ground, everything is fine, BUT, with the engine running, and also in flight, I am getting interference in the intercom, with the strobes on. Kind of a high pitch squeal whenever they fire.
I have checked the shield ground and it appears OK. Could this be a plug wire or mag wire problem?
Thanks
Al

Norman CYYJ · #2 12-13-2010, 10:00 AM

Have you grounded the shield at each end of the cables feeding the strobe lights?
If so disconnect the the shield at each light. Make sure that you have a well bonded ground from the power supply to the airframe and as short as possible. Keep all strobe lighting wires away from any antennae cables and audio cables. Sometimes it is very difficult to completely eliminate that whine that you are hearing. You can also turn off your noise canceling headset or put a small spacer between your head and the ear cup on the headset. This will allow enough cabin noise in to over power the strobe noise. lol

N941WR · #3 12-13-2010, 10:24 AM

Quote:

Originally Posted by Norman CYYJ

Have you grounded the shield at each end of the cables feeding the strobe lights?
If so disconnect the the shield at each light. Make sure that you have a well bonded ground from the power supply to the airframe and as short as possible. Keep all strobe lighting wires away from any antennae cables and audio cables. Sometimes it is very difficult to completely eliminate that whine that you are hearing. You can also turn off your noise canceling headset or put a small spacer between your head and the ear cup on the headset. This will allow enough cabin noise in to over power the strobe noise. lol

^^^^ Good advice.

Also, where did you ground the shield and the power pack? Initially I ran those grounds all the way to the firewall and had the same issue. When I put in a plate nut and ground right next to the power pack, the noise went away. All I can think of is that those long runs to the firewall, which paralleled the antenna but four inches away, acted like a long antenna.

algrajek · #4 12-13-2010, 10:48 AM

Both the shield and the power supply are grounded right where the power supply is mounted. In the tail. And the shield is ONLY grounded at the Power supply end.
Ill check to make sure they are not running near any antenna cable, although I think They are not.
Thanks
AL

Norman CYYJ · #5 12-13-2010, 11:18 AM

It might be wise to move the power supply power line away from any other lines all the way to the bus.

David_Nelson · #6 12-13-2010, 12:05 PM

Hi Al,

Is this a fresh build or an existing one?

Did the problem just suddenly start or did it progressively get worse?

Quote:

When I turn on my strobes on the ground, everything is fine, BUT, with the engine running, and also in flight I am getting interference in the intercom, with the strobes on.

I think it's interesting that the problem surfaces only when the engine is running. With the engine running, does the problem exist when the alternator(s) is/are off?

Does the problem exist during the ground mag-check?

Does the pitch change w/ RPM?

algrajek · #7 12-13-2010, 01:06 PM

Quote:

Originally Posted by David_Nelson

Hi Al,

Is this a fresh build or an existing one?

Did the problem just suddenly start or did it progressively get worse?

I think it's interesting that the problem surfaces only when the engine is running. With the engine running, does the problem exist when the alternator(s) is/are off?

Does the problem exist during the ground mag-check?

Does the pitch change w/ RPM?

Ill have to get back with you on some of that, but:
It is a newly built RV8
The problem was not evident on the first test flight, but every one since.
I will check Alt on and off to see what happens, and
YES the pitch does change with rpm.

RFazio · #8 12-13-2010, 03:23 PM

If the pitch changes with the RPM it means your hearing the alternator. I have a similar noise. Try starting your plane and flying without turning on the alternator, if you have that option. A short flight with a fully charged battery will not be a problem. Once you have confirmed that there is no noise with the alternator off you can flip it on. Be carefull, some alternators do not like being turned off when under load. So I would not suggest you just flip it off while flying. You could damage the unit. I would also drop to idle when turning it on in flight, then go back to normal RPMs. Anyway if it is the alternator you will have other options to cure that.