Strobe Interference

[brilin_air]

Hi all!

 

Just got my 160 going with a microair radio. When the strobe light is working, I can hear it through the headsets. It is alot quieter with the noise reduction on, but is still noticable. Radio check is a 5, for transmitting and receiving.

 

Any ideas? Anybody else had this problem?

 

Thanks

 

Brian

 

 

[Guest The Bushman]

interferance To Radio

 

Did you get an answer to your query as to interferance from Strobe to Radio

 

The bushman

 

 

[nong]

Yes. Sold plane.

 

 

[brilin_air]

Used ferrite clamps around the system and it reduced a lot of the interference.

 

Thanks

 

 

[Ross]

Strobe radio interference on my J160 kit with Microair

 

I tried replacing the original unshielded cable to the strobe with some 4 core shielded cable from Jaycar for the high voltage supply between the strobe and the strobe power box.

 

The outer shield was earthed/connected to the body of the strobe power box.

 

I also used shielded wire for the low voltage supply from the A/C bus etc to the strobe power box. It was also earthed to the strobe power box.

 

It did make a big difference for most stations to the noise from the strobe but it did not reduce it evenly from all stations or eliminate it completely. That may be quite different once the A/C is flying with the engine going and tuned to the closest transmitter which would usually be the case.

 

I am testing my MICROAIR, an early model now 4 years old, on the ground in the garage at my home home with the scanner going as it would be illegal to transmit until the aircraft is registered. In normal operations I presume the scanner would not be used.

 

The channel that generates the most interference is usually the distress frequency. I have no trouble using the squelch to eliminate the interference on any frequency that I can pick up.

 

I can pick up traffic inbound for Melbourne from the West, Sydney traffic inbound from the West and inbound for Mildura, Griffith, Mt Gambier, Dubbo and Ivanhoe plus plenty of Melbourne centre flight level traffic when there is any sort of weather to contend with. I hear plenty of calls where Melbourne Centre is notifying airline traffic that they are out of radar coverage.

 

For some reception it appears that some background interference is being generated by the transmitting radio or it's wiring arrangement because other transmitters on the same frequency generate no interference noise at all.

 

For different frequencies & (distances??) the amount of squelch required above the background noise with the strobe turned off to having the probe turned on ranges from none extra for some stations to a maximum of about half a turn extra of the squelch knob for the worst of other stations.

 

All these results are with the engine not running which might introduce an extra amount of interference.

 

At Leeton township in my garage (J160), I am probably about 20 NM from the transmitter at Mt Bingar near Griffith for the area frequency for Melbourne centre and the Griffith CTAFR and about the same distance from Narrandera for the CTAF there.

 

After some experimentation I am sure that most of the noise comes from the strobe, not the strobe power box, because of its proximity to the Jabiru Dipole aerial mounted on the back of the vertical stabiliser only about 200 mm away.

 

Even temporarily sitting the strobe on the front of the static probe in front of the vertical stabiliser further away from the aerial reduces the interference noise.

 

I had rung Jabiru about this problem and they seemed reluctant to talk about it. They inferred that replacing the original not shielded high tension leads to the strobe on the tail with shielded cable would probably improve things. They were not in a hurry to supply me with the shielded cable.

 

I was tempted to try mounting the strobe on top of the cabin or to use wing strobes instead which would have increased the cost dramatically and may not have worked anyway going by the first Jab LSA 55 that I flew which has wing strobes.

 

Despite the strobe noise occasionally, the Microair radio is still miles better than the radio in the Piper PA28-140 a/c that I first soloed in at Narromine in about 1971.

 

 

[Guest hatrack]

radio interference

 

Where do the ferrite clamps go and where do you get them from?

 

Cheers, Grant.

 

 

[brilin_air]

Ferrite clamps

 

Hi Grant,

 

If you go to Dick Smiths you will be able to get the ferrite clamps,they are cheap to buy so get a hand full and start playing,If you fit them as far back on the antenna wire as you can it will help also on the power leads into the strobe box is another fix that has worked, basically it all depends on the interference that you are getting as to the way you have to place the clamps.

 

All the best.

 

Brian

 

 

[Ross]

Hi Grant

 

If I come back in another life and buy a kit aeroplane I will not buy anything for it including the engine until it is finished.

 

Hi Grant

 

I have discovered that there are now strobes available for use in "experimental" aeroplanes using Extra bright LEDs at a few more $ than standard strobes which require about a 400 or 500 volt pulse to generate the flash power thus creating a radio signal.

 

The LED type do not create RF interference according to the manufacturers. See the following site for their specifications on their range of LED fitted landing lights, spot lights and LED type strobes.

 

http://www.aeroleds.com/media/pdfs/grid_comparison.pdf

 

As you can expect they are made in the USA and are dearer than the standard ones that Jabiru supply which are also from the USA.

 

I got my ferrite clamps and 4 core shielded wire online from Jaycar electronics.

 

Regards

 

 

[sain]

actually there are a fair few reports out there of LED strobes still generating interferrence on the radio, and also some of the other LED lighting packs (NAV, landing etc). These devices seem to be using switching power supplies (much more efficient than the normal ones), which are unfortunately a touch noisy.

 

The most effective option seem to be to install a simple filter inline with the device. I'll poke around and see if I can find some links.

 

 

[dewie]

Some of this info may help :thumb_up:

 

NOISEin Radio and / or intercom

 

 

 

Our strobe driver units are designed with filtering and internal shielding to keep radio interference to a minimum, however occasionally noise will be heard over the radio or intercom. This noise is almost always caused by the way the systems have been installed.

 

One must remember that noise does not always come from the power that is being supplied to your equipment. Especially if the radio has it's own power source (battery ) and the strobe is powered by the aircraft battery. Installations vary greatly from aircraft to aircraft. Do both systems share the same power source? Is there an external antenna? How close is the antenna, radio, wires, etc. to the strobe driver box and wiring? If both systems are not sharing the same power, then where is the common thread? In most, if not all cases the problem is GROUNDING. The ground path is very, very important. The strobe circuit draws high current through the ground circuit. The radio, intercom, head set and mic circuits use that same ground so it is important that there is NO voltage drop between where all these grounds are connected. In other words lets say the strobe driver is getting negative battery or ground from a bus near the battery that is also grounded to the metal frame of the aircraft. The ground plane for the radio antenna is connected to the aircraft frame further back near the tail and the radios are grounded near the cockpit to a screw in the frame. This array of connections can be a source of noise. The following list is intended to help in eliminating noise.

 

1. Power for the strobe system should be on the first fuse of the power bus. In other words the closest fuse to the battery. It is also very helpful to run BOTH the POWER and GROUND in a twisted pair all the way from the source to the strobe driver. In other words don’t pick up ground for the strobe near the driver and the hot on a single wire from another location.

 

2. The strobe driver's metal case should be solidly connected with a ground strap or 16 ga. wire to the aircraft ground system.

 

3. The audio ground and aircraft ground should be commonly connected only at ONE SINGLE POINT. Ground all the audio equipment; radio, mic, antenna, headphones, intercom, etc. to an "audio ground bus" (16 Ga. or larger wire). Then connect that bus at one end only to the aircraft central grounding point, preferably near the point the battery is grounded.

 

4. Do not run audio related wires next to power supply wires.

 

5. Shielded wire is not normally necessary, however, if it is being used ground that shield at only ONE end. Usually the end closest to the source.

 

 

[Dieselten]

It's hard to beat genuine single-point-grounding! Solves a lot of problems.

 

 

[Ross]

Being the owner of a fibreglass aeroplane kit makes the aircraft ground a fairly difficult concept for me especially as mention is usually only made of the metal aeroplane situation.

 

For a fibreglass a/c there is no such thing as an earth return based on the aeroplane structure so I would have thought that this would eliminate some problems and generate some others.

 

Regards