Fixing the Transponder with Duct Tape and Aluminum Foil

Or send Jim a SASpaddedE and he'll send you what is left of a few rolls we've
used around here for "magazine projects", if y'know what I mean.

Jim



"Gerry Caron"
shared these priceless pearls of wisdom:

-Use what the pros use -- copper tape. Call friendly neighborhood EMI
-engineer or go to McMaster-Carr; www.mcmaster.com. Search for "copper
-tape".
-
-Gerry
-


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Ron Wanttaja wrote:

I'd installed my new Microair transponder a month ago, but have been having
troubles with interference. The transponder was inducing bad clicking
sounds into the comm radio receiver, making the radio difficult to
understand.

I couldn't really blame the Microair, since the Terra transponder I'd had
before did exactly the same thing. But I'd been hoping the new transponder
and installation would eliminate the problem...especially since I'd
reworked all the transponder wiring and moved the antenna to a different
location. But the interference continued.

The main suggestion I got from the avionics guys around here is that the
transponder was interfering via the cables running to the headset jacks. I
installed shielded braid over those cables, though, and the problem
continued.

All the electrical connections to the radio (except the antennas) are made
via an unshielded flat connector. Since the wires had to spread out to fit
the connector, I hadn't been able to run the braid all the way to the
radio...it terminated about two inches away, and I ran a ground wire from
the braid to the radio chassis.

It seemed to me that the most likely culprit was that last two inches of
unshielded wiring and the unshielded connector...especially since they were
the closest part of the wiring harness to the transponder.

So, today I took a roll of aluminum foil out to the airplane and wrapped
foil around the back of the radio, leading it down the wires until it
contacted the braid. Duct tape, of course, to hold it in place.

I'm happy to report that this solved the problem. Radio signals were
perfectly clear.

I figure the foil isn't worthwhile as a permanent solution. A guy at the
airport suggested using aluminum window-screen material. It appeals to the
cheap side of me. Any drawbacks, or suggestions for alternates?

Ron Wanttaja
Try your local Home Depot 'A/C supply'.

Go to the insulation section & look for 'aluminized mylar' radiant
barrier insulation. It comes in various forms. Best for you would be the
mylar sheet with an aluminum foil bonded to the mylar. Other types may
look like either bubble wrap or foam wrap sheets for protecting delicate
stuff for shipment, but will still have the aluminum foil coating. More
durable than just foil; you can make a 'boot' by stitching a sheet into
a cone shape.

Charlie

On Sun, 07 Mar 2004 07:53:16 -0600, Charlie England
wrote:

Try your local Home Depot 'A/C supply'.

Go to the insulation section & look for 'aluminized mylar' radiant
barrier insulation. It comes in various forms. Best for you would be the
mylar sheet with an aluminum foil bonded to the mylar. Other types may
look like either bubble wrap or foam wrap sheets for protecting delicate
stuff for shipment, but will still have the aluminum foil coating. More
durable than just foil; you can make a 'boot' by stitching a sheet into
a cone shape.

Neat idea, thanks, Charlie. Don't have a Home Depot A/C Supply real close,
but Lowe's Aerospace is right across the road from the airport. :-)


Ron Wanttaja

Charlie England wrote:

Try your local Home Depot 'A/C supply'.

Go to the insulation section & look for 'aluminized mylar' radiant barrier
insulation. It comes in various forms. Best for you would be the mylar sheet
with an aluminum foil bonded to the mylar. Other types may look like either
bubble wrap or foam wrap sheets for protecting delicate stuff for shipment,
but will still have the aluminum foil coating. More durable than just foil;
you can make a 'boot' by stitching a sheet into a cone shape.

Ron Wanttaja replied:

Neat idea, thanks, Charlie. Don't have a Home Depot A/C Supply real close,
but Lowe's Aerospace is right across the road from the airport. :-)

It probably isn't an issue in Ron's case, but having recently seen the Nova
program on the investigation into the causes of the crash of SwissAir #111 I
feel compelled to point out that some aluminized Mylar insulation is
flammable.

Russell Kent

On Mon, 08 Mar 2004 14:06:44 -0600, Russell Kent wrote:

It probably isn't an issue in Ron's case, but having recently seen the Nova
program on the investigation into the causes of the crash of SwissAir #111 I
feel compelled to point out that some aluminized Mylar insulation is
flammable.

Considering that there's a manly pilot leg running on the left side of the
avionics box, and another manly pilot leg on the RIGHT side of the box,
it's something I should keep in mind.

But I actually came up with the perfect solution this afternoon...assuming
the technology cooperates. I was mulling over how I'd cut the sheet, wrap
it around the radio and the wiring harness, and realized that what I needed
was a aluminized mylar funnel.

Something very much like the bottom of a shiny aluminum toy balloon....

So I'm going to pick up a couple of (uninflated) balloons and turn my
multimeter loose on them. Maybe I'll find a left-over Valentine's Day
balloon on sale..

I'm really hoping they'll work out. The idea of buying an aircraft part at
a store called "Party Universe" is almost irresistible. :-)

Ron Wanttaja

Ron Wanttaja wrote:


I'm really hoping they'll work out. The idea of buying an aircraft part at
a store called "Party Universe" is almost irresistible. :-)

Ron Wanttaja


This is just too cool for school, Ron!



Richard

There are those fancy condoms that they sell in the mens' room at the truck
stops... {;-)


Jim


Ron Wanttaja
shared these priceless pearls of wisdom:

-So I'm going to pick up a couple of (uninflated) balloons and turn my
-multimeter loose on them. Maybe I'll find a left-over Valentine's Day
-balloon on sale..

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Why can't you just continue to use what worked? Namely the aluminum foil.

Signed,
Not Understanding, Captain of the least resistance


"Ron Wanttaja" wrote in message
...
On Mon, 08 Mar 2004 14:06:44 -0600, Russell Kent wrote:

It probably isn't an issue in Ron's case, but having recently seen the
Nova
program on the investigation into the causes of the crash of SwissAir
#111 I
feel compelled to point out that some aluminized Mylar insulation is
flammable.

Considering that there's a manly pilot leg running on the left side of the
avionics box, and another manly pilot leg on the RIGHT side of the box,
it's something I should keep in mind.

But I actually came up with the perfect solution this afternoon...assuming
the technology cooperates. I was mulling over how I'd cut the sheet, wrap
it around the radio and the wiring harness, and realized that what I
needed
was a aluminized mylar funnel.

Something very much like the bottom of a shiny aluminum toy balloon....

So I'm going to pick up a couple of (uninflated) balloons and turn my
multimeter loose on them. Maybe I'll find a left-over Valentine's Day
balloon on sale..

I'm really hoping they'll work out. The idea of buying an aircraft part
at
a store called "Party Universe" is almost irresistible. :-)

Ron Wanttaja

Ron

More free advice from a long time Ham.

Have you tried a toroid? Radio Shack used to carry some that snapped
apart and then back together so you could put several turns on one
without cutting the wire(s). Price was a couple of dollars so not
expensive to try.

Also, we used to take a piece of aluminum foil from the kitchen and
just wrap around the wire(s) and then slide it back and forth to find
a spot where the interference stopped. Again, very cheap to test.

We also on occasion used some small (.02- .002) ceramic caps.

Also, any coax you use be sure it is double shielded. Some of the
cheap stuff on the market has very 'porous shielding.

Robert and my daughter are still in FL working on their boat. He could
have built another plane in the time they are spending rebuilding that
damn boat. G Haven't said if they are going to go by S-N-F this year
before heading back to WA?

Any words the spell checker didn't catch, I take full responsibiity
for G

And the best up there in the land of the every day rain.

Big John

On Sat, 06 Mar 2004 23:53:02 GMT, Ron Wanttaja
wrote:

I'd installed my new Microair transponder a month ago, but have been having
troubles with interference. The transponder was inducing bad clicking
sounds into the comm radio receiver, making the radio difficult to
understand.

I couldn't really blame the Microair, since the Terra transponder I'd had
before did exactly the same thing. But I'd been hoping the new transponder
and installation would eliminate the problem...especially since I'd
reworked all the transponder wiring and moved the antenna to a different
location. But the interference continued.

The main suggestion I got from the avionics guys around here is that the
transponder was interfering via the cables running to the headset jacks. I
installed shielded braid over those cables, though, and the problem
continued.

All the electrical connections to the radio (except the antennas) are made
via an unshielded flat connector. Since the wires had to spread out to fit
the connector, I hadn't been able to run the braid all the way to the
radio...it terminated about two inches away, and I ran a ground wire from
the braid to the radio chassis.

It seemed to me that the most likely culprit was that last two inches of
unshielded wiring and the unshielded connector...especially since they were
the closest part of the wiring harness to the transponder.

So, today I took a roll of aluminum foil out to the airplane and wrapped
foil around the back of the radio, leading it down the wires until it
contacted the braid. Duct tape, of course, to hold it in place.

I'm happy to report that this solved the problem. Radio signals were
perfectly clear.

I figure the foil isn't worthwhile as a permanent solution. A guy at the
airport suggested using aluminum window-screen material. It appeals to the
cheap side of me. Any drawbacks, or suggestions for alternates?

Ron Wanttaja

On Tue, 09 Mar 2004 08:27:50 -0600, Big John wrote:

Also, any coax you use be sure it is double shielded. Some of the
cheap stuff on the market has very 'porous shielding.

Actually, that's one thing I did wonder about. The coax I use is RG-58,
but I buy premade LAN cables from the local electronics emporium. I
shortened the one I bought for the transponder, installing a new BNC
fitting at one end. Still, the noise did exist with the old transponder,
before I went to the LAN cable stock.

But the store's bulk stock is probably the same brand, so I can't see the
LAN cable as being a second choice.

One thing that did occur to me was to take copper braid and slide some over
the transponder coax as an additional shield. Shouldn't affect the RF
characteristics, I guess, but didn't really think it would help the noise
problem.

Ron Wanttaja