Weir Article in KP: "Watt's Up Doc?"

[scottloftin]

ATC has been complaining on and off about my radio being "weak",
"garbley" and just about every other word that describes a bad radio.
The #1 Com is relatively new, but the airplane is old. I tried the
light bulb trick as described in Jim's article, using the light bulb as
a simple wattmeter connected to the coax at the #1 COM antenna
connection. I get NOTHING when I key the mike and talk into it.

My avionics doctor tells me this doesn't mean anything. So far, he's
had me put in a portable PTT switch, put new mikes on 2 different
headsets, clean the coax connector at the radio, change the BNC
connector at the antenna and finally replace the antenna. I say it
means the coax is bad! It's an 8 watt transmitter so I soldered a 313
bulb to a BNC connector and hooked it up. Everything I learned about
electronics (I'm an EE for Pete's sake) says that the bulb should glow
brightly and modulate in intensity with my voice. Should I just change
the coax and be done with it?

[Stealth Pilot]

On 23 Mar 2006 00:39:43 -0800, "scottloftin"
> wrote:

>ATC has been complaining on and off about my radio being "weak",
>"garbley" and just about every other word that describes a bad radio.
>The #1 Com is relatively new, but the airplane is old. I tried the
>light bulb trick as described in Jim's article, using the light bulb as
>a simple wattmeter connected to the coax at the #1 COM antenna
>connection. I get NOTHING when I key the mike and talk into it.
>
>My avionics doctor tells me this doesn't mean anything. So far, he's
>had me put in a portable PTT switch, put new mikes on 2 different
>headsets, clean the coax connector at the radio, change the BNC
>connector at the antenna and finally replace the antenna. I say it
>means the coax is bad! It's an 8 watt transmitter so I soldered a 313
>bulb to a BNC connector and hooked it up. Everything I learned about
>electronics (I'm an EE for Pete's sake) says that the bulb should glow
>brightly and modulate in intensity with my voice. Should I just change
>the coax and be done with it?

from your description of the circuit surely there is nothing else left
to change :-)

you could try turning the master on :-) :-)
g,d,r.
Stealth Pilot

[clare at snyder.on.ca]

On Thu, 23 Mar 2006 22:54:55 +0800, Stealth Pilot
> wrote:

>On 23 Mar 2006 00:39:43 -0800, "scottloftin"
> wrote:
>
>>ATC has been complaining on and off about my radio being "weak",
>>"garbley" and just about every other word that describes a bad radio.
>>The #1 Com is relatively new, but the airplane is old. I tried the
>>light bulb trick as described in Jim's article, using the light bulb as
>>a simple wattmeter connected to the coax at the #1 COM antenna
>>connection. I get NOTHING when I key the mike and talk into it.
>>
>>My avionics doctor tells me this doesn't mean anything. So far, he's
>>had me put in a portable PTT switch, put new mikes on 2 different
>>headsets, clean the coax connector at the radio, change the BNC
>>connector at the antenna and finally replace the antenna. I say it
>>means the coax is bad! It's an 8 watt transmitter so I soldered a 313
>>bulb to a BNC connector and hooked it up. Everything I learned about
>>electronics (I'm an EE for Pete's sake) says that the bulb should glow
>>brightly and modulate in intensity with my voice. Should I just change
>>the coax and be done with it?
>
>from your description of the circuit surely there is nothing else left
>to change :-)
>
>you could try turning the master on :-) :-)
>g,d,r.
>Stealth Pilot

How about connecting the bulb right at the tray? As a "dummy load"
without any cable you SHOULD be able to prove the cable one way or the
other by elimination.

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[RST Engineering]

"scottloftin" > wrote in message
ups.com...
> ATC has been complaining on and off about my radio being "weak",
> "garbley" and just about every other word that describes a bad radio.
> The #1 Com is relatively new, but the airplane is old. I tried the
> light bulb trick as described in Jim's article, using the light bulb as
> a simple wattmeter connected to the coax at the #1 COM antenna
> connection. I get NOTHING when I key the mike and talk into it.

What happens when you put the light bulb right at the back of the
transceiver? Eliminate the coax question by putting the bulb right at the
source of the power.
>
> My avionics doctor tells me this doesn't mean anything. So far, he's
> had me put in a portable PTT switch, put new mikes on 2 different
> headsets, clean the coax connector at the radio, change the BNC
> connector at the antenna and finally replace the antenna.

Your avionics doctor apparently needs a Hawaii vacation. Elsewise why would
he not put a real Bird wattmeter at the antenna end, read zero watts, put it
at the radio end and either read power or not. What the hell does putting a
PTT switch, microphones, coax connectors, and antennas have to do with
output power? So far all you've done is fatten the doctor's bank account.

The light bulb has done exactly what it was supposed to do, tell you whether
or not there was a slug of power at a particular point in the transmission
chain. Back up a link and see what happens.

Jim

[scottloftin]

Jim (et. al.),
Thanks for the reply. I will do exactly that (connect the bulb
directly to the transceiver output) and post my findings.
Scott Loftin

[DABEAR]

This is way out of left field, but have you checked the antenna? I had
a friend who was having similar problems with a good radio, only to
learn he had a bad antenna in the loop. He ultimately swapped the
whole mess out for a Garmin, but the root of the trouble was a problem
with the antenna and not the radio itself. The antenna was so bad he
just file thirteen'ed the rest.

Apologies in advance if I've missed the root of the problem...

BRDB!!! (= Best Regards DA BEAR!!!)

[DABEAR]

P.S. I went back and re-read and did miss the root of the problem.
So, I'm going to lean on this: My friend spent so much time, money and
effort trying to get the problem solved (the aircraft is old design and
the cockpit cramped, extraordinarily hard to work in, that he finally
threw in the towel, bought an entire new system to include the antenna,
and told me that he should have just replaced the entire mess in the
first place, considering the money it cost him to troubleshoot an
unsuccessful repair. I look at the advice you've been given, "replace
this, replace that," and wonder if you shouldn't take your current
radio out back behind the barn and shoot it, and bring something
altogether new in to restart from scratch? New equipment requires less
maintenance is the old expression...

[Lou]

DABEAR wrote:
> P.S. I went back and re-read and did miss the root of the problem.
> So, I'm going to lean on this: My friend spent so much time, money and
> effort trying to get the problem solved (the aircraft is old design and
> the cockpit cramped, extraordinarily hard to work in, that he finally
> threw in the towel, bought an entire new system to include the antenna,
> and told me that he should have just replaced the entire mess in the
> first place, considering the money it cost him to troubleshoot an
> unsuccessful repair. I look at the advice you've been given, "replace
> this, replace that," and wonder if you shouldn't take your current
> radio out back behind the barn and shoot it, and bring something
> altogether new in to restart from scratch? New equipment requires less
> maintenance is the old expression...

I don't own a plane but do fly my club's planes. A similiar situation
happened to me with the
garbled and weak communication. The radio was checked out fine, it was
my headphones.
Lou

[Ernest Christley]

DABEAR wrote:
> P.S. I went back and re-read and did miss the root of the problem.
> So, I'm going to lean on this: My friend spent so much time, money and
> effort trying to get the problem solved (the aircraft is old design and
> the cockpit cramped, extraordinarily hard to work in, that he finally
> threw in the towel, bought an entire new system to include the antenna,
> and told me that he should have just replaced the entire mess in the
> first place, considering the money it cost him to troubleshoot an
> unsuccessful repair. I look at the advice you've been given, "replace
> this, replace that," and wonder if you shouldn't take your current
> radio out back behind the barn and shoot it, and bring something
> altogether new in to restart from scratch? New equipment requires less
> maintenance is the old expression...
>

For some reason, people (myself included) have a hard time coming to
grips with the idea that troubleshooting is a divide-and-conquer
activity. Maybe it is the methodical, step-by-step procedural approach
and a requirement to truly understand the system that throws us all
off. We all want to jump to an intuitive answer and immediately fix the
offending component.

I'm not throwing stones, but your friend made an expensive mistake
(unless he just wanted a new system anyway). Couldn't he have tried
hooking the radio to someone else's antennae or some such method to
prove that one component or the other was faulty?

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[Ron Wanttaja]

On Sat, 01 Apr 2006 13:53:25 GMT, Ernest Christley > wrote:

>I'm not throwing stones, but your friend made an expensive mistake
>(unless he just wanted a new system anyway). Couldn't he have tried
>hooking the radio to someone else's antennae or some such method to
>prove that one component or the other was faulty?

I went through somewhat the same thing when trying to troubleshoot my Narco's
transmit problems. One problem I had is that the Escort II doesn't use a
rack...using my radio in someone else's plane would have required disconnecting
two antenna connectors and an awkward power/headset connector, and either
physically unbolting the radio from their panel or trying to lead the coaxes and
power/headset connector to somewhere where I could hook them to my own radio.

The opposite way has an additional problem...if the problem *did* lie in the
antenna or power system of my plane, what are the odds I'd blow my buddy's radio
when I hooked it in?

In my particular case, I only knew for sure my Narco was blown when I
disconnected its transmit antenna, plugged a battery-powered handheld into it,
and monitored the transmission with a third radio.

Ron Wanttaja