Com Radio Problems - Jul 2004

I would like to ask the group if anyone has run into com radio problems
with their Ximango while using the King-97A radio.  I had mine bench
checked by a qualified avionics guy and it checked out fine on the bench

===================================================

Date:         Tue, 27 Jul 2004 01:10:54 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Rob Morgan <ls484@AOL.COM>
Subject:      Com Radio Problems

I would like to ask the group if anyone has run into com radio problems
with their Ximango while using the King-97A radio.  I had mine bench
checked by a qualified avionics guy and it checked out fine on the bench,
putting out about 6.5 watts over much of its frequency band.  Once we put
it back in the Ximango we checked the power output and antenna match.  With
11.9v from the battery (not tested with the engine running), the power out
dropped to between 4 and 5 watts.  The antenna match was real good at the
lower frequencies, but showed more reflection back from the antenna at the
higher frequencies. Still, power radiated from the antenna should be
sufficient to get out with the radio across the entire frequency band. What
is more disturbing is the fact that I get a squeal and garbled audio when
trying to transmit (especially evident at the higher frequencies).  No one
is able to read my transmissions beyond 2 or 3 miles line of site.  I tried
both PTT switches and two different headseats, all with the same results.
I don't note any difference in radio behavior with the engine/alternator on
or off.

I'm thinking of doing some testing with an independent battery wired as
directly as possible to the radio, as about the only thing I can think of
at this point is perhaps I have a poor connection/ground to the radio.
Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Mon, 26 Jul 2004 22:20:08 -0700
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Fitz Gary <wfrg@EARTHLINK.NET>
Subject:      Re: Com Radio Problems
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

good letter


----- Original Message -----
From: "Rob Morgan" <ls484@AOL.COM>
To: <XIMANGO@HOME.EASE.LSOFT.COM>
Sent: Monday, July 26, 2004 10:10 PM
Subject: Com Radio Problems


> I would like to ask the group if anyone has run into com radio problems
> with their Ximango while using the King-97A radio.  I had mine bench
> checked by a qualified avionics guy and it checked out fine on the bench,
> putting out about 6.5 watts over much of its frequency band.  Once we put
> it back in the Ximango we checked the power output and antenna match.
With
> 11.9v from the battery (not tested with the engine running), the power out
> dropped to between 4 and 5 watts.  The antenna match was real good at the
> lower frequencies, but showed more reflection back from the antenna at the
> higher frequencies. Still, power radiated from the antenna should be
> sufficient to get out with the radio across the entire frequency band.
What
> is more disturbing is the fact that I get a squeal and garbled audio when
> trying to transmit (especially evident at the higher frequencies).  No one
> is able to read my transmissions beyond 2 or 3 miles line of site.  I
tried
> both PTT switches and two different headseats, all with the same results.
> I don't note any difference in radio behavior with the engine/alternator
on
> or off.
>
> I'm thinking of doing some testing with an independent battery wired as
> directly as possible to the radio, as about the only thing I can think of
> at this point is perhaps I have a poor connection/ground to the radio.
> Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Tue, 27 Jul 2004 00:24:00 -0700
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         john adbon <adbinoutdoor@YAHOO.COM>
Subject:      Re: Com Radio Problems
In-Reply-To:  <000b01c47399$66bd77a0$6302a8c0@Belkin>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii

Rob,
I have  similar radio problem
. recently in  the receive mode isworks fine but very weak in the transmit mode. So far I have not been able to determne the problem. I have eliminted the obvious causes such as a flat battery , head sets and antenna connection. I suspect it might be the antenna connection at the junction of the tail and fuselarge but I cannot be certan at this time. I am still trying to find the fault.
John thirwall

Fitz Gary <wfrg@EARTHLINK.NET> wrote:
good letter


----- Original Message -----
From: "Rob Morgan"
To:
Sent: Monday, July 26, 2004 10:10 PM
Subject: Com Radio Problems


> I would like to ask the group if anyone has run into com radio problems
> with their Ximango while using the King-97A radio. I had mine bench
> checked by a qualified avionics guy and it checked out fine on the bench,
> putting out about 6.5 watts over much of its frequency band. Once we put
> it back in the Ximango we checked the power output and antenna match.
With
> 11.9v from the battery (not tested with the engine running), the power out
> dropped to between 4 and 5 watts. The antenna match was real good at the
> lower frequencies, but showed more reflection back from the antenna at the
> higher frequencies. Still, power radiated from the antenna should be
> sufficient to get out with the radio across the entire frequency band.
What
> is more disturbing is the fact that I get a squeal and garbled audio when
> trying to transmit (especially evident at the higher frequencies). No one
> is able to read my transmissions beyond 2 or 3 miles line of site. I
tried
> both PTT switches and two different headseats, all with the same results.
> I don't note any difference in radio behavior with the engine/alternator
on
> or off.
>
> I'm thinking of doing some testing with an independent battery wired as
> directly as possible to the radio, as about the only thing I can think of
> at this point is perhaps I have a poor connection/ground to the radio.
> Thoughts anyone? Anyone experienced similar problems?


---------------------------------
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=========================================================================
Date:         Tue, 27 Jul 2004 07:33:20 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         heinz peier <heinzpeier@MINDSPRING.COM>
Subject:      Re: Com Radio Problems
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Hi Rob

Check out all the Headset & Mike Plugs wires on the back side , if they are
to close you could get some squeals.
Many Radio problems starting right there.
Regards

Heinz
----- Original Message -----
From: "Fitz Gary" <wfrg@EARTHLINK.NET>
To: <XIMANGO@HOME.EASE.LSOFT.COM>
Sent: Tuesday, July 27, 2004 1:20 AM
Subject: Re: Com Radio Problems


> good letter
>
>
> ----- Original Message -----
> From: "Rob Morgan" <ls484@AOL.COM>
> To: <XIMANGO@HOME.EASE.LSOFT.COM>
> Sent: Monday, July 26, 2004 10:10 PM
> Subject: Com Radio Problems
>
>
> > I would like to ask the group if anyone has run into com radio problems
> > with their Ximango while using the King-97A radio.  I had mine bench
> > checked by a qualified avionics guy and it checked out fine on the
bench,
> > putting out about 6.5 watts over much of its frequency band.  Once we
put
> > it back in the Ximango we checked the power output and antenna match.
> With
> > 11.9v from the battery (not tested with the engine running), the power
out
> > dropped to between 4 and 5 watts.  The antenna match was real good at
the
> > lower frequencies, but showed more reflection back from the antenna at
the
> > higher frequencies. Still, power radiated from the antenna should be
> > sufficient to get out with the radio across the entire frequency band.
> What
> > is more disturbing is the fact that I get a squeal and garbled audio
when
> > trying to transmit (especially evident at the higher frequencies).  No
one
> > is able to read my transmissions beyond 2 or 3 miles line of site.  I
> tried
> > both PTT switches and two different headseats, all with the same
results.
> > I don't note any difference in radio behavior with the engine/alternator
> on
> > or off.
> >
> > I'm thinking of doing some testing with an independent battery wired as
> > directly as possible to the radio, as about the only thing I can think
of
> > at this point is perhaps I have a poor connection/ground to the radio.
> > Thoughts anyone?  Anyone experienced similar problems?
>
=========================================================================
Date:         Tue, 27 Jul 2004 08:42:09 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Bruce Schimmel <bruce@SCHIMMEL.COM>
Subject:      Re: Com Radio Problems
In-Reply-To:  <001501c473cd$85dc8c50$7c00a5d1@heinz>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

Got some questions:

1. Is the dB drop the same amount from all angles?
2. My battery generally outputs 11.9 to 13.5. What happens if you
increase power to the radio?


I'd definitely look for crossed wires, especially near the mic and
headset sockets between the seats.

B




At 07:33 -0400 7/27/04, heinz peier wrote:
>Hi Rob
>
>Check out all the Headset & Mike Plugs wires on the back side , if they are
>to close you could get some squeals.
>Many Radio problems starting right there.
>Regards
>
>Heinz
>----- Original Message -----
>From: "Fitz Gary" <wfrg@EARTHLINK.NET>
>To: <XIMANGO@HOME.EASE.LSOFT.COM>
>Sent: Tuesday, July 27, 2004 1:20 AM
>Subject: Re: Com Radio Problems
>
>
>>  good letter
>>
>>
>>  ----- Original Message -----
>>  From: "Rob Morgan" <ls484@AOL.COM>
>>  To: <XIMANGO@HOME.EASE.LSOFT.COM>
>>  Sent: Monday, July 26, 2004 10:10 PM
>>  Subject: Com Radio Problems
>>
>>
>>  > I would like to ask the group if anyone has run into com radio problems
>>  > with their Ximango while using the King-97A radio.  I had mine bench
>>  > checked by a qualified avionics guy and it checked out fine on the
>bench,
>>  > putting out about 6.5 watts over much of its frequency band.  Once we
>put
>>  > it back in the Ximango we checked the power output and antenna match.
>>  With
>>  > 11.9v from the battery (not tested with the engine running), the power
>out
>>  > dropped to between 4 and 5 watts.  The antenna match was real good at
>the
>>  > lower frequencies, but showed more reflection back from the antenna at
>the
>>  > higher frequencies. Still, power radiated from the antenna should be
>>  > sufficient to get out with the radio across the entire frequency band.
>>  What
>>  > is more disturbing is the fact that I get a squeal and garbled audio
>when
>>  > trying to transmit (especially evident at the higher frequencies).  No
>one
>>  > is able to read my transmissions beyond 2 or 3 miles line of site.  I
>>  tried
>>  > both PTT switches and two different headseats, all with the same
>results.
>>  > I don't note any difference in radio behavior with the engine/alternator
>>  on
>>  > or off.
>>  >
>>  > I'm thinking of doing some testing with an independent battery wired as
>>  > directly as possible to the radio, as about the only thing I can think
>of
>>  > at this point is perhaps I have a poor connection/ground to the radio.
>>  > Thoughts anyone?  Anyone experienced similar problems?
>>
=========================================================================
Date:         Tue, 27 Jul 2004 07:54:40 -0600
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Holly&Denis <neditate@COMCAST.NET>
Subject:      Re: Com Radio Problems
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Hey Hey, this one sounds familiar...

I believe this subject was covered years ago, possibly before the XOG was
created. I had S/N 47, with exactly this problem. I spent hundreds of
dollars at the avionics shop, to no avail, until they grounded the intercom.
Seems that unless a hard ground to the intercom was provided, the
intercom/radio had a floating ground, and some of the electrons found their
way into the control rods etc... We could tune the squeal by moving the
stick fore and aft! Running a hard ground straight off the intercom up to
the battery eliminated the problem. I bought the aircraft in '95, we did the
ground in '96 and cured it for good. It is my understanding from then that
this is a fairly common problem in composite aircraft-getting solid grounds
can be tricky. Never depend on the airframe, or things will go in all sorts
of unexpected directions. Good luck...

Denis Michaud
----- Original Message -----
From: "Fitz Gary" <wfrg@EARTHLINK.NET>
To: <XIMANGO@HOME.EASE.LSOFT.COM>
Sent: Monday, July 26, 2004 11:20 PM
Subject: Re: Com Radio Problems


> good letter
>
>
> ----- Original Message -----
> From: "Rob Morgan" <ls484@AOL.COM>
> To: <XIMANGO@HOME.EASE.LSOFT.COM>
> Sent: Monday, July 26, 2004 10:10 PM
> Subject: Com Radio Problems
>
>
> > I would like to ask the group if anyone has run into com radio problems
> > with their Ximango while using the King-97A radio.  I had mine bench
> > checked by a qualified avionics guy and it checked out fine on the
bench,
> > putting out about 6.5 watts over much of its frequency band.  Once we
put
> > it back in the Ximango we checked the power output and antenna match.
> With
> > 11.9v from the battery (not tested with the engine running), the power
out
> > dropped to between 4 and 5 watts.  The antenna match was real good at
the
> > lower frequencies, but showed more reflection back from the antenna at
the
> > higher frequencies. Still, power radiated from the antenna should be
> > sufficient to get out with the radio across the entire frequency band.
> What
> > is more disturbing is the fact that I get a squeal and garbled audio
when
> > trying to transmit (especially evident at the higher frequencies).  No
one
> > is able to read my transmissions beyond 2 or 3 miles line of site.  I
> tried
> > both PTT switches and two different headseats, all with the same
results.
> > I don't note any difference in radio behavior with the engine/alternator
> on
> > or off.
> >
> > I'm thinking of doing some testing with an independent battery wired as
> > directly as possible to the radio, as about the only thing I can think
of
> > at this point is perhaps I have a poor connection/ground to the radio.
> > Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Tue, 27 Jul 2004 10:22:31 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Bruce Schimmel <bruce@SCHIMMEL.COM>
Subject:      Re: Com Radio Problems
In-Reply-To:  <001901c473e1$45861ef0$0500a8c0@THETRAVELER>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

Before going ahead and installing add'l groundstraps,
is it possible to check whether various parts of the airframe
are properly grounded --  using the battery negative
as a reference point?



At 07:54 -0600 7/27/04, Holly&Denis wrote:
>Hey Hey, this one sounds familiar...
>
>I believe this subject was covered years ago, possibly before the XOG was
>created. I had S/N 47, with exactly this problem. I spent hundreds of
>dollars at the avionics shop, to no avail, until they grounded the intercom.
>Seems that unless a hard ground to the intercom was provided, the
>intercom/radio had a floating ground, and some of the electrons found their
>way into the control rods etc... We could tune the squeal by moving the
>stick fore and aft! Running a hard ground straight off the intercom up to
>the battery eliminated the problem. I bought the aircraft in '95, we did the
>ground in '96 and cured it for good. It is my understanding from then that
>this is a fairly common problem in composite aircraft-getting solid grounds
>can be tricky. Never depend on the airframe, or things will go in all sorts
>of unexpected directions. Good luck...
>
>Denis Michaud
>----- Original Message -----
>From: "Fitz Gary" <wfrg@EARTHLINK.NET>
>To: <XIMANGO@HOME.EASE.LSOFT.COM>
>Sent: Monday, July 26, 2004 11:20 PM
>Subject: Re: Com Radio Problems
>
>
>>  good letter
>>
>>
>>  ----- Original Message -----
>>  From: "Rob Morgan" <ls484@AOL.COM>
>>  To: <XIMANGO@HOME.EASE.LSOFT.COM>
>>  Sent: Monday, July 26, 2004 10:10 PM
>>  Subject: Com Radio Problems
>>
>>
>>  > I would like to ask the group if anyone has run into com radio problems
>>  > with their Ximango while using the King-97A radio.  I had mine bench
>>  > checked by a qualified avionics guy and it checked out fine on the
>bench,
>>  > putting out about 6.5 watts over much of its frequency band.  Once we
>put
>>  > it back in the Ximango we checked the power output and antenna match.
>>  With
>>  > 11.9v from the battery (not tested with the engine running), the power
>out
>>  > dropped to between 4 and 5 watts.  The antenna match was real good at
>the
>>  > lower frequencies, but showed more reflection back from the antenna at
>the
>>  > higher frequencies. Still, power radiated from the antenna should be
>>  > sufficient to get out with the radio across the entire frequency band.
>>  What
>>  > is more disturbing is the fact that I get a squeal and garbled audio
>when
>>  > trying to transmit (especially evident at the higher frequencies).  No
>one
>>  > is able to read my transmissions beyond 2 or 3 miles line of site.  I
>>  tried
>>  > both PTT switches and two different headseats, all with the same
>results.
>>  > I don't note any difference in radio behavior with the engine/alternator
>>  on
>>  > or off.
>>  >
>>  > I'm thinking of doing some testing with an independent battery wired as
>>  > directly as possible to the radio, as about the only thing I can think
>of
>>  > at this point is perhaps I have a poor connection/ground to the radio.
>>  > Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Tue, 27 Jul 2004 08:27:59 -0600
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Holly&Denis <neditate@COMCAST.NET>
Subject:      Re: Com Radio Problems
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Once the avionics shop decided this was the likely problem, we decided it
wasn't worth the expense of tracking down and checking all the grounds. It
was far more expedient to simply run a ground wire...

Denis
----- Original Message -----
From: "Bruce Schimmel" <bruce@SCHIMMEL.COM>
To: <XIMANGO@HOME.EASE.LSOFT.COM>
Sent: Tuesday, July 27, 2004 8:22 AM
Subject: Re: Com Radio Problems


> Before going ahead and installing add'l groundstraps,
> is it possible to check whether various parts of the airframe
> are properly grounded --  using the battery negative
> as a reference point?
>
>
>
> At 07:54 -0600 7/27/04, Holly&Denis wrote:
> >Hey Hey, this one sounds familiar...
> >
> >I believe this subject was covered years ago, possibly before the XOG was
> >created. I had S/N 47, with exactly this problem. I spent hundreds of
> >dollars at the avionics shop, to no avail, until they grounded the
intercom.
> >Seems that unless a hard ground to the intercom was provided, the
> >intercom/radio had a floating ground, and some of the electrons found
their
> >way into the control rods etc... We could tune the squeal by moving the
> >stick fore and aft! Running a hard ground straight off the intercom up to
> >the battery eliminated the problem. I bought the aircraft in '95, we did
the
> >ground in '96 and cured it for good. It is my understanding from then
that
> >this is a fairly common problem in composite aircraft-getting solid
grounds
> >can be tricky. Never depend on the airframe, or things will go in all
sorts
> >of unexpected directions. Good luck...
> >
> >Denis Michaud
> >----- Original Message -----
> >From: "Fitz Gary" <wfrg@EARTHLINK.NET>
> >To: <XIMANGO@HOME.EASE.LSOFT.COM>
> >Sent: Monday, July 26, 2004 11:20 PM
> >Subject: Re: Com Radio Problems
> >
> >
> >>  good letter
> >>
> >>
> >>  ----- Original Message -----
> >>  From: "Rob Morgan" <ls484@AOL.COM>
> >>  To: <XIMANGO@HOME.EASE.LSOFT.COM>
> >>  Sent: Monday, July 26, 2004 10:10 PM
> >>  Subject: Com Radio Problems
> >>
> >>
> >>  > I would like to ask the group if anyone has run into com radio
problems
> >>  > with their Ximango while using the King-97A radio.  I had mine bench
> >>  > checked by a qualified avionics guy and it checked out fine on the
> >bench,
> >>  > putting out about 6.5 watts over much of its frequency band.  Once
we
> >put
> >>  > it back in the Ximango we checked the power output and antenna
match.
> >>  With
> >>  > 11.9v from the battery (not tested with the engine running), the
power
> >out
> >>  > dropped to between 4 and 5 watts.  The antenna match was real good
at
> >the
> >>  > lower frequencies, but showed more reflection back from the antenna
at
> >the
> >>  > higher frequencies. Still, power radiated from the antenna should be
> >>  > sufficient to get out with the radio across the entire frequency
band.
> >>  What
> >>  > is more disturbing is the fact that I get a squeal and garbled audio
> >when
> >>  > trying to transmit (especially evident at the higher frequencies).
No
> >one
> >>  > is able to read my transmissions beyond 2 or 3 miles line of site.
I
> >>  tried
> >>  > both PTT switches and two different headseats, all with the same
> >results.
> >>  > I don't note any difference in radio behavior with the
engine/alternator
> >>  on
> >>  > or off.
> >>  >
> >>  > I'm thinking of doing some testing with an independent battery wired
as
> >>  > directly as possible to the radio, as about the only thing I can
think
> >of
> >>  > at this point is perhaps I have a poor connection/ground to the
radio.
> >>  > Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Tue, 27 Jul 2004 13:35:15 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         "Dr. Gary Keefer" <gbk3@PSU.EDU>
Subject:      Re: Com Radio Problems
In-Reply-To:  <LISTSERV%200407270110549260@HOME.EASE.LSOFT.COM>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed

I had a problem with intermittent transmission caused by the headset jacks
being in contact with each other.  They were separated and I have not
experienced any additional problems.

Gary Keefer

At 01:10 AM 7/27/2004 -0400, you wrote:
>I would like to ask the group if anyone has run into com radio problems
>with their Ximango while using the King-97A radio.  I had mine bench
>checked by a qualified avionics guy and it checked out fine on the bench,
>putting out about 6.5 watts over much of its frequency band.  Once we put
>it back in the Ximango we checked the power output and antenna match.  With
>11.9v from the battery (not tested with the engine running), the power out
>dropped to between 4 and 5 watts.  The antenna match was real good at the
>lower frequencies, but showed more reflection back from the antenna at the
>higher frequencies. Still, power radiated from the antenna should be
>sufficient to get out with the radio across the entire frequency band. What
>is more disturbing is the fact that I get a squeal and garbled audio when
>trying to transmit (especially evident at the higher frequencies).  No one
>is able to read my transmissions beyond 2 or 3 miles line of site.  I tried
>both PTT switches and two different headseats, all with the same results.
>I don't note any difference in radio behavior with the engine/alternator on
>or off.
>
>I'm thinking of doing some testing with an independent battery wired as
>directly as possible to the radio, as about the only thing I can think of
>at this point is perhaps I have a poor connection/ground to the radio.
>Thoughts anyone?  Anyone experienced similar problems?
=========================================================================
Date:         Sun, 22 Aug 2004 23:43:58 -0400
Reply-To:     Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       Ximango Owners Group <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Rob Morgan <ls484@AOL.COM>
Subject:      Re: Com Radio Problems

Its time to share what has transpired since my original email and the
numerous responses received.

I went out to the field on a Friday morning about 3 weeks ago and proceeded
to do 2 things.  #1 was to take a careful look at the contacts and wiring
of the headset jacks between the seats.  I discovered nothing unusual; no
frayed or loose wires and no obvious signs of shorts.  #2 was to run a
jumper wire using alligator clips from the negative terminal of the battery
to the intercom case.  Once I had the jumper in place I plugged in a
headset and did a single transmission test from inside a metal hangar to
Cessna in the pattern; loud and clear.  From that successful single test I
took the time to properly route an 18 AWG wire from the negative terminal
of the battery to the intercom case.  I didn't have a good way to attach
the wire to the intercom, so I temporarily soldered an alligator clip to
the end of the wire and attached it to the intercom.  I've now flown with
it 5 or 6 times and I must say the radio situation is much improved.  I can
now transmit and people are able to hear me from a longer distance, saying
the signal is strong.  I've have experienced a squeel only once when
transmitting at the upper end of the frequency band, but have had
absolutely no problems within the lower area of the band.  At some point
(when the flying isn't so good; which isn't too often here in southern
California) I'm going to take off the alligator clip and make a more
permanent ground to the intercom and at the same time run a grounding
jumper from the same wire up to the radio case.  With a little luck, that
will result in a fix that provides no transmission squeel over any part of
the frequency band.

My thanks to all of you who responded to my initial email with your
suggestions.

Rob