Replacing com antennas

[Mike Noel]

I've ordered a pair of CI-291 Comant com antennas to replace the well worn
antennas on my Archer. Besides removing any oxidation where the aluminum
base contacts the aircraft and making sure the coax connector is clean and
serviceable and the mechanical connection robust, are there other mounting
considerations? For instance, is a conductive grease used between the
antenna base and the aluminum panel? Does Comant include any extra goodies
for the installation?

The 3 mounting holes in the new antennas are in exact alignment with the old
antennas. The interesting part will be backing the spinning nuts in the
tail cone while removing the outside screws. I should be able to capture
the coax with nylon ties to keep them from falling back into the fuselage
while preparing to mount the new antennas.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel

[Larry]

Mike: Does your new antenna have a BNG terminal.? I've been told that
is the way to go instead of a separate coax ground wire. Maybe I'm
confused what you have.

Larry

[Mike Noel]

Hi Larry. I think what is on the end of the coax is called a male bnc
connector.

--
Mike Noel,
Tucson, Arizona

'Men never do evil so completely and cheerfully as when they do it from
religious conviction.'

-Blaise Pascal
"Larry" > wrote in message
ups.com...
> Mike: Does your new antenna have a BNG terminal.? I've been told that
> is the way to go instead of a separate coax ground wire. Maybe I'm
> confused what you have.
>
> Larry
>

[Jay Beckman]

"Mike Noel" > wrote in message
...
> Hi Larry. I think what is on the end of the coax is called a male bnc
> connector.
>
> --
> Mike Noel,
> Tucson, Arizona

Hi Mike,

Just as a point of clarification for all (not specifically aimed at you...):

BNC: A "cam-lock" style connector needing only about 1/4 turn to lock in
place via curved channels that ride down pins on the opposite connector.

UHF: 1/4" to 1/2" diameter threaded connector which needs multiple turns to
screw into place.

One of these two types of connectors are usually what you'll find at the end
of a Coaxial cable. The UHF connectors of the world have pretty much been
replaced by BNC connectors, but you still find UHF on older wiring.

Jay Beckman
PP-ASEL
Chandler, AZ

[Mike Noel]

I can now partially answer my own question since I've received the antennas
from Spruce. The only thing in the box is the antenna and a base gasket.
I'll need to purchase new nuts and screws and evidently no 'conductive
grease' is needed.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel
"Mike Noel" > wrote in message
. ..
> I've ordered a pair of CI-291 Comant com antennas to replace the well worn
> antennas on my Archer. Besides removing any oxidation where the aluminum
> base contacts the aircraft and making sure the coax connector is clean and
> serviceable and the mechanical connection robust, are there other mounting
> considerations? For instance, is a conductive grease used between the
> antenna base and the aluminum panel? Does Comant include any extra
> goodies for the installation?
>
> The 3 mounting holes in the new antennas are in exact alignment with the
> old antennas. The interesting part will be backing the spinning nuts in
> the tail cone while removing the outside screws. I should be able to
> capture the coax with nylon ties to keep them from falling back into the
> fuselage while preparing to mount the new antennas.
>
> --
> Best Regards,
> Mike
> http://photoshow.comcast.net/mikenoel
>

[Don Tuite]

On Wed, 10 May 2006 13:13:56 -0700, "Mike Noel" >
wrote:

>I can now partially answer my own question since I've received the antennas
>from Spruce. The only thing in the box is the antenna and a base gasket.
>I'll need to purchase new nuts and screws and evidently no 'conductive
>grease' is needed.

It's probably just my ignorance, but the only conductive grease I've
ever encountered in electronics is the stuff you used to use between
the bottom of a power transistor in a TO3 can and the mica washer.
(Or was it between the washer and the heat sink?) It was thermally,
rather than electrically, conductive.

Don

[RST Engineering]

Don ...

Both the graphite grease and the copper grease we use on spark plugs to make
them easier to remove are electrically conductive as well as thermally
conductive. HOWEVER, no such grease is needed (or wanted) on the COM
antenna(s).

On the other hand, I generally put a VERY thin film (almost a whisper) of
Dow Corning silicone grease (NOT SILICONE SEAL) on both sides of the rubber
gasket to keep rainwater out of the aircraft.

Jim


>
> It's probably just my ignorance, but the only conductive grease I've
> ever encountered in electronics is the stuff you used to use between
> the bottom of a power transistor in a TO3 can and the mica washer.
> (Or was it between the washer and the heat sink?) It was thermally,
> rather than electrically, conductive.
>
> Don
>

[Mike Noel]

Evidently the antennas have a special coating over the fiberglass to allow
them to conduct away static charges that can build up. I think the charge
is allowed to pass to the airframe via the antenna base and the mounting
screws and then out the static wicks. If the static is allowed to build up
it is said to cause noise in the radio. I would imagine the idea of
conductive grease was to allow a more robust path for static drain to the
airframe.

The countersink surfaces on the antenna base for the mounting screws are
bare metal. I suppose this is intentional to allow static discharge. When
corrosion occurs at these small conductive surfaces perhaps the performance
of the antenna will be compromised when conditions are right for static
buildup. I understant that when an antenna ages and the conductive coating
on the outside of the fiberglass degrades, this can also cause static
problems. Supposedly these are the rational for replacing antennas when
installing new radios.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel
"Don Tuite" > wrote in message
...
> On Wed, 10 May 2006 13:13:56 -0700, "Mike Noel" >
> wrote:
>
>>I can now partially answer my own question since I've received the
>>antennas
>>from Spruce. The only thing in the box is the antenna and a base gasket.
>>I'll need to purchase new nuts and screws and evidently no 'conductive
>>grease' is needed.
>
> It's probably just my ignorance, but the only conductive grease I've
> ever encountered in electronics is the stuff you used to use between
> the bottom of a power transistor in a TO3 can and the mica washer.
> (Or was it between the washer and the heat sink?) It was thermally,
> rather than electrically, conductive.
>
> Don
>

[RST Engineering]

Where do you get the "evidently"?

Jim


"Mike Noel" > wrote in message
. ..

> Evidently

[Mike Noel]

What I was proposing is based on discussions or articles I've run across on
usenet, and some dealer sites like Avionics West. I mean them as points
for further discussion, not well know facts.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel
"RST Engineering" > wrote in message
.. .
> Where do you get the "evidently"?
>
> Jim
>
>
> "Mike Noel" > wrote in message
> . ..
>
>> Evidently
>
>