N6030X(at)DaveMorris.com
Guest
|
 Posted: Fri Feb 02, 2007 12:39 pm Post subject: Sharing ship's COMM antenna with the hand-held (additional |
 |
|
I think you're on the right track here, Bob. Anything that prevents
that connection from being exceedingly clean will cause a diode
effect, and rectification in an RF circuit can cause really nasty
intermittent problems.. The kind of problem you take to your avionics
guy and say "this squealing only happens when it is raining outside",
and he laughs at you.
Also the insertion of things into RF transmission lines is not
something to be taken lightly. You are changing the impedance at
that point, and that will cause some amount of loss. Jim Weir says
the amount of loss is insignificant in the case of the IC-ANT-SB, but
a poorly constructed switchbox might introduce just enough loss to
interfere with one's ability to contact ATC at a distance when it's
needed most.
Dave Morris
At 01:55 PM 2/2/2007, you wrote:
| Quote: |
<nuckollsr(at)cox.net>
I've been getting some direct e-mails that suggest a need
for further explanation.
Take a peek at this photo . . .
http://www.aeroelectric.com/Pictures/Connectors/3p5_mm_Jack.jpg
I've pointed to the little hunk of exposed brass that is supposed
to maintain connection between the antenna and the panel mounted
comm when the hand held is unplugged.
This contact is exposed to the environment and not plated
for longevity. Further, the wire connection terminals are
relatively flimsy . . . if you recall - the Shop Notes
I published recommended splicing short, flexible pigtails
to the stub ends of coax center conductors so as to isolate
the switch terminals from potential forcing by the stiffer
coax.
Alternatives? Maybe. See . . .
http://www.aeroelectric.com/Pictures/Connectors/3p5_mm_Jack_2.jpg
These are ECB mounted, closed circuit jacks. No stresses
will be input to the switch structure due to coax . . .
See also . . .
http://www.aeroelectric.com/Pictures/Connectors/3p5_mm_jack_schematic.pdf
Specs for these switches speak to silver plating of some parts.
I need to explore this further. What I'm considering is a small
ECB assembly that mounts one of these jacks and two right angle
BNC jacks to take antenna and transceiver coaxes off the board
and into ships wiring.
I think this could be a quantum jump up from the Shop Notes design
and perhaps more robust and compact than the ICOM product. We'll
see . . .
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
