 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
nuckollsr(at)cox.net
Guest
|
 Posted: Fri Feb 02, 2007 5:46 am Post subject: Sharing ship's COMM antenna with the hand-held |
 |
|
At 10:36 PM 2/1/2007 -0500, you wrote:
| Quote: |
<retasker(at)optonline.net>
Bob, Now you are confusing us! In one email you say that this method of
switching from the internal radio to the handheld is not so good and you
are going to take it off your web site and the next email you are saying
that the one ICOM has their name on seems a viable option and offer to
sell it to anyone who wants one. What gives??? This product does exactly
what the one on your web site does!
Confused...
Dick Tasker
|
They have the same end function and even perhaps identical
implementation. The design I proposed depended on a miniature,
closed-circuit headset jack acquired from local parts sources.
The "closed circuit" switch in the jack is always in series
with the antenna lead from the panel mounted radio. It represents
a risk to operability of the panel mounted radio whether or not
one ever uses the jack to connect the hand held.
Because this is an ICOM product, I'm presuming/hoping/wishing
that they've acquired a source for a more robust connector
than what most of us can buy locally. About a dozen folks have
requested this product and I've only ordered 5! But before I
ship any of them, I'll take one apart and look it over. Photos
and a tear down report will be published on my website.
We could consider a DIY project perhaps based on a jack
from Switchcraft . . . if a "robust" version of that device
exists, probability is high that Switchcraft makes it.
Alternatively, I'm mulling over a design that makes use
of a miniature, sealed relay who's normally closed contacts
do not pose so high a risk to functionality of the panel
mounted radio as the design I proposed originally.
The article I published wasn't the best-we-know-how-
to-do and needed to be replaced or refined.
Bob . . .
| | - 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 |
|
|
|
| Back to top |
|
 |
nuckollsr(at)cox.net
Guest
|
| Posted: Fri Feb 02, 2007 11:13 am Post subject: Sharing ship's COMM antenna with the hand-held |
|
|
At 10:02 AM 2/2/2007 -0800, you wrote:
| Quote: | Echoing Dick Tasker's comments.
Casting about on the web, came across remarks that the IC-ANT-SB device
would significantly degrade performance of COM-1 when the Handheld was not
in use, and that the 3.5 mm jack was "crude".
Listers?
|
Good feedback sir. We'll see what they look like when
I get them in hand. I may very well need to return them.
Can you cite the location where this comment was found?
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 |
|
|
|
| Back to top |
|
|
jonlaury
Joined: 06 Nov 2006
Posts: 336
|
| Posted: Sat Feb 03, 2007 7:55 pm Post subject: Sharing ship's COMM antenna with the hand-held |
|
|
Bob,
Re website with discussion on IC-ANT-SB
www.flight.org/forums/showthread.php?t=274288
[quote][b]
| | - 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 |
|
|
|
| Back to top |
|
|
N6030X(at)DaveMorris.com
Guest
|
| Posted: Sun Feb 04, 2007 11:14 am Post subject: Sharing ship's COMM antenna with the hand-held |
|
|
John, I don't think it's as simple as that.
If you put a 50 ohm resistor at the end of a piece of coax you are
transmitting into, the resistor becomes a "dummy load", and will heat
up to the extent that it is rated near the power level of the
transmitter. You cannot then simply add a T connector to another
device and assume that the dummy load will be invisible to the system.
If you connect a handheld radio with a 2W output into the receiver
input of a panel mounted radio, you'd better hope that receiver's
input section is capable of handling that level of power. I'm not
sure any of them are.
Dave Morris
At 12:19 PM 2/4/2007, you wrote:
[quote]
If you short a 50 ohm resistor across the end of a 50 ohm coax, you
will effectively remove that "leg" of the cable from the circuit so
far as back reflection is concerned. This is called
terminating. Basically, the 50ohm resistor acts the same as an
infinitely long coax, if that makes sense?
So if radio manufacturers where clever, they would setup their
antenna inputs to short across a 50ohm load when the unit is off,
effectively terminating their end of the cable. On the panel, you
use a T with a 50 ohm terminator in the panel side. If you need to
use a handheld, you can turn off the panel mount and replace the 50
ohm terminator with your handheld input. The downside is that you
will loose range.
Don't take any of this as a suggestion. It was just something that
flashed into my brain this morning when I thought about how to make
every compatible. I think this would work but you'd sacrifice
performance, so it's probably not viable.
-John
Doug Windhorn wrote:
>
><N1DeltaWhiskey(at)comcast.net>
>
>John,
>
>Not sure what you are getting at here, but simply measuring the in
>"resistance" of the antenna input will, I think, tell you
>little. Or, maybe I am missing what you are suggesting.
>
>Did a quick look at "characteristic impedance" on Wikipedia. When
>one talks about transmission cables (and matching connections),
>impedance is the "apparent resistance" to AC signals that the line
>is rated in, not simple resistance. I believe you are talking
>about measuring the impedance, not solely the resistance, of the input.
>
>I could surmise some thing about this, but probably make myself
>look a little (maybe a lot) unknowledgeable, so will leave further
>clarification to those with a better understanding of the subject.
>But a good starting place for discussion is to have an
>understanding of the relevant terms
>
>Regards,
>
>Doug Windhorn.
>
>
>---
| | - 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 |
|
|
|
| Back to top |
|
|
john(at)ballofshame.com
Guest
|
| Posted: Sun Feb 04, 2007 11:55 am Post subject: Sharing ship's COMM antenna with the hand-held |
|
|
Yes, of course you're right Dave. I was just thinking out loud, I guess.
-John
Dave N6030X wrote:
[quote]
<N6030X(at)DaveMorris.com>
John, I don't think it's as simple as that.
If you put a 50 ohm resistor at the end of a piece of coax you are
transmitting into, the resistor becomes a "dummy load", and will heat
up to the extent that it is rated near the power level of the
transmitter. You cannot then simply add a T connector to another
device and assume that the dummy load will be invisible to the system.
If you connect a handheld radio with a 2W output into the receiver
input of a panel mounted radio, you'd better hope that receiver's
input section is capable of handling that level of power. I'm not
sure any of them are.
Dave Morris
At 12:19 PM 2/4/2007, you wrote:
>
> <john(at)ballofshame.com>
>
> If you short a 50 ohm resistor across the end of a 50 ohm coax, you
> will effectively remove that "leg" of the cable from the circuit so
> far as back reflection is concerned. This is called terminating.
> Basically, the 50ohm resistor acts the same as an infinitely long
> coax, if that makes sense?
>
> So if radio manufacturers where clever, they would setup their
> antenna inputs to short across a 50ohm load when the unit is off,
> effectively terminating their end of the cable. On the panel, you
> use a T with a 50 ohm terminator in the panel side. If you need to
> use a handheld, you can turn off the panel mount and replace the 50
> ohm terminator with your handheld input. The downside is that you
> will loose range.
>
> Don't take any of this as a suggestion. It was just something that
> flashed into my brain this morning when I thought about how to make
> every compatible. I think this would work but you'd sacrifice
> performance, so it's probably not viable.
>
> -John
>
> Doug Windhorn wrote:
>>
>> <N1DeltaWhiskey(at)comcast.net>
>>
>> John,
>>
>> Not sure what you are getting at here, but simply measuring the in
>> "resistance" of the antenna input will, I think, tell you little.
>> Or, maybe I am missing what you are suggesting.
>>
>> Did a quick look at "characteristic impedance" on Wikipedia. When
>> one talks about transmission cables (and matching connections),
>> impedance is the "apparent resistance" to AC signals that the line
>> is rated in, not simple resistance. I believe you are talking about
>> measuring the impedance, not solely the resistance, of the input.
>>
>> I could surmise some thing about this, but probably make myself look
>> a little (maybe a lot) unknowledgeable, so will leave further
>> clarification to those with a better understanding of the subject.
>> But a good starting place for discussion is to have an understanding
>> of the relevant terms
>>
>> Regards,
>>
>> Doug Windhorn.
>>
>>
>>
>>
>> ---
| | - 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 |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
