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Connecting hand-held to ships antenna

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kesleyelectric(at)chooseb
Guest

Posted: Wed Jan 31, 2007 4:38 pm Post subject: Connecting hand-held to ships antenna

Bob,

  

 I checked back in  the articles archive and found one that described a small box fabricated from  sheet brass for connecting a handheld to the com antenna.  I liked this  approach because if you keep the short length of coax attached to your handheld,  all you have to do is pull it out and plug the connector into the dash  mounted jack.  To me this is easier than disconnecting and  reconnecting a coax line.  Does this jack disconnect the panel mounted comm  from the antenna line when the plug from the handheld is inserted? Is  this still an acceptable alternative, or is there a reason that you did not  mention it?

  

 Thanks to all on  your thoughts about great teachers we have been privileged to learn from.   I have a few I need to find...

  

 Tom  Barter

 Kesley,  IA

 Avid Magnum  (a  work in progress)

   [quote][b]

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nuckollsr(at)cox.net
Guest

Posted: Wed Jan 31, 2007 6:03 pm Post subject: Connecting hand-held to ships antenna

At 06:38 PM 1/31/2007 -0600, you wrote:



Bob,



I checked back in the articles archive and found one that

described a small box fabricated from sheet brass for connecting

a handheld to the com antenna.  I liked this approach because

if you keep the short length of coax attached to your handheld,

all you have to do is pull it out and plug the connector into

the dash mounted jack.  To me this is easier than disconnecting

and reconnecting a coax line.  Does this jack disconnect the

panel mounted comm from the antenna line when the plug from the

handheld is inserted? Is this still an acceptable alternative,

or is there a reason that you did not mention it?



     Yeah  . . . in fact, I thought I'd pulled that article.

     Thanks for reminding me about it. I do want to take it

     down.



     THE problem is the kind of jack needed to achieve the

     automatic switching of antenna from panel mounted radio

     to the hand held as the hand-held's cable is plugged in.

     This is called a "closed circuit" jack and is the same

     style of connector that disconnects the speaker from a

     small radio when you plug in headphones.



     The potential for problems arises because signals for

     the panel mounted radio are carried across low pressure

     contacts that are not especially designed for longevity

     in the cockpit environment. Probability that the pilot

     will NEED to use the hand-held is probably lower than

     probability that corrosion in the closed circuit jack

     will make the panel mounted radio un-reliable or noisy.

     It's a case of not being able to make sure that the

     cure is not more lethal than the disease!



     Not everyone is REALLY good at building these jacks,

     especially the miniature ones. Breaking into the coax

     by opening BNC connectors is many times more robust

     than those little jacks. Had some fun putting that

     article together but in retrospect, it wasn't all that

     good an idea.



     The REALLY cool solution is a solid state relay (PIN

     diodes) but these take power to make them work . . . and

     the whole idea behind an antenna jack for hand helds

     is to service the hand-held radio even if power in the

     airplane is down completely.



     The other alternative is an antenna relay that is

     held energized by ship's power to keep the panel mounted

     radio serviced . . . and defaults to the hand-held's

     antenna jack when switched off or ship's power is down.



     In retrospect, since we are all (repeat after me) building

     failure tolerant electrical systems, perhaps the PIN diode

     switch is the best way to do the transfer.  I'll think about

     it some more. In the mean time, breaking into the coax is

     really easy, cheap and super-robust.

Thanks to all on your thoughts about great teachers we have been privileged

to learn from.  I have a few I need to find...



     Good luck! I hope you find them.



     Bob . . .

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