Matronics Email Lists :: View topic - Two Txrs on one antenna

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Two Txrs on one antenna

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

VE3LVO(at)rac.ca
Guest

Posted: Fri May 04, 2007 10:16 am Post subject: Two Txrs on one antenna

I've been following the discussion regarding running two transceivers on one 

coax line......... some very enlightening opinions!

Wouldn't a 12vDC coaxial relay do the job?

See any local ham over forty for details......

Ferg Kyle

Europa A064 914 Classic



---

- 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

nuckollsr(at)cox.net
Guest

Posted: Sun May 06, 2007 9:26 am Post subject: Two Txrs on one antenna

At 02:13 PM 5/4/2007 -0400, you wrote:



 	  Quote: 	
		  



I've been following the discussion regarding running two transceivers on 

one coax line......... some very enlightening opinions!

Wouldn't a 12vDC coaxial relay do the job?

See any local ham over forty for details......


	


    A relay (or switch) is useful for the selective connection

    of two devices to a single device. In this case, one

    could have a single antenna and two transceivers, or two

    antennas and one transceiver. We do the later on an

    agile military trainer where under certain flight

    conditions, the airframe masks the ability of a single

    antenna to provide omnidirectional performance. But

    in either instance only ONE of the TWO switched

    devices gets the benefit of the single at any given

    time.



    For dual transceivers to share a common antenna

    such that both may listen and either may transmit

    requires a device referred to as a diplexer. See:



http://en.wikipedia.org/wiki/Diplexer



    An alternative product would consist of a pair

    of relays combined with an distribution amplifier

    that takes a single antenna and drives two receivers

    but senses when PTT for any one transceiver is active

    and captures the antenna for the exclusive use of the

    active transmitter.



    The amplifier/switch can be less expensive than

    a diplexer but it adds complexity to the system and

    new failure modes. A malfunction in the amplifier/switch

    might not only cripple ability of both transceivers to

    talk, it might couple transmitter energy into the

    other transceiver's input and damage the receiver.

    After the pilot tries one transceiver and finds that

    it doesn't work he tries the other and finds that

    it doesn't work either . . . now both receivers

    are hosed as well.



    Anecdotally, consider this. I work in a factory that

    produces a lot of $high$ aircraft ranging from 1/2 to

    15 million dollars. If any group of owner-operators

    perceived a lower cost of ownership for having installed

    either a passive device like a diplexer or an active

    device such as an amplifier/switch, for the purpose of

    eliminating one antenna, they would have asked for it

    and we would no doubt have provided it.



    The reason for TWO systems is redundancy. Bringing

    two transceivers into a single antenna has not passed

    muster with the reasoning of a whole lot of folks.

    Let's not spend too much time wishing for 0.25K more IAS

    by the elimination of one antenna traded for a

    demonstrated risk to loss of redundancy and possibility

    of unhappy failure modes.



    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

list(at)toddheffley.com
Guest

Posted: Tue May 08, 2007 6:36 pm Post subject: Two Txrs on one antenna

I support Jet aircraft with these coax relays.



They are often the source of intermittant problems.



the worst are coax relays that split two transponders to one blade antenna.



Higher Frequncy IMHO.



My experince leads me to think two working antennas are more valuable  

than one antenna and one unreliable relay.



My opinion is colored by maintenance experience, not building experience.



Todd

- 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

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

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