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Radio interlock

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jpx(at)qenesis.com
Guest

Posted: Sun Nov 18, 2007 8:38 am Post subject: Radio interlock

I had interesting plans to install my com antennas on each wing to  

keep them farther apart.  The idea was that two pilots could each use  

one of the radios simultaneously - say to talk with ATC and FSS (as  

opposed to merely monitoring the second channel).

An avionics tech I talked with recently said there was no way to  

transmit simultaneously.  The intense field strength produced by one  

radio transmitting would damage the receive section of the other  

radio.  Thus there is a lockout connection wired between the radios,  

so that the non-transmitting radio grounds its antenna as self  

protection while the other transmits.

This sounds quite logical and valid, but I have no pinouts for radios  

to confirm this is indeed the case.

True ??

Jeff Page

Dream Aircraft Tundra #10

mprather(at)spro.net
Guest

Posted: Sun Nov 18, 2007 9:41 am Post subject: Radio interlock

Huh..  Sounds logical, but I recently got a ride in a Pilatus that had a

comm system that allowed talking/receiving on two different frequencies at

the same time.  I was talking to an FBO on the unicom while the pilot was

talking to the SLC approach controller.  Not sure how they make that work,

but it seemed to be okay.  Possibly each receiver was being relayed-out

while the other transmitter was operating and I just didn't notice it.

Matt-



 	  Quote: 	
		   



 I had interesting plans to install my com antennas on each wing to

 keep them farther apart.  The idea was that two pilots could each use

 one of the radios simultaneously - say to talk with ATC and FSS (as

 opposed to merely monitoring the second channel).

 An avionics tech I talked with recently said there was no way to

 transmit simultaneously.  The intense field strength produced by one

 radio transmitting would damage the receive section of the other

 radio.  Thus there is a lockout connection wired between the radios,

 so that the non-transmitting radio grounds its antenna as self

 protection while the other transmits.

 This sounds quite logical and valid, but I have no pinouts for radios

 to confirm this is indeed the case.

 True ??

 Jeff Page

 Dream Aircraft Tundra #10

BobsV35B(at)aol.com
Guest

Posted: Sun Nov 18, 2007 9:55 am Post subject: Radio interlock

Good Morning Matt,

  

 Every air carrier aircraft I ever flew that was equipped with VHF  Communication radios allowed simultaneous use of both transmitters. My WAG would  be that it is, and was, a matter of proper spacing of the antennas.

  

 I wonder if an antenna on the top of a metal airplane would interfere with  one on the belly?  My Bonanza Has such an arrangement, but I have never  attempted simultaneous use of the radios.

  

 Inquisitive minds want to know!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630 985-8503   

  In a message dated 11/18/2007 11:43:55 A.M. Central Standard Time,  mprather(at)spro.net writes:

  	  Quote: 	
		  Huh..  Sounds logical, but I recently got a ride in a Pilatus that    had a

comm system that allowed talking/receiving on two different    frequencies at

the same time.  I was talking to an FBO on the unicom    while the pilot was

talking to the SLC approach controller.  Not sure    how they make that work,

but it seemed to be okay.  Possibly each    receiver was being relayed-out

while the other transmitter was operating    and I just didn't notice  it.

Matt-

	






See what's new at AOL.com and Make AOL Your Homepage.

  [quote][b]

rjquillin

Joined: 13 May 2007
Posts: 123
Location: KSEE

Posted: Sun Nov 18, 2007 10:01 am Post subject: Radio interlock

At 08:35 11/18/2007, you wrote:

 	  Quote: 	
		  



I had interesting plans to install my com antennas on each wing to

keep them farther apart.


	


Anetnna separation is indeed a factor, but not the only one.  Small 

A/C inherently have a more difficult time due to the difficulties 

encountered in achieving separation.  Small composite or fabric makes 

it even more difficult due to the lack of metal ground plane 

area.  OTOH, large metal A/C can take advantage of both separation, 

as well as the RF shadow created by the ground referenced skin, and 

place antennae on the top and bottom; thus achieving both separation 

and shielding.  This type of an installation can be quiet effective 

for satisfactory, simultaneous com usage.



 	  Quote: 	
		  The idea was that two pilots could each use

one of the radios simultaneously - say to talk with ATC and FSS (as

opposed to merely monitoring the second channel).


	


This is a supported function, split, on at least some of the PS audio 

panels, with caveats mentioned above perhaps necessary for a 

successful outcome.



 	  Quote: 	
		  An avionics tech I talked with recently said there was no way to

transmit simultaneously.

The intense field strength produced by one

radio transmitting would damage the receive section of the other

radio.  Thus there is a lockout connection wired between the radios,

so that the non-transmitting radio grounds its antenna as self

protection while the other transmits.


	


Some radios do have an interlock function to prevent inadvertent 

transmissions from one interfering with reception on the other.  This 

is an option, not a requirement, and not all radios or audio panels 

have this 'feature'.



 	  Quote: 	
		  This sounds quite logical and valid, but I have no pinouts for radios

to confirm this is indeed the case.

True ??

Jeff Page

Dream Aircraft Tundra #10


	




Ron Q.

BobsV35B(at)aol.com
Guest

Posted: Sun Nov 18, 2007 10:05 am Post subject: Radio interlock

Just another thought. 

  

 My recollection is that we were told to avoid transmitting on the same  frequency that the other radio was receiving. Other than that caution, I recall  no difficulties involved.

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630 985-8503   

  In a message dated 11/18/2007 11:57:30 A.M. Central Standard Time,  BobsV35B(at)aol.com writes:

  	  Quote: 	
		     Every air carrier aircraft I ever flew that was equipped with VHF    Communication radios allowed simultaneous use of both transmitters. My WAG    would be that it is, and was, a matter of proper spacing of the    antennas.

	




  [quote][b]

mlas(at)cox.net
Guest

Posted: Sun Nov 18, 2007 7:43 pm Post subject: Radio interlock

Jeff,



We use more then one VHF transmitter on the airliners all the time.  I

have used both VHF transmitters on my Lancair at the same time with only

36" between antennas without a problem.



Mike Larkin



--

nuckolls.bob(at)cox.net
Guest

Posted: Sun Nov 18, 2007 8:23 pm Post subject: Radio interlock

At 11:35 AM 11/18/2007 -0500, you wrote:



 	  Quote: 	
		  



I had interesting plans to install my com antennas on each wing to

keep them farther apart.  The idea was that two pilots could each use

one of the radios simultaneously - say to talk with ATC and FSS (as

opposed to merely monitoring the second channel).

An avionics tech I talked with recently said there was no way to

transmit simultaneously.  The intense field strength produced by one

radio transmitting would damage the receive section of the other

radio.  Thus there is a lockout connection wired between the radios,

so that the non-transmitting radio grounds its antenna as self

protection while the other transmits.

This sounds quite logical and valid, but I have no pinouts for radios

to confirm this is indeed the case.


	


  Not true. Depending on the quality of the receivers

  in each radio, the "listening" transceiver may be

  overloaded by an adjacent "talking" radio but the further

  apart they are in frequency of interest, you may be able

  to carry on dual conversations. I've never found it

  necessary to "protect" a non-transmitting radio from

  one that is transmitting.



  Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

mprather(at)spro.net
Guest

Posted: Sun Nov 18, 2007 9:08 pm Post subject: Radio interlock

Thanks Bob..  That jogged my memory.  The real challenge would be to run

multiple transceivers through a single antenna..

Matt-



 	  Quote: 	
		   

 <nuckolls.bob(at)cox.net>



 At 11:35 AM 11/18/2007 -0500, you wrote:



>

>

>I had interesting plans to install my com antennas on each wing to

>keep them farther apart.  The idea was that two pilots could each use

>one of the radios simultaneously - say to talk with ATC and FSS (as

>opposed to merely monitoring the second channel).

>An avionics tech I talked with recently said there was no way to

>transmit simultaneously.  The intense field strength produced by one

>radio transmitting would damage the receive section of the other

>radio.  Thus there is a lockout connection wired between the radios,

>so that the non-transmitting radio grounds its antenna as self

>protection while the other transmits.

>This sounds quite logical and valid, but I have no pinouts for radios

>to confirm this is indeed the case.



   Not true. Depending on the quality of the receivers

   in each radio, the "listening" transceiver may be

   overloaded by an adjacent "talking" radio but the further

   apart they are in frequency of interest, you may be able

   to carry on dual conversations. I've never found it

   necessary to "protect" a non-transmitting radio from

   one that is transmitting.



   Bob . . .

         ----------------------------------------)

         ( . . .  a long habit of not thinking   )

         ( a thing wrong, gives it a superficial )

         ( appearance of being right . . .       )

         (                                       )

         (                  -Thomas Paine 1776-  )

         ----------------------------------------

fvalarm(at)rapidnet.net
Guest

Posted: Sun Nov 18, 2007 11:06 pm Post subject: Radio interlock

If transmitting simultaneously on two radios was dangerous for the radios,

why would the high end audio panels allow this?



Bevan 



--

nuckolls.bob(at)cox.net
Guest

Posted: Mon Nov 19, 2007 6:33 am Post subject: Radio interlock

At 10:02 PM 11/18/2007 -0700, you wrote:



 	  Quote: 	
		  



Thanks Bob..  That jogged my memory.  The real challenge would be to run

multiple transceivers through a single antenna..


	


    That CAN be done. It's most commonly accomplished with

    carefully crafted filters that go in series with the antenna

    feedlines for each radio. A good example of this technology

    is a critter called a "duplexer".



    Back in the days when I was working with amateur radio repeater

    stations, it was useful have a single antenna for both

   RECEIVING an exceedingly tiny incoming signal (0.5 microvolts)

    on one frequency while simultaneously TRANSMITTING that same

    information on a second frequency (typically 600 KHz removed from

    receive) with a strength on the order of 50 volts or 10 million

    times stronger!



    I've built the device shown here several times:



http://www.repeater-builder.com/rbtip/2mduplexer.html



    The thing is built of pieces of 4" copper tubing. The

    six cavities are distributed with three in the transmitter

    antenna line, three in the receiver. They are crafted with

    mirror image band-pass/band-reject response curves

    shown here:



http://www.repeater-builder.com/pix/dupfig15.jpg



    Note that each cavity set strongly rejects one

    frequency while strongly passing another. With these

    devices properly crafted and tuned to match the

    frequencies of the transmitter and receiver, full

    duplex operation of the two devices can be accomplished

    on one antenna.



    Obviously, this technology is useful ONLY for one

    pair of frequencies. For example, I could craft a

    duplexer to allow a pair of transceivers to use

    a single antenna on 119.5 and 121.6 . . . but as

    soon as I rotated set the frequencies to any other

    combination, this finely tuned isolation between

    the two transceivers would be lost. The other down

    side of this technology is that the duplexer would use

    up most of your baggage compartment!



    Bob . . .

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Mon Nov 19, 2007 7:13 pm Post subject: Radio interlock

 	  Quote: 	
		  From: Jeff Page <jpx(at)qenesis.com>

Subject: Radio interlock

I had interesting plans to install my com antennas on each wing to  

keep them farther apart.  The idea was that two pilots could each use  

one of the radios simultaneously - say to talk with ATC and FSS (as  

opposed to merely monitoring the second channel).

  Do you really need it? I fly two crew planes and we rarely if ever are chatting on two radios at the some time, even though we have 4 radios.

  I think one antenna on top of the plane and bottom would be a better separation than wing tips. G

        Be a better pen pal.  [quote][b]

jpx(at)qenesis.com
Guest

Posted: Mon Nov 19, 2007 10:24 pm Post subject: Radio interlock

Thanks for the numerous replies and comments to my question concerning  

transmitting simultaneously with two radios.

Unanimously everyone said it can be made to work, with the usual  

caveats of mounting the antennas with sufficient spacing, etc.

I was also pointed to commercial audio panels that offer this configuration.

So I am back to planning this and will report back in a couple of  

years when my airplane is flying to indicate how it all worked out.

Meanwhile, there is a particular avionics tech's advice I will be  

ignoring from here on !



Thanks !

Jeff Page

Dream Aircraft Tundra #10

jpx(at)qenesis.com
Guest

Posted: Tue Nov 20, 2007 6:37 am Post subject: Radio interlock

 	  Quote: 	
		   >I had interesting plans to install my com antennas on each wing to   

 >keep them farther apart.  The idea was that two pilots could each  

 use  >one of the radios simultaneously - say to talk with ATC and  

 FSS (as  >opposed to merely monitoring the second channel).

      Do you really need it? I fly two crew planes and we rarely if ever are

   chatting on two radios at the some time, even though we have 4 radios.

      I think one antenna on top of the plane and bottom would be a better

   separation than wing tips. G


	


Yes.  When flying in the USA, I am often trying with difficulty to  

raise FSS so I can open my flight plan immediately after takeoff.   

This is a high workload time, since I am watching for other traffic  

near the airport and also contacting departure to get flight  

following.  With two pilots and two radios, one can talk with ATC and  

the other to FSS.



Top and bottom would be better separation, but I will be installing  

amphibious floats, so I am concerned that the wires and floats will  

interfere with the radio (assuming I don't manage to break the antenna  

off by accident).



Jeff Page

Dream Aircraft Tundra #10

bicyclop(at)pacbell.net
Guest

Posted: Tue Nov 20, 2007 10:32 pm Post subject: Radio interlock

Bob Archer used to sell (and probably still does) an antenna switch 

which allows for reception on two radios simultaneously and locks out 

the non-transmitting radio (whichever one it is) upon closing the PTT of 

either.



Pax,



Ed Holyoke



Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   

 <nuckolls.bob(at)cox.net>



 At 10:02 PM 11/18/2007 -0700, you wrote:



> 

> <mprather(at)spro.net>

>

> Thanks Bob..  That jogged my memory.  The real challenge would be to run

> multiple transceivers through a single antenna..

    That CAN be done. It's most commonly accomplished with

    carefully crafted filters that go in series with the antenna

    feedlines for each radio. A good example of this technology

    is a critter called a "duplexer".



    Back in the days when I was working with amateur radio repeater

    stations, it was useful have a single antenna for both

   RECEIVING an exceedingly tiny incoming signal (0.5 microvolts)

    on one frequency while simultaneously TRANSMITTING that same

    information on a second frequency (typically 600 KHz removed from

    receive) with a strength on the order of 50 volts or 10 million

    times stronger!



    I've built the device shown here several times:



 http://www.repeater-builder.com/rbtip/2mduplexer.html



    The thing is built of pieces of 4" copper tubing. The

    six cavities are distributed with three in the transmitter

    antenna line, three in the receiver. They are crafted with

    mirror image band-pass/band-reject response curves

    shown here:



 http://www.repeater-builder.com/pix/dupfig15.jpg



    Note that each cavity set strongly rejects one

    frequency while strongly passing another. With these

    devices properly crafted and tuned to match the

    frequencies of the transmitter and receiver, full

    duplex operation of the two devices can be accomplished

    on one antenna.



    Obviously, this technology is useful ONLY for one

    pair of frequencies. For example, I could craft a

    duplexer to allow a pair of transceivers to use

    a single antenna on 119.5 and 121.6 . . . but as

    soon as I rotated set the frequencies to any other

    combination, this finely tuned isolation between

    the two transceivers would be lost. The other down

    side of this technology is that the duplexer would use

    up most of your baggage compartment!



    Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Wed Nov 21, 2007 4:05 pm Post subject: Radio interlock

At 10:23 PM 11/20/2007 -0800, you wrote:



 	  Quote: 	
		  



Bob Archer used to sell (and probably still does) an antenna switch which 

allows for reception on two radios simultaneously and locks out the 

non-transmitting radio (whichever one it is) upon closing the PTT of either.


	


   Now, THAT'S a different set of circumstances and design

   goals. Here there is acknowledgment of risk to a receiver

   from a transmitter's output for DIRECTLY paralleled transceivers

   on a single antenna. This is a very useful alternative to the

   dual antenna installation where it's acceptable to have

   the non-transmitting transceiver become unusable while

   talking on the other.



   Bob . . .

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