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coax splitter

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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Tue May 16, 2017 11:52 am Post subject: coax splitter

So I am revisiting my (untested) installation that allows me to use my com antenna with a handheld. First I was going to use that little iCom box until Bob revealed that it is junk. So instead I installed a good quality splitter with a bulkhead connector on the panel. My brain must not have been working very well when I did the installation because I didn't think it through. I just blindly hooked the com radio to the "S" the panel to the "1" and the com antenna to the "2"



Later I got thinking that probably the com antenna should go to the "S" and the com radio and panel connector should use the "1" and the "2"

So I pulled the thing out and got out my continuity tester, and all the center pins test for continuity with each other. So now I am thinking that it doesn't matter which goes where, and that I can just put it back the way it was.

Before I do, I would like to confirm that all this thing is doing is connecting all three connectors together equally, and that there is no need or advantage to any particular order.

I am attaching a spec sheet for the part, which is a Mini-Circuits Splitter ZFSC-2-1+

Thanks,

Ken

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Tue May 16, 2017 1:03 pm Post subject: Re: coax splitter

I'm no RF engineer, but I don't think this will work as you hope.  With both radios attached, one will be transmitting into the final amplifier of the other, in parallel with the antenna.  It might work if you remove the non-transmitting radio and attach a 50-ohm terminator in its place (which obviously defeats the purpose of the installation).  Otherwise impedance will probably not be seen as 50 ohms by the active transmitter, SWR will likely not be very good, and you risk damaging the non-transmitting radio.



Also, from the data sheet you attached, see the Maximum Ratings table at the upper left corner: "Power input (as a splitter): 1W" -and- "Permanent damage may occur if any of these limits are exceeded."  Typical handheld RF transmit power is 3-5W and panel mount radios are typically rated around 8W in 14V aircraft and 16W in 28V aircraft.  I don't think this splitter is intended for this kind of application, but rather as an instrumentation tool, or as a means to connect two receivers to one antenna.  I suspect the 1W rating allows some overhead if an active (amplified) antenna is used.



Eric

 	  kenryan wrote: 	
		  So I am revisiting my (untested) installation that allows me to use my com antenna with a handheld. First I was going to use that little iCom box until Bob revealed that it is junk. So instead I installed a good quality splitter with a bulkhead connector on the panel. My brain must not have been working very well when I did the installation because I didn't think it through. I just blindly hooked the com radio to the "S" the panel to the "1" and the com antenna to the "2"



Later I got thinking that probably the com antenna should go to the "S" and the com radio and panel connector should use the "1" and the "2"



So I pulled the thing out and got out my continuity tester, and all the center pins test for continuity with each other. So now I am thinking that it doesn't matter which goes where, and that I can just put it back the way it was.



Before I do, I would like to confirm that all this thing is doing is connecting all three connectors together equally, and that there is no need or advantage to any particular order.



I am attaching a spec sheet for the part, which is a Mini-Circuits Splitter ZFSC-2-1+



Thanks,



Ken

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Tue May 16, 2017 1:29 pm Post subject: Re: coax splitter

 	  Eric Page wrote: 	
		  I'm no RF engineer... 	




Um, yeah, like I said...



Ever hit the "submit" button and shortly regret it?



OK, ignore the bit about one radio transmitting into the other.  After reading an application note about splitter/combiners on Mini-Circuits' website, it's obvious these things offer isolation between the ports.  So, one radio on port 1, one radio on port 2, antenna on the sum port.



Power handling is another issue.  The unit you have isn't rated for the power levels we're talking about.  It looks like they have plenty of units that are, however.



Eric



With fingers crossed, tapping "submit" again... now!

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Tue May 16, 2017 1:34 pm Post subject: Re: coax splitter

 	  Eric Page wrote: 	
		  After reading an application note about splitter/combiners on Mini-Circuits' website... 	




Here's the application note, in case anyone else is interested:



https://www.minicircuits.com/app/AN10-006.pdf



Eric

ceengland7(at)gmail.com
Guest

Posted: Tue May 16, 2017 7:40 pm Post subject: coax splitter

On 5/16/2017 2:49 PM, Ken Ryan wrote:

 	  Quote: 	
		   So I am revisiting my (untested) installation that allows me to use my 

 com antenna with a handheld. First I was going to use that little iCom 

 box until Bob revealed that it is junk. So instead I installed a good 

 quality splitter with a bulkhead connector on the panel. My brain must 

 not have been working very well when I did the installation because I 

 didn't think it through. I just blindly hooked the com radio to the 

 "S" the panel to the "1" and the com antenna to the "2"



 Later I got thinking that probably the com antenna should go to the 

 "S" and the com radio and panel connector should use the "1" and the "2"



 So I pulled the thing out and got out my continuity tester, and all 

 the center pins test for continuity with each other. So now I am 

 thinking that it doesn't matter which goes where, and that I can just 

 put it back the way it was.



 Before I do, I would like to confirm that all this thing is doing is 

 connecting all three connectors together equally, and that there is no 

 need or advantage to any particular order.



 I am attaching a spec sheet for the part, which is a Mini-Circuits 

 Splitter ZFSC-2-1+



 Thanks,



 Ken

Don't do it.
	




A splitter doesn't do the same thing as a switch box (hence, the 

different names).



A splitter will send an antenna's signal to two *receivers*.



The switch box (cheesy though it is) actually switches the antenna 

between two radios. Because it switches, it's ok to attach both 

*transceivers* to the box. Only one gets connected at a time.



If you connect two transceivers through the splitter to one antenna, 

then one transmitter will attempt to transmit directly into the other's 

receiver. Not a good plan.



Charlie



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kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Wed May 17, 2017 5:35 am Post subject: coax splitter

Charlie,



I *thought* I was following Bob's advice, using the splitter instead of the cheezy switch. I can't find the thread but I think what he said was that the switch is far more likely to damage something (due to failure) than it is to perform as designed, when needed.Â 

Again, I am trying to recall ... but I think the idea is that if I ever need to use the handheld, the first thing I do is turn off the (non-functioning) com radio and only then use panel jack to connect the handheld to the antenna.

So now I guess I have two questions--my original (Does it make any difference which coax goes to what connector?) and now a second: As long as I turn off the com radio before connecting the handheld to the antenna, am I safe from damaging either radio?

Ken

On Tue, May 16, 2017 at 7:39 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

 

 On 5/16/2017 2:49 PM, Ken Ryan wrote:

  	  Quote: 	
		   So I am revisiting my (untested) installation that allows me to use my com antenna with a handheld. First I was going to use that little iCom box until Bob revealed that it is junk. So instead I installed a good quality splitter with a bulkhead connector on the panel. My brain must not have been working very well when I did the installation because I didn't think it through. I just blindly hooked the com radio to the "S" the panel to the "1" and the com antenna to the "2"

 

 Later I got thinking that probably the com antenna should go to the "S" and the com radio and panel connector should use the "1" and the "2"

 

 So I pulled the thing out and got out my continuity tester, and all the center pins test for continuity with each other. So now I am thinking that it doesn't matter which goes where, and that I can just put it back the way it was.

 

 Before I do, I would like to confirm that all this thing is doing is connecting all three connectors together equally, and that there is no need or advantage to any particular order.

 

 I am attaching a spec sheet for the part, which is a Mini-Circuits Splitter ZFSC-2-1+

 

 Thanks,

 

 Ken

 	




 Don't do it.

 

 A splitter doesn't do the same thing as a switch box (hence, the different names).

 

 A splitter will send an antenna's signal to two *receivers*.

 

 The switch box (cheesy though it is) actually switches the antenna between two radios. Because it switches, it's ok to attach both *transceivers* to the box. Only one gets connected at a time.

 

 If you connect two transceivers through the splitter to one antenna, then one transmitter will attempt to transmit directly into the other's receiver. Not a good plan.

 

 Charlie

 

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ceengland7(at)gmail.com
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Posted: Wed May 17, 2017 6:28 am Post subject: coax splitter

On 5/17/2017 8:33 AM, Ken Ryan wrote:

     

      	  Quote: 	
		         Charlie,         

         

         I *thought* I was following Bob's advice, using the           splitter instead of the cheezy switch. I can't find the thread           but I think what he said was that the switch is far more           likely to damage something (due to failure) than it is to           perform as designed, when needed.Â 

         

         

         Again, I am trying to recall ... but I think the idea is           that if I ever need to use the handheld, the first thing I do           is turn off the (non-functioning) com radio and only then use           panel jack to connect the handheld to the antenna.

         

         

         So now I guess I have two questions--my original (Does it           make any difference which coax goes to what connector?) and           now a second: As long as I turn off the com radio before           connecting the handheld to the antenna, am I safe from           damaging either radio?

         

         

         Ken

       

       

         On Tue, May 16, 2017 at 7:39 PM,           Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>           wrote:

            	  Quote: 	
		  -->             AeroElectric-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>                            

                 

                 On 5/16/2017 2:49 PM, Ken Ryan wrote:

                  	  Quote: 	
		                     So I am revisiting my (untested) installation that                   allows me to use my com antenna with a handheld. First                   I was going to use that little iCom box until Bob                   revealed that it is junk. So instead I installed a                   good quality splitter with a bulkhead connector on the                   panel. My brain must not have been working very well                   when I did the installation because I didn't think it                   through. I just blindly hooked the com radio to the                   "S" the panel to the "1" and the com antenna to the                   "2"

                   

                   Later I got thinking that probably the com antenna                   should go to the "S" and the com radio and panel                   connector should use the "1" and the "2"

                   

                   So I pulled the thing out and got out my continuity                   tester, and all the center pins test for continuity                   with each other. So now I am thinking that it doesn't                   matter which goes where, and that I can just put it                   back the way it was.

                   

                   Before I do, I would like to confirm that all this                   thing is doing is connecting all three connectors                   together equally, and that there is no need or                   advantage to any particular order.

                   

                   I am attaching a spec sheet for the part, which is a                   Mini-Circuits Splitter ZFSC-2-1+

                   

                   Thanks,

                   

                   Ken

                 	
               

             

             Don't do it.

             

             A splitter doesn't do the same thing as a switch box (hence,             the different names).

             

             A splitter will send an antenna's signal to two *receivers*.

             

             The switch box (cheesy though it is) actually switches the             antenna between two radios. Because it switches, it's ok to             attach both *transceivers* to the box. Only one gets             connected at a time.

             

             If you connect two transceivers through the splitter to one             antenna, then one transmitter will attempt to transmit             directly into the other's receiver. Not a good plan.

             

             Charlie

           	
         

       

     	
     You might get away with it, but I wouldn't do it.

     

     The ports are not symmetrical in all three directions. See the     labels on the data sheet. The 'S' (sum, as in adding) port is the     combining of ports 1 & 2. If you were using two simple radio     *receivers*, the antenna would go on the S port and the radios would     go on ports 1 & 2. Or if using 2 antennas to feed one radio (not     common, but it does happen), the radio would go on the S port.

     

     Why not just duplicate the electrical schematic of the cheesy     switch, but replace the 1/8" normalizing jack with a simple     miniature toggle switch? Replace the jack function of the     normalizing jack with another BNC connector. That way, you can leave     the handheld *and* the panel radio both plugged into the box, and if     there's a problem with the panel radio, reach under the panel &     flip the switch to connect the antenna to the hand held. 

     

     Realistically, if the handheld is for emergency communications only,     why not just use the rubber ducky that comes with it? It'll work for     10-15 miles, so what's not to like? Simple, reliable, no extra parts     to fail, etc etc.

     

     Charlie

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alec(at)alecmyers.com
Guest

Posted: Wed May 17, 2017 6:38 am Post subject: coax splitter

 	  Quote: 	
		  On May 17, 2017, at 10:29 AM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

why not just use the rubber ducky that comes with it? It'll work for 10-15 miles, so what's not to like? Simple, reliable, no extra parts to fail, etc etc.

	




A 1.5W battery-powered hand-held in to a rubber whip antenna has difficulty transmitting more than a mile. Itâ€™s even worse when youâ€™re inside a metal skinned aircraft.

nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 17, 2017 7:12 am Post subject: coax splitter

At 09:29 AM 5/17/2017, you wrote:

  	  Quote: 	
		  On 5/17/2017 8:33 AM, Ken Ryan wrote:

  	  Quote: 	
		  Charlie, 



 I *thought* I was following Bob's advice, using the splitter instead of the cheezy switch. I can't find the thread but I think what he said was that the switch is far more likely to damage something (due to failure) than it is to perform as designed, when needed.Â 



 Again, I am trying to recall ... but I think the idea is that if I ever need to use the handheld, the first thing I do is turn off the (non-functioning) com radio and only then use panel jack to connect the handheld to the antenna.



 So now I guess I have two questions--my original (Does it make any difference which coax goes to what connector?) and now a second: As long as I turn off the com radio before connecting the handheld to the antenna, am I safe from damaging either radio? 	
	


   The only recommendation I have posted for

   this application is the idea of a crew-accessible

   splice connection in the antenna's feed line.



   This allows the pilot to open the feed line

   and connect it to the hand-held.  There ARE

   devices that will allow two transceivers

   to share a common antenna but they are expensive,

   big and heavy.



   The 'power splitter' is used to let two small

   signal devices to share the same source/load.

   They are used with two receivers and in some

   bench test situations. As others have pointed

   out, it is not suited to the proposed task.



   I once proposed a panel mounted dpdt toggle

   switch and dummy load that would transfer

   a single antenna between two transceivers

   while presenting a proper load to the transceiver

   not in service. 



 [img]cid:.0[/img]

   The switch can be a miniature toggle.

   Coax to the hand/held can be routed

   of the switch to a bnc jack on the

   panel . . .



   But give the reliability of modern elex,

   it seems a bit of over-kill. A

   splice in the feed line mitigates

   the rare failure event with a minimum of

   cost. 



 

 

   Bob . . .

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alec(at)alecmyers.com
Guest

Posted: Wed May 17, 2017 7:18 am Post subject: coax splitter

Bob, 

How damaging is it to a modern 5W or 10W transmitter to transmit into an open circuit?

 	  Quote: 	
		  On May 17, 2017, at 11:10 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  At 09:29 AM 5/17/2017, you wrote:  	  Quote: 	
		  On 5/17/2017 8:33 AM, Ken Ryan wrote:  	  Quote: 	
		  Charlie,  I *thought* I was following Bob's advice, using the splitter instead of the cheezy switch. I can't find the thread but I think what he said was that the switch is far more likely to damage something (due to failure) than it is to perform as designed, when needed.Ã‚  Again, I am trying to recall ... but I think the idea is that if I ever need to use the handheld, the first thing I do is turn off the (non-functioning) com radio and only then use panel jack to connect the handheld to the antenna. So now I guess I have two questions--my original (Does it make any difference which coax goes to what connector?) and now a second: As long as I turn off the com radio before connecting the handheld to the antenna, am I safe from damaging either radio? 	
	
   The only recommendation I have posted for   this application is the idea of a crew-accessible   splice connection in the antenna's feed line.   This allows the pilot to open the feed line   and connect it to the hand-held.  There ARE   devices that will allow two transceivers   to share a common antenna but they are expensive,   big and heavy.   The 'power splitter' is used to let two small   signal devices to share the same source/load.   They are used with two receivers and in some   bench test situations. As others have pointed   out, it is not suited to the proposed task.   I once proposed a panel mounted dpdt toggle   switch and dummy load that would transfer   a single antenna between two transceivers   while presenting a proper load to the transceiver   not in service.  <325e15d9.jpg>   The switch can be a miniature toggle.   Coax to the hand/held can be routed   of the switch to a bnc jack on the   panel . . .   But give the reliability of modern elex,   it seems a bit of over-kill. A   splice in the feed line mitigates   the rare failure event with a minimum of   cost.   

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 17, 2017 7:31 am Post subject: coax splitter

At 10:17 AM 5/17/2017, you wrote:

  	  Quote: 	
		  Bob, 



 How damaging is it to a modern 5W or 10W transmitter to transmit into an open circuit? 	


   Probably none . . . it's stone simple to

   incorporate internal swr sense hardware

   that will reduce drive to the transmitter's

   output stage under poor swr conditions.



   I've not studied the constellation of

   products out there but I cannot imagine

   anyone NOT making this part of their

   elegant design . . . cost of doing

   so is trivial . . . return on investment

   is significant.



 

 

   Bob . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Wed May 17, 2017 8:23 am Post subject: coax splitter

Thanks everybody, for saving me from my myself. I have tried to review all the previous threads, and cannot figure out how I came up with doing what I did.



On Wed, May 17, 2017 at 7:30 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 10:17 AM 5/17/2017, you wrote:

  	  Quote: 	
		  Bob, 



 How damaging is it to a modern 5W or 10W transmitter to transmit into an open circuit? 	


 Â  Probably none . . . it's stone simple to

 Â  incorporate internal swr sense hardware

 Â  that will reduce drive to the transmitter's

 Â  output stage under poor swr conditions.



 Â  I've not studied the constellation of

 Â  products out there but I cannot imagine

 Â  anyone NOT making this part of their

 Â  elegant design . . . cost of doing

 Â  so is trivial . . . return on investment

 Â  is significant.



 

 

 Â  Bob . . .

jim(at)PoogieBearRanch.co
Guest

Posted: Wed May 17, 2017 10:16 am Post subject: coax splitter

<<  A 1.5W battery-powered hand-held in to a rubber whip antenna has

difficulty transmitting

<<  more than a mile. Itâ€™s even worse when youâ€™re inside a metal

skinned aircraft.



Not sure what hand-held radio you're using, but using my Sporty's SP-400

with the "rubber ducky" antenna, I was able to talk to my local tower

crew from 15 miles away. They said I was a bit "scratchy" but

understandable. At 10 miles, it was pretty much crystal clear. 



That said, I have a coax connector in my plane so I can plug it into the

external antenna. Using it that way, I was talking to ATC from about 25

miles away.



Jim Parker

alec(at)alecmyers.com
Guest

Posted: Wed May 17, 2017 10:20 am Post subject: coax splitter

ICOM A24. I have a Sportyâ€™s SP400 but even when off it drains the batteries in 7 days, then they leak all over the inside. Piece of trash.





 	  Quote: 	
		   On May 17, 2017, at 2:14 PM, <jim(at)PoogieBearRanch.com> <jim(at)PoogieBearRanch.com> wrote:

 

 

 

 <<  A 1.5W battery-powered hand-held in to a rubber whip antenna has

 difficulty transmitting

 <<  more than a mile. Itâ€™s even worse when youâ€™re inside a metal

 skinned aircraft.

 

 Not sure what hand-held radio you're using, but using my Sporty's SP-400

 with the "rubber ducky" antenna, I was able to talk to my local tower

 crew from 15 miles away. They said I was a bit "scratchy" but

 understandable. At 10 miles, it was pretty much crystal clear. 

 

 That said, I have a coax connector in my plane so I can plug it into the

 external antenna. Using it that way, I was talking to ATC from about 25

 miles away.

 

 Jim Parker

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Fri May 19, 2017 7:30 am Post subject: Re: coax splitter

I did a little more poking around online and found this device:



http://shakespeare-ce.com/marine/product/as-2-switch/



It covers DC-600MHz and handles 30W.  It sells for between $70 and $130 online.  I found it on eBay, Walmart and a number of marine retailers.



One big caveat, however: it requires 12VDC to operate, so in the event of total electrical failure, it won't switch.  If the panel radio was the last to transmit, your handheld/backup radio would not see the antenna.  That said, how likely is total electrical failure?



If you want an active, automatic switching device, perhaps one that defaults to a handheld-to-antenna connection when not powered would be the best solution.  Haven't found one of those yet...



Eric



EDIT:  This will need a few PL-259 male to BNC female adapters.  Cheap on eBay.

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