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Handheld Comm. to Outside Antenna

Karetaker

Well Known Member
Howdy everyone. Looking for options to swap the coax cable from my remote mounted Trig TY91 radio to my Icom handheld so that the handheld can use the aircraft antenna if the Trig unit fails in flight. I am not opposed to making my own switch box, just need guidance on how to do it/parts required.

Options/thoughts?

Much obliged.
 
Howdy everyone. Looking for options to swap the coax cable from my remote mounted Trig TY91 radio to my Icom handheld so that the handheld can use the aircraft antenna if the Trig unit fails in flight. I am not opposed to making my own switch box, just need guidance on how to do it/parts required.

Options/thoughts?

Much obliged.

Icom used to make a switchbox to bypass the external antenna when plugged in. I used one on my Pazmany and it worked great.

Icom-ANT-SB-a-s.jpg

They no longer offer it. If you can find a used one great. If not you can try to make one from their diagram.

Icom-ANT-SB-s.jpg
 
I have seen this, and it is a lucky accident that it works well. Apparently using a mini jack, as shown, does not introduce a large impedance bump (something other than 50 ohms).
I would suggest something like this instead: Bring the coax from the antenna to a panel mounted female BNC. Label it ‘antenna’. Bring the coax from your TY91 to another panel mounted female BNC. Label it ‘TY92’. Finally, use a short length of coax with male BNCs on both ends to go between the two. To use the handheld, disconnect the coax jumper from the TY and connect it to the handheld. You’ll need to find an out of the way location for this, but one that you can access if needed. Finally, do not attempt to transmit on any radio that is disconnected from the antenna.
 
In lieu of the unavailable switch box, perhaps someone more astute than me in RF matters can offer an opinion on using a 50-ohm "power combiner" device such as https://www.minicircuits.com/WebStore/dashboard.html?model=ZA2CS-600-10W ?

IOW, use the device as a pass-through for normal use (Port 1) with Port 2 being available for the handheld comm. to plug into if needed.

Would a) such a device work for this application, and b) if so, would placement in-line result in significant degradation of range for the normal radio and handheld unit use cases? Thanks!
 
I have seen this, and it is a lucky accident that it works well. Apparently using a mini jack, as shown, does not introduce a large impedance bump (something other than 50 ohms).
I would suggest something like this instead: Bring the coax from the antenna to a panel mounted female BNC. Label it ‘antenna’. Bring the coax from your TY91 to another panel mounted female BNC. Label it ‘TY92’. Finally, use a short length of coax with male BNCs on both ends to go between the two. To use the handheld, disconnect the coax jumper from the TY and connect it to the handheld. You’ll need to find an out of the way location for this, but one that you can access if needed. Finally, do not attempt to transmit on any radio that is disconnected from the antenna.

I did exactly this and secured it with velcro under the panel directly in front of the pilot. Works well. :cool:
 
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In lieu of the unavailable switch box, perhaps someone more astute than me in RF matters can offer an opinion on using a 50-ohm "power combiner" device such as https://www.minicircuits.com/WebStore/dashboard.html?model=ZA2CS-600-10W ?

IOW, use the device as a pass-through for normal use (Port 1) with Port 2 being available for the handheld comm. to plug into if needed.

Would a) such a device work for this application, and b) if so, would placement in-line result in significant degradation of range for the normal radio and handheld unit use cases? Thanks!

The disadvantage of the Mini-Circuits device or similar devices is the 3dB+ signal loss thru the device. Anytime a large heat sink is mounted on a passive device is a dead give away that something is designed to get warm and in this case over 1/2 of the Transmitter RF is producing heat instead of going to the antenna.

I suggest Bob Turner's method, it works well and does not have the loss or cost of the power combiner.
 
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The disadvantage of the Mini-Circuits device or similar devices is the 3dB+ signal loss thru the device. Anytime a large heat sink is mounted on a passive device is a dead give away that something is designed to get warm and in this case over 1/2 of the Transmitter RF is producing heat instead of going to the antenna.

Thank you, answers my question!
 
A simple two antenna switch is available from places like DX Engineering, Allied and others.

But, another way is to put a 2’-3’ pig tail that goes to the radio, that goes to a double female BNC connector and then to the original antenna line. Now have a pigtail long enough on your handheld reach the double female connector. To use, disconnect the radio pigtail and replace with the hand held pigtail.

Don’t forget to have some procedure that provides confidence the handheld batteries are always charged.

Carl
 
The disadvantage of the Mini-Circuits device or similar devices is the 3dB+ signal loss thru the device. Anytime a large heat sink is mounted on a passive device is a dead give away that something is designed to get warm and in this case over 1/2 of the Transmitter RF is producing heat instead of going to the antenna.
.

It’s worse than that: some of the first transmitter’s power is going directly into the handheld receiver!
 
Thanks everyone. I had thought of the same idea as Bob T. but just wasn't sure it could be that easy!

I believe I will go that route and see what gives.
 
I have seen this, and it is a lucky accident that it works well. Apparently using a mini jack, as shown, does not introduce a large impedance bump (something other than 50 ohms).
I would suggest something like this instead: Bring the coax from the antenna to a panel mounted female BNC. Label it ‘antenna’. Bring the coax from your TY91 to another panel mounted female BNC. Label it ‘TY92’. Finally, use a short length of coax with male BNCs on both ends to go between the two. To use the handheld, disconnect the coax jumper from the TY and connect it to the handheld. You’ll need to find an out of the way location for this, but one that you can access if needed. Finally, do not attempt to transmit on any radio that is disconnected from the antenna.

This is what I did on my 6. Works well and pretty much zero risk of failure or damaging radio.

Larry
 
Thanks everyone. I had thought of the same idea as Bob T. but just wasn't sure it could be that easy!

I believe I will go that route and see what gives.

Jim Weir wrote an article in Kitplanes regarding this very topic.

Aero ‘lectrics: Rubber ducky, you're the one. By Jim Weir - February 8, 2011

https://www.kitplanes.com/aero-lectrics-143/

ae-jumper.jpg

ae-faceplate.jpg
 
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