MGL Avionics User Forum

Hi All,

A bit of advice required for something I have never done before.

Currently, I have a Funke ATR833 in my aircraft. But I also own a MGL V16 which I have never installed. I am using a N16 with a Blaze control head. Because everything is in place, it would be easy for me to install the V16 box and have a 2nd radio. I would just hookup the PTT to a selector switch so it would only send the PTT press to a single radio.

My problem comes with the antenna. It would be a lot of work to install a 2nd antenna so ideally I would want to run both radios off the same antenna. I am aware you can't just splice them both to the same antenna else the transmitting radio would just send all it's power in to the other one and possibly damage it.

I just wondered if there was an easy solution to this. I know RAMI make a device that will automatically isolate the 2nd radio when the primary transmits, but the cost of it just doesn't make that solution financially viable.

I was thinking maybe a coaxial relay but not sure which one would be suited to the task. I could even configure everything that if you power on the 2nd radio, the first one would power off as realistically, only one radio at a time needs to be powered on.

Any advice would be much appreciated. So to summarise, I need to connect 2 transceivers to the same antenna, but only 1 transceiver needs to be powered on.

You would need a fast coaxial relay that can handle the power and not have too much insertion loss.
However in the case of the V16 it typically pushes 12W into a 50 ohm load - and that's without any modulation. Peak can easily reach 30W or more.
You would need, in addition a pin diode limiter at the receiver on the other side. But that needs to be "off" when you transmit there. So that is not going to happen.
Yes it can be done - but it will not be simple and certainly not cheap - you would need good quality directional couplers. You will loose a db or two in TX power and receive sensitivity.
I think you will find a second antenna a far more viable and cleaner solution.

I could put in a 2nd antenna. It's a composite aircraft so can't just go anywhere. The ideal place for it would mean it would be located about 1.5m from the primary antenna.

I do intend that only one radio would be powered on so one would be a primary and the 2nd purely a backup that would only ever be powered on occasionally to test or if the primary radio was to fail.

The transmitter of one of the radios will blow the receiver on the other radio to high heaven instantly regardless of if switched on or not.

Rainier, do you mean that even with 2 separate antennas that close, I still risk blowing the receiver?

Yes that is possible. If two antennas are very close and aligned you will have a very large coupling of energy between the two. A strong transmitter can blow the receiver on the other side quite easily.
It depends a bit on how the receiver is constructed. In most cases the first stage is closely coupled to the antenna to get gain early which improves sensitivity. But that also means the first stage is sensitive to damage.
In our V16 it's different as the receiver deviates completely from the norm and the first active stage is completely decoupled from the antenna - the signal has to first travel over a precisely cut quartz crystal over about a 1/4 inch distance. That path is almost indestructible.