Auburntsts

Auburntsts

Well Known Member
I'll be powering up my panel on the bench for the first time pretty soon and was wondering if there's any issues applying power to the radios (GTN 650 & SL 30) without the antennas connected?

My understanding is that attempting to transmit without an antenna is a no-no, and I have no plans to do so, but I'm not sure about just simply turning it on.
 
Call Stein.

I powered up my new SL 30 minus antennas, and all was fine----until I started pushing buttons on the nav side, and then some little critter that lives inside there got real mad at me, and started making some real nasty noise in the headphones.:mad:

I quickly shut off the radio power, and am not going to try that again till the antennas are all hooked up.

I hope I did not hurt anything:confused:
 
Use an antenna

I would not power up the radios without a proper antenna connected. If your PTT activates and calls the radio to transmit, all that energy will be reflected back to the radio and is definatelty not good for it.

Bevan
 
I've been wondering the same thing about powering-up the radios lately. I have the GTN650 & SL40. Both COM & GPS antennas are hooked-up. I have the RG400 for the wingtip NAV coiled-up outside the fuse, ready to run through the wing. I want to test it all before I attach the wings & rivet the top forward fuse skin. Will a temporarily attached COM antenna (for the NAV) suffice to confirm operation? I know the real test for NAV is when the wings are attached and my Archer NAV antenna is hooked-up. I mainly want to make sure I don't cause some problem from some electronic "back-wash".

Thanks for any advice.
 
Radios are not such a huge problem (so long as you don't transmit either on purpose OR accidentally), but transponders CAN be a huge problem. The mode S buggers specifically will blow themselves up without popping a breaker if you don't have an antenna hooked up, OR if your antenna cable has a short in it....ask me how I know! :)

Cheers,
Stein
 
For anything that transmits, DON'T transmit without a properly tuned antenna attached. Do whatever it takes to make you feel comfortable that won't happen, be it ensuring no PTT is pressed (or inadvertently grounded - something you may not know for sure!) or going the safest route and just hooking up an antenna. Harder? Yes. Fry your radio? Nope.

For anything that receives only (VOR, GPS, glideslope, ADF (why?), Marker Beacon, etc.) with very few exceptions powering without an antenna connected will cause no harm.

But whatever Stein says, do that. He's way smarter about this stuff...
 
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During development of the V6 radio we did many tests relating to transmit without antenna connected and we could not blow anything up. This is partly due to the transmitter getting throttled down if it gets hot.

However, there are other conditions that can be much worse. A very badly matched antenna (or cable of specific lengths without antenna connected at the end) can cause severe stress at the transmitter as reflected power comes back to the transmitter at the wost possible phase angle. This can prove destructive even for a V6 and there is not much that can be done about that.

I concur with Stein on the transponders. Modern transponders with semiconductor transmitters very definitely do not like transmitting without antenna load. This is a problem with mode-S if the transponder has an extended squitter which will attempt transmission at intervals even if there is no radar interrogation received. That is the killer.
A mode-C should never transmit without being interrogated so those are quite safe without antenna.

Rainier
CEO MGL Avionics
 
I just waited until the system was hooked up complete before testing

I would not do it. Nothing more to say. It ranks right up there with engine starts and taxi tests with no wings in my opinion.

Bob Axsom
 
All, thanks for the advice. I'm going to err on the side of caution and hook the antennas up even though I have no plans to transmit--better safe than sorry.
 
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