Powering on avionics without an antenna

[Swingwing]

I'm sure it is answered somewhere on this forum, but I can't find it.

What avionics should have the antennas connected before power on to reduce the chance of burning them up?

Thank,
Nick

 

[jakej]

I'm sure it is answered somewhere on this forum, but I can't find it.

What avionics should have the antennas connected before power on to reduce the chance of burning them up?

Thank,
Nick

Applies to 'transmitting' avionics normally eg Radios, Transponder etc.

 

[D-Dubya]

One of my roommates in college was an electrical engineer that was deep into radios and antenna theory. Yes, I realize that this is the equivalent for me of sleeping in a Holiday Inn Express. But I remember him saying you can "blow the finals" (whatever that means) if you keyed a mic without the antenna connected. For that reason, he never powered up a radio without the antenna being connected to take the load.

So yeah, if you're just powering up to see the pretty displays (we ALL like that part), then you're probably okay. But if something is amiss and you're unintentionally transmitting when you power up, a trip to the avionics shop may be in your future. You gotta ask yourself if the benefit is worth the risk.

 

[wirejock]

Dummy load

Buy a few dummy loads and connect them at the antenna end of the Com and XPonder.

 

[Walt]

Mode S xpdrs are aways transmitting and are high power, so DO NOT power those up without an antenna.
Com/Navs usually no problem just don't hit the PTT SW if you can avoid it.

 

[Bill Boyd]

Are you sure?

I cannot find anything online to suggest that Mode-S transponders transmit without receiving an interrogation (hence keeping the "spond" in "transponder").

No antenna connected means it's highly unlikely that the device will successfully detect an interrogation from SSR/TCAS sources and presumably therefore will not transmit without a load (antenna) attached.

Admittedly a gamble, but it seems the odds are in your favor.

Educate me if I'm wrong.

 

[Walt]

Are you sure?

I cannot find anything online to suggest that Mode-S transponders transmit without receiving an interrogation (hence keeping the "spond" in "transponder").

No antenna connected means it's highly unlikely that the device will successfully detect an interrogation from SSR/TCAS sources and presumably therefore will not transmit without a load (antenna) attached.

Admittedly a gamble, but it seems the odds are in your favor.

Educate me if I'm wrong.

Guess you better keep looking, hint: the S stands for squitter.

 

[Thermos]

If your transponder is ADS-B Out capable, there's a good chance it will try to broadcast position on the ground if it has valid GPS input. That's party of the squittering that Walt mentioned. Without a properly-matched antenna the transponder's power amplifier (the "finals") will be very unhappy and you may release magic smoke from your very expensive box.

HTH

Dave

ps - not trying to be picky Walt, the S actually stands for "Select" . If the rest of you want to gross yourselves out, google "squitter" .

 

[Walt]

ps - not trying to be picky Walt, the S actually stands for "Select"

My bad, that’s correct.

 

[Canadian_JOY]

Be careful with ELT's... Make sure they have an antenna attached to them FIRST, before attaching any of the control wiring. Yes, some ELT's, especially 406MHz ones, can be damaged if allowed to transmit without an antenna load in place.