Antennae resistance

[cdeerinck]

Today I put a BNC connector on the end of the RG-400 to my Com antennae (a DeltaPop Red Tail VHF Com Antenna) and tested to ensure no short circuit. But it beeped...

So I tested the resistance, and it reads 0.1ohm. I am not talking impedance, just a simple DC resistance. I tried web searches to get an answer if this was ok, and I think my mind imploded with all the electronics that I can't understand.

Then I realized the other end is plugged into the antennae... under the floors...

Can anyone tell me if:

• a) It should read a completely open circuit when plugged in, so I have to cut off the end, and redo it.
• b) I have to pull up the floors, unplug it, then measure it to know for sure. (the floors are secured with screws, not rivets)
• c) This is normal, and is safe to plug in the radio.

[Fred.Stucklen]

Pull the floors, disconnect the coax from the antenna, then measure the coax resistance between the inside and outside conductors. It should be an OPEN circuit. If it's not OPEN, then you have a coax short and will have to figure out which end is shorted.

Then measure the antenna resistance the same way. Chances are the antenna will have a very low resistance. Very few modern antennas don't have loading coils that result in the low resistance reading.

[dpansier]

The Delta Pop VHF Com antenna is designed as a grounded element antenna, when measuring with a VOM it will show a DC short from the center pin to ground. At the RF frequency it will show 50 ohms impedance. What you are measuring is not a manufacturing defect.

If you have additional questions let me know.

Regards,

[cdeerinck]

Sometimes you just need to be told to do that hard thing that you know is the right thing to do.

Floors pulled, cable tested ok. I will put the floors back in the morning.

I still feel better for having done it right. Far better to check now, than to have something pop up in the future during a flight, and think "I should have".