Radio Antenna

Derrick Stikeleather
Wed, 10 Jul 2002 12:04:16 -0500

> Remember though the antenna lead is not just a simple wire it is actually
> Coaxial Cable. This has one wire inside another wire with an insulator in
> between them. Continuity can be checked between the center pin of the lead
> the tip of the antenna as you have said but you can also check the
> of the antenna with an ohm meter as well.

> You will need to put the meter on about a 100 Ohm setting and touch one
> to the center pin of the connector at the radio and the other lead to the
> that folds back around the outside. You should get about 50 Ohms IIRC.
> more or less than that could be an indication of an internal breakdown in
> insulator inside the cable.

The Coaxial lead is 50 ohm...  but not DC resistance, it's 50 ohm impedance.
You need an Oscilloscope or Time Domain Refractometer to figure out what the
impedance of the cable/antenna is.  If you have a TDR just laying around,
give me a call!  :-)  With a DVM you will just read an open (hopefully)
between the shield and conductor.  I would use the DVM to check the ground
of that coax and make sure there is not a high resistance connection at
either end, as well as the center conductor as has been said before.  If
these things check out fine, then I don't know what to tell you;  it's
probably something else.  It's unlikely, though not impossible, that the
coax has obtained a characteristic impedance other than something right
around 50 ohms.  Same with the antenna, unless there is a high resistance
connection somewhere.

Good luck
Derrick Stikeleather