Hello Paul,

You do not need to ground the J-Pole antenna because it is a half-wave
dipole feeded with a quarter-wave length.
That's why the total antenna lentgh = (1/2 + 1/4) x lambda

I have built several 2m J-Pole antennae (with copper pipes) without any
problems. The last one was clipped to the TV mast (as yours). The only
problem I have experienced was with a dual band (2m/70cm) J-Pole (your
case). It was solved by ajusting some of the dimensions.

If it is your first J-Pole, I suggest you to built first a mono-band (2m).
You will succed because this is the most easier antenna I have ever built!!!
Then you will be able to handle a dual band J-Pole.

Do not vanish!!!.... This is a very nice antenna. It's main benefit is the
very low angle of its radiation over the horizon (between 3 and 4 degrees).
I did a contact with Marocco from my location (IN88HR) with 10 watts!!! OK
!!! It was a sporadic .... ;-)))

Good luck. Contact me if you want more details.

Best regards

Jean-Marc
F4DRH
www.barbaxoops.com







"
Antenna: Copper Pipe Dual Band 2M/70CM. Bottom of long leg is tee. lower
leg of tee goes 14" w/ 1/2" copper then transitions to 1" x 36". This is
clamped to two tv mast mounts, anchored to a wooden chimney chase.

When I built the antenna, it displayed a relatively flat SWR across both
bands, using an MFJ-269. Antenna was free standing in yard, away from
anything to affect it.

After mounting, the SWR seems to vary from as measured (1:1.2) to off the
map. Thought it was maybe bad coax (LMR-400) but as I checked it, the SWR
came back into line. Someone told me to ground the lower end of the
j-pole, as if it were clamped to a tower. I did this and the SWR goes off
the map.

Should a J-pole be grounded? if not, how do you protect it or the
structure from a lightning strike?

Thanks

Paul P