Hello.

I live in a third floor apartment without a balcony. As such, finding a
way to erect an antenna has been a challenge. My home station is a 2M
mobile transceiver (Yaesu FT-2800M) which I've been attempting to find
an optimal antenna arrangement without satisfaction.

I originally constructed a J-pole from 450-ohm ladder line that I had
hanging in our bedroom corner (the corner where it displayed the best
SWR), but the walls of this apartment apparently have alot of metal in
them that apparently affect my signal from it. I've attempted hanging it
in various places around our place and I've not gotten good reports.
Also, I exceed RF safety when I work simplex on 65W with this. My power
supply also lets me know this by buzzing during transmission. So.. I had
to find a different method.

We've got a wall air conditioner sticking out the side of our building
with a metal box covering it. I can place a mag mount on and attach a
mobile antenna to with satisfactory results. However, a small base
magmount like an MFJ dual band (a 3" diameter mag base) seems to work
quite well with a flat SWR, but I'd like to attach a more efficient
antenna to it.

I've got a 5" base Comet mag mount that I've attached both a Diamond
NR2C (2M 4.1dB center loaded mobile antenna) and a Diamond SG7900 (a
huge dualband antenna giving 5.0dB on 2M). Upon testing them on my AC
box placement, the SWRs exceed 2.0:1! Nothign I can do seems to improve
the SWR with these more efficient antennas.

My speculation is that the larger mag-mount base needs a larger ground
plane than the AC box can provide, while the smaller MFJ magmount is
sufficiently matched.

Does anyone have a suggestion on why this is occuring? Better yet, is
there a way I can possibly put a larger mobile antenna on this AC box
and get satisfactory SWR?

Thanks for any suggestions!

73s
Jeff
DE KB1HOL/AG
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J. Rogers KB1HOL
KB1HOLatARRLdotNET