In article ,
Cecil Moore wrote:

Jeff wrote:
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.

What does a plot of SWR Vs frequency look like across the band?

With the smaller (3") MFJ magmount, its as follows:

144Mhz 1.8
145Mhz 1.7
146Mhz 1.5
147Mhz 1.1
148Mhz 1.1

Clearly the antenna is not optimally tuned for the 2M amateur bandwidth,
and I could probably get the SWR bell curve down to 146 by lengthening
the antenna. However, 99% of my use is on the high end of the band so
it works just fine. Its a small antenna and I want something with more
gain, thus I've not fiddled with it to improve the SWR.

With the larger 5" mag-mount on the SG7900:

144Mhz 3.0
145Mhz 3.0
146Mhz 2.5
147Mhz 2.5
148Mhz 3.0

SWR profile is similar with both this antenna and the 2M monobander
Diamond NR2C.

73s
Jeff
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J. Rogers KB1HOL
KB1HOLatARRLdotNET