Can't really offer you much help. But, about six months ago, I did what you
are trying to do with my Five element M2. I did it without adjusting element
lengths. (I agree, moving the shorting bars out, goes against the grain) Yes,
the antenna is really made to operate in the low end of the band. Here is the
best I could do:
50.080 1:150.125 1:1
50.200 1.1:150.318 1.3:1
Before re-tuning I think I was close to 2:1 @50.318. Doubt if this helps you.
But, maybe it will spur on an M2 Five Element owner or two.
Buddy WB4OMG
-----Original Message-----
From: Paul Rollinson <Paulrollinson@sbcglobal.net>
To: 'VHF Contesting Reflector' <vhfcontesting@contesting.com>
Sent: Sat, Jan 2, 2021 9:01 am
Subject: [VHFcontesting] Tech Help needed
Good morning all,
I hope you had a nice holiday.
Part of prepping for the January contest included taking down the stack ofM2
6M7antennas and tuning them a bit higher to accommodate FT8/4 frequencies
where the swr runs close to 2:1
After several hours of tweaking we were unsuccessful in elevating the
frequencies. Moving the shorting bars had little effect and the elements are
crimped together so shortening them would be permanent; I prefer not to do
this.
After diving thru the specs, the antennas are 6M7 and not the modern
versions 6M7JHV. Below is a link to the manual.
https://dl-mail.ymail.com/ws/download/mailboxes/@.id==VjN-j4MNikUvGG6dI72pGt
Fnbtnm78WZEHQ84kCP5dKOEa_RWizZIRV1VtWw7y3GBuOyPtJBEyjJRlraKdU25EkUFw/message
s/@.id==AOqprj4WDiqnX--apQiykLPEILk/content/parts/@.id==2/raw?appid=YMailNor
rin
<https://dl-mail.ymail.com/ws/download/mailboxes/@.id==VjN-j4MNikUvGG6dI72pG
tFnbtnm78WZEHQ84kCP5dKOEa_RWizZIRV1VtWw7y3GBuOyPtJBEyjJRlraKdU25EkUFw/messag
es/@.id==AOqprj4WDiqnX--apQiykLPEILk/content/parts/@.id==2/raw?appid=YMailNo
rrin&ymreqid=117033b5-9242-646b-1c92-e7000301a500&token=zitEzqOML3j84e6ealFT
T5U7-km5qEQF52lp7AcCuBZYNpCJiKFonMipX0nRikauD7BKLkpZAtQ_aN6eUBTbi2UcMC60Zo-i
fhoLye8kBZhFaDq07_sCfvo7gxJ36C_A>
&ymreqid=117033b5-9242-646b-1c92-e7000301a500&token=zitEzqOML3j84e6ealFTT5U7
-km5qEQF52lp7AcCuBZYNpCJiKFonMipX0nRikauD7BKLkpZAtQ_aN6eUBTbi2UcMC60Zo-ifhoL
ye8kBZhFaDq07_sCfvo7gxJ36C_A
I'm looking for advice. The manual states that moving the shoring bars out
will increase the tuned frequency (which doesn't make sense to me). If this
is true, I may experiment with either adding push on rings to act as
capacitance hats, electrically lengthening the t match, or swedge on lengths
of rod to extend the t matches.
The design freq of the antenna is very sharp: 49.5 to 50.5MHZ but I can't
seem to stay within 2:1 at 50.315. Running 1 kw is an issue for the amp.
The other, not preferred option is to run a short segment of 70 ohm coax as
a transformer but I will lose output/receive in the form of heat.
We hung the antennas about 10 ft in the air to sweep so the numbers are
fairly accurate.
Any help or suggestions would be appreciated.
Thanks,
Paul Rollinson, KE1LI
FN41AU
860-928-5147
860-208-8814 Cell/Text
<mailto:Paulrollinson@sbcglobal.net> Paulrollinson@sbcglobal.net
Happy Holidays
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