When the FT8 bug infected everyone a few years back, I retuned 2 original
6M7's high enough to be 1.5:1 at 50.313 by moving the t-match shorting bars
as far outboard as they would go.
Yes, the original M² antennas were pretty narrowband - back then it was
fine. You could also rip the whole t-match feed off and replace it with a
hairpin match, which would cure a lot of the other M² issues. There are a
lot of those antennas out there where this was done.
-W9RM
Keith Morehouse
via MotoG
On Sat, Jan 2, 2021, 9:30 AM Jim Worsham <wa4kxy@bellsouth.net> wrote:
> Hello Paul. I had the exact same problem last year when I was setting up
> to operate from home in the June and September contests. I also have a 6M7
> and after a weekend of trying I was also unable to tune it high enough in
> the band to get an SWR less than 2 at 50.318 to make the solid state
> amplifier happy. Like you the shorting bars seem to have little or no
> effect. It seems like the M2 antennas of that time were built to operate at
> 50.100 plus or minus 100 kHz and that was it. Luckily I had another 6M
> antenna available that I was able to tune so I put it up instead. The 6M7
> sits in my basement now unused. I would really like to hear what the result
> of your conversation with M2 is. Thanks.
>
> 73
> Jim, W4KXY
>
>
> > On Jan 2, 2021, at 9:02 AM, Paul Rollinson <Paulrollinson@sbcglobal.net>
> wrote:
> >
> > 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
> >
> >
> >
> >
> >
> > --
> > This email has been checked for viruses by Avast antivirus software.
> > https://www.avast.com/antivirus
> > _______________________________________________
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>
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