[VHFcontesting] Tech Help needed

[Jim Worsham]

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 at 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 at sbcglobal.net> Paulrollinson at sbcglobal.net
> 
> 
> 
> 
> 
>                  Happy Holidays
> 
> 
> 
> 
> 
> -- 
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