M2 40 Mtr Yagi

[Pete Raymond]

At 08:36 AM 11/8/96 -0600, you wrote:
>     A local station recently purchased a couple of the M2 3 element 40 
>     meter antennas.  We were impressed with the antennas while we were 
>     putting them together...things fit well, nicely machined parts, etc.
>     
>     However, they've been up now for about four weeks and problems have 
>     developed.  The SWR on the antennas is all over the place.  While the 
>     SWR varies somewhat in windy conditions (to be expected), the antennas 
>     show widely varying SWR from day to day.  The antennas' SWR are 
>     normally about 1.6 at the bottom of the band.  As you go up in 
>     frequency, they go to 1:1, then rise. (again, as you would expect).    
>     However, on some days they're flat across most of the band...other days 
>     they start out at 3:1 at the bottom of the band, drop to about 2:1 at 
>     7040, then going up from there.  We've also seen the SWR take quick 
>     "jumps" which would seem to imply problems with electrical/mechanical 
>     connections.
>     
>     We have pulled down the antennas and examined them closely (several 
>     times).  We found that the set screws which hold the linear loading 
>     rods had worked lose.  After talking with M2, we've tried various 
>     arrangments on the set screws including double set screws (one to lock 
>     the other in place), stainless steel machine screws with locking nuts, 
>     etc.  None of these solutions have held up more than a few days.
>     
>     A good connection with the linear loading rods is obviously crucial to 
>     the operation of the antenna.  Anyone out there have similar problems 
>     with the large M2 antennas which use linear loading??  Any solutions??
>     
>     We haven't really gotten any good solutions yet from M2.
>     
>     73,
>     
>     Dave
>     WA0FLS
>     
>
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>
>Hi Dave,  I had a similiar experience.  I purchased their 4el 20m yagi
along with another element to make it a 5el 20 and used my measurments etc.
I had a lot of problems with their T-Match and the set screws that they
used.  They would create groves in the solid 1/4 inch rod, and caused
erratic swr etc.  Mine was first noticed on receive and while runing low
power.  I believe the groves in the rod were caused by the 
driven element flexing etc.  I wrote Mike a couple of times and he never
responded.  
This year at Dayton I approached him and advised him that I had completely
removed his T-Match and made one of my own.  Their rods and set screw
arrangements are no good and I told him that.  Wish I could tell you how to
fix it.  It really is a shame Mike does not change his T-Match and set screw
arrangement.  The rest of his antenna hardware I believe is the best on the
market.  GL 72 Pete N4KW


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