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M2 40 Mtr Yagi

To: <towertalk@contesting.com>
Subject: M2 40 Mtr Yagi
From: Dave_Raymond-CSUS04@email.mot.com (Dave Raymond-CSUS04)
Date: Fri, 8 Nov 1996 8:36:00 -0600
     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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