[Towertalk] 40 m yagi matching

[Kent Miller]

Hi Mark,

How high is your swr on the upper end ?  My 40-2cd is tuned for 7.150,
but at the worst case at 7.000 the swr is only 2.2 to 1.0 and at 7.300
it is only 1.7 to 1.0.......
My antenna is at 130 ft. and is fed with 350 ft. of 52 ohm coax.  I'm
using a coax balun wound on a 6 inch core mounted at the driven element.

I find an swr of 2.2 to 1.0 acceptable, but many hams would not, I
suppose.

73,
Kent - K4MK 

Mark Pride wrote:

> Fellow TTer's:  Problem - Have a 2 element yagi on 40 M that is currently tuned for the CW end of the band.  In order to use it on the SSB end, past techniques have included locating a Transmatch at the base of the tower and adjusting the match so the amplifier can tune properly - this has proved difficult as it was inconvenient to re-tune for other portions of the phone band (tower base is 300 ft. from the shack and the bandwidth with the tuner was not too great); another approach used was to locate the tuner in the shack - made it convenient to re-adjust as necessary, but caused severe voltage breakdown conditions on the feed line (high SWR plus the amplifier proved disasterous for connectors).

 What are others doing to make the SWR better on the opposite end of the
 band the antenna was originally tuned?  Have considered adding stubs
 somewhere on the feedline, but have not tried as yet.  Looking for a  
way to allow the amplifier to tune properly across the entire phone  
band even though the antenna's performance is degraded due to a 
non-optimzed setting of the elements for that part of the band.  40 M 
phone is not my favorite but with this problem fixed, I can at least 
make a better score in those DX contests.  (That's the plan anyway!)
 
 I realize this is transmission line theory 101, but thought there
might  be a quick answer out there!
 
 The yagi is a Cushcraft 402 at 100 ft. fed with 3/4 - inch diameter 75 
ohm hardline (300 ft. plus 100 ft. up tower).

 Regards,

 Mark, K1RX
 
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