Hello Ivy.
30 Sep 97 14:06, Ivy Iverson wrote to Roy Witt:
 RW>>> o
 RW>>> /          top view
 RW>>> o------o-------o-------o-------o------o
 RW>>> \    DE
 RW>>> o
 II>>
 II>> Ah yes, the good old corner reflector... Now if you were to
 II>> replace the dipole elements with a 5/8 J-pole and suitably-sized
 II>> elements, mount them vertically on a boom, (about 6-8 Ft long?),
 II>> I wonder what ERP you would get with about 40 Watts at the
 II>> antenna, (50W xmtr)? ...
 II>
 RW>> Build it correctly.  Mount it behind the reflector...This is
 RW>> about a 7.5dbd  antenna with a much better F/B ratio than you'll
 RW>> find in a normal Yagi.
 II>
 II> I'm sure!  Are you talking 1/4 wave elements?  If it's built with 6 dB
 II> J-poles, what would the gain be?  How about adding more 5/8 elements
 II> to the J-poles?  Hey, might as well dream big, right?
I've never liked j-poles, so you'll never convince me that such an animal you 
discribe above should exist.  It's nice to experiment with antennas, but this 
has got to be a nightmare...
 II> And if you have a 6-8 Ft boom, that would be quite a strain to mount
 II> it from behind.  I think it would be more effective to mount it at
 II> the center of balance, on top of the supporting mast.
You still mount it from behind and use a counter-balance to compensate for 
the overhang.  I did this for a local cable provider who couldn't recieve a 
certain FM station without interference.  I built them a yagi designed for 
the frequency of the station and mounted it from the rear with a 
counter-balance. A 5 element yagi for 97-100MHz...
 II>   Do you REALLY want a 2M "cannon"?
Nope. I work UHF, exclusively.
 II>   Have the J-poles paired, above AND below the mast!
 II> Also, what difference would it make if the corner had a screen
 II> instead of duned reflectors?
                tuned? round? ??
The screen will give you a higher F/B ratio.
 II>   This would require a non-metallic mast unless it were rear-
 II> mounted, but if the DE's were properly phased and everything
 II> optimized (resistors in the directors, etc?).
Why would it require a non-metallic mast?  Because of the J-pole?
 II> ..  That just MIGHT be hot enough for moonbounce if it were mounted
 II> on AZ-EL rotors!
 II> (It would also be about 15 Ft high and quite heavy with a lot of wind
 II> resistance!)
And more trouble than it's worth...:)
... It's time for Plan B[subpart 2.56]!
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