[TowerTalk] Trying to test out my old 40 meter cushcraft

[terry burge]

Quite a few years back I had a 40' Rohn tower with a system 36 by Wilson on it. The tower was setup to tilt over on a hand winch with a ginpole. I could tilt the tower over very near the ground with the system 36 tribander facing up into the sky and tune it. The reflector was only about a foot off the ground. You could predict the shift in the SWR curve when raised up after a couple of tries and it worked very well. The system 36 needed to be adjusted for 10 meters and  I moved those traps in slightly to shift up the resonance on 10 and readjusted the 15/20 section out slightly. Was really a nice little setup.Learned a lot about tribanders there even though I didn't think the system 36 by Wilson was very good. Unlike the Mosley System 36 it was copied off of. 


But the point is you can adjust a yagi pointing it up in the air with the reflector near the ground and predict which way and how much the SWR curve will shift. Can't do this with a quad though is my experience.


Terry

KI7M

> On February 23, 2018 at 6:46 AM Charles Morrison wrote:
> 
> 
>     Last year I prepared a Cushcraft 40-2CD and a HyGain 402BA for Field Day.
>     Each would not show good sweep results and would not radiate well while the
>     boom pointed up and even with the reflector end raised up three feet.
>     40M yagis just need to be up higher to test.
>     -Charlie N1RR
> 
> 
>     On Fri, Feb 23, 2018 at 9:26 AM, john at kk9a.com mailto:john at kk9a.com wrote:
> 
>         > > I have never tried tilting the a beam up. It seems like a lot of trouble,
> >         especially with a long boom and I would not be confident that it is still
> >         tuned properly. It is quite easy to pull a beam up the side of a tower
> >         about a wavelength high and take measurements though 1/2 wl multiples of
> >         coax and then bring it back down to make any adjustments. I have done this
> >         completely by myself many times and my antennas have a nearly perfect SWR
> >         curve when mounted.
> > 
> >         John KK9A
> > 
> > 
> >         From: "Ed Sawyer"
> >         Date: Fri, 23 Feb 2018 05:57:39 -0500
> > 
> >         I don't find that the "point the beam skyward" method works that well on
> >         40M
> >         beams for doing the initial SWR test. The typical 40M beam is a loaded
> >         element and on a boom that is usually 20 - 24 ft long. 24ft high is not
> >         enough to have the DE up and away from the ground.
> > 
> > 
> > 
> >         It will tell you its not shorted or open but as to whether its tuned right,
> >         it needs to be in the air.30 to 40 ft up is usually a minimum and even
> >         then,
> >         the SWR low point will shift by another 20 - 50khz by the time its up at 70
> >             * 100 ft in my experience.
> > 
> > 
> > 
> > 
> >         Ed N1UR
> > 
> > 
> >         _______________________________________________
> > 
> > 
> > 
> >         _______________________________________________
> >         TowerTalk mailing list
> >         TowerTalk at contesting.com mailto:TowerTalk at contesting.com
> >         http://lists.contesting.com/mailman/listinfo/towertalk
> > 
> >     > _______________________________________________
> 
> 
> 
>     _______________________________________________
>     TowerTalk mailing list
>     TowerTalk at contesting.com mailto:TowerTalk at contesting.com
>     http://lists.contesting.com/mailman/listinfo/towertalk
>