Working a lot of countries is no indication of antenna performance.
John KK9A
On 2013-10-02 12:45, David Blake wrote:
> From personal experience I have found the shortened
> Mosley trap 40 meter elements effective. I had the
> Mosley TA40KR 40 meter add on kit on an old TA33
> and worked over 200 DXCC on 40M with it at less than
> 50 feet. I then moved from Virginia to Ohio and put up
> a Mosley PRO67B and then worked over 320 DXCC on
> 40 meters with it. I know Mosley has been beaten up
>
> pretty bad on this reflector, but with mine I have Honor
> Roll Mixed, Phone and CW and #1 Honor Roll.
>
> BTW my PRO-67B was only at 50 feet. It was designed
> to work on 6 bands, and I managed over 300 countries on
> all 6 bands. On 40M I had a choice to set for the low end
> of the band, center or top end. I chose low end but still
> had an SWR less than 2.0 to one up to about 7.230Mhz.
>
> YRMV 73
>
> Dave -N4DB-
>
> -------------------------
> FROM: "john@kk9a.com" <john@kk9a.com>
> TO: TOWERTALK@contesting.com
> CC: k5er@arrl.net
> SENT: Tuesday, October 1, 2013 9:43 PM
> SUBJECT: Re: [TowerTalk] : 40 meter rotating dipole question
>
> The price of a full size 40m element is considerably more. Not only do you
> need more aluminum and a stronger center piece, you also need a stronger
> tower and rotator. I have had full size 40m beams and they are great. You
> will get better bandwidth and higher efficiency. If you do wish to shorten
> it, split the element and use a Hi-Q coil or some type of linear loading.
> As far as designing and building one that requires no adjustment, I think
> that will be a challenge, especially of you load it. I model all of my yagis
> and have always needed to make an adjustment to the DE.
>
> John KK9A
>
> To:towertalk@contesting.com
> Subject:[TowerTalk] 40 meter rotating dipole question
> From:"Mark, K5ER" <k5er@arrl.net>
> Date:Tue, 01 Oct 2013 14:24:58 -0500
>
> Hi Guys, I have checked the archives, but not found specific answers, so
> forgive me if this has already been covered and I am asking the wrong
> questions. To help a friend, I am building a 40 meter rotatable dipole, to
> live at 90' on his mast. It will be about 12' above his 36' boom 20M OWA. I
> will fabricate a heavy duty mount/center insulator, and incorporate 2 truss
> cables, either dacron or kevlar. He delivered to me two (used) elements from
> a previous unidentified antenna. Each element is abt 28' long, with the
> taper schedule going from 1 1/4 down to 5/8. I have spare material in stock,
> so I could easily add a 1/2" x 5' tip to each and end up with a full size
> dipole.
>
> Question one - The price of material isn't much more, so why does it seem
> that "nobody" builds rotatable dipoles to the full 66-67 feet?
>
> Question two - IF a shortened antenna is better, is there a "better" length?
> I see many in the range from 38 to 55 feet.
>
> Question three - If shortened, I know the ant will be capacitive, and
> therefore can be matched by adding an inductor across the feed. I find many
> pages of formula with lots of Latin characters, but missed that day in math
> class. If someone had a hint of a starting point, ie> 4" long, 5 turns on 2"
> diam. , or 4 turns on 3" diam, etc. I could then work backwards and make
> this work for him.
>
> I have EZnec 5+, but have only used it to build OWA antenna so far, which
> makes a beautiful direct feed, so I have no experience with adding a load. I
> plan to input the taper schedule into EZnec, but if a given length is known
> to be superior, I am not too proud to ask for it, rather than spend hours
> building model after model working my way through the possibilities.
>
> I understand that height can affect performance and feed point impedance,
> however, neither the owner nor I climb. I need to model and build this
> antenna, and then expect it to work as modeled when the climber puts it in
> place, so any ideas would be appreciated.
> Thanks,
> Mark, K5ER
>
> _______________________________________________
>
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