Hi Gang,
There is magic about a 43 foot vertical but it isn't what most people
think. It's 5/8 wavelength at 20 meters, clearly a good maximum
performance antenna for DX on that band with a vertical. That's why
many broadcast stations use to use it (per Brown etal). I haven't
modeled one lately but the 5/8 wave vertical is often used on 2 meter
mobiles with about a 49" whip. They usually are matched with just a
series inductor.
However, on the bands above 20 meters, there should be lots of cloud
warming lobes.
73,
Joe, W1JR
At 11:33 AM 11/20/2008, James Chaggaris wrote:
>
>A great discussion has been taking place on eham regarding 43' verticals.
>
>http://www.eham.net/forums/Elmers/201882
>
>
>
>73,
>
>Jim N9WW
>
>
>James E. Chaggaris
>President
>PowerOne Corp.
>1020 Cedar Ave.
>Suite 203
>St. Charles, IL 60174
>Phn:(630) 443-6500
>Fax:(630) 443-6505
>Cell:(630) 669-2241
>Web: www.pwrone.com
>
>
>This e-mail is intended solely for the use of the individual or entity to
>which it is addressed. If you are not the intended recipient of this e-mail,
>you are hereby notified that any dissemination, distribution, copying, or
>action taken in relation to the contents of and attachments to this e-mail
>is strictly prohibited and may be unlawful. If you have received this e-mail
>in error, please notify the sender immediately and permanently delete the
>original and any copy of this e-mail and any printout.
>
>-----Original Message-----
>From: towertalk-bounces@contesting.com
>[mailto:towertalk-bounces@contesting.com] On Behalf Of Pete Smith
>Sent: Thursday, November 20, 2008 10:21 AM
>To: towertalk@contesting.com
>Subject: Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type
>
>You clearly need a tuner at the base of such an antenna, rather than in the
>shack, but there are a number of possible choices for that service now. A
>more interesting question is what the radiation pattern will look like on
>the various bands. I ran a quick-and-dirty, and it appears that the optimum
>(highest-gain) takeoff angle varies from 26 to 16 degrees on 80-20, then 37
>and 57 on 15 and 10. That obviously makes a big difference in the
>subjective reports on the various bands, depending on the distance.
>
>There was a series of articles in National Contest Journal a few years ago,
>using NEC-4 to evaluate on-the-ground/buried radials. The message I took
>away from that series was "Them as has, gets." That is, at a QTH with very
>good ground conductivity, the improvement afforded by many radials is
>relatively small. At a QTH with poor ground conductivity, even a full-up AM
>broadcast radial field will only get you somewhere close to the station with
>very good ground and a few radials.
>
>My 2 cents.
>
>73, Pete N4ZR
>
>
>
>At 10:55 AM 11/20/2008, Rick Stealey wrote:
>
> >Michael,
> >It would sure seem to me that a 43 ft vertical is essentially a random
> >length antenna.
> >I saw the web site too where they offer a balun to go with it. "It
> >tunes all bands"
> >they say, WITH YOUR TUNER in the shack, or at the base of the antenna !!!
> >I did a quick and dirty check with 4NEC and got 122-j466 at the base on
> >20 meters, an swr of 38:1 ! A sweep shows an SWR of >9:1 from 7 to 15
> >MHz.
> >On 40 m you get 150+j210, an swr of 9:1 On 80 you get 17-j257, an swr
> >of 79:1 !!
> >So it would seem to me you have a lot of work to do to match this thing
> >at the base.
> >It would not be a good idea to run coax straight into the house with a
> >79:1 SWR
> >and hope a tuner will fix things.
> >I know there is a guy in Chicago on 20 meters running one of them with
> >no radials who comes into NJ 20 over 9 at times and claims no knowledge
> >as to how he does it.
> >Guys he talks to rave about his rock crushing signal. Wouldn't it be
> >interesting to compare his signal in real time with his neighbor
> >running a beam, or a quarter wave vertical. I mean.... the laws of
> >physics haven't been rewritten lately have they, and I missed out on
> >it?
> >Rick K2XT
> >
> >
> >_________________________________________________________________
> >Proud to be a PC? Show the world. Download the "I'm a PC" Messenger
> >themepack now.
> >hthttp://clk.atdmt.com/MRT/go/119642558/direct/01/
> >_______________________________________________
> >
> >
> >
> >_______________________________________________
> >TowerTalk mailing list
> >TowerTalk@contesting.com
> >http://lists.contesting.com/mailman/listinfo/towertalk
>
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|