Topband: Fw: GAP VERTICAL QUESTION

[DAVID CUTHBERT]

Mike that QTH looks alot like the Great Salt Lake of Utah where I have
operated a few 160 meter 'tests running a balloon vertical.

     Dave WX7G

On Fri, Dec 14, 2012 at 9:52 AM, Michael Tope <W4EF at dellroy.com> wrote:

>
>
> On 12/13/2012 3:14 PM, Tom W8JI wrote:
>
>> Somehow they thought moving the feedpoint eliminated the need for radials
>> with an electrically short antenna, when the real mechanism was a 1/2 wave
>> vertical was converted to a 1/4 wave groundplane 1/4 wave above ground and
>> it only got a tiny bit weaker. The groundplane still had 8 radials, but
>> they were hundreds of feet in the air.
>>
>> There was some more stuff about offsetting the feedpoint in that handout,
>> but nothing that remotely applied to a fractional wavelength vertical just
>> sitting on the dirt with a few radials laying directly on the lawn.
>>
>> They got rid of lossy traps and loading coils by using even lossier coax
>> and some folded wires for a loading system.
>>
>> This is all why, as frequency increases and the current and voltage moves
>> up the antenna, the GAP on most bands isn't terribly bad.  This also why it
>> is a real dog of an antenna on 160 and 80, where it is very short
>> electrically, has no ground system, has an exceptionally poor loading
>> method, and where it folds the radiator back and forth which suppresses
>> radiation resistance.
>>
>> This is why a ten foot mobile antenna can tie it or beat it on 160, and
>> why it is reasonably on par with anything else on most bands above 80
>> meters.
>>
>> 73 Tom
>>
>
> I got hold of a brand new voyager about 7 years ago. The first thing I did
> was throw away all that yellow coax stuffed inside the bottom half. The
> fiberglass "GAP" for the elevated feed point makes a nice insulator for a
> center loading coil. Then I added some top hat wires with dimensions per
> WX7G's recommendation and fed the antenna from the bottom as a standard
> ground mounted vertical with a bunch of radials.  For 80 meters, I put a
> short "yard arm" at the top with a pulley and hung a wire in parallel with
> the aluminum radiator. For only being 45ft tall this antenna has worked
> surprisingly well. I've since lengthened it to 56ft and added an additional
> parallel wire for 40 meters. I use an Ameritron RCS-4 remote switch at the
> base to select between 160 or 80/40 (the 80 and 40 meter vertical wires are
> tied together). I use a 50 to 12.5 ohms Unun on the 160 side to raise the
> feedpoint Z up to 50 ohms. With all these modifications done in haste
> before various contests it aint pretty to look at, but it does seem to hold
> its own against folks with shunt-fed towers and inverted-Ls (at least the
> ones who don't use overly active antenna tuners :-)  ).
>
> Here are some pictures of it when I took a trip to one of the dry lake
> beds north of here:
>
> http://www.dellroy.com/W4EF's-**Ham-Radio-Page/CQ160/2006.htm<http://www.dellroy.com/W4EF's-Ham-Radio-Page/CQ160/2006.htm>
>
> 73, Mike W4EF...............
>
>
>
>
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