[Antennas] Re: Antennas Digest, Vol 11, Issue 17

Fri Dec 31 11:00:00 EST 2004

Pastor/KC1DI wrote:
>>>>>> -------Original Message-------
>>>> From: fkamp at comcast.net
>> Date: 12/31/04 09:44:16
>> To: W0OXJ
>> Cc: antennas at mailman.qth.net
>> Subject: Re: [Antennas] Re: Antennas Digest, Vol 11, Issue 17
>>>>>> W0OXJ wrote:
>> >
>> > I believe since you are using balanced feed line and will, of course, use
> a
>> > tuner this problem will be taken care of by the tuner.I would make my
>> > radials the same length as the radiator to keep the antenna balanced.It
>> > should work just fine.
>> >
>>>>>> Yes, the tuner should take care of any matching problems. However, I
>> wanted to keep the electrical length of the antenna as close to a
>> quarter wavelength as possible to improve its efficiency. That was
>> when I started wondering about top loading. I only have 26 feet of
>> tubing which is fine for 30 meters and higher frequencies. It would
>> have been nice to top load the thing and get it be an electrical quarter
>> wavelength for 40 meters. Then, since I want to guy it at the center, I
>> began wondering if maybe center loading would get me electrical length I
>> needed for 40 meters.
>>>> I think that was just wishful thinking, but not being sure about how
>> much deviation from top loading I could get away with and still get
>> results, I had to ask.
>>>> In retrospect, seems a silly question. Now it is going to be insulated,
>> non-conductive guys and a horizontal, 26 foot top wire working against a
>> counterpoise. An inverted-L.
>>>> That should pretty well tap me out as far as usable antenna space. I
>> already have a 80/40 meter trap dipole, a four element tri-band beam,
>> and a 40 meter right angle full wave loop. I guess I could be concerned
>> about interaction between these antennas. I have a corner lot but it
>> still is in the suburbs and not all that large a plot of land.
>>>> Regards,
>> Frank Kamp
>> K5DKZ
>> Hi all
>> Actually the 26 foot (I'd go with about 22 ft. ) .. if you are feeding a
> vertical radiator with open wire. and expect good results on say 40 through
> 10 meters you do not want to make the vertical so that it is much longer
> than 5/8 wave at the hightest frequency you plan on operating. Once you
> start to approach 3/4 wave the radiation angle goes high and you will have
> an effective clound warmer which would be ok if you only want local stuff.
> In my experience 22 to 24 feet works great 40 through 10 m .. 33 feet of
> course will work but it presents an increasing angale of radiation as you
> raise the frequence 33 feet is almost a full wave on 10 meters and thus
> would not be a good dx antenna on that band .. it also will not work well on
> 15m for dx. but would be resonable on 40 through 20 or 17 meters. you have
> to decide what your goal is.. 40meters or an all round good vertical. for 40
> through 10m ... if the later forget the top loading and go with something in
> the area of 18 to 24 feet. With open wire it's been a good performer for me
> here... mine by the way was mounted at 35 feet and had only two equal
> radials. the same 22 feet as the radiator.
>
Thanks Dave, that is good information.
While I certainly would not mind an antenna optimized for DX work, that
is not my primary objective.
I can always use the four element beam when I get serious about working
DX. 
The new antenna needs to be more of an all-band device because it will
be the only antenna supporting work in the workshop. I am also limiting
myself to using materials on hand hoping for a near zero cost
installation.
I already have the open wire line installed. It was used to feed an 88
foot dipole that got replaced with an 80/40 meter trap dipole. Got
tired of tweaking the tuner during normal operation.
Being on an average sized corner lot also limits the size, hence the
smaller footprint of the vertical. Yes, I know that verticals without a
decent set of radials dont do well and the footprint required by a
decent set of radials rivals the space required for the antenna itself. 
That is why I had originally considered a vertical section working
against a single counterpoise. Now I am considering turning that setup
upsidedown and making an inverted-L.
All this antenna stuff gets very complicated when you start considering
all the factors. Still, there is no reason to settle for a less than
optimum system if the effort is reasonable. I guess in this case
'optimum' would be defined as a system with the least amount of easily
avoided compromises of negative impact.
Regards,
Frank Kamp
K5DKZ