Hamstick dipole into yagi (40m)

[Steve Murdock]

A recent QST article suggested using two 40m hamstick antennas to make a
very short 40 m dipole. I know this probably is pitiful for recieving,
but anyway...

If one wanted to extend the idea, why not make ~ 4 pairs of them, and put
them on the ridge of ones house ( save the "difficult to rotate"
comments, please) or on a beam to make a Yagi ? Would one space the
elements on the beam as if they were full length for optimum gain and/or
front/back ratio? Do existing antenna analyzer software packages model
such a thing?

Some previous posts refered to two hams wanting to communicate from
limited space locations, might this work if locations happened to be laid
out favorably? Seems to me the hamstick device could be homebrewed with
pvc and #14 magnet wire for non-mobile applications/experments such as
this.

Any comments would be appriciated.

-----------------------------------------------------------------------
Steve Murdock, N0ZYE || Like the Zen Monk said to the hot dog vendor:
mur...@graceland.edu || make me One with everything
-----------------------------------------------------------------------

[Bill Meahan]

Steve Murdock <mur...@graceland.edu> wrote:
>A recent QST article suggested using two 40m hamstick antennas to make a
>very short 40 m dipole. I know this probably is pitiful for recieving,
>but anyway...
>
>If one wanted to extend the idea, why not make ~ 4 pairs of them, and put
>them on the ridge of ones house ( save the "difficult to rotate"
>comments, please) or on a beam to make a Yagi ?

Off hand, this sounds like a "semi-commercial" version of the helically-wound
compact beam in the ARRL Handbook (or the ARRL Antenna Book). Other
than using commercial parts for the radiators, isn't this the same thing?

(I've thought of doing the same thing for 30M myself).

73 de wa8tzg

--
Bill Meahan, Senior Developer | wme...@ef0424.efhd.ford.com
Electrical & Fuel Handling Division, Ford Motor Company
Opions expressed herein are those of the author and in no way represent
any official statement or opinion of Ford Motor Company

[W8JI Tom]

Only problem is the basic antenna is very lossy, and adding second element
to make yagi will increase loss greatly. Probably won't be much for
transmitting but will work for rx over narrow freq range, especially if
you drive both elements with phasing network.

[Chester (Chet) Bowles]

> A recent QST article suggested using two 40m hamstick antennas to make a
> very short 40 m dipole.

I wrote the article which appeared in _QST_. While the antenna is
certainly a comprimise, it _does_ work.

I had also considered building a beam using the "shortened" dipoles.
If it works as a dipole, then logic would tell you that adding
directors/reflectors would work as well. However, I just never got
around to doing any modeling and I don't know if typical modeling
programs would help. On the other hand, the hamstick antennas are
nothing more than helically-wound antennas.....

Coincidentally, this article seemed to strike a responsive chord with
lots of folks. I've gotten more than 30 letters from folks who had
questions or wanted to make comments.

Chet, AA1EX
bow...@cmf.org
http://www.cmf.org

[dray...@america.com]

>
>
> > A recent QST article suggested using two 40m hamstick antennas to make a
> > very short 40 m dipole.
> I wrote the article which appeared in _QST_. While the antenna is
> certainly a comprimise, it _does_ work.
> I had also considered building a beam using the "shortened" dipoles.
> If it works as a dipole, then logic would tell you that adding
> directors/reflectors would work as well. However, I just never got
> around to doing any modeling and I don't know if typical modeling
> programs would help. On the other hand, the hamstick antennas are
> nothing more than helically-wound antennas.....

> Chet, AA1EX

Chet I agree that it works. But like you have said it is a compromise at best.

The really hard part about making it into a beam is being able to helically
wind a 60' boom I never have figured out that one. HIHI

Needless to say It has been tried but the boom length still had to be there. I
tried modeling it on 10 meters. My reason was I could get 11mtr wound ants
really cheap. and tried it.just had to cut them back a little. Also found that
I had to make the directors resonate at a higher frequncy and the reflectors at
a lower one. It also cut back on the bandwidth. I was able to get it to show
under a 2.5 swr for about 28.5mhz -29.5 mhz but still had to have a boom 16'
long to get much in the way of gain and front to back. By the way the gain was
only about 6dbd. If that. Most of the time it didnt show up on either end
compared to a dipoled antenna. Except on the front to back. At the time I did
this I had never heard of using a computer for modeling. Course radio shack was
just coming out with the trs80. That was the winter you could buy a really
cheap radio to convert for sideband use on 10 meters. Don't let my observations
stop anyone, people have been doing the impossible for thousands of years. But
at my age I forget what it is. HIHI.
73 Tnx for good article.
Ray AD4RR

[Paul Knupke (CS)]

: Coincidentally, this article seemed to strike a responsive chord with

: lots of folks. I've gotten more than 30 letters from folks who had
: questions or wanted to make comments.

I was visiting the local ham store and was talking to one of the guys who
works there and he says that after the article came out they sold out of
all their stock on the resonators for 40 meters and people adapted it for
other bands too.

I've thought about doing it too. It is quiet a neat idea --

73 KR4YL
--
* ======================================================================= *
> Paul Knupke, Jr. University of South Florida Computer Engineering <
> knu...@babbage.csee.usf.edu Fidonet 1:377/61 <
> Tampa, FL * Amateur Radio Callsign KR4YL * Packet @WA1GUD.#TPA.FL.NOAM <
* ======================================================================= *
"We're only immortal for a limited time ..." -- Neil Peart

[W8JI Tom]

Chet AA1EX writes

> I had also considered building a beam using the "shortened" dipoles.
> If it works as a dipole, then logic would tell you that adding
> directors/reflectors would work as well. However, I just never got
> around to doing any modeling and I don't know if typical modeling
> programs would help.

Chet, At times I don't make a point well. The point I was making was that
if you include the losses in a short helical antenna I would doubt that
transmitting performance would be that good, especially in a Yagi
configuration.

Remember that efficiency is the ratio of the loss resistances to the
radiation resistance (or the current in the elements). Consider the
following
points:

1.) The radiation resistance (and efficiency) of an short dipole element
is
highest with lumped end loading, and lowest with lumped feedpoint loading.
The helical antenna is certainly somewhere between the two extremes.

2.) Adding a second element to "force" a tighter radiation pattern will
usually increase losses drastically because of the increased current.

3.) The second element also has losses greater than the original dipole in
this type of array.

4.) The mutual coupling (that a Yagi depends on) would limit the F/B ratio
and gain with such short radiating areas in each element.

I am sure that while some directivity could probably be obtained, it
probably would not produce any worthwhile transmitting gain. The
"radiation removed" from unwanted directions would mostly be dissipated as
heat because of element loss instead of being re-radiated in the desired
direction.

My suggestion is that if the antenna is modeled one would have to be very
careful to include the very significant losses that occur in the short
helical elements.

This reminds me of a time many years ago when I tried to construct a 160
meter beam with four 160 meter mobile antennas. A time I enjoyed very much
as I developed real world experience! ;-)

73 Tom