Jouko,
I had the same problem, despite assurances from the wholesaler in the USA
where I bought the the two Hamsticks, they were resonant at their lowest at
3750 kHz. I needed to operate them at a lower frequency of no more than 3650
kHz

I tried extending the stainless steel "stinger" but I couldn't find anything
long enough.

Then I tried a disk of aluminium 1.6mm x 75 mm in diameter, fitted between
the stainless whip and the antenna proper, and that reduced the resonanant
frequency to 3575 kHz, adjusting the stinger length was necessary of course.

You may have to make the diameter of the disk slightly larger to get it to
resonate at the lower frequency, just a matter of cut and try.

Using my MFJ Analyser, the feedpoint resistance was close to 50 ohms.

It was a very simple fix!

73
John VK2KCE

"JN" wrote in message
...
Hamsticks and their clones are for US 75m (4MHz) and not directly tunable
to 80m (3,5 MHz)

I plan a Hamstick dipole for Digimodes and CW for say 3560 kHz.

What is the best way to lower the resonance frequency
Some type of capasitive loading at the end of base(coil) section
or an inductance at center wich could maybe also function as impedance
transformer?
What is the feedpoint resistance of Hamstick dipole?

Any ideas or experiences?

73 Jouko OH5RM

John,

Yes I think using capasitive loading at the end of coil parts is the right
way to move the frequency.
What kind of results did you get with the hamstick dipole?
OK 50Ohm feedpoint resistance. I thought it is lower, but maybe it is so
due to high loss resistance in coils.

73 Jouko OH5RM

Hi Jouko,

I made up a 4 band "spider" mount, to which you can screw in 4 sets of
hamsticks. I have a full set of hamstick whips from 80m down to 6m.

So I have a multiband hamstick dipole array!

When one thinks about the feedpoint impedance, even without the capacitive
disk, it certainly should be lower, but as I am using them at 7 metres from
groundlevel in a portable situation, I use a small antenna tuner.

At that height, they act like a "cloud warmer" or a NVIS antenna, so at 80m
its good for up to 350km. I haven't really given the other frequencies a try
yet.

Let me know I can email you with a few pics of my multiband "spider mount",
as I have a small lathe and milling machine in my workshop, it wasn't hard
to make.

73
de VK2KCE John
"JN" wrote in message
...
John,

Yes I think using capasitive loading at the end of coil parts is the right
way to move the frequency.
What kind of results did you get with the hamstick dipole?
OK 50Ohm feedpoint resistance. I thought it is lower, but maybe it is so
due to high loss resistance in coils.

73 Jouko OH5RM

In article ,
"HRBE" wrote:

I made up a 4 band "spider" mount, to which you can screw in 4 sets of
hamsticks. I have a full set of hamstick whips from 80m down to 6m.

So I have a multiband hamstick dipole array!

HRBE-

I think it was the December, 2007, issue of QST that had an article on
the "Octopus" antenna made of 4 pairs of mobile whips for 75/40/20/15
meters. I plan to also add a vertical 10 Meter whip.

I've collected the parts but haven't assembled it yet. It will be
interesting to see how the monstrosity works!

Fred
K4DII

Fred McKenzie wrote:
I've collected the parts but haven't assembled it yet. It will be
interesting to see how the monstrosity works!

Hope you enjoy 75m QRP.
--
73, Cecil http://www.w5dxp.com

In article ,
Cecil Moore wrote:

Fred McKenzie wrote:
I've collected the parts but haven't assembled it yet. It will be
interesting to see how the monstrosity works!

Hope you enjoy 75m QRP.

Cecil-

I can appreciate that a mobile whip used on an auto, does not have the
efficiency of a full quarter wave vertical over an array of counterpoise
wires. But it does work.

I want to use a pair of mobile whips as a horizontal dipole. (Or more
in the case of the Octopus.) Are you suggesting that such a dipole on
75 or 40 Meters, will not perform as well as just one of the whips
mounted on an automobile?

Fred
K4DII

Fred McKenzie wrote:
I want to use a pair of mobile whips as a horizontal dipole. (Or more
in the case of the Octopus.) Are you suggesting that such a dipole on
75 or 40 Meters, will not perform as well as just one of the whips
mounted on an automobile?

The radiation resistance of a 75m hamstick is roughly
about 0.5 ohms. The feedpoint impedance is roughly
about 20 ohms if one subtracts out the ground losses.
Very roughly, that would make a 75m hamstick dipole
have a radiation resistance of about 1 ohm and a
feedpoint impedance around 40 ohms. That's about 2.5
watts out for 100 watts in. I would say that qualifies
for QRP and is actually an improvement over a 75m mobile
hamstick with a measured signal strength that is 12 dB
down from a good screwdriver which itself is about 10 dB
down from a 1/2WL dipole.

Almost any other antenna in the world will beat a
75m hamstick dipole. One can radiate ten times as
much power simply by lengthening it by 50% and using
high-Q loading coils.
--
73, Cecil http://www.w5dxp.com