Hamstick dipole for 80m
 

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

Hamstick dipole for 80m
 

JN wrote:
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?

A hamstick has measured 12 dB down from a screwdriver
during 75m mobile CA antenna shootouts. That screwdriver
was about 10 dB down from a 1/2WL dipole. A 75m hamstick
is little better than a dummy load having a radiation
resistance of maybe 0.5 ohm and an efficiency in the
ballpark of 1%, i.e. 100 watts in, 1 watt out.

That said, the best way to accomplish what you are trying
to do is to use extenders on the bottom sections. The
longer the section underneath the coil, the greater the
radiation efficiency. I have extenders in 1, 2, 3, 4, 5,
and 6 foot lengths. They really come in handy for antenna
experiments.

If you could use 6 foot base extenders, that would make
the dipole 8+6+6+8 = ~28 feet long overall. Assuming you
could get that antenna up at a decent height (50+ feet),
I think the performance might be "not bad".
--
73, Cecil http://www.w5dxp.com

Hamstick dipole for 80m
 

"JN" wrote in
:

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


Hi Jouko:

I ran a “ham stick” dipole for a while and was able to compare it to a
full size dipole when I put one up. To compare the two antennas, a “ham
stick” dipole at 25’ verses a full size dipole at 35’. On 80/75m the “ham
stick” was down about 20db from the dipole. The 2:1 SWR bandwidth was
about 65KHz for the “ham stick” verses about 200+Khz for the dipole. The
way to get a “ham stick” down the bottom of 80m is to lengthen the whip
that sticks out the top. I can’t remember how much but it was not much.
The Z of a whip of the length of a “ham stick” should be only a few ohms,
but they are close to 50 Ohms when used as a dipole. The difference
between 50 Ohms and the modeled 2 to 3 Ohms is the loss in the coils.
The long, small diameter coils made with small gage wire cause most of
the loss. The “ham stick” dipole is better than no antenna but not by
much on 80m. As you go up in frequency the performance of dipoles made
out mobile antennas improve. On 40m my “ham stick” dipole was 12db down
from a full size dipole and on 20m and above it was less than an S-unit
down. Note that I’m talking about dipoles made out “ham sticks” made for
the respective bands, not using a tuner. Using a turner is a waste of
time as you move farther away from the center frequency the loss goes way
up and your signal goes away! I still use my 80m “ham sticks” but not as
dipole. I have them ground mounted with 4 10’ radials each, spaced 1/16
wavelength apart and feed 90 deg. out of phase. This makes a directional
receive antenna for the DX window on 80m that rivals a beverage antenna.
It makes DXing on 80m fun. The only disadvantage is that unlike a
beverage it only works over about a 65Khz chunk of the band.

John Passaneau, W3JXP

Hamstick dipole for 80m
 

On Tue, 25 Mar 2008 14:05:13 +0200, "JN" wrote:

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


The ham stick dipole isn't very great for 80 meters. I know from
experience that the hustler mobile antenna works better than the ham
stick on 75 meters. I have used the ham stick on 80 meters mobile
with an antenna tuner. The antenna tuner gave me a much broader
bandwidth as far as SWR is concerned without having to retune.

On the other hand, you are not operating mobile. I don't know how
this compares. I know when I did it, it gave me a very weak, but
readable signal. I had a ground rod in the ground below my window. I
connected the shield side of my coax to the ground stake and the
center to one end of a long spool of wire. I stretched the wire out
about 1/4 wave on the ground and checked the SWR. It was flat on the
frequency I wanted (I got lucky) so I checked into the then GA SSB Net
on 3975. I was weak, but readable and could pass my traffic.

If you can make loading coils, make a couple with large diameters.
The larger the better. Center load each element and make them so you
can tap to the coil. This will work better than the ham stick. You
may find that tapping at two different points works better for you so
you have a bit of an offset in the electrical lengths of the antennas
on either side of the coax. This is because the impedance of a
shortened dipole antenna is lower than 50 ohms. The offset finds a
better match.

Hope this helps.

Buck
N4PGW
--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

Hamstick dipole for 80m
 

Thanks for everybody for good comments,
They are quite in balance with the information I have red from net.

The antenna which I am planning is for portable use and should be
easy to erect and transport.

Your remarks led me to some comments:

- Yes the efficiency on 80m may be too low, because of small size.
- Adding center extenders could help but then 75m hamsticks are out of 80m
band
- By using 40m hamsticks and maybe center loading coil and extenders tuning
to 80m possible?
- Then also operating on 40m without extenders OK
- 80 operation only needed for domestic qsos, no DX
- On 30m and 20m hamstick dipole would work OK

Any comments on these?

73 Jouko OH5RM

Hamstick dipole for 80m
 

If you could use 6 foot base extenders, that would make
the dipole 8+6+6+8 = ~28 feet long overall. Assuming you
could get that antenna up at a decent height (50+ feet),
I think the performance might be "not bad".



Cecil, I would be interested in finding out what you are using for
base extenders..... varying lengths of ? with 3/8"-24 female one end, male
another. You make something, or is something commercially available?


Ed K7AAT

Hamstick dipole for 80m
 

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

Hamstick dipole for 80m
 

- Yes the efficiency on 80m may be too low, because of small size.
- Adding center extenders could help but then 75m hamsticks are out of 80m
band
- By using 40m hamsticks and maybe center loading coil and extenders tuning
to 80m possible?
- Then also operating on 40m without extenders OK
- 80 operation only needed for domestic qsos, no DX
- On 30m and 20m hamstick dipole would work OK

Any comments on these?

73 Jouko OH5RM



Ok, the antenna is portable. Toss a wire over a couple of tree limbs
and either use full-sized 80 meter dipole, or load it with loading
coils. If you load the antenna with coils located at the end point of
40 meters, you may find yourself with a dual band antenna -- 40/80.
Since you are operating primarily local 80 meter operation, any height
above ground up to about 20 feet will result in NVIS, pretty good
signal there.

You could also try a tree-limb somewhat vertical. Drop a short ground
rod into the ground, tap shield to that and toss other end of 65 foot
wire (plus or minus) over a tree limb. It will operate, but not
perfect. However, it should work as well or better than the
hamsticks.


Just another thot
Buck

--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

Hamstick dipole for 80m
 

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

Hamstick dipole for 80m
 

JN wrote:
- Adding center extenders could help but then 75m hamsticks are out of 80m
band ... Any comments on these?

This is not necessarily true. Since the length of
the top stinger has a much greater effect on resonant
frequency than the length of the bottom section, you
can increase that bottom section length by a large
amount and then adjust the top stinger length by a
smaller amount to achieve the desired resonant
frequency. And you are going down in frequency to
the CW portion of 80m.

For instance, you might extend the bottom portion
by 6 feet and only have to shorten the top stinger
by 2 feet. (When you shorten the stinger, you may
have to hacksaw off a portion to keep the stinger
bottom from residing in the middle of the loading
coil.)

Let's say you have an eight foot long base-loaded
mobile antenna. You decide to move the loading coil
farther up the antenna to the center-loaded position.
If you keep the *same length and same coil*, the resonant
frequency will increase. You have to add more stinger
length to bring it back to the original resonant
frequency (or more coil). Moving the fixed coil farther
away from the feedpoint requires the antenna length to
be increased. That fact works in your favor.

Since the additional bottom section is moving the
fixed loading coil farther away from the feedpoint,
the above effect will occur for your extended
configuration. Experiment with it and see what
happens. You could just use wire for the
experimentation and hang it between two supports.

-----/////-----+-----FP-----+-----/////-----
hamstick wire wire hamstick

--
73, Cecil http://www.w5dxp.com