Hello ! I just bought a 2m Hamstick antenna at the Orlando Hamfest, the
model 9100. I would like to trim this antenna for 156 mhz, for marine
use on my boat. Can someone tell me "about" how much I should shorten the
whip to achieve this ? Remember, this is the 5/8 wave antenna with a loaded
base.

Thank you very much !!


73 de Jim K4PYT

James wrote:
Hello ! I just bought a 2m Hamstick antenna at the Orlando Hamfest, the
model 9100. I would like to trim this antenna for 156 mhz, for marine
use on my boat. Can someone tell me "about" how much I should shorten the
whip to achieve this ? Remember, this is the 5/8 wave antenna with a loaded
base.

Thank you very much !!


73 de Jim K4PYT


IRRC the Hamstick is a quarter wave antenna and requires a counterpoise
to operate correctly. You would be better off getting a marine 1/2 wave
antenna for you boat as most fiberglass boats do not have enough metal
to provide the counterpoise.

Dave WD9BDZ

Dave, as stated in my OP, this is a 5/8 wave antenna. It is the antenna
that I have bought and that I will use temporarily. This will be for a very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT

"James" wrote in message
. ..
Dave, as stated in my OP, this is a 5/8 wave antenna. It is the antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT



Triming alone want do it, the base is designed to match the 5/8 2m to 50
ohms. Unless you can also figure out a way to modify the matching network
you cant do it.

"James" wrote in message
. ..
Dave, as stated in my OP, this is a 5/8 wave antenna. It is the antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT


You can start bu scaling the antenna length . That is devide 146 by 156
and get around .94. Then multiply the length of the element by .94.
As pointed out the loading (matching) coil will probalby need to be modified
somewhat for a perfect match, but this should get you close.

Start trimming by 1/4 " at a time.

"Ralph Mowery" wrote in message
ink.net...

"James" wrote in message
. ..
Dave, as stated in my OP, this is a 5/8 wave antenna. It is the
antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT


You can start bu scaling the antenna length . That is devide 146 by 156
and get around .94. Then multiply the length of the element by .94.
As pointed out the loading (matching) coil will probalby need to be
modified somewhat for a perfect match, but this should get you close.

Jimmie D wrote:

"James" wrote in message
. ..

Dave, as stated in my OP, this is a 5/8 wave antenna. It is the antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT




Triming alone want do it, the base is designed to match the 5/8 2m to 50
ohms. Unless you can also figure out a way to modify the matching network
you cant do it.



B as in B, S as in S. It is plenty close enough to work just fine with
a little trimming.

And B means Bull, and S means ****.

tom
K0TAR

"Tom Ring" wrote in message
. ..
Jimmie D wrote:

"James" wrote in message
. ..

Dave, as stated in my OP, this is a 5/8 wave antenna. It is the
antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT




Triming alone want do it, the base is designed to match the 5/8 2m to 50
ohms. Unless you can also figure out a way to modify the matching network
you cant do it.

B as in B, S as in S. It is plenty close enough to work just fine with a
little trimming.

And B means Bull, and S means ****.

tom
K0TAR



No need for the vulgarities but you are correct, it will probably work.
Sorry didnt mean to bring out any hostility.

Jimmie

"Jimmie D" wrote in message
...

"Tom Ring" wrote in message
. ..
Jimmie D wrote:

"James" wrote in message
. ..

Dave, as stated in my OP, this is a 5/8 wave antenna. It is the
antenna
that I have bought and that I will use temporarily. This will be for a
very
temporary use, and I agree with your suggestion about a marine 1/2 wave,
which I will do later on.

My question is "about" how much to trim for 156 mhz use. I will use
an
SWR meter to get it right on spot, but I would like a feel for how much
to
trim. It is tricky to calculate , even using the "468" formula,
because of it being base-loaded.

73 de Jim K4PYT




Triming alone want do it, the base is designed to match the 5/8 2m to 50
ohms. Unless you can also figure out a way to modify the matching
network you cant do it.

B as in B, S as in S. It is plenty close enough to work just fine with a
little trimming.

And B means Bull, and S means ****.

tom
K0TAR



No need for the vulgarities but you are correct, it will probably work.
Sorry didnt mean to bring out any hostility.

Jimmie


Anyway, I was kind of thinking keeping it as a 5/8th's, I guess I am guilty
of having a one track mind. I agree with Tom that the hamstick will probably
resonate but cut somewhat shorter than a 5/8ths to make up for the extra
wire the 2 meter matching coil has. You will probably wind up with a 9/16ths
antenna |. If memory serves the hamstick does not use a tapped coil
matching network, just a series coil. I have tried cutting one of tapped
coil types for 153Mhz and was barely able to get it to work at with an
acceptable SWR, good luck

Jimmie

Jimmie D wrote:
I agree with Tom that the hamstick will probably
resonate but cut somewhat shorter than a 5/8ths to make up for the extra
wire the 2 meter matching coil has.

Hamsticks usually have an adjustable stinger. Can
the stinger be adjusted from longest to shortest
and those two resonant frequencies be measured?
Is this the 9007 "Mobile Colinear Antenna" from
Lakeview? They don't say it is 5/8WL.
--
73, Cecil http://www.w5dxp.com