Looking for reference: modifying CB whip for lower bands
 

Some years ago I read a magazine article on modifying a base-loaded CB
magnetic mount antenna for lower bands. These antennas have a coaxial
mount -- the bottom of the coil is grounded and the feed connection is
made to a tap on the coil. By rewinding the loading coil (more turns of
smaller wire) and properly connecting the tap you can get an antenna
that is resonant and provides a good match -- as I recall, the article
described doing this for bands as low as 40 meters.

I made one that worked well on 15 meters. I know it's not as efficient
as a bigger antenna, but it is easy to put it on a car roof for casual
operation and you can go under bridges that you'd have to detour around
with a full size antenna.

Does anyone remember this, can anyone send me a reference, or, better,
a photocopy of the article? It was probably in 73, it could also have
been in CQ or Ham Radio. Somewhere along the way I decided I just
couldn't save all my old magazines, they are all long gone mow.

73, Al, N1AW

Looking for reference: modifying CB whip for lower bands
 

On 21 Nov 2006 11:15:13 -0800, Al, N1AW wrote:

Some years ago I read a magazine article on modifying a base-loaded CB
magnetic mount antenna for lower bands. These antennas have a coaxial
mount -- the bottom of the coil is grounded and the feed connection is
made to a tap on the coil. By rewinding the loading coil (more turns of
smaller wire) and properly connecting the tap you can get an antenna
that is resonant and provides a good match -- as I recall, the article
described doing this for bands as low as 40 meters.

I made one that worked well on 15 meters. I know it's not as efficient
as a bigger antenna, but it is easy to put it on a car roof for casual
operation and you can go under bridges that you'd have to detour around
with a full size antenna.

Does anyone remember this, can anyone send me a reference, or, better,
a photocopy of the article? It was probably in 73, it could also have
been in CQ or Ham Radio. Somewhere along the way I decided I just
couldn't save all my old magazines, they are all long gone mow.

73, Al, N1AW

Is this for a mobile antenna?
VE3JUA

Looking for reference: modifying CB whip for lower bands
 

Eskay wrote:
Al, N1AW wrote:

Some years ago I read a magazine article on modifying a base-loaded CB
magnetic mount antenna for lower bands.
[snip]

Is this for a mobile antenna?

I guess I should have said so, yes, such antennas are meant for roof-
or trunk-mounting on a vehicle.

- Al

Modifying CB whip for HF bands
 

"Al, N1AW" wrote in message
oups.com...
Eskay wrote:
Al, N1AW wrote:

Some years ago I read a magazine article on modifying a base-loaded CB
magnetic mount antenna for lower bands.
[snip]

Is this for a mobile antenna?

I guess I should have said so, yes, such antennas are meant for roof-
or trunk-mounting on a vehicle.

- Al


Al -

There were a large number of articles during the 1970s on this subject (73,
CQ, Ham Radio magazines) -- as well as conversion of CB mobile whips to
2-meter 5/8 wave antennas.

Although a significant amount of information is electronics (Internet
accessible) -- there is also a considerable amount that is still available
through your local library. At best, you may find an electronic index of
the materials.

For example, Herb Freidman wrote a number of articles in Popular
Electronics, Electronics Illustrated as well as the amateur radio
journals -- yet I have to go through my local library's magazine and
periodicals request network -- to get reprints of his Electronics
Illustrated articles and materials.

w9gb

Modifying CB whip for HF bands
 

I made 3 of these antennas many years ago - 10m,15m and 20m - and use
them almost daily. They are modified Radio Shack 5/8 wave base-loaded.
They work very well, and are only about 2 feet tall. It involved
re-wiring just the coil. I use a trunk-lip mount, but they also work
with a magnetic mount. I don't have the article anymore, but I believe
it was in QST (maybe around the mid-80's) .

Jeff

On Wed, 22 Nov 2006 18:27:15 -0600, "w9gb"
wrote:

"Al, N1AW" wrote in message
roups.com...
Eskay wrote:
Al, N1AW wrote:

Some years ago I read a magazine article on modifying a base-loaded CB
magnetic mount antenna for lower bands.
[snip]

Is this for a mobile antenna?

I guess I should have said so, yes, such antennas are meant for roof-
or trunk-mounting on a vehicle.

- Al


Al -

There were a large number of articles during the 1970s on this subject (73,
CQ, Ham Radio magazines) -- as well as conversion of CB mobile whips to
2-meter 5/8 wave antennas.

Although a significant amount of information is electronics (Internet
accessible) -- there is also a considerable amount that is still available
through your local library. At best, you may find an electronic index of
the materials.

For example, Herb Freidman wrote a number of articles in Popular
Electronics, Electronics Illustrated as well as the amateur radio
journals -- yet I have to go through my local library's magazine and
periodicals request network -- to get reprints of his Electronics
Illustrated articles and materials.

w9gb

Modifying CB whip for HF bands
 

Jeff L wrote:
I made 3 of these antennas many years ago - 10m,15m and 20m - and use
them almost daily. They are modified Radio Shack 5/8 wave base-loaded.
They work very well, and are only about 2 feet tall. It involved
re-wiring just the coil. I use a trunk-lip mount, but they also work
with a magnetic mount. I don't have the article anymore, but I believe
it was in QST (maybe around the mid-80's) .

Thanks Jeff! I'm pretty sure the article I was thinking of did not
come from QST. Seib, VE3JUA found and sent to me an article from 73,
Sept 91, pp. 26-28 titled "Economical Mobile HF Antenna" which is
probably the one I remembered.

I'd also like to find a copy of the QST article. I used to have a
complete collection of QST back to the 70's but that went away too, I
just couldn't continue to store all my old magazines. The ARRL website
allows a search for articles, but in most cases the article text can't
be retrieved. I found a number of possibilities, but I can't tell from
the titles if one of them is really the one you mentioned. If anyone on
the list can help to pin this down I'd appreciate it. At this point
it's not so much for the sake of the information, but just to be able
to properly give credit in an article I may write about some of my own
mobile antenna experiments.

Both the 73 article and the QST article you refer to mention modifying
new antennas from Radio Shack, in one case a CB antenna and in the
other case a 5/8 wave 2 meter antenna. Both of these types of antenna
typically use a coaxial base with a tapped loading coil, and so either
is a good starting point for a modification project. However, for me
the attractiveness of the technique is that it can also be used with
used CB antennas that can be found for just a dollar or two at
neighborhood tag sales. They are not as easy to find as they used to
be, but I'm sure there are still a lot of them in garages and attics.

Modifying CB whip for HF bands
 

"Al, N1AW" wrote in message
ups.com...
Jeff L wrote:
I made 3 of these antennas many years ago - 10m,15m and 20m - and use
them almost daily. They are modified Radio Shack 5/8 wave base-loaded.
They work very well, and are only about 2 feet tall. It involved
re-wiring just the coil. I use a trunk-lip mount, but they also work
with a magnetic mount. I don't have the article anymore, but I believe
it was in QST (maybe around the mid-80's) .

Thanks Jeff! I'm pretty sure the article I was thinking of did not
come from QST. Seib, VE3JUA found and sent to me an article from 73,
Sept 91, pp. 26-28 titled "Economical Mobile HF Antenna" which is
probably the one I remembered.

I'd also like to find a copy of the QST article. I used to have a
complete collection of QST back to the 70's but that went away too, I
just couldn't continue to store all my old magazines. The ARRL website
allows a search for articles, but in most cases the article text can't
be retrieved. I found a number of possibilities, but I can't tell from
the titles if one of them is really the one you mentioned. If anyone on
the list can help to pin this down I'd appreciate it. At this point
it's not so much for the sake of the information, but just to be able
to properly give credit in an article I may write about some of my own
mobile antenna experiments.

Both the 73 article and the QST article you refer to mention modifying
new antennas from Radio Shack, in one case a CB antenna and in the
other case a 5/8 wave 2 meter antenna. Both of these types of antenna
typically use a coaxial base with a tapped loading coil, and so either
is a good starting point for a modification project. However, for me
the attractiveness of the technique is that it can also be used with
used CB antennas that can be found for just a dollar or two at
neighborhood tag sales. They are not as easy to find as they used to
be, but I'm sure there are still a lot of them in garages and attics.


The best antennas for these modifications were the Antenna Specialists
loading coils (about 2 to 3 inches tall) Motorola also sold these under
their brand name for a few years.
The ASPS177 was that typical model.
http://wildcard.pctel.com/images_pro...sp553_p473.pdf

You can also find these surplus as many public services are moving to higher
frequencies (and away from 150 -172) in some areas. I also find ones with
broken whips, etc. The whip replacements (K41 for this model) are available
from either Tower Electronics or Antenna Specialists (PCTEL company).
http://www.antenna.com/product_overv...0459&styleid=6

w9gb

Modifying CB whip for HF bands
 

another take on modified antennas ...

I have a magmount dual-bander on the roof of my mini van. It terminates in
a BNC for use on an HT.

The stock AM/FM car radio antenna went bad with an open shield and it was
picking up lots of noise. I pulled the radio far enough out of the dash to
unplug the bad antenna. I plugged in a Moto-to-BNC adapter and dropped a
short piece a piece of RG-58 down to where I could mate it with the mag
mount's cable connector. Works great. Quick disconnect BNC lets me go back
and forth as necessary.

BONUS: For our regular trips across the desert, I have an extra-long whip
element that I substitute in the magmount base. I lose the match at 440 but
it still works like a champ for 2M or AM/FM, my choice.

I have not played with diplexing as swapping connectors seems too easy.
Yeah, a switch maybe ... someday.