"R. Scott" wrote in message
...
Have been looking around for plans for a 1/2 or 5/8 2 meter mobile antenna
to play with. I have several Iron Horse whips I no longer use
and thought id use them as a starting point for a 5/8 2 meter mobile
whip I could use on my CB mount for most of the time. (I use the CB only
when our RV club travels as a group).


I did a ton of google/bing searches but have come up fairly empty. I know
I could buy one cheap but thats not what ham radio is about .

I have used several MFJ magmounts as the start-point of antenna building.
They stick on a metal car top, obviously, but they also stick on anything
else ferro-magnetic, like the lid of a can full of rocks (yes, I did) or an
old, discarded chassis slide (yes, again). Added counterpoise may be
required.

Check this before you buy ... but I think the item is the MFJ 1724B. The
base I used has the 3/8 inside thread you described and the MFJ threaded
insert can take a whip of any length -- just loosen the setscrew and replace
the existing whip with one of your choice or your design. The base thread
also accepts Hustler HF elements and maybe some others. Added physical
support may be required for HF elements.

BONUS: On my minivan, I often use a particular insert into which I
installed a long, untuned whip. When it's connected to the built-in car
radio instead of the stock vehicle antenna, that roof-mounted long whip is a
dynamite AM antenna on my long trips across the western desert.

"Sal"
(KD6VKW)

On 1/28/2014 1:25 AM, wrote:
On Monday, January 27, 2014 8:01:29 PM UTC-6, wrote:

With a 3/8x24 thread mount, I would just use a 1/4 wave.. So much

easier and better looking. Most loading/matching coil schemes are going

to look fairly ugly in a case like that as you usually can't enclose

them in anything.

Pondering.. About the only other easy way to make a 5/8 whip
that would screw into that mount would be to take a glass whip
and then rebuild it into a 5/8 for 2m. You would need to strip
the original wire, or at least partly, then wind a loading coil
at the base, and then pretty much straight up to make the
5/8 element.
That would work.. The reason I call the coil for the 5/8 a
loading coil, rather than matching coil, is the coil is
tuning the 5/8 whip to be a 3/4 wave electrically, which is
resonant. Some ground the coil, and tap at the best match.
But I prefer an ungrounded coil. Why? If it's ungrounded, it
can also be used on other bands. IE: a 1/4 wave whip on a lower
freq.. I used to use my 10m 5/8 ground planes on 30m as 1/4 waves.
But you can't do that with a grounded coil. Works fine ungrounded.






I will give that a try. Thanks for the discussion gents, let me clear
some things up that I should have posted from the start.

The Iron Horse Whips are loaded HF Whips, I have them for all the bands,
but I dont have a 706 anymore as I changed to a 746pro and that doesnt
do Mobile well. Plus I have several CB antenna whips as people give
them to me thinking I could use them HI. So I could easily go buy a
3/8x24 2 meter antenna I would rather experiment with the whips on a 5/8
loaded base.

Im in the Seattle area so most of the 2 meter repeaters are high up ...
not an issue with hitting them. I have not used my FT-1500 in a while
and thought I would see if anyone is on any more.

The vehicle is a 2011 F-350 and I have the Fender Mount CB. Like I said
I use it only for the RV runs. Thus I would like to experiment with one
of the whips to run a 2 meter. I could have easily did a 1/4 wave
vertical but thought that 5/8 would be better experiment.

the loaded 5/8 ungrounded as NM5K posted just might be what I need. I
was looking for how many turns of wire might do the trick. Problem is I
dont have a GDO to get the right turns so thats why I was hoping to
find someone whom ad done it before .

Anyway ... Ill start with 3/4 wave of wire and wrap the 1/2 wave section
in a coil and have the last 1/4 go vertical up the fiberglass ...

Ill let you know how it comes out.


Scotty W7PSK.

"R. Scott" wrote in message
...
On 1/28/2014 1:25 AM, wrote:

The vehicle is a 2011 F-350 and I have the Fender Mount CB. Like I said I
use it only for the RV runs. Thus I would like to experiment with one of
the whips to run a 2 meter. I could have easily did a 1/4 wave vertical
but thought that 5/8 would be better experiment.

the loaded 5/8 ungrounded as NM5K posted just might be what I need. I was
looking for how many turns of wire might do the trick. Problem is I dont
have a GDO to get the right turns so thats why I was hoping to find
someone whom ad done it before .


I saw an antenna similar to what you are wanting to do. I think it was 47
inches long. The coil will only be a few turns. I don't recall the number
of turns on the form for that antenna, but it was only about 2 or 3 turns.
I would start with 3 turns and check the swr and trim the turns for a low
swr.



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In message , Ralph
Mowery writes

"R. Scott" wrote in message
...
On 1/28/2014 1:25 AM, wrote:

The vehicle is a 2011 F-350 and I have the Fender Mount CB. Like I said I
use it only for the RV runs. Thus I would like to experiment with one of
the whips to run a 2 meter. I could have easily did a 1/4 wave vertical
but thought that 5/8 would be better experiment.

the loaded 5/8 ungrounded as NM5K posted just might be what I need. I was
looking for how many turns of wire might do the trick. Problem is I dont
have a GDO to get the right turns so thats why I was hoping to find
someone whom ad done it before .


I saw an antenna similar to what you are wanting to do. I think it was 47
inches long. The coil will only be a few turns. I don't recall the number
of turns on the form for that antenna, but it was only about 2 or 3 turns.
I would start with 3 turns and check the swr and trim the turns for a low
swr.

Most 5/8ths on 2m are more-or-less electrically 6/8th (=3/4) waves, but
with the first 1/8th being the coil. With mine, the whip is 50" long,
and the coil is 3.5 turns, 1" dia, appx 10 gauge well spread steel
spring, 1.75" long. The feed impedance over a flat groundplane (7"
magmount in the centre of the car roof) should be around 50 ohms,
whereas a 1/4 is more like 37 ohms. In most situations, I've not found
it remarkably better the a 1/4 wave (maybe a couple of dB on a good
day).
--
Ian

On Wednesday, January 29, 2014 11:15:17 AM UTC-6, R. Scott wrote:


Anyway ... Ill start with 3/4 wave of wire and wrap the 1/2 wave section

in a coil and have the last 1/4 go vertical up the fiberglass ...

That will be way too much coil, and not enough vertical.
I think a 5/8 for 2m is around 48-50 inches or so, depending on
freq. The coil will only be a few turns. If the converted base
loaded CB version is 5 turns, with the thinner glass whip form,
it would take just a few more turns. Like maybe 8 or so using a
thin glass whip form. You could hang a 5/8 length of wire from
something, and then wind a coil on a pencil or something about
the same dia as the whip to get an idea on the number of turns.
The vertical section up the glass must be the correct length.
IE: 48-50 inches. Otherwise it will not be a 5/8 whip.
With a 1/4 wave going up the whip, it's a 1/4 wave with a loading
coil at the base detuning it.

On 1/29/2014 9:25 AM, Ralph Mowery wrote:

"R. Scott" wrote in message
...
On 1/28/2014 1:25 AM, wrote:

The vehicle is a 2011 F-350 and I have the Fender Mount CB. Like I said I
use it only for the RV runs. Thus I would like to experiment with one of
the whips to run a 2 meter. I could have easily did a 1/4 wave vertical
but thought that 5/8 would be better experiment.

the loaded 5/8 ungrounded as NM5K posted just might be what I need. I was
looking for how many turns of wire might do the trick. Problem is I dont
have a GDO to get the right turns so thats why I was hoping to find
someone whom ad done it before .


I saw an antenna similar to what you are wanting to do. I think it was 47
inches long. The coil will only be a few turns. I don't recall the number
of turns on the form for that antenna, but it was only about 2 or 3 turns.
I would start with 3 turns and check the swr and trim the turns for a low
swr.

Thanks, My figuring was all wrong . Just so everyone knows, its a
standard Firestik wound loaded about 4ft long. So its not base loaded,
they distributed the coil from top to bottom (tighter winding at the top).

Ill experiment when I have time.

W7PSK

Ive experimented with many wire antennas over the years, but never
loading types. Thats why I came to the experts .

"R. Scott" wrote in message
...
On 1/29/2014 9:25 AM, Ralph Mowery wrote:

Thanks, My figuring was all wrong . Just so everyone knows, its a
standard Firestik wound loaded about 4ft long. So its not base loaded,
they distributed the coil from top to bottom (tighter winding at the top).

Ill experiment when I have time.

W7PSK

Ive experimented with many wire antennas over the years, but never loading
types. Thats why I came to the experts .


The antennas you have to start with are almost the opposit of what you want
to do. The ones you have are physically too short to be a 1/4 wave on the
low bands and need lots of wire to make up the differance. When used on 2
meters and above it is easy to go over 1/4 wave and still mout them on a
car. You may get some gain by doing this. To use the whips that have wire
wrapped around it for several feet on 2 meters, you will need to strip off
all the old wire and just run a single wire up the whip and put just a few
turns around the bottom to match it.

Always fun to expirment with what you have.



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On Thursday, January 30, 2014 2:03:04 PM UTC-6, Ralph Mowery wrote:

The antennas you have to start with are almost the opposit of what you want

to do. The ones you have are physically too short to be a 1/4 wave on the

low bands and need lots of wire to make up the differance. When used on 2

meters and above it is easy to go over 1/4 wave and still mout them on a

car. You may get some gain by doing this. To use the whips that have wire

wrapped around it for several feet on 2 meters, you will need to strip off

all the old wire and just run a single wire up the whip and put just a few

turns around the bottom to match it.



Always fun to expirment with what you have.

The glass whips do make a handy platform which is light.
All of my HF mobile antennas are plastic bugcatchers built
from various fire sticks, ham sticks, etc.
My main version is center loaded and 11 ft tall counting
the 5 ft whip attached to the 6 ft glass stick. When parked,
I can also add a solid 3 ft hustler mast below the glass stick
to raise the coil level to 8 ft, and a total of 14 ft tall.
Works all bands 80-10, and on the higher bands, I use
shorter "stinger" whips with the coil bypassed with a
jumper.
What is handy is I get bugcatcher performance with a much
lower weight, which makes it a lot easier to mount and use.

I've built the exact 2m 5/8 whip that I earlier described using a
glass whip. and is still around somewhere.. If I can find it,
it would tell me exactly how many turns the loading coil was on
the one I built. I remember on mine, the glass whip was a tad
bit short, and I had to add a short stinger to the top to get the
full 5/8 wave. I used it on the back of a Honda Accord for a
while.. I've still been too chicken to drill any holes in my
newer Toyota, and haven't run any radios from it yet.
If I want to run mobile, I have to use one of my old trucks. :|

wrote in message
...
On Thursday, January 30, 2014 2:03:04 PM UTC-6, Ralph Mowery wrote:

I've still been too chicken to drill any holes in my
newer Toyota, and haven't run any radios from it yet.
If I want to run mobile, I have to use one of my old trucks.

I have seen some clever mounts that slide into a trailer receiver. Some
home brew, some commercial.

"Sal"

On Friday, January 31, 2014 3:34:25 PM UTC-6, Sal M. O'Nella wrote:
wrote in message

...

On Thursday, January 30, 2014 2:03:04 PM UTC-6, Ralph Mowery wrote:



I've still been too chicken to drill any holes in my

newer Toyota, and haven't run any radios from it yet.

If I want to run mobile, I have to use one of my old trucks.



I have seen some clever mounts that slide into a trailer receiver. Some

home brew, some commercial.



"Sal"

There isn't much way to attach one of those on that car. There
is no real bumper per say, and underneath is just trunk floor,
which doesn't look too strong.
But even if I could do it, I'm not sure I would bother.
Hitch mounts are a horrible place to mount as far as performance.

I've pretty much given up trying to do anything with that car.
If I really had to have it, I'd drill a hole in the truck like
I did the Accord. But I found with that car, after a period of
using the antennas, the flexing and such sort of warped the
trunk lid a bit around the hole. And that was with it reinforced
underneath with a steel plate. I don't want to risk that with this
one. I'd pondered maybe using a trunk lip mount, but even that
makes me nervous.