I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max

wrote in message
ps.com...
I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max


General rule: If you are willing to mess with an antenna for long enough to
get the VSWR nice and low at some freq, it will probably perform well.
http://www.mfjenterprises.com/produc...prodid=MFJ-842 is a VSWR meter
that will help you with that.
(http://www.mfjenterprises.com/produc...prodid=MFJ-864 will do HF,
also -- perhaps a better buy than two separate units.) Not everyone likes
MFJ.

As to your antenna, what form will it take? How will you use it? Will it
mount directly onto the antenna jack on the radio or will it be on the end
of a length of coax? Up on a stick? Does it need to be directional, as for
service in the far boonies or for a t-hunt?

I have built several 70cm antennas, including two j-poles out of copper
pipe. I also built two ground-plane quarter-wave antennas; one was a
serious one for hoisting aloft with fishing line. The other one I built
directly on/into an old hard-hat as a novelty. I used a BNC panel-mount
jack as the basic structure of both of these antennas, with whip and radials
sprouting from the jack. I kept messing with the length, angle and shape of
the radials until I had a low VSWR. These antennas weren't tested under
extreme conditions, but they did a fine job on the local repeaters. (The
hard-hat antenna was operated on low power; why risk compounding the
existing "drain bamage"?)

If it needs to be super-light for portability, a wire j-pole out of #10 or #
12 AWG copper wire would seem workable. Feed it with a short length of coax
and you're golden. A j-pole out of TV-twinlead is also a possibility; I've
made a few for 2m, encapsulating them in PVC pipe, but never one for 70cm.
(I smell a project.) http://cs.yrex.com/ke3fl/prgms/JPOLEFRM.HTM and click
j-pole calculations.

Look a some commercial designs and say, "Oh, I can copy that with a stick
and some coat hangers." You probably can.

"Sal"

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wrote:
I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max


I have found tons of information on the web about building antennas.
Here is just a few links.

http://www.mattstuff.nq.nu/antennas/quarter-wave.html

http://www.arrl.org/tis/info/antproj.html

http://www.hamuniverse.com/antennas.html

Jim
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wrote in message
ps.com...
I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max


I made a helical talkie antenna once from a piece of rubber rod, some wire,
shrink sleeving and a connector. I don't have any detailed constuction
dimensions. But the tuning involved pulling the end of the wire from the
shrink sleeving, and snipping off small sections of the wire while measuring
field strength. Several iterations were required, but it worked.

On Oct 30, 8:51 pm, wrote:
I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max

One super simple antenna can be built using a BC to SO-239
adapter. Stick a 1/4 wave length of thick wire or rod that will fit
snug into the SO 239 end hole of the adapter. Screw onto radio.
Presto! Instant antenna. You can change bands too if you change
the rod or wire to another one of different length.
MK

wrote in message
ups.com...
On Oct 30, 8:51 pm, wrote:
I am looking for plans to build some 70cm antennas for my handheld
radios. Cannot find much on the net. Has anybody on this forum built
their own, if so, how did they perform?
Any suggestions or pointers would be appreciated.
Cheers
Max

One super simple antenna can be built using a BC to SO-239
adapter. Stick a 1/4 wave length of thick wire or rod that will fit
snug into the SO 239 end hole of the adapter. Screw onto radio.
Presto! Instant antenna. You can change bands too if you change
the rod or wire to another one of different length.
MK


In the 1980's, Bruce Brown W6TWW came up with a similiar scheme for 2M using
thick copper wire in a BNC connector. Half way up the rod, the wire was
shaped into a coil. On top of the wire was a copper circular plate for a top
hat. The antenna was compact, worked well, and of course was an eye-catcher.
Maybe some gurus can model it for dimensions and you can try it out.

Lamont

Thanks to all that replied. What I am wanting to build is an antenna
that will replace the "rubber duckie" one that came with the radio. It
is a 2m/70 cm hand held and I found when I replaced the original
antenna with a telescoping one on 2m my transmitting distance on 2m
improved dramatically. So I am trying to do the same thing on 70cm. I
would like to make an antenna that will connect directly to the BNC
socket on the radio. Not one that is connected to coax and the antenna
erected higher or whatever. I will probably just try a 1/4 wave length
connected to the centre of a BNC plug and see how it goes.
Cheers
Max

wrote in message
oups.com...
Thanks to all that replied. What I am wanting to build is an antenna
that will replace the "rubber duckie" one that came with the radio. It
is a 2m/70 cm hand held and I found when I replaced the original
antenna with a telescoping one on 2m my transmitting distance on 2m
improved dramatically. So I am trying to do the same thing on 70cm. I
would like to make an antenna that will connect directly to the BNC
socket on the radio. Not one that is connected to coax and the antenna
erected higher or whatever. I will probably just try a 1/4 wave length
connected to the centre of a BNC plug and see how it goes.
Cheers
Max


Proceed, certainly. But know that while the ever-present rubber duckie is a
serious compromise at 2m, it is more nearly appropriate for 70 cm. Thus,
improvement over the rubber duck is more likely to be seen at 2m than at
70cm.

You might try using a small capacity hat -- at the risk of poking yourself
with it, so be careful, there.