Backpack Antenna, help please
 

Hi All

I want to construct a backpack antenna that can be left on my rucksack and
used when walking.

The plan is to have a FT817 on my waist and the antenna fitted to the
rucksack. I been playing with a mobile antenna today and can not get the SWR
down without trailing a wire. I don't want a wire trailing behind me.

Any ideas for a 2m antenna that can be left on a rucksack when walking and
used for transmittion. Height is not a major problem but it has to realistic
and robust.

Thanks
Steve

--
The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk
The UK Weather Guide" @ www.ukstorms.com

Backpack Antenna, help please
 

Hi Steve

Many years ago I use to do early morning exercise walks in the mountain
range immediately to the west of Sydney's metro area. As soon as I
dropped off the western mountain edge all rptr sigs were still audible
on my IC2A but they couldnt hear me.

I made up a 2M jpole out of 10mm aluminium and tied it to my backpack
with rope and/or rubber straps. The thing wobbled a bit but stayed more
or less vertical. The backpack was very floppy, a more rigid one would
have been better. There was about a 1/2 metre metal extension from the
base of the matching section to faciltate the rope binding. The thing
was about 1.3 metres max height above my head.

I also built a 10W PA running off 12 D cell NiCd's. Worked very well
until the constant battery pack flexing shorted something and the hot
wiring melted a hole through the backpack pocket it was sitting in!

If the extra matching section length is an issue you might find other
ways of end/voltage feeding the 1/2 wave. Lots of possibilities here.
You could also use a fibreglass rod with 300 ohm ribbon tied to it in a
jpole or slim jim form. Handy in a region of low flying trees.

Height on LOS frequencies is everything . Getting the antenna above your
head will make a huge difference. Everyone thinks you are a
extraterrestrial visitor too!

Your present mobile antenna will need a counterpoise. (aka groundplane)
I suggest you discard the idea of using it unless you can get use to the
trailing 1/4 wave wire(s). Maybe it would work by mounting the antenna
on an extension so its base is about head height, then wrapping three
ground radials down the sides of the backpack. You could make it more
permanent by weaving the wire into the backpack itself.

Cheers Bob VK2YQA (in W5)

Steve - www.ukspeedtraps.co.uk wrote:
Hi All

I want to construct a backpack antenna that can be left on my rucksack and
used when walking.

Backpack Antenna, help please
 

TRY HF PACK WEB SITE
http://www.hfpack.com/

--
CL -- I doubt, therefore I might be !


"Steve - www.ukspeedtraps.co.uk" wrote in message
...
Hi All

I want to construct a backpack antenna that can be left on my rucksack and
used when walking.

The plan is to have a FT817 on my waist and the antenna fitted to the
rucksack. I been playing with a mobile antenna today and can not get the
SWR down without trailing a wire. I don't want a wire trailing behind me.

Any ideas for a 2m antenna that can be left on a rucksack when walking and
used for transmittion. Height is not a major problem but it has to
realistic and robust.

Thanks
Steve

--
The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk
The UK Weather Guide" @ www.ukstorms.com

Backpack Antenna, help please
 

A half wave antenna such as the AEA Hot Rod or the MFJ copy of it works
well with no ground plane or trailing wire. The models I mentioned are
telescoping, so you can collapse them when not walking.

Roy Lewallen, W7EL

Steve - www.ukspeedtraps.co.uk wrote:
Hi All

I want to construct a backpack antenna that can be left on my rucksack and
used when walking.

The plan is to have a FT817 on my waist and the antenna fitted to the
rucksack. I been playing with a mobile antenna today and can not get the SWR
down without trailing a wire. I don't want a wire trailing behind me.

Any ideas for a 2m antenna that can be left on a rucksack when walking and
used for transmittion. Height is not a major problem but it has to realistic
and robust.

Thanks
Steve

Backpack Antenna, help please
 

"Roy Lewallen" wrote in message
...
A half wave antenna such as the AEA Hot Rod or the MFJ copy of it works
well with no ground plane or trailing wire. The models I mentioned are
telescoping, so you can collapse them when not walking.

Roy Lewallen, W7EL

Steve - www.ukspeedtraps.co.uk wrote:
Hi All

I want to construct a backpack antenna that can be left on my rucksack
and used when walking.

The plan is to have a FT817 on my waist and the antenna fitted to the
rucksack. I been playing with a mobile antenna today and can not get the
SWR down without trailing a wire. I don't want a wire trailing behind me.

Any ideas for a 2m antenna that can be left on a rucksack when walking
and used for transmittion. Height is not a major problem but it has to
realistic and robust.

Thanks
Steve


Many thanks for the help, some good usefull stuff.
Thanks
Steve

The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk
The UK Weather Guide" @ www.ukstorms.com

Backpack Antenna, help please
 

2m antenna?

-Simple!

Cut a piece of wire, 1/4 wave long.

Solder wire to inner lead of the end of a coaxial cable.

Find a stick of wood, plastic or fiberglass, at least 3/4 wl long.

Tape wire and coax to stick.

Fix stick to rucksack, so that the antenna wire is as high as possible.

Connect coax to radio.

That's it!


73 de Hans, SM3PXG




Steve - www.ukspeedtraps.co.uk wrote:

Hi All

I want to construct a backpack antenna that can be left on my rucksack and
used when walking.

The plan is to have a FT817 on my waist and the antenna fitted to the
rucksack. I been playing with a mobile antenna today and can not get the SWR
down without trailing a wire. I don't want a wire trailing behind me.

Any ideas for a 2m antenna that can be left on a rucksack when walking and
used for transmittion. Height is not a major problem but it has to realistic
and robust.

Thanks
Steve

Backpack Antenna, help please
 

"HS" wrote in message
...
2m antenna?

-Simple!

Cut a piece of wire, 1/4 wave long.

Solder wire to inner lead of the end of a coaxial cable.

Find a stick of wood, plastic or fiberglass, at least 3/4 wl long.

Tape wire and coax to stick.

Fix stick to rucksack, so that the antenna wire is as high as possible.

Connect coax to radio.

That's it!


73 de Hans, SM3PXG



Thanks for that, so a 1/4 wave does not need a counterpoise then?

Steve

Backpack Antenna, help please
 

Steve - www.ukspeedtraps.co.uk wrote:
Thanks for that, so a 1/4 wave does not need a counterpoise then?

Strip 1/4WL of insulation from the coax. Fold the outside
braid back along the coax. That will leave you 1/4WL of
center conductor exposed (you can leave the center
insulation in place) and the braid will provide the
other half of the antenna which should be insulated
to avoid backpacking RF burns. Kraus calls such a
"vertical 1/2WL sleeve antenna. On edge it looks like:

-------------------+
-------------------------------+ 1/4WL
================================================== ==
-------------------------------+
-------------------+
1/4WL
--
73, Cecil http://www.qsl.net/w5dxp

Backpack Antenna, help please
 

"Cecil Moore" wrote in message
m...
Steve - www.ukspeedtraps.co.uk wrote:
Thanks for that, so a 1/4 wave does not need a counterpoise then?

Strip 1/4WL of insulation from the coax. Fold the outside
braid back along the coax. That will leave you 1/4WL of
center conductor exposed (you can leave the center
insulation in place) and the braid will provide the
other half of the antenna which should be insulated
to avoid backpacking RF burns. Kraus calls such a
"vertical 1/2WL sleeve antenna. On edge it looks like:

-------------------+
-------------------------------+ 1/4WL
================================================== ==
-------------------------------+
-------------------+
1/4WL
--
73, Cecil http://www.qsl.net/w5dxp

In that case I do that, and feed it all up the inside of the top element of
a fishing pole I also use for SOTA work with a small beam. I can then seal
it in with aradite.
Thanks again
Steve