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Author Topic: Super portable antenna  (Read 3800 times)
KF7GTU
Member

Posts: 36




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« on: January 20, 2012, 08:30:29 AM »

Hi folks... Smiley

I have heard it said that before the rig must come the antenna. Smiley

I will keep it short... I would like a couple ideas for antennas that can be erected in less than 30 minutes inside of a motel/hotel room for QRP HF action. I thought this might be a tall order until I found this:

http://www.universal-radio.com/catalog/hamantm/5578.html

I am wondering if this antenna is worth the investment, or other ideas you may have.

Also, I love the look/sound of this antenna (connected to the IC-703) but cannot find suitable plans:

http://www.youtube.com/watch?v=NC3SwMilWvo

I have yet to decide on a rig or exactly what bands I would like to work on HF (40m and 10m possibly?). However, I will be happier with the portability of the antenna and maybe choosing bands from that aspect. For me, portability is key.

Thanks again folks... Smiley

Jason
Bandon, Oregon
KF7GTU
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W1JKA
Member

Posts: 1777




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« Reply #1 on: January 20, 2012, 10:09:40 AM »

  Check out the PAR end fedz halfwave antennas,or better yet make your own efhw with a homebrew coupler.See (www.AA5TB ) website
« Last Edit: January 20, 2012, 10:14:16 AM by W1JKA » Logged
WX7G
Member

Posts: 6146




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« Reply #2 on: January 20, 2012, 10:58:23 AM »

The price of that multband antenna is certainly right. One resonant radial for the band of interest and you are on the air.

It should work well on 20 meters and up.
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WB6BYU
Member

Posts: 13353




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« Reply #3 on: January 20, 2012, 12:36:31 PM »

Operation inside a building is always tricky.  You don't know how the wiring / ducting
in the walls will affect the antenna, and performance will be greatly dependent on
the building materials used.  Being able to get an antenna outside - putting it on your
balcony, sticking it out a window, or running coax out to an antenna on your car - is
likely to give much better performance.  Hotel rooms are often plagued with electrical
noise, making it difficult to hear much of anything.

It isn't difficult to wind a loading coil to use with a telescoping whip of whatever length
you can find:  there are many such designs available, both commercial and home-made.
For use in a hotel room, you'll need to be able to work in a height less than 8', and 6' for
a vertical is probably more practical (to avoid proximity to the ceiling, which may contain
wiring, etc.)  Efficiency of such an antenna can be reasonable on 20m through 10m, but
drops on the lower frequencies.  You'll need at least one radial for each band you are
going to operate, which can be laying on the floor.

The most successful operation I've managed from a motel was where I could step out
on the balcony on the top floor and toss a wire over the peak of the roof.  Another
time I made a grappling hook out of a wire coat hanger and tossed it out the window
into the rain gutter across the alley.  If the window frames are aluminum they are
often all bonded together and make a good ground plane for a whip antenna stuck out
the window.

Unfortunately, many hotel windows don't open, and you need to take a different
approach.  For 10m I'd try a dipole strung across the room - it certainly is cheap
and can be made from light wire.  You'll either need adjustable ends or a tuner,
however, as you can't count on the resonant frequency when installed indoors.

Where you can't get a full length antenna, you can fold the ends around.  A small
antenna with the ends already folded up is the "Notebook Antenna":
http://www.n5ese.com/notebk_ant.htm
Probably the simplest approach is to make such an antenna that resonates close
to 40m and feed it with twinlead to a tuner - that should work up through 10m.

Another option is some sort of small "magnetic" loop antenna.  Here is a homebrew
example:  http://www.qsl.net/7n3wvm/mag-loop.html, and there are also
commercial ones available.  Such an antenna should give good results on 20 - 10m,
and some versions will tune as low as 40m, though efficiency will be lower.
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KF7GTU
Member

Posts: 36




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« Reply #4 on: January 20, 2012, 01:37:56 PM »

 Check out the PAR end fedz halfwave antennas,or better yet make your own efhw with a homebrew coupler.See (www.AA5TB ) website

Thanks! I'll check it out now...

Take care...

Jason
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KF7GTU
Member

Posts: 36




Ignore
« Reply #5 on: January 20, 2012, 01:46:50 PM »

The price of that multband antenna is certainly right. One resonant radial for the band of interest and you are on the air.

It should work well on 20 meters and up.


Well, it seems to get pretty decent remarks from the folks here @ eHam. I might just do it. I'll be looking into it more.

Thanks!

Jason
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KF7GTU
Member

Posts: 36




Ignore
« Reply #6 on: January 20, 2012, 01:48:39 PM »

Operation inside a building is always tricky.  You don't know how the wiring / ducting
in the walls will affect the antenna, and performance will be greatly dependent on
the building materials used.  Being able to get an antenna outside - putting it on your
balcony, sticking it out a window, or running coax out to an antenna on your car - is
likely to give much better performance.  Hotel rooms are often plagued with electrical
noise, making it difficult to hear much of anything.

It isn't difficult to wind a loading coil to use with a telescoping whip of whatever length
you can find:  there are many such designs available, both commercial and home-made.
For use in a hotel room, you'll need to be able to work in a height less than 8', and 6' for
a vertical is probably more practical (to avoid proximity to the ceiling, which may contain
wiring, etc.)  Efficiency of such an antenna can be reasonable on 20m through 10m, but
drops on the lower frequencies.  You'll need at least one radial for each band you are
going to operate, which can be laying on the floor.

The most successful operation I've managed from a motel was where I could step out
on the balcony on the top floor and toss a wire over the peak of the roof.  Another
time I made a grappling hook out of a wire coat hanger and tossed it out the window
into the rain gutter across the alley.  If the window frames are aluminum they are
often all bonded together and make a good ground plane for a whip antenna stuck out
the window.

Unfortunately, many hotel windows don't open, and you need to take a different
approach.  For 10m I'd try a dipole strung across the room - it certainly is cheap
and can be made from light wire.  You'll either need adjustable ends or a tuner,
however, as you can't count on the resonant frequency when installed indoors.

Where you can't get a full length antenna, you can fold the ends around.  A small
antenna with the ends already folded up is the "Notebook Antenna":
http://www.n5ese.com/notebk_ant.htm
Probably the simplest approach is to make such an antenna that resonates close
to 40m and feed it with twinlead to a tuner - that should work up through 10m.

Another option is some sort of small "magnetic" loop antenna.  Here is a homebrew
example:  http://www.qsl.net/7n3wvm/mag-loop.html, and there are also
commercial ones available.  Such an antenna should give good results on 20 - 10m,
and some versions will tune as low as 40m, though efficiency will be lower.

This seems like better than excellent advice. I just looked at the notebook antenna. REMARKABLE. At least, in theory. I'll just have to try that out, you have really helped me to get a great idea for my next antenna project.

Smiley

Jason
Bandon, Oregon
KF7GTU
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KATEKEBO
Member

Posts: 117




Ignore
« Reply #7 on: January 21, 2012, 07:36:14 PM »

PAR End Fedz EF-10/20/40 is certainly a great antenna but it requires open space.  From personal experience, it works best in vertical (or nearly vertical sloper) configuration, either hanging from a tall building, or using a nearby tree as support.  It can also be used horizontally, but for best results it needs to be hung at least 1/2 wavelength above the ground.

However the antenna that I use most for portable operations is Miracle Whip.  It's ultra portable, covers all HF and VHF bands, and it works.  I have made several 5000 miles contacts with the Miracle Whip, using only 5W (Yaesu FT-817), all in SSB phone.  Contacts up to 2000 miles are not particularly challenging, if propagation is good.  It works best for 10 and 15m, OK-ish for 20m.  For 40m and lower frequencies it's basically a listening-only antenna, but ocassionally you can make QSOs on 40m up to few hundred miles.  For best results, you need a counterpoise, preferably 1/4-wavelength long.  Or, if you use the radio with an external power supply, the power cable works well as counterpoise if it's long enough and you keep it extended.  Given, you won't get "20 over 9" signal reports, but I have plenty "55's" and "56's" at distances of 4000 or 5000 miles.




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KB2FCV
Member

Posts: 1252


WWW

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« Reply #8 on: January 23, 2012, 01:55:48 PM »

For my KX1 I have a random length wire and a counterpoise. My wire is about 28 ft and I think the counterpoise is about 16 feet. I haven't tested deployment methods but from asking around, it seems a small weight or a water bottle and some mason twine allow for a quick and easy installation.

I've had poor to nil results in hotels with windows that don't open. Those places make great faraday cages. If I know I want to operate I tend to look for places with windows that open.
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HFHAM2
Member

Posts: 32




Ignore
« Reply #9 on: January 23, 2012, 10:57:02 PM »

Would recommend an MFJ 1780 "Box Fan" magnetic loop - 14 to 30 MHz.

Very portable but not waterproof.

Works like Gangbusters!

http://www.mfjenterprises.com/Product.php?productid=MFJ-1780

Alternatively, one of the MFJ Loop Tuners (e.g. MFJ-932 (20 Watts), MFJ-935B or MFJ-936B (150 Watts).

These'll work well on balconies but like someone else said, a lot of these hotel rooms are like Faraday Cages inside.
« Last Edit: January 23, 2012, 11:03:18 PM by HFHAM2 » Logged
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