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Author Topic: Need indoor/portable antenna suggestions.  (Read 1570 times)
VA6SGI
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Posts: 6




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« on: December 24, 2011, 10:03:56 PM »

Hi Folks,

I've recently picked up my first HF rig while I study to uprade my license (basic in Canada).  It's a Yaesu FT-890.  I'd like to be able to monitor the HF bands in the meantime but don't have an antenna other than a 30ft piece of copper wire I have been shoving into the antenna jack on the back of the radio which is producing less than satisfactory results.  All I have been able to pick up is a time signal and some CB'ers.

What I would like is an antenna that is quick to set up, takes up as little space as possible and is relatively portable.  I know it's a tall order, but I am moving in the next couple of months and don't want to make any kind of permanent installation at my current rental property.  Also I will be monitoring only for a while so I don't need something that will be efficent for transmitting on all bands, in fact I would be happy to be able to monitor and eventually transmit on 40-10m in the interest of keeping the antenna smaller.

Also plan on taking the radio on car camping trips or day trips outside the city in search of some elevation.

I am thinking buddipole or buddistick but they seem a little large for indoor use which, at least for now, is a consideration.

I've seen end fed antennas all over eBay that look like the would fit the bill ergonomically but I am unsure of how they actually perform.

Any suggestions are appreciated.

Cheers!

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WB6BYU
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Posts: 13342




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« Reply #1 on: December 25, 2011, 12:06:40 AM »

For just receiving, your 30 foot wire should be quite adequate if it is stretched out rather than
being rolled up in a ball.

Does your problem appear to be lack of signals overall, or a high noise level that is masking
signals?  The former might be due to the building materials.  The latter may be due to noise
from a florescent lamp, computer network or router, TV power supply, battery charger, or
any of a number of other electrical noise sources in the modern home.
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VA6SGI
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Posts: 6




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« Reply #2 on: December 25, 2011, 10:06:31 AM »

Certainly the noise level is very high.  I figure due to the exposed wire being indoors its hard to tell if there are any signals at all.  I think getting some hamsticks and using the radio mobile might be a good temporary solution but I would like a more flexible antenna solution.

Thanks.
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WB6BYU
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Posts: 13342




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« Reply #3 on: December 25, 2011, 11:00:01 AM »

Making a wire dipole and stringing it from a tree in a local park is a great way to get on the air
with an efficient antenna.
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VA6SGI
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Posts: 6




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« Reply #4 on: December 25, 2011, 09:30:53 PM »

I think thats what I will do.  Is it correct to assume a 1/2 wire dipole for 20m will act as a regular dipole on 10?
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K5BJS
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Posts: 50




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« Reply #5 on: December 26, 2011, 07:51:15 AM »

Look into a magnetic loop for indoors.  The MFJ-933 and MFJ-935B tuners use an MFJ-19 capacitor while the MFJ-936B tuner uses an MFJ-23 capacitor.  I would run QRP indoors though.   Smiley

http://www.mfjenterprises.com/antennatalk6.php
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WB6BYU
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Posts: 13342




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« Reply #6 on: December 26, 2011, 08:49:38 AM »

Quote from: VA6SGI

Is it correct to assume a 1/2 wire dipole for 20m will act as a regular dipole on 10?




No, at least not if I understand your question correctly.

A half-wave dipole for 20m would be a full-wave dipole for 10m.  While on 20m it has
a low SWR using coax feed, a full-wave center-fed wire has a high impedance, so the
SWR may be 20 : 1 or worse on 10m.

There are three simple solutions for multi-band use:

First, use separate dipole wires for each band with a common feedpoint and coax.  This
is what I do with my portable dipole kits - I carry a length of coax attached to a center
insulator with wing nuts, along with dipole wires (2 x 1/4 wave) for each band I am
likely to want to operate.  Each time I set it up I attach some combination of wires
to the insulator depending on band conditions, time of day, space available, etc.  Sometimes
it covers 80m through 10m, sometimes just one band such as 20m or 10m.  I tie the ends
of the wires on each side to different points to separate them somewhat, and it allows
me to work multiple bands without a tuner.

The second method is to put up an antenna (such as a 20m dipole) and feed it with twinlead
or other low-loss balanced line to a tuner.  With that you can operate on any frequency for
which the antenna is long enough (minimum length for good efficiency is around 1/3 wavelength.)
This is much simpler to install, being only a single set of wires, and allows many more bands
(especially for 20 / 17 / 15 / 12 / 10m) but requires a wide-range tuner.

A third method is to use some sort of multi-band antenna where the antenna is designed to
have a low SWR on some number of bands.  Examples would be a trap dipole or vertical, OCFD,
G5RV, etc.  This takes more work and adjustment to build (or more expense to buy) and some
types only work well over a limited number of bands, but they work well for some people. 
Certainly if you were only interested in 10m and 20m, a trap dipole might be a good choice,
as it would allow operation of both bands with coax feed without a tuner and only a single
wire to string up.
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W1JKA
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Posts: 1773




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« Reply #7 on: December 27, 2011, 07:52:01 AM »

       Simple solution but cost money,PAR end fedz for your particular band or bands.My cheap solution a few end half waves with a cheap homebrew coupler(AA5TB.website for info).These will work well indoors(better hanging out a window)and of course excellent for easy outside portable use and no need to mess with cumbersome tuners or long coax feed lines.
« Last Edit: December 27, 2011, 08:05:01 AM by W1JKA » Logged
N8TI
Member

Posts: 115




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« Reply #8 on: December 27, 2011, 08:22:07 AM »

I agree with W1JKA. Go to Home Depot and get 33 feet of lamp cord, i.e., normal 110 volt line. Rip it apart do you have two pieces 33 feet long. Hook one to your rig's ground with the wing but that is likely there and insert the other end in the center of the antenna jack. Then hang up the center conductor portion or better yet throw it out the window, drape it over some bushes, whatever. The ground (counterpoise), just lay it out in a different direction from the antenna element. You should be able to hear fine. It would be nice if you could get a solid connection into the antenna, but it is ok as long as you hear.

Sometimes bare copper wire is varnished, so make sure your's is not. Take a nail file or sandpaper to it so you get a good connection.

Joe
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WX7G
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Posts: 6136




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« Reply #9 on: December 28, 2011, 04:51:57 AM »

The MFJ loop tuners are good for making small (about 1/4 wavelength circumference) loops with fair efficiency.
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KC5CQW
Member

Posts: 98




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« Reply #10 on: December 30, 2011, 11:24:24 AM »

MFJ has a new telescopic 17' portable vertical with base loading coil, counterpoise wires and a simple mount for about $100.
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K9WJL
Member

Posts: 183




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« Reply #11 on: December 30, 2011, 12:38:54 PM »

Consider one of the bigger mobile screwdriver setups, Like the High Sierra's, or Tarheels. They work pretty good on the mobiles, and should work even better fixed/portable with some radials.
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