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Author Topic: indoor antenna  (Read 14990 times)
KJ4DHI
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Posts: 39




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« on: January 13, 2013, 07:43:50 AM »

Help. My station is located in my business office. The office is located on the ground floor of a concrete block 2 story building that has no windows. My operating preferences are pretty much whatever my tech licenses priveledges are. Any help would be greatly appreciated, and I know I'll get it because I always get good advice from you guys out there.
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K5LXP
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« Reply #1 on: January 13, 2013, 09:53:14 AM »

A 2M/440 mag mount on a filing cabinet connected to an HT would be an easy/quick start and would give you an idea of the viability of your location for indoor antennas that are more involved.  Any aspirations for HF operating?  What equipment do you have?

Your expectations should be tempered by the fact that the building will be your limiting factor, not any  antenna.  You won't know how/if it will work until you try something.


Mark K5LXP
Albuquerque, NM

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KJ4DHI
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« Reply #2 on: January 13, 2013, 06:40:04 PM »

My operating is mostly HF QRP CW on an HW-8.
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VE3WMB
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Posts: 288




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« Reply #3 on: January 13, 2013, 08:33:38 PM »

Have you considered operating portable from a local park?  You would probably do better with a temporary portable antenna than an indoor antenna at your office.  I would recommend building something like a segmented dipole for the bands of interest and erecting it as an inverted vee, either using a line over a tree as a center support or a 30 ft fiberglass mast such as the DK9SK, MFJ or Jackkite.

Here is a link to a typical segmented dipole design which can be modified to cover other bands.
I build mine using spade lugs and alligator clips to connect the segments together.

http://wa3wsj.homestead.com/iditarod_mini__dipole.pdf

Best of luck

Michael VE3WMB


Help. My station is located in my business office. The office is located on the ground floor of a concrete block 2 story building that has no windows. My operating preferences are pretty much whatever my tech licenses priveledges are. Any help would be greatly appreciated, and I know I'll get it because I always get good advice from you guys out there.
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WB2WIK
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« Reply #4 on: January 14, 2013, 02:06:00 PM »

A concrete block building with no windows is unlikely to work for VHF-UHF with an indoor antenna, but it's easy to give it a try.

I'd try to get something up on the roof.
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WB6BYU
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« Reply #5 on: January 14, 2013, 05:43:48 PM »

Quote from: KJ4DHI

My operating is mostly HF QRP CW on an HW-8.



That does complicate matters a bit, especially if the building has a metal roof.

Given the bands available on the HW-8, that means mostly 40m and 15m CW,
possibly with 80m if we can squeeze in the antenna, but that isn't as likely
to be productive unless you are working at night.

The ideal thing would be to put an antenna on the roof and drop the coax down
to your office.  (Even better might be to run the antenna off the side of the
roof to another support, so the wire is over the parking lot rather than the
roof.)  But those aren't always easy to accomplish.

If your building has a large metal roof like many other commercial buildings, then
putting a vertical antenna of some sort up there may work well.  However you
may not be able to contact the roof directly because it will be coated with
sealant, and the building maintenance staff really doesn't like people putting
screws through it.  This takes some creativity.

I have worked with horizontal dipoles on top of such buildings with good results,
but you might not find much in the way of a support that gets you more than
10' above the roof.  That's not too bad for local work on 80m and 40m (when the
bands permit) but the feedpoint impedance may be low due to it being so close
to the metal roof.  We fixed this in one case with a shunt coil connected across
the center insulator.

If you are limited to indoors, you may have trouble finding anything that will
work well.  You can try various sorts of wires strung wherever you can to
see how they work, but it will be heavily dependent on the interior configuration
of the building.  If the roof is metal then you may have best results trying
vertical polarization and/or placing the antenna as close to an outside wall
as possible.  If there is a large open assembly or shop area you may be able
to string up a dipole across the open space above the workers, but without
more information about what space is available to you we're really just
shooting in the dark.
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AI4NV
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« Reply #6 on: January 24, 2013, 10:24:35 AM »

A word of caution, be careful with your power levels if you should transmit with an indoor antenna among office equipment. I keyed my 2 meter transceiver in my home office once with too much power and it instantly fried the circuitry in my battery backup. 73
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KB2FCV
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« Reply #7 on: January 24, 2013, 01:19:24 PM »

Is home operations out of the question?

An office will be tough with no windows and another floor on top of you.

Perhaps another thought is your car - maybe you can use a mobile HF antenna and do some operating from there? This way you have an outdoor antenna and that opens up more operating time / places.
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ONAIR
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« Reply #8 on: February 02, 2013, 01:01:33 AM »

If you want to try 2M/440, pick up one of those small Elk beam antennas.  It's amazing what they can do, even from the inside of a building at ground level.
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SP9HZX
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« Reply #9 on: February 02, 2013, 06:53:56 AM »

Hi,

I would try magnetic loop, mobile whip or microvert ant.
Or horizontal loop,2-3m over the ground.I used to have such a loop for 20m and 1W QRP.
I worked easily with all Eu.


73 Andy
=====================
http://spearo.republika.pl

http://www.qsl.net/sp9hzx
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N5RDE
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Posts: 16




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« Reply #10 on: February 09, 2013, 05:20:44 PM »

If you can get any kind of signal out at all, my suggestion also would be to try a small, tuned vertical loop.   They are easy to build.  Here are two websites that provide all the information you will need:

http://www.qsl.net/pa3hbb/magloop2.htm

http://www.aa5tb.com/loop.html
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N5RDE
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« Reply #11 on: February 10, 2013, 08:42:56 AM »

Here is KR1ST's web page relating to his apartment magnetic loop antenna.  He adds capacitance by using lengths of coax that he can patch in as needed:

http://www.kr1st.com/magloop.htm
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KC4MOP
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Posts: 733




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« Reply #12 on: February 16, 2013, 04:08:12 AM »

Would the building engineer / owner allow you to erect something on the roof?? A dipole? Flat roof?
And indoor antenna, ground floor, on HF is not going to do much.
That's why there have been a lot of responses to go with 2M and up.

Fred
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KC4MOP
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Posts: 733




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« Reply #13 on: February 16, 2013, 04:52:50 AM »

Here is KR1ST's web page relating to his apartment magnetic loop antenna.  He adds capacitance by using lengths of coax that he can patch in as needed:

http://www.kr1st.com/magloop.htm
And may I comment that the magloop can be a great antenna indoors. 100W and your privileges should be good operating. And the magnetic loop will reduce local noise. But be aware of office equipment and RFI to and from these devices. They do not have to be FCC certified for interference as home equipment is supposed to be.
Fred
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K5LXP
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« Reply #14 on: February 16, 2013, 08:59:57 AM »

be aware of office equipment and RFI to and from these devices. They do not have to be FCC certified for interference as home equipment is supposed to be.

Can you tell me where I could find that exclusion in Part 15?


Mark K5LXP
Albuquerque, NM

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