K3 - Indoor HF Antenna

[Chuck Teeter KE9CE]

Hello:

I am unable to get my Windom in the air due to weather conditions, snow, etc., so I'm wondering if anyone has any experience with any indoor antennas that at least would allow me to have a few QSO's even if they're relatively close.  Any suggestions would be greatly appreciated.  Thanks, guys.

73,
Chuck KE9CE
K3 #4073

[John Ragle]

Chuck...

I have a Buddipole that works inside (20/15/10 meters), and I suspect a
half-wave wire dipole or a 300-ohm twin-lead folded dipole would work
well if tacked to the room molding at ceiling height. I have used both
of the latter in compromised situations and have had QSOs without
problems (on CW). Even a random length wire tossed out the window will
work if you have a matching network. All my experience in these
situations has been on CW.

The Buddipole will also make up into a 2-element yagi for 6 meters, and
there is some occasional CW activity there also.

John Ragle == W1ZI

=====

On 12/30/2010 2:51 PM, Chuck Teeter KE9CE wrote:

> Hello:
>
> I am unable to get my Windom in the air due to weather conditions, snow,
> etc., so I'm wondering if anyone has any experience with any indoor antennas
> that at least would allow me to have a few QSO's even if they're relatively
> close.  Any suggestions would be greatly appreciated.  Thanks, guys.
>
> 73,
> Chuck KE9CE
> K3 #4073

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[Jim Brown-10]

On 12/30/2010 2:51 PM, Chuck Teeter KE9CE wrote:
>> I am unable to get my Windom in the air due to weather conditions, snow,
>> etc., so I'm wondering if anyone has any experience with any indoor antennas
>> that at least would allow me to have a few QSO's even if they're relatively
>> close.

If your home is not electrically shielded by a metal frame, and if you
have an antenna tuner, almost any random wire can be made to work as an
antenna if you give it a reasonably effective counterpoise.  In general,
the more closely the wire and the counterpoise each approximate a
quarter wave, the better it will work (and the less likely that an
antenna tuner will be needed). Something as simple as a quarter wave
wire connected to the center conductor and a second quarter wave wire
connected to the outer conductor will load just fine with no antenna tuner.

In general, the higher the better.  Loaded antennas like the Buddipole,
and other antennas designed for mobile operation are NOT a good choice
for indoor use, mostly because their loading coils make them pretty
inefficient (that is, far too much of the power goes into heat) and
because they tend to be pretty narrow band.

The counterpoise can be almost any available conductor (or group of
conductors.  KK9H used the HVAC ducts in his home as a counterpoise on
160M for a while (and may still).  I've used a wrought iron fence, or
building structure, or even the green wire in the nearest wall outlet.  
Such a counterpoise system can couple RFI into equipment in your home,
both by proximity, and also because of a common defect in many products
called "The Pin One Problem."

It's also possible to build a classic dipole and install it indoors.  
When I got back on the air in 2003 after a long period off the air, I
ran a half wave dipole through my attic.  I used that for a month or so
until I could get something better on the roof. It worked fine.

With any indoor antenna you're more likely to have RFI issues, simply
because the antenna and the equipment is in closer proximity. Your
transmitter is more likely to cause problems with poorly designed
consumer equipment, and that equipment is more likely to radiate trash
that you hear in your receiver.  If you encounter problems, see the RFI
tutorial on my website for solutions.  
http://audiosystemsgroup.com/RFI-Ham.pdf

73, Jim K9YC
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