[Qcwa] "Hidden" HF antenna

Sat, 16 Feb 2002 18:14:18 -0500

On Sat, 16 Feb 2002 11:08:04 -0500 "Keith Kotch" <[email protected]>
writes:
> Last month I passed my General and want to get on HF.  I'm in the 
> usual
> predicament these days, living in an antenna restricted community so 
> I need
> to have a very low profile or hidden antenna.  I do have a roller 
> inductor
> antenna tuner so I'm thinking of a couple of options.
>
THAT'S GREAT.  THE ANTENNA TURNER WILL BECOME YOUR
BEST FRIEND WITH ANY SORT OF SHORTENED ANTENNA,
AND PARTICULARLY SO IF YOU FEED IT WITH OPEN-WIRE LINE
THRU A BALUN--SUCH AS THE ONE INTERNAL TO YOUR TUNER. 
>
> Option 1 is an attic mounted dipole but in order to get on 75 meters 
> I will
> probably have to zig-zag or bend the wire along the trusses to fit 
> it all
> in.  Total attic length is approx 69'.  I thought of taking the 
> "leftover"
> ends and putting them through the gable ends of the attic and bend 
> them
> toward the ground. 
>
THAT OUGHT TO WORK.  MAXIMUM RADIATION FROM ANY
ANTENNA IS AT THE POINT OF MAXIMUM ANTENNA CURRENT.
SO IF THAT PART OF THE ANTENNA IS IN THE CLEAR (USUALLY
AT THE CENTER OF A RESONANT DIPOLE),  YOU'LL BE OK.
>        
 My problems/questions here are two-fold.  First 
> the main
> AC duct runs down the middle of the attic.  It's the fiberglass box 
> type
> duct, not the metal cylinder. It does have the aluminum foil type 
> wrap on
> the outside.  I don't know what affect it'll have on the wire 
> antenna except
> maybe act as a reflector?  
>
IT ALL DEPENDS UPON THE DISTANCE FROM THE ANTENNA.
IF IT IS  AT LEAST ONE-TENTH OF A WAVE LENGTH OR MORE 
AWAY FROM THE ANTENNA,  IT WILL ACT AS A REFLECTOR.
>
The second problem is how to fasten the 
> wire to
> the trusses.  I feel I need some type of standoff insulator and the 
> only
> ones I know of are the types used to stand off tv twin-lead. 
>
THEY WILL WORK,  AS WILL ANY KIND OF NON-CONDUCTOR.
I'VE SEEN ATTIC ANTENNAS HUNG WITH STRING,  PLASTIC 
CABLE TIES, AS WELL AS STAND-OFF INSULATORS,  USING
SMALL NAILS OR EVEN WRAPPING THE SUPPORT AROUND 
A 2X4 STRINGER.
> 
Also,  if I
> were to go through the gable ends, what type of insulating grommet 
> should I
> use.  Max power expected would be 100 watts.
> 
ANYTHING CERAMIC WILL DO FINE,  AS WILL PVC PIPE.
JUST STAY AWAY FROM ANYTHING METALLIC.
>
> Option 2 is a loop wire run just under the eves of the house.  Same 
> issue
> about insulators and how to fasten the wire up.  Another 
> consideration in my
> mind is height above ground and the fact there's an aluminum gutter 
> running
> across the front of the house.
>
THE GUTTER WILL PRESENT A REAL PROBLEM,  AND 
ATTACHING THE WIRE WILL ALSO BE A CHALLENGE.
I'D GO WITH THE ATTIC OPTION,   MYSELF,  AND EVEN
CONSIDER BENDING THE ENDS OF THE ANTENNA 
DOWN ALONG THE INSIDE OF THE ROOF LINE INSTEAD
OF GOING THRU THE GABLE ENDS.
>
> There are no trees available that I could hide a vertical or long 
> wire in.  I would like to work 10-80 meters at this time.
> 
> Any suggestions?
> 
> Keith, KF4BXT
> 
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