[30m] Re: 30M Stealth Antenna

[David Dorrance]

I think this was meant for the list, but emailed to me privately.

Dave WA6YSO


>From: <ik2ihy at libero.it>
>To: "David Dorrance" <dldorrance at hotmail.com>
>Subject: Re: [30m] Re: 30M Stealth Antenna
>Date: Wed, 31 May 2006 23:41:19 +0200
>
>Maybe someone feel some interest in a strange kind of a short antenna, 
>namely a µVERT form DL7PE?
>Will some minutes of surfing 
>http://download.antennex.com/preview/archive4/Apr601/microvert.pdf be a 
>well spent time?
>
>Best 73 ... Piero IK2IHY
>*******************
>----- Original Message ----- From: "David Dorrance" 
><dldorrance at hotmail.com>
>To: <30m at mailman.qth.net>
>Sent: Wednesday, May 31, 2006 4:24 PM
>Subject: [30m] Re: 30M Stealth Antenna
>
>
>>I have never operated on 30M, but the more I read about, and look at
>>propagation information, the more I realize that this is an amazing band!! 
>>I
>>live in a deed restricted community, and I'm wondering if anyone has ideas
>>for a stealth antenna for 30M. I was thinking about a random wire, from an
>>MFJ-969, using insulated wire, run under the aluminum window and screen, 
>>and
>>then run around the house on the facia. From what I've seen, it doesn't
>>appear that you need a lot of power. I also will be using digital modes
>>exclusively. Any ideas will be greatly appreciated.
>>
>>73... Jon W1MNK
>>
>>Hi Jon,
>>
>>I also use digital modes exclusively and although I do not live in a deed 
>>restricted community, I do not have sufficient space to string up a 1/2 
>>wavelength antenna.  Maximum power here is 40W into an SWR of under 1.2:1.
>>
>>My solution is a small transmitting loop antenna.  For 30 meters the 
>>footprint could be a 3 to 4 foot diameter  pipe or a 3 to 4 foot square 
>>copper pipe arrangement.  Currently I am using a commercial version made 
>>by MFJ which is a bit expensive.  But I have built these loops out of 
>>copper water pipe and high voltage variable capacitors.  For qrp one might 
>>be able to use standard variable capacitors.  The MFJ unit is mounted at 
>>18 feet on my roof; it would also work mounted on a 6 foot stand in my 
>>backyard.
>>
>>The advantages:  They are bidirectional, may be mounted close to the 
>>ground, have a very narrow bandwidth which nulls out qrm and qrn and, 
>>propagation wise,  work about as well as a dipole at 1/2 wavelength in the 
>>air.
>>
>>The disadvantages:  Remote tuning requires a geared motor due to the 
>>narrow bandwidth.  You must re-tune when you move frequency.
>>
>>The retuning is less of a problem with PSK-31 where the entire band is 
>>within the bandwidth of the antenna; remote tuning is still needed to keep 
>>the loop on center frequency as it changes with ambient temperature.
>>
>>Here is a link to several versions of a homebrew unit for 20 meters, which 
>>would work on 30 meters; make it twice as large and it would go down to 40 
>>meters as well:
>>http://www.elecraft.com/TechNotes/loop_ant/wd8puoloop.pdf
>>
>>There are literally hundreds of sites for small loop antenna, magnetic 
>>loop antenna or small transmitting loop antenna, on Google.  Write me off 
>>list if you have any interest.
>>
>>Dave WA6YSO
>>
>>
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>