[Elecraft] K3 & FD multi band antenna

[Tom W8JI]

Don and all,

The 88 foot dipole, and the 44 foot dipole, are examples of an antenna 
designed for pattern alone with no consideration of feedline losses or 
matching systems.

http://www.w8ji.com/short_dipoles_and_problems.htm

With an 88 foot antenna the 80 meter SWR on a 400 ohm line (most ladder line 
is 400 ohms, not 450) is over 100:1.

That does not make for an efficient system, and it can be hell on antenna 
tuners and baluns.

While any mismatched dipole would require consideration of feedline length 
and antenna length, the minimum sensible length of a dipole is about 80% of 
full size. Below that things get very rough for tuners and feedlines.

73 Tom



----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: <Gary at ka1j.com>
Cc: <elecraft at mailman.qth.net>
Sent: Friday, June 11, 2010 12:29 AM
Subject: Re: [Elecraft] K3 & FD multi band antenna


> Gary,
>
> For 80 thru 20 meter operation, I would advocate an 88 foot dipole.  44
> feet on each side and fed with either 300 or 450 ohm ladder line (use
> 300 ohm for portable because it is lighter).
>
> A push-up pole will allow that antenna to be erected in minutes - The
> feedline and center of the dipole are at the tip of the pole and the
> ends are spread out in inverted Vee fashoin to whatever bushes, shrube,
> or trees are available.
>
> A 44 foot dipole will work fine for 40 thru 10 meters.
>
> See the L B Cebik archives - My Favorite 5 Backyard Antennas for more
> details.
>
> 73,
> Don W3FPR
>
> Gary Smith wrote:
>> I have the internal tuner in my K3 and want to be able to put up a
>> wire antenna that can be assembled in minutes for both FD and public
>> event locations. I used to have a Mor-Gain antenna & while it wasn't
>> a great performer, it would have been fine for this use. Danged if I
>> can find it though, I must have lent it out & never got it back.
>>
>> I've thought to use my spud gun to send a random wire over a tree top
>> & have a counterpoise wire on the ground, using the K3's ATU to match
>> the wire to the band. The goal would be to cover 80-20 meters. Above
>> 20 would be nice but there's not much activity there and I'd like to
>> be able to demonstrate Ham Radio.
>>
>> Any suggestions on something else that is convenient and works well
>> would be appreciated.
>>
>> Thanks
>>
>> Gary
>> KA1J
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