[Elecraft] Antenna Question

[Willis]

Indeed!  The purpose of the inverted V was for local NVIS coverage and was mentioned anecdotally to illustrate that folded back elements can be very effective if needed.  They reduce the mechanical problems of erecting and turning a rotating dipole with minimal degradation.  I can see a significant advantage where a shorter antenna is needed.  We are fortunate to have a wide range of designs for our wide range of antenna problems.

Sent from my iPhone

On Jun 18, 2012, at 10:27, Vic K2VCO <k2vco.vic at gmail.com> wrote:

> I agree that folding the low-current parts of an antenna is a good way to make it smaller.
> 
> But there are several things at work in the comparison between the Steppir element and the 
> V. Of course the height is one of them. But if you model an inverted V (90 degree angle 
> between wires) and a dipole at the same height you will see that the dipole has 
> significantly more gain. Many inverted V's are constructed with even smaller angles, which 
> are worse. The V pattern also has smaller nulls on the ends.
> 
> Finally, the Steppir undoubtedly has some kind of balun, and its feedline runs 
> perpendicular to the antenna for 1/2 wavelength. All of these things improve the nulls. 
> They also reduce noise pickup on the feedline.
> 
> On 6/18/2012 5:26 AM, WILLIS COOKE wrote:
>> A note on folded back antennae.  I have a 3 element SteppIR with the 30/40 kit.  The
>> antenna is mounted at about 67 feet above the ground.  I have compared the folded
>> antenna at 67 feet to a full sized inverted V at 40 feet and find it noticeably
>> stronger.  Even though it is only a dipole which is a little more than half length it
>> is noticeably bi-directive with deep nulls off the element ends.  It is quite effective
>> as a DX antenna and I believe the SteppIR claim that it is only one or two dB down from
>> a full sized rotatable dipole.  Of course, its improved performance over the inverted V
>> is mostly because of the elevation difference, but I would not hesitate to fold the
>> ends of a dipole if restricted by lot size or other physical restraints.
>> 
>> Willis 'Cookie' Cooke K5EWJ&  Trustee N5BPS, USS Cavalla, USS Stewart
>> 
>> 
>> ----- Original Message ----- From: Don Wilhelm<w3fpr at embarqmail.com> To: Niel
>> Skousen<nskousen at talisman-intl.com> Cc: Elecraft Reflector<elecraft at mailman.qth.net>;
>> QRP-L at mailman.qth.net Sent: Monday, June 18, 2012 6:18 AM Subject: Re: [Elecraft]
>> Antenna Question
>> 
>> Neil,
>> 
>> When you see an antenna element folded back on itself like that, think "linear loading"
>> (look it up in the ARRL Handbook or similar).  There is no "magic", but it is one way
>> of shortening an antenna.  It is not as efficient as a full length antenna, but is more
>> efficient than using loading coils.  Everything is relative. If you have the space to
>> put up full size half wave dipole antennas, that is the way to go.  If you need
>> shortened antennas for the lower bands, linear loading is one way to achieve resonance
>> with shortened length.
>> 
>> 73, Don W3FPR
>> 
>> On 6/17/2012 11:26 PM, Niel Skousen wrote:
>>> I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have
>>> I been able to find a link to a description / design data.
>>> 
>>> The county ERC has a 'shortened fan dipole' with three parallel elements, spaced
>>> about 18-24" apart on each side.   the longest element folds back around the
>>> mid-length element toward the shortest element.   The antenna end insulator / guy
>>> rope is attached to the long element, where it folds back.   There appears (from the
>>> ground) to be a 6~8" insulator / gap between the end of the shortest element, and the
>>> longest element where its been folded back.  no traps, loading coils, or loading
>>> resistors that I can see.
>>> 
>>> I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a
>>> 40m dipole (with 15m as a freebie), and a 20 m dipole.   but would be interested in
>>> more technical details if anyone can decipher my text description above…
>>> 
>>> Thanks Niel
> 
> -- 
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
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