[FARC] Kirk's antenna gremlins

[Bob Moroney]

Kirk,

The bottom line is that, whether it's a piece of wire laying on the 
ground or a beam 200 ft. in the air, an antenna is a tuned circuit, 
naturally resonant at some frequency or frequencies, the sum of the 
various physical and electrical components that make up that circuit.

You can use exactly-cut, optimally high-strung dipoles, fed with ladder 
line and keep it really simple like some "old hands" might advise for 
optimal performance with a wire antenna.  (Of course, you'll still need 
a transmatch (tuner/balun) if your transmitter has solid-state finals.  
Tube finals will be happy with the higher impedance of ladder line, but 
the transistor finals most of us have won't.) 

But if those "optimal" antennas don't suit your circumstances, you can 
also tweak one or more of the components of the antenna circuit and 
still get very good to excellent performance on one or more bands.  In 
some cases you can even get some *gain*, just like a beam.  (You won't 
see that with the dipole on its naturally resonant freq.)

The tweaking may be electrical or it may be mechanical, or it may be a 
combination.  But you're not violating any laws of physics, you're 
simply acknowledging and obeying them, then putting them to work for 
your purposes. 

True, the antenna circuit tweaking process *can* be frustrating, but the 
good part is that many, many folks have been through it, some in the 
same or very similar circumstances as you, and there are many 
distillations of their experiences available in books and magazine 
articles and on the web, as well as via discussion groups such as this.

73, Bob K9CMR
~~~~~~~~~~~~~~~~~~~~~~~~~

kirktal7237 at msn.com wrote:
> Yep Bob I'm sure the Windom antenna probably does work well for some 
> folks at some locations.  I've heard that G5RV's work great for some 
> and other hams think they're garbage.  Same goes for verticals, some 
> swear by them and some swear at them.
>
> But the "old hands" at amateur radio say you can't violate the 
> physical laws in regard to dipole antennas.   For 40 meters a half 
> wavelength dipole is supposed to be 65 ft. long at 7.200 Mhz. and 58 
> ft. 6 inches high.  If you shorten it or lower it then it can't be 
> resonant at 7.200 Mhz, can it? Multiband antenna manufacturers 
> supposedly get around the length issue for the various bands with 
> traps, but how do you get around the wavelength height issue?  Mount 
> it 200 ft. high and you're covered?
>
> Now my 80 meter wire is resonant at 3.800 to 3.850 MHz. and it would 
> probably be even more resonant if it were up at the required height 
> and in a flat top configuration.  I'm ok with this as it is right in 
> the middle of my General class phone frequencies and it is what you 
> would expect; an 80 meter antenna that works on 80 meters.  It is not 
> resonant on any other HF band. So how can any other manufactured wire 
> antenna cut at a certain length for one band and mounted at the 
> wavelength height for that band possibly be resonant on multiple HF 
> bands ?  There is a way based on multiples I've been told but they 
> have to be on odd harmonics which an 80 meter dipole won't have for 
> the other  HF bands.
>
> I guess what you Bob and others are trying to tell me is that close, 
> as in horseshoes, to resonance in an antenna can allow you to make 
> contacts.   Are the radio and antenna putting out all the power you 
> expect them to?  No, they  can't be and an antenna tuner allows the 
> radio to operate in this condition and I can actually make some 
> contacts this way.  I don't have a very strong signal but then I 
> shouldn't have.
>
> 73
> KB3ONM
> Kirk