[FARC] Kirk's antenna gremlins

[kirktal7237 at msn.com]

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


--------------------------------------------------
From: "Bob Moroney" <windbrkr at erols.com>
Sent: Thursday, February 14, 2008 11:56 AM
To: "Frederick, Maryland ARC" <farc at mailman.qth.net>
Subject: Re: [FARC] Kirk's antenna gremlins

> Kirk,
> You can definitely get a respectable signal out on multiple bands with the 
> Windom-type antenna that Dave describes, so I'd say you probably shouldn't 
> reject it out of hand.  The design he linked to works down to 80m and 
> requires 140 ft. to string it up, but if you don't have that sort of 
> unimpeded distance to hang a wire antenna, the design can be scaled down 
> to work on 40m and up or even 20m and up for very restricted spaces. 
> Radio Works used to sell a scaled down "Carolina Windom", but they don't 
> seem to offer it as a stock item any more.  If you wanted to try a 
> shortened Windom, you could try emailing K3MT to see if he has any 
> recommendations.  The "Grasswire" antennas K3MT describes on his web site 
> also looks very interesting (at least to me).  Good luck!
>
> 73, Bob K9CMR
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> kirktal7237 at msn.com wrote:
>> The lack of response must be due to impatience with rookies.  Thanks for 
>> your response Dave, any and all help and advice I can get is welcomed 
>> though not always understood.
>>
>> I've been in ham radio for a year now and the lesson I've learned from 
>> many hams is that there is no quick and easy answer to getting radios and 
>> antennas to work despite antenna/radio manufacturer and advertising 
>> claims to the contrary.  Try and cut a corner and you end up cutting 
>> performance. This is frustrating because we spend big bucks for multiband 
>> radios and there isn't an easy way to make use of all the bands.  Unless 
>> you have acres and acres of property to erect a dipole for every band, 
>> you kind of have to pick an operating frequency area and stick with it 
>> and let all the other band capability of the radio go to waste.
>>
>> I've learned that the basic formula, 468/Freq in Mhz. gives you the 
>> length of your dipole and 421/Freq in Mhz. gives you the wavelength 
>> height.  Do it any other way and you're subtracting performance from the 
>> antenna/radio combination; add poor propagation conditions and like me 
>> you'll have little success in making contacts.
>>
>> As for the technical aspects of HF antenna theory, that's light-years 
>> over my head, so far in fact that the study of it is painful.   I 
>> understand a piece of wire cut to length for a specific frequency, 
>> mounted at the wavelength height for that frequency, and fed with a 
>> matched feedline will give the best results.    I know this is a narrow 
>> (mono-frequency) viewpoint but like you indicated, anything else is a 
>> compromise, another word for losing ground.   Multiband antenna?  Has to 
>> be an oxymoron in reference to dipoles.  What you've got here is mediocre 
>> performance on all the bands.
>>
>> Now I also know this from a year of listening to hams.  Those guys with 
>> the multiband beams mounted on very tall towers with rotators and using 
>> linear amps are ALWAYS HEARD with commercial radio studio quality sound 
>> all over the world.  Must be something to this.
>>
>> 73
>> KB3ONM
>> Kirk
>>
>>
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