[ARC5] Impedance of an end-fed short aerial/antenna

[Tom Dawson]

Durn, I've been a member of the wrong society all these years: IEEE Antennas 
and propagation.  No wonder management never listens!

If I recall correctly, that capacitor on the back of the antenna relay was 
for antennas that were too long so the inductor in the tranmsitters could 
resonate, consistent with decreasing capacitive reactance of longer err.. 
short antennas.


regards,

Tom

----- Original Message ----- 
From: "Mike Everette" <radiocompass at yahoo.com>
To: "Leslie Smith" <vk2bcu at operamail.com>; "Brooke Clarke" 
<brooke at pacific.net>
Cc: "ARC-5 List" <arc5 at mailman.qth.net>
Sent: Friday, February 01, 2013 11:35 PM
Subject: Re: [ARC5] Impedance of an end-fed short aerial/antenna


> For the record:
>
> ANTENNA is singular; one antenna.
>
> ANTENNAE is plural; not two antennas, but rather, two antennae.
>
> It's from Latin.  (I took Latin in high school; this is one of the few 
> things I actually remember....)
>
> 73
>
> Mike
> W4DSE
>
> --- On Thu, 1/31/13, Brooke Clarke <brooke at pacific.net> wrote:
>
>> From: Brooke Clarke <brooke at pacific.net>
>> Subject: Re: [ARC5] Impedance of an end-fed short aerial/antenna
>> To: "Leslie Smith" <vk2bcu at operamail.com>
>> Cc: "ARC-5 List" <arc5 at mailman.qth.net>
>> Date: Thursday, January 31, 2013, 10:39 PM
>> Hi Leslie:
>>
>> This web page and those it links to may answer your
>> question.
>> http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/radimp.html
>>
>> In general a length of wire that's shorter than 1/4
>> wavelength is a small value capacitor
>>
>> Have Fun,
>>
>> Brooke Clarke, N6GCE
>> http://www.PRC68.com
>> http://www.end2partygovernment.com/2012Issues.html
>>
>> Leslie Smith wrote:....
>>  Second, there are many pages on the web that will calculate
>> the proper length for a resonant aerial. (hehe - no antennae
>> here - we follow the "Brits" in how we use language). I'm
>> interested in the load impedance of "off-resonant" end fed
>> wires. So - for example if I have a 35 foot length of wire
>> trailing out the back of an aircraft, what complex "Z" will
>> that present to the 1625's in the PA at, say 3.550 MHz. What
>> it the wire is 55 feet long? Anyway, in the past I found a
>> page that made that calculation - not for an aircraft, but
>> for an end fed random wire. The calclulation allowed for a
>> good many parameters, eg the dia of the wire (1mm, 2.5mm
>> etc), height of the wire above ground and even soil type.
>> The calculation result gave the impdedance as resistive and
>> reactive components. Having searched (googled) for about and
>> hour or so - I can't find it. Any pointers, clever types? 73
>> de VK2-land Les
>>
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