[Elecraft] Small QRP antenna

[Don Wilhelm]

I think this is mixing up 1/2 wave radiators and 1/4 wave radiators.
To be resonant, a 1/4 wave wire needs another 1/4 wave "counterpoise" - 
think of a center fed dipole - it has 1/4 wave on each side whether one 
side is a monopole (vertical) and the other 1/4 wave is an elevated 
radial or buried radials of indeterminate length, or whether it is a 
dipole with the center in the air.

A 1/2 wave radiator fed at the end theoretically does not need any 
counterpoise, but in practice it does - but only needs to be about 0.05 
wavelength long.

Refer to some antenna books (the ARRL has a good one) or the ARRL 
Handbook for good information about basic antennas.

73,
Don W3FPR

On 12/29/2016 10:30 AM, Fred Moore wrote:
> With an end fed 1/4 wave you only need a counterpoise that is about .05
> wave length.  it can be the coax or another counterpoise.  Although a
> counterpoise has some effect on radiation pattern of a quarter wave
> radiator, it is minimal.   You won't see much improvement in performance
> by going above .05 wave length..  it's not worth the trouble to increase
> the counterpoise length..   Fred
>
>
> On 12/29/16 9:01 AM, mjisted wrote:
>> Looking at your text message on the elecraft board. About a half wave
>> length ...here is a question for you. I'm going to put up a half
>> wavelength of wire for the 5 mhz band. ..hyendfed can I use a quarter
>> wave length of counter point as a radiator ground plane. ..
>> The. ..G0MVP.
>>
>> mjisted at btinternet.com
>>
>>
>> Sent from Samsung Mobile
>>
>>
>> -------- Original message --------
>> From: Fred Moore
>> Date:29/12/2016 13:04 (GMT+00:00)
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] Small QRP antenna
>>
>> Don,
>>
>> Thank you very much, for pointing out a very common issue that gets
>> mixed up into discussions.  Your point is so valid the random wire
>> always seems to get mixed into the 1/2 wave discussion for some
>> reason..  and should never be mixed together.  you are absolutely
>> correct..   thanks again regards..  Fred
>>
>>
>> On 12/29/16 12:33 AM, Don Wilhelm wrote:
>>> Scott,
>>>
>>> If the radiator is not a half wave long, it is not a "half wave".
>>> Yes, a random length wire may work, but please do not call a random
>>> length a half wave - the length of a half wave is quite specific.
>>> Similarly, a quarter wavelength is a specific length at a particular
>>> frequency.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 12/28/2016 11:20 PM, K9MA wrote:
>>>> The counterpoise for an end fed half wave (or multiple) really doesn't
>>>> have to be anywhere near a quarter wave long.
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>>
>> --
>> Fred Moore
>> email: fred at fmeco.com
>>        fred at safes.com
>> phone:  321-217-8699
>>
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>