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[See also my previous followup - also shifting to alt.

On 2025-12-24, John R Walliker  wrote:
> On 24/12/2025 12:16, The Natural Philosopher wrote:
>> On 24/12/2025 07:58, mm0fmf wrote:
>>> On 11/12/2025 21:18, Carlos E.R. wrote:
>>>> Home made with a box of Pringles. just google for "pringles wifi 
>>>> antenna".
>>>
>>> Also Google cutoff frequency and see that the Pringle tube is too 
>>> small in diameter to be effective at 2.4GHz.
>>>
>> Assuming that is a relevant issue.
>> 
>> Shouting down a pipe whose diameter is way less than the wavlength of 
>> voice frequencies, still works....
>> 
>>> Of course, designs on the internet do not have to follow the laws of 
>>> physics! :-)
>>>
>> 
>> ..especially for people who don't fully understand them...
>
> Indeed.  And I'm sure you are perfectly well aware of the difference
> between longitudinal sound waves propagating down a narrow pipe and
> transverse electromagnetic waves in a waveguide.
> If a Pringles can were highly conductive it would have a cutoff
> frequency of close to 2.4GHz so the attenuation would be very high.
> However, a very thin layer of aluminium on the inside of a cardboard
> tube will be so resistive that it will not make a lot of difference.
> For many purposes a well made half-wave dipole or quarter-wave
> monopole gives excellent results which are far better than anything
> that can be achieved with small pcb antennas.
>
> A quarter wave monopole made from relatively thick wire or rod can
> be an excellent match to 50 ohm coax so long as the ground plane
> is at least a few wavelengths across.
>
> A half-wave dipole combined with a coaxial balun can also be a very
> good match but has a slightly narrower bandwidth due to the
> frequency dependency of the coax balun.  The choice of which one to
> use depends mostly on how the antenna is to be mounted.
>
> An almost omnidirectional antenna with very low losses can be
> more effective than a lossy directional one.
>
> John
>


-- 
Lars Poulsen - an old geek in Santa Barbara, California

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