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   On 24/12/2025 14:04, 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.ÿ 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.   
      
   An antenna is not 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.   
   A statement which clearly contradicts the well known skin effect of    
   conductirs at high frequencies.   
      
   > 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.   
   >    
   Sure. Most routers come with wavelength sized wobbly penises that give    
   you a few dB.   
      
   > 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.ÿ 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   
   >    
      
   Nevertheless I have seem that sort of design work.   
   I worked around radar antennae briefly in the 1960s.   
      
   What I learned was that theory is too simplified to actually be able to    
   design a real antenna: All our designs were field tested and adjusted.   
      
   I am not advocating Pringle cans.  I wouldnt use one myself. But I am    
   not so quick to rubbish them as you are.   
      
   RF propagation is tricky, and real world objects of no apparent value    
   often have enormous effects.   
      
      
   --    
   The lifetime of any political organisation is about three years before    
   its been subverted by the people it tried to warn you about.   
      
   Anon.   
      
      
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