[AMRadio] Antennas


D. Chester k4kyv at charter.net
Thu Jun 24 12:08:00 EDT 2010


> From: "Larry Szendrei" <ne1s at securespeed.us>

>>> There have been some interesting cases with short loaded antennas
>> in the BC band, the bandwidth has occasionally been so narrow that the AM
>> sidebands become attenuated!  Not going to see that effect in the amateur
>> bands unless someone is running an antenna only a few feet long!!
>
> Correct. This has been observed on my 75M AM mobile signal, with reports
> of one sideband being attenuated relative to the other. Antenna is a
> Webster bandpanner ("a few feet long").
>
> 73,
> -Larry/NE1S

The first commercial use of SSB was around 1920 for transatlantic telephone 
links using VLF.  Even the tallest tower in the world would be only a tiny 
fraction of a wave length at those frequencies. The bandwidth was too narrow 
to pass both sidebands, but they found that they could get by transmitting 
only one.  Thus, the sideband filter was the antenna itself! The balanced 
modulator circuit was known during the WW1 era. I have seen descriptions of 
the circuit in old radio books of that day.

The first SSB ham rig was described in a series of construction articles in 
R/9 magazine in 1933 and 1934.  I have the issues with the articles.

A lot of to-day's Hammy Hambones think that SSB was invented during or 
shortly after WW2.

Don k4kyv

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