Topband: History of directional MF antennas

[Grant Saviers]

Thanks for an interesting article.

I did a little reverse engineering from the KYW 1934 "4 square" picture 
and commentary.  A figure 8 pattern was the objective.

It seems to have used 8 radials elevated 10ft per tower.  The text says 
"55,000 feet of wire" in radial "cages".  A little tough to tell but I 
can resolve 3 or 4 wire cages.  For a frequency of 1020Khz and 32 
radials/4 wire cages that is roughly 1/8wl.  Or maybe ~3/8wl if they are 
3 wire cages.  A 200ft tall vertical. Whatever it was, they could put 
50Kw into it.

The reference book of patterns for 2 and 3 element verticals is
Directional Antennas, by Carl E. Smith, E.E., Cleveland Institute of 
Radio Electronics, 1946
and is available in pdf from scribd.com

It has hundreds of fascinating patterns created by Carl Smith's analog 
computer.  Antenna patterns for every possible need, if you have the 
space and expertise to work out the feed.

One comment in article had me wondering.  "The towers were fed by 
individual transmission lines from a phasing circuit that separately 
controlled the current and phase of each tower."

The 4 square was replaced with two 450ft towers for "increased radiation 
efficiency" in 1949 per https://www.broadcastpioneers.com/kywstory.html

Some pretty clever engineering by pioneers 88 years ago.

Grant KZ1W

On 3/29/2022 09:31, Radio KH6O wrote:
> This article describes the history of the development of directional MF
> antennas on our neighbor, the AM broadcast band.
> 
> 73,
> Jeff KH6O
> 
> https://www.radioworld.com/columns-and-views/roots-of-radio/the-development-of-the-directional-am-broadcast-antenna?utm_source=SmartBrief&utm_medium=email&utm_campaign=0028F35E-226C-4B60-AC88-AB2831C8A639&utm_content=8E01A4B9-193C-4BAE-B25D-23D973D5E345&utm_term=5e35c2b9-3044-4235-9961-04d879406e09
> _________________
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