[TowerTalk] Baluns/tutorial/notes applied to the AV640

[Ian White GM3SEK]

Jim Brown wrote:
>>If I understand that correctly that is the
>>difference between the Guanella balun and the experiments run by W8JI?
>
>That series/parallel configuration is a well established design by 
>Guanella (from the 60s, I think).

The devices that we are (mostly?) discussing here date back to 1949:
“High-Frequency Matching Transformer,” US Patent 2,470,307, 17 May 1949

> An important part of that balun is the design of the common mode 
>chokes that make up each leg. What I've been talking about here with 
>Steve is using chokes in that circuit that are each 5K ohms resistive 
>over the operating range. This provides excellent choking action and 
>rather low dissipation.
>

Unfortunately Guanella muddied the waters by publishing another patent 
in the 1960s:
“High Frequency Balancing Units,” US Patent 3,025,480, 13 March 1962.pdf

This patent featured no less than 39 different examples... and some of 
those are *very* different! The first few are devices that build on the 
1949 patent. But then the claims wander off to include devices that have 
no common mode choking action at all, and even impedance transforming 
ununs. Almost the only feature that some of them have in common is the 
name "Guanella".

So whenever we see that term "Guanella balun", we need to be a little 
careful. It doesn't necessarily define any one electrical class of 
devices.



-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek