[TowerTalk] Balun Recommendation

[Steve Hunt]

Ian,

Yes, when the choke reactance and the CM path reactance have the same 
sign there's a bonus. But what I was actually trying to show in that 
analysis is that the CM path reactance may have an upper limit; and if 
that's the case, even when the signs are opposite there may still be a 
very useful contribution from the choke reactance.

Jim's own figures show a #61 choke having >5000 Ohms reactance over a 
2:1 frequency range; if the worst-case path reactance is 2000 Ohms, we 
know that choke is going to provide a "net" 3000 Ohms impedance over 
that frequency range, no matter what. That seems to me pretty useful, 
particularly as it will handle a lot more power than an equivalent 3000 
Ohm choke wound on one of the lossy mixes.

I'm simply questioning whether we have too readily dismissed reactive 
chokes because "only a choke's resistance counts".

73,
Steve G3TXQ



On 24/04/2012 11:03, Ian White GM3SEK wrote:
> Steve has provided some new insights showing that reactances will often
> combine in our favor as well. When reactances add significantly to the
> installed impedance of the choke, then of course that is a very welcome
> bonus; but in a new RFI situation with no time for an in-depth analysis,
> I wouldn't want to bet on retaining that bonus across every amateur
> band. The only part of the impedance that we can depend upon in every
> possible situation is the broadband resistive component.
>
>