[Amps] Manganin RF choke?

[Manfred Mornhinweg]

Hi Colin,

> Anyone built an amplifier using such an rf choke, or tested such a choke on 
> a network analyzer?

I haven't heard that idea before, but it is very common to place a 
resistor in parallel with a choke, to lower its Q and discourage 
self-oscillations. At least in solid state VHF amplifiers, it's more 
common to do this, than to use a choke without resistor!

The advantage of using the parallel resistor, instead of distributed 
series resistance in the case you mention, is avoiding voltage drop of 
the DC supply. RF-wise, the two arrangements work differently over the 
spectrum, but both can be used to gain stability at the expense of 
efficiency, and for a single, give frequency, a system with series 
resistance or parallel resistance can be designed to behave exactly the 
same way.

Interesting idea, anyway!

Manfred.

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