On 5/4/2010 6:39 PM, Owen Duffy wrote:

Tom,

My use of "lossy" was to remind readers that capacitive reactance
obtained by using such a transmission line element is a relatively lossy
'capacitor'. For example. an o/c stub of RG213 for a reactance of -10
ohms at 144MHz has a resistance of about 0.1 ohms, or a Q of about 100.
That is not a huge loss, but quality capacitors achieve much higher Q
than that.

So, I don't know why one might use such a thing in a driven element,
introducing say 0.2 ohms of resistance which consumes about 0.4% of the
power if it was a R=50 feedpoint, when a similar reactance could be
obtained by a slight shortening. The purpose is probably not for
frequency compensation, it works the wrong way.

Is the loss significant, not really in this case, and it won't melt the
PE, but TL derived capacitors are relatively lower Q.

Owen

I'll take the .4%. I'll take 4%. It's a bulletproof easy way to make a
gamma match. I've never had one fail, and I've made quite a few.

And you need to define where you think lossy starts, because nothing
that we can afford to use isn't, and true room temperature
superconductors still aren't available.

tom
K0TAR