Transmission Line Question

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ab3al:
But all of this only makes sense until you include the angle of the dangle in proportion to the droop of the hoop
   

R. Fry SWL:
Just to note that, although a transmitter may be specified for the nominal r-f output power it can safely produce across a given load Z connected to its output terminals, this does not mean that the r-f source within the transmitter has the same impedance as that load.

If that was true, then 50% of the r-f power produced by the final amplifier would be dissipated in the amplifier circuitry itself, rather than being available at the output connector of the transmitter.

It is evident that this belief is not valid just by comparing the r-f power in the specified load Z at the transmitter output connector to the total d-c input power supplied to its final r-f amplifier.  The d-c to r-f conversion efficiency of a transmitter using a Class C or D final stage r-f amplifier can be 75%, or better.  Some AM broadcast transmitters using digital processes in the final r-f amplifier have d-c to r-f conversion efficiencies of better than 90%.

The final r-f amplifier circuits in many transmitter designs using FM, CW or high-level amplitude modulation, and specified for 50 Ω loads have an effective output source impedance of just several ohms.  The lower that source impedance, the greater the conversion efficiency of that amplifier.

WD8BIL:
Quote

50 Ohm source driving 100 feet of RG213 with 200 Ohms connected at the far end - the Z seen by the source will be 105 - j80.

Uh duh.... thus the advent of the coaxial transformer! Thanks Steve! I forgot!  :-\

Which brings up another point: Not working for a few months slows the brain down!!

KD6VXI:
Quote from: ab3al on December 14, 2017, 01:41:42 AM

But all of this only makes sense until you include the angle of the dangle in proportion to the droop of the hoop
   


Now see, we where taught the angle of the dangle was inversely proportional to the square root of the beat of the meat???

I'm confused now.

--Shane
KD6VXI

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