Richard Harrison wrote:
Ian White, GM3SEK wrote:
"But here you pick up the pace. Instead of the detailed argument above,
suddenly whole chapters rush by in a single sentence."

Fair criticism. It reflects tiring of posting before its conclusion.

The Bird wattmeter`s firectional coupler distinguishes between incident
and reflected waves by their singular difference. Upon reflection of a
wave, either the voltage or the current it generates is reversed in
phase, but not both.

Bird takes equal samples of voltage and current from the wave.. When
there has been a reflection, the samples have opposite polarity and
cancel. When there has been no reflection the samples from that
direction of travel are in-phase and the sample total is double the
contribution of either sample.

Bird assumes the wave reflection model is valid, i.e.
Vsample proportional to Vtotal = vector sum of (Vfor+Vref)
Isample proportional to Itotal = vector sum of (Ifor+Iref)
Vfor in phase with Ifor, RMS Vfor/Ifor = 50 ohms, Vfor*Ifor=Pfor
Vref 180 deg out of phase with Iref, RMS Vref/Iref = 50 ohms
Vref*Iref=Pref

These assumptions are valid for a 50 ohm feedline of reasonable
length.

These assumptions are obviously not valid if no feedline exists
or if Z0 is not 50 ohms, which is, as I infer, Ian's objection.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---