"JGBOYLES" wrote in message
...

All radio people suffer from delusions of measuring accuracy.

RF power measurements are the most inaccurate of all.

The accuracy of measurements are a function of the instrument user.


They who attempt to grasp support by stating the manufacturer's type
number
of the instruments used are most in need of the self-confidence it falsly
generates.

Hi Reg. What exactly are you talking about? I had a few minutes in
between
Hurricane Ivans wrath to get the Emergency generator cranked up and had a
chance to read this. Lucky you don't have these things in the UK.
73 Gary N4AST

Gary,

I saw an interesting curve at a resistor manufacturer's web site. It plotted
resistor error as a function of F(MHz) x R(Meg) for 1/4 W carbon resistors.
To make a long story short, the resistor error will be about 20% where the
Megahertz x MegaOhms = 1. That means the resistor value will be 1/
Frequency. So, at 30 MHz, the resistor will be in error by 20% if it is
bigger than 1/30 =.033 Meg, or 33K. That, I believe ignores capacitive
effects. Personally, I have never tried to put RF through a resistor bigger
than a few hundred Ohms.

It occurs to me that you can ignore capacitive effects if you make all
resistors identical. For instance, if you want a 3:1 divider make the series
resistor 10K, and the shunt resistor two 10K resistors in parallel. Of
course, you will need a high impedance load on it. Let's see if anybody
shoots this down.

Tam