[Yaesu] Fwd: RF Metering

[Bob]

-----Original Message-----
From: Rob Atkinson <robk5uj at gmail.com>
To: Bob <kc3vo at aol.com>
Sent: Sun, Jun 5, 2011 11:41 am
Subject: Re: [Yaesu] RF Metering


Bob, I don't want to be the sole beneficiary of this; I suggest you 
share it with the entire Yaesu email list.

73

Rob
K5UJ


On Sun, Jun 5, 2011 at 9:38 AM, Bob <kc3vo at aol.com> wrote:

The better "Peak-Reading" RF power meters use a DIODE detector, and 
store/hold the peak RF level, so it CAN be reasonably accurately 
displayed on an analog meter. A 100 watt SSB rig will typically show 
only 30 to 40 watts, if properly adjusted for 100 watt peak SSB voice 
power, when the power is measured by a thermocouple type CW power 
meter, or a diode type CW power meter, without the PEAK circuit.  A 
meter such as the bird #43P,  set to indicate PEAK power, will 
accurately show the power as 100 watts, and will also show a 100 watt 
CW level as 100 watts, without changing any meter settings.  (With a CW 
signal, the PEAK and AVERAGE power levels are the same-It STAYS at its 
PEAK level) The electronic circuitry holds the peaks long enough for 
the mechanical meter to display them.  (This is why the PEAK meters 
require a battery or power supply)--73, KC3VO-Bob Curry




-----Original Message-----
From: Rob Atkinson <robk5uj at gmail.com>
To: Bob <kc3vo at aol.com>
Cc: david.kirkby at onetel.net; yaesu at mailman.qth.net
Sent: Sun, Jun 5, 2011 8:19 am
Subject: Re: [Yaesu] RF Metering


Well certainly the power being measured is carrier power or some 
continuous wave perhaps generated in SSB mode by a tone at a level the 
same as peak voice amplitude.  An electro-mechanical meter's ballistics 
won't allow for measuring the peak power from a speaking voice.   And 
always to this measuring into a 50 ohm resistance-J0 load, or whatever 
characteristic transmitter output and feedline Z the system is. 

73

Rob
K5UJ




On Wed, Jun 1, 2011 at 11:45 AM, Bob <kc3vo at aol.com> wrote:

Thermocouples in RF meters are a very POOR choice for measuring SSB
voice signals, due to the slow response! A Bird 43P is MUCH better for
SSB peak power, the thermocouple is OK for CW of FM type, AVERAGE power
readings, but finding a thermocouple with low enough inductance for
UHF/ MICROWAVE accuracy is likely to be a problem.--73, KC3VO, Bob Curry