[Yaesu] Fwd: RF Metering

[Bob]

SOME 100 watt rated SSB rigs are indeed, clipping at 30-40% average 
power indication.  The actual level indicated at clipping varies 
GREATLY, as it is dependent on the tonal characteristics of the person 
speaking into the mike, as well as the audio characteristics of the 
mike and radio circuitry, to include filter, carrier point, and 
alc/speech compression.  Attempting to get any sort of ACCURATE power 
setting of a SSB radio using an AVERAGE power meter is almost 
impossible, due to the MANY variables in both the METER, as well as the 
radio and operators voice!
     I gave the 30 to 40% level as what a typical new ham, or "CB radio 
convert" might see as a MAXIMUM power reading on his/her average power 
meter when transmitting into a dummy load, and attempting to see if the 
output is OK--often, these unknowing operators will crank up the mike 
gain beyond normal levels, to attempt to see 100% output, only to be 
dissapointed when only 30-$40% of rated power is shown on their average 
power meter.  This is typically what is SHOWN under such condititions, 
but NO, it is NOT indicative of any radio defect, NOR is it necessarily 
indicative where you should set your mike gain for good transmitted 
signals!  As before, I advise all operators to spend some time to 
actually study the theory behind SSB and other aspects of amateur 
radio, using a good reference such as the ARRL HANDBOOK.--73, KC3VO, 
Bob Curry


-----Original Message-----
From: Dr. Gerald N. Johnson <geraldj at weather.net>
To: yaesu at mailman.qth.net
Sent: Sun, Jun 5, 2011 1:17 pm
Subject: Re: [Yaesu] Fwd: RF Metering


A rig showing 30 to 40% power on an average reading wattmeter is
clipping, its being over driven. Should should be more like 20 to 25% 
of
peak though that will depend on the voice, the microphone, and the SSB
filter and their relative phase responses. Some combinations will do
better, some will do worse.

73, Jerry, K0CQ

On 6/5/2011 11:36 AM, Bob wrote:
>
>
>
> -----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
>
>
>
______________________________________________________________
Yaesu mailing list
Home: http://mailman.qth.net/mailman/listinfo/yaesu
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Yaesu at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html