[AMRadio] Testing a modulator


RICHARD GEORGE k6kwq at msn.com
Thu Feb 28 18:37:47 EST 2008


Great idea thanks!

K6KWQ Dick
 Amps by "MORE POWER"


----- Original Message ----- 
From: "John Coleman" <jc at pctechref.com>
To: "'Discussion of AM Radio in the Amateur Service'" 
<amradio at mailman.qth.net>
Sent: Thursday, February 28, 2008 2:57 PM
Subject: RE: [AMRadio] Testing a modulator


Hey Rick
Put a 300 ohm resistor in series with the bottom leg of you parallel
resistors then probe across the 300 ohm there will be about 1/10 the voltage
therefore safer for you and the scope.  100 Watts into 3000 ohms would mean
about 547 volts RMS (about 1320 volts peak to peak) across the whole load
but only about 54 volts RMS (132 volts peak to peak) across the 300 ohm.

John, WA5BXO





-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of RICHARD GEORGE
Sent: Wednesday, February 27, 2008 10:03 PM
To: amlist
Subject: [AMRadio] Testing a modulator

How does one test a modulator. I will soon have a modulator capable of
around 100 watts of audio. I know that I do not want to run the secondary of

the transformer unloaded. Would it be OK to make dummy load out of a bunch
of parallel connected 3 watt resistors, say about 60 watts worth at the dc
resistance I will be looking at (3000 ohms).
I know that this would only be good for short tests using my O scope and
audio gen. Any better ways.

I ran a lot of VHF AM back in the day, but only at 5 - 10 watt levels.

K6KWQ Dick
 Amps by "MORE POWER"

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