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testing modultion no meter
- Thread starter Splash1
- Start date
In order to make a true test of modulation you need either a REAL modulation meter (not like what most CB type modulation/power/SWR meters are) or better yet an oscilloscope.
a cheap and dirty way of doing it is have a extra radio no antenna hooked to it
about 2-3 feet away and monitor your audio. if it squeals either move the monitor
radio futher away or just turn down the volume knob as it will be very quiet
with no antenna but will pickup your signal if close enough.yea this is cheap
and dirty but it does work .an oscope is really the right way
about 2-3 feet away and monitor your audio. if it squeals either move the monitor
radio futher away or just turn down the volume knob as it will be very quiet
with no antenna but will pickup your signal if close enough.yea this is cheap
and dirty but it does work .an oscope is really the right way
Hotrod..thats a great idea..never thought of that one..i remember a long time ago i read somwhere to put a constant tone to the radio whilst turning up the mic gain and when the needle stops going up thats where you leave it..not sure on the particulars though,thats why i posted the question....
Put your radio in SSB mode with the mic gain turned all the way down. Key up and talk normal into the mic as you slowly increase the mic gain. Keep an eye on your meter, and once you get to where you no longer see an increase in power, stop, then back the mic gain off a hair.
Please tell me how this is even remotely accurate??
You can't tell percentage of modulation by ear. Even a bit of over modulation of a few percentage will not be detectable by ear.
See my comment above. This method is just as (in)accurate or even worse as it simply shows where the transmitter's alc level is set and has nothing to do with modulation level.
See comment one post above. You cannot accurately set modulation levels by watching an RF power meter and adjusting audio for maximum output especially using a complex waveform such as speech.
Most external meters for CB use aren't the best for critical testing - true. But they are better than nothing and can get reasonably close. Provided it has some quality to it. The margin of error is generally too high with them.
The ParaDynamics brand meters are probably the best of the bunch. Ham-type quality meters don't have a modulation function - at least the ones I've seen or know about. Seen the PD's go for about $50/used. Same cost to have a shop set the entire radio up for you. I would go for the latter . . .
http://www.pacetronics.com/prodpage...ed=75&Group_Selected=230&product_Selected=697
The ParaDynamics brand meters are probably the best of the bunch. Ham-type quality meters don't have a modulation function - at least the ones I've seen or know about. Seen the PD's go for about $50/used. Same cost to have a shop set the entire radio up for you. I would go for the latter . . .
http://www.pacetronics.com/prodpage...ed=75&Group_Selected=230&product_Selected=697
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Best bet is to get a decent rf power meter, in avg mode your peak output would be roughly 1 and 1/2 times the resting carrier @100% modulation and in pep mode you should see a 4 to 1 ratio and the same modulation.
Again I ask, how do you test mod levels using this method which has nothing to do with modulation and everything to do with RF output and alc levels NOT related to audio. What is the electronic principle behind it or is it simply word of mouth that started at Bubba's CB shop and Steakhouse.
Even then you could be off by as much as 10% or more depending on the accuracy of the power meter. You would also be hard pressed to make a good measurement using regular voice and not a steady tone.
like i said in my first post a quick and dirty way. another words its NOT the
best way ,and i did admit the best way was a oscope.his question was
if he DIDNT have a meter .if he dont have a meter im sure he wouldnt have
a oscope
Yeah I know, what if a guy were to just use amps drawn from a resting carrier to peak draw and then if he were smarter than me were somehow able to figure out the gain of his rf device and then figure in the loss in the push/pull amp out then deduce a close gestimate?