Any value in obtaining one of the CB/HAM modulation meters for use when adjusting an AM transmitter for the best sound? To date, I've been setting things by ear using the controls on the Metzo transmitter and a good quality receiver to judge audio quality. It works, but the process can be slow.
Metzo features built in metering, but it isn't very helpful. Consisting of three LED's.
Any value in obtaining one of the CB/HAM modulation meters for use when adjusting an AM transmitter for the best sound? To date, I've been setting things by ear using the controls on the Metzo transmitter and a good quality receiver to judge audio quality. It works, but the process can be slow.
Metzo features built in metering, but it isn't very helpful. Consisting of three LED's.
Hello 1710AM (hmmmm....interesting choice of frequency).
About these meters, it is probably not worth it. The major effect you want to determine on AM modulation is minimum carrier amplitude at audio peaks. You do not want the carrier to "pinch off" because this will produce extreme wideband interference and audio distortion. I do not know if these meters detect this. The ones I have seen respond to the maximum peak of the carrier and this is not what you need to check.
The best way to monitor modulation is with an oscilloscope. Decent scopes are available on a popular auction website in the $25 to $50 range. Watch out for the S/H charges though. Anything with above 5 MHz. bandwidth will work well for AM modulation monitoring. Almost anything with a BNC connector will work as a probe for this purpose. "Real" probes will cost a lot more than the scope.
If you get one with an X-Y capability (most two channel scopes have this), there is a great technique called "trapezoidal display" that is very useful for setting up and monitoring an AM transmitter. It not only gives a display of the modulation level but also shows the linearity (fidelity) of the transmitter modulation.
I use my scope (Hitachi V-125-F) to set the levels on my SSTRAN and Ramsey AM transmitters and it is really easy and the audio sounds great. I use a 1 mH. inductor from the probe to ground to eliminate 60 Hz. interference and attach a short piece of wire to the probe as a test antenna. The patterns I get are "textbook" in quality. A scope is not useful for monitoring FM.
I recommend you consider getting a used scope instead of getting a meter.
Neil
Neil, You mention owning a SSTRAN and Ramsey, I assume AM25. I have both yet haven't much success with the AM25. Poor audio mainly, and it doesn't reach a sharp peak when tuning to antenna, therefore not the greatest range. Understand that the AM25 will only do about 80% modulation. Would sure like any help that you'd be willing to share about the unit. JimB
Jim,
Glad to share my experience and I would like to hear yours. How about I start a new thread on this so we don't hijack this one?
Neil