AM Redux: Beyond FM translators

ProcessingLab Jeff_2560

V6N7 8.15.15
AM gets a bad rap. Fortunately, recent changes to FCC regulations are helping some AM operators turn things around with the use of FM translators.

We’re firm believers in translators to extend coverage, which explains why we’ve just come out with the FM-25 audio processor for this purpose (we also make a step-up version, the FM-55).

But we’re also firm believers in AM radio and began to wonder why so little in the way of new technology is available to adequately process the AM signal. So for our engineers Jeff Keith, Steve Dove and Mike Erickson, it was back to the drawing board --- and Mike’s large collection of AM radios. “We went beyond the usual thought process that every single AM radio made in the last 30 years is ‘bad’ and actually found some that were quite good,” says Mike, who got his start in AM radio and is now Wheatstone’s field engineer. “Yes, there are examples of bad AM radios out there today, and it may take some hunting to find a good one, but they are out there and not horribly expensive.”

ProcessingLabWIthFolks 2000With this knowledge, the trio set out to build a modern AM audio processor that could make the best possible tradeoffs between radios with narrow bandwidths and radios that were more forgiving. “The multiband limiters and the entire backend are different from what we offered in our previous AM-10 audio processor and in our more recent VP8 processor,” says Lead Product Development Engineer Jeff Keith. “Those are great boxes, but we wanted to take our new offering to the next level.”

Included in the resulting AM-55 audio processor is what Mike Erickson calls “a real world” AGC/compressor/limiter that’s specifically tuned to the challenges of AM bandwidth. “We’ve seen what happens when you take an FM processor and slap AM filtering and limiting onto the back of it. That’s not where we wanted to go here. This was a complete rethinking of AM processing,” he says.

The new AM-55 is in production and expected to ship by next quarter.

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