AM digital

[secondchoice]

I just did a quick read but apparently the commission is making it easyer to go all digital. If I read this correctly you have to reduce power by 6 DB., and fill out a couple of forms. That will save a little on the power bill. Also there is an interesting comment on "extra" bit rate".

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I really haven't done a lot with AM lately except repairing over the hill transmitters. Who makes a "reliable" 1 and 5 KW rig that can do all digital under $10,000 for the 1KW unit would be good?

 

[ContinuousWave]

All digital has been allowed for almost a year if not longer...just need to notify the commission...there is NO power drop AFAIK ....not sure of the J1000 Nautel is digital capable...the DAX is but you won't find a SS 1kw below10k these days unless it's used

 

[24pulsar]

The Nautel J1000 is capable of digital -- and therefore, the all-digital MA3 mode -- and is essentially the only 1kw AM on the market today besides the BE AM1A (which is also capable of digital). I am surprised that BE, under Elenos, is continuing to manufacture these units. Perhaps they are simply selling overstock.

There is the Armstrong X1000B, which is closer to $10k and can pull off digital, but everything I've read indicates that these units should be well avoided. I haven't heard a single good story about this box. Last I heard, Armstrong's main source of revenue was the contract for NOAA Weather Radio transmitters, which were RVR-made anyway.

 

[Kelly A]

All digital has been allowed for almost a year if not longer...just need to notify the commission...there is NO power drop AFAIK ....not sure of the J1000 Nautel is digital capable...the DAX is but you won't find a SS 1kw below10k these days unless it's used

I believe the comment about 6dB is a standard PA stage designed for analog AM isn't capable for full power MA3. WWFD ran into this with their original BE transmitter. They had to reduce power to accommodate a continuous broadband digital carrier running RMS rather than peak modulation. Even I believe the J1000 still needs to be limited to 500W in MA3 mode.

 

[frankberry]

I believe the comment about 6dB is a standard PA stage designed for analog AM isn't capable for full power MA3. WWFD ran into this with their original BE transmitter. They had to reduce power to accommodate a continuous broadband digital carrier running RMS rather than peak modulation. Even I believe the J1000 still needs to be limited to 500W in MA3 mode.

In my television experience, our 25kW analog transmitter was only capable of producing 12.5kW in the digital mode. The difference had to do with the method of measuring transmitter output power.

 

[Kelly A]

In my television experience, our 25kW analog transmitter was only capable of producing 12.5kW in the digital mode. The difference had to do with the method of measuring transmitter output power.

Yep similar thing Frank. Peak sync visual power, vs RMS.

 

[secondchoice]

Looking at the financial side would a class C (with 99 percent of the audience listening to its’s FM translator) save enough money on the power bill going all digital to justify the cost of a new transmitter? Is there enough “extra” data to cancel lightning’s “crackle”?

 

[Kelly A]

Looking at the financial side would a class C (with 99 percent of the audience listening to its’s FM translator) save enough money on the power bill going all digital to justify the cost of a new transmitter?

It depends. One station owner in Florida, and Hubbard made the ground breaking decisions to take a beleaguered AM station and make it full MA3 mode. Honestly, the cost of doing this isn't just purchasing an expensive transmitter. If a station is directional, many hours of work 'broad-banding' the antenna system to allow-for the most bits to reach the airwaves. Using consulting engineers may be involved to either redesign antenna phasing or antenna tuning units, then hours spent tuning it all up. Of course the new antenna gear needs to be custom built by someone. That costs money too.

Is there enough “extra” data to cancel lightning’s “crackle”?

If you're talking about bit error correction, where duplicate bits are sent in case some get lost, with AM MA3 mode, not really. Some radios have a couple second buffer that cache some packets which might carry you over during a quick interference event, but not long.
Remember, AM doesn't allow for much real estate within a channel, so there's barely enough room to transmit audio and some PAD data. That doesn't leave hardly any headroom for sending extra bits.

 

[secondchoice]

IMHO Digital only AM should have a higher bit rate. I get 10 years+ ago they wanted both analog and digital in the existing 10K slots because there was still analog listenership. They should have anticipated that someday there would be digital only usage. assuming there is a 2K "guard" that leaves 8k hertz. The old internet dialup operated in a slightly less than 4 K channel and could deliver 50+kb data. There are many data compression schemes. Someone with a higher pay grade than me should be able to come up with scheme that provides a higher bit rate that will work with the few existing digital AM radios in place yet still allows for 2 stereo channels that sound better than the current satellite radio.

 

[Kelly A]

IMHO Digital only AM should have a higher bit rate.

How would one get a higher bit rate with only 10kHz of channel to work with?

I get 10 years+ ago they wanted both analog and digital in the existing 10K slots because there was still analog listenership. They should have anticipated that someday there would be digital only usage. assuming there is a 2K "guard" that leaves 8k hertz.

The thought was IBOC as a transition someday to full digital mode. Unfortunately, it took too long for HD-anything to take hold, let alone be available to consumers. Listeners had abandoned AM years earlier. Whereas I applaud stations who have taken the leap to go MA3, it all came too late to save AM as a form of traditional media.
It didn't help that old Luddites have fought IBOC for AM all along the way. They'll end up taking AM with them to the grave.

The old internet dialup operated in a slightly less than 4 K channel and could deliver 50+kb data. There are many data compression schemes. Someone with a higher pay grade than me should be able to come up with scheme that provides a higher bit rate that will work with the few existing digital AM radios in place yet still allows for 2 stereo channels that sound better than the current satellite radio.

MA3 mode actually sounds as good, if not better than FM stereo. The audio quality is impressive, until an electric bus drives by, or you drive under a overpass, high voltage power lines...etc.