Audio Bandwidth of an AM Broadcast Station

AM Radio discussion. Directional arrays are FUN!
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Deep Thought
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Re: Audio Bandwidth of an AM Broadcast Station

Post by Deep Thought » Sat Mar 24, 2018 4:56 pm

kkiddkkidd wrote:
Sat Mar 24, 2018 10:30 am
Less mud and grunge from overdriving the highs.
And less crap coming back to the transmitter causing intermodulation products 30 KHz away.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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Dale H. Cook
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Re: Audio Bandwidth of an AM Broadcast Station

Post by Dale H. Cook » Sun Mar 25, 2018 4:53 am

I thought he meant that the entire transmission system was flat to 15 kHz including the audio. If everything beyond the transmitter is flat but he is using an NRSC filter then I agree that it should sound very good.

One of my AM clients has made the grade in the latest FM translator cycle. We initially thought we might get MXed, but of the three stations who had applied for the same frequency the one in between us and the other remaining station dropped out, and the remaining two will protect each other, so I'll be putting another translator on soon. The ATU will be getting a rebuild as part of the process so I'll have my first chance to broadband an AM in more than twenty years. The last one I did was a 1947 DA design that was screaming for it and, unfortunately, was torn down several years after the broadbanding. What a pity, as it had one of the last tank/jeep coil inputs in my career and I was so glad to see those go. Only one of my other current AM clients (another non-D) is broadbanded, and that was done years before I came on board, so it will be nice to do this one.

I still have two customers with two-tower DAs that I would love to broadband, but I am backup for both (the contract engineer has a full-time day job so they call me in only for time-intensive major problems). Neither is likely to ever get broadbanded as both run talk formats.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
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kkiddkkidd
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Re: Audio Bandwidth of an AM Broadcast Station

Post by kkiddkkidd » Sun Mar 25, 2018 6:07 am

Deep Thought wrote:
Sat Mar 24, 2018 4:56 pm
kkiddkkidd wrote:
Sat Mar 24, 2018 10:30 am
Less mud and grunge from overdriving the highs.
And less crap coming back to the transmitter causing intermodulation products 30 KHz away.
Yep...
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

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kkiddkkidd
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Re: Audio Bandwidth of an AM Broadcast Station

Post by kkiddkkidd » Sun Mar 25, 2018 6:18 am

Dale H. Cook wrote:
Sun Mar 25, 2018 4:53 am
I thought he meant that the entire transmission system was flat to 15 kHz including the audio. If everything beyond the transmitter is flat but he is using an NRSC filter then I agree that it should sound very good.
I don't recall the exact post but I think that his antenna was flat to 15khz AND he is running a 4.5khz wide short wave processor setting for voice only programming but no NRSC filtering. It probably sounds ghastly with music but fairly natural and loud for voice.

Later,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

W2XJ
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Re: Audio Bandwidth of an AM Broadcast Station

Post by W2XJ » Sun Apr 01, 2018 10:59 pm

What usually is overlooked is that audio bandwidth control should be separated from RF bandwidth control. In other words if you want 5 KHz audio response, put a filter with a Butterworth response BEFORE the processor and then set the processor output filter to something higher. That way you’re not processing frequencies that will get chopped off at the output and will avoid a lot of ringing around the output filter cutoff frequency.

I hear too many stations with a lot of HF intermod that could be eliminated by an input filter.

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