Suggestion - [HD] Digital "AM" section (for WMGG et al.)

[kfbkfb]

I didn't see a place to make suggestions for dedicated sections, so...

Given that [HD only] WMGG is on 24 hours/day, 7 days/week (reduced power at night) and that some Forum participants are able to receive WMGG, it might be useful to have a "clearinghouse" section for info about reception issues (during thunderstorms, far from the transmitter, near a computer producing interference in the AM band etc.)


Kirk Bayne

 

[Kelly A]

I didn't see a place to make suggestions for dedicated sections, so...

Given that [HD only] WMGG is on 24 hours/day, 7 days/week (reduced power at night) and that some Forum participants are able to receive WMGG, it might be useful to have a "clearinghouse" section for info about reception issues (during thunderstorms, far from the transmitter, near a computer producing interference in the AM band etc.)

For who, DX'ers? If someone cared enough to track that sort of information for the .0001% of the world population who were into that hobby, I supposed a database could be created. As of today, the number of MA3 stations can be counted on one hand.

 

[frankberry]

I didn't see a place to make suggestions for dedicated sections, so...

Given that [HD only] WMGG is on 24 hours/day, 7 days/week (reduced power at night) and that some Forum participants are able to receive WMGG, it might be useful to have a "clearinghouse" section for info about reception issues (during thunderstorms, far from the transmitter, near a computer producing interference in the AM band etc.)


Kirk Bayne

I've moved this thread into the HD Radio forum.

 

[frankberry]

I didn't see a place to make suggestions for dedicated sections, so...

Given that [HD only] WMGG is on 24 hours/day, 7 days/week (reduced power at night) and that some Forum participants are able to receive WMGG, it might be useful to have a "clearinghouse" section for info about reception issues (during thunderstorms, far from the transmitter, near a computer producing interference in the AM band etc.)


Kirk Bayne

While I have zero concrete evidence, I'm betting that digital AM reception would suffer badly from impulse noise such as thunderstorms and electrical interference. With analog AM, you hear the static "crashes" but with digital, I'm guessing that the digital audio will simply disappear until the receiver can re-lock onto the data stream. This could take several seconds.
If anyone has any further information, please share it with us.

 

[bulwnkl]

If you can get someone in Phoenix to turn an AM digital transmitter on, I'll happily listen for that and report here during this summer's monsoon season!
(-:

 

[kfbkfb]

Digital Radio Mondiale | DRM Digital Sound Vs Analogue

www.drm.org

Looks like 1470 WMGG is the lowest frequency Digital Radio broadcast in a band subject to all kinds of interference.

OT...the DRM people do answer a question about DRM in the FM band, but don't address using DRM in a fully packed FM band, in other words, using DRM in an unusable for FM frequency slot because it's used in a nearby market.


Kirk Bayne

 

[JBraddock]

While I have zero concrete evidence, I'm betting that digital AM reception would suffer badly from impulse noise such as thunderstorms and electrical interference. With analog AM, you hear the static "crashes" but with digital, I'm guessing that the digital audio will simply disappear until the receiver can re-lock onto the data stream. This could take several seconds.
If anyone has any further information, please share it with us.

Here's my report on WWFD's MA-3 reception during a storm in 2018. They've since made improvements to the signal acquisition time, so the 5-second drop-outs may be shorter now. I'll power up the XDR-F1HD the next time a thunderstorm moves through the area and see if the situation has changed.

 

[kfbkfb]

5 seconds...will listeners put up with that or change stations?

Anyone know how DRM copes with impulse noise?

(correction to previous post - 820 WWFD is the lowest frequency AM HD signal)


Kirk Bayne

 

[kevtronics]

Also wondering... when a digital-only HD AM signal drops out, does the receiver mute, or does it revert to analog, and thus give the listener a blast of noise until it recovers the digital signal?

 

[kenglish]

For who, DX'ers? If someone cared enough to track that sort of information for the .0001% of the world population who were into that hobby, I supposed a database could be created. As of today, the number of MA3 stations can be counted on one hand.

0.0001% would be 331 people in the United States (2021 projected population: 331,420,000), or 7875 people in the whole world (2021 projected population: 7,874,965,825).
Did you count them all, or is it part of the Census questionnaire?

 

[Kelly A]

0.0001% would be 331 people in the United States (

That's probably about the total number of DXer's in the United States.

 

[Kelly A]

While I have zero concrete evidence, I'm betting that digital AM reception would suffer badly from impulse noise such as thunderstorms and electrical interference. With analog AM, you hear the static "crashes" but with digital, I'm guessing that the digital audio will simply disappear until the receiver can re-lock onto the data stream. This could take several seconds.
If anyone has any further information, please share it with us.

In my commute listening to the fringe of WWFD, my experience has been:
* Going under high tension power lines will cause the station to mute until you're out the other side.
* If not much audio is cached, going under a series of overpasses will cause the audio to mute.
* If electrical noise is way over the digital signal, my radio will think the noise is analog and switch to analog. Then you hear the noise instead of the station' carrier. Same effect with an analog AM signal.
* Surprisingly, the amount of time for my radio to lock back on the station is pretty quick, but it depends on what the cause is. For example, going under power lines takes longer because the noise they emit has a long tail as you travel away from the lines. Going under an overpass, and the signal locks back on as soon as you cross under.

 

[kenglish]

Sounds like we are now discussing what Kirk was suggesting.
So why was he trolled for asking?

Also, might there be others on the board who would be interested in hearing the information, even if they aren't died-in-the-wool "DX'ers"?
BTW, I'm glad Kelly responded with his experiences...just curious how far out in the "fringe" does the signal get ugly?

 

[Kelly A]

Also, might there be others on the board who would be interested in hearing the information, even if they aren't died-in-the-wool "DX'ers"?
BTW, I'm glad Kelly responded with his experiences...just curious how far out in the "fringe" does the signal get ugly?

Just like analog, that depends on your personal threshold of acceptance. Being a curious listener, I'm willing to stick with dropouts probably longer or more frequently than a soccer mom who has no clue, nor cares, about how the music gets to her minivan radio.

The good news/bad news about what I hear from WWFD, is when my receiver is locked on, it sounds great. Even with quite low field strength. The bad is, too many missing packets just cause a mute.

I don't have an FIM 41 AM field strength meter anymore, but it would be an interesting experiment to see how low the field strength needs to get before one crosses into too many lost packets for your average receiver to decode. Just like analog, I'm sure a lot depends on weather and atmospheric conditions, antenna setup on the test mule, plus the noise floor in the area being measured. Any and all of those combinations could skew the results.

 

[kenglish]

I wonder if Hubbard would be interested in having MS&W do some test runs. They are set up for that sort of thing.

 

[Schroedingers Cat]

Just like analog, that depends on your personal threshold of acceptance. Being a curious listener, I'm willing to stick with dropouts probably longer or more frequently than a soccer mom who has no clue, nor cares, about how the music gets to her minivan radio.

The good news/bad news about what I hear from WWFD, is when my receiver is locked on, it sounds great. Even with quite low field strength. The bad is, too many missing packets just cause a mute.

I don't have an FIM 41 AM field strength meter anymore, but it would be an interesting experiment to see how low the field strength needs to get before one crosses into too many lost packets for your average receiver to decode. Just like analog, I'm sure a lot depends on weather and atmospheric conditions, antenna setup on the test mule, plus the noise floor in the area being measured. Any and all of those combinations could skew the results.

I doubt that even digital only broadcasts could be heard below the 0.5 mV/m analog contour. Currently in Michigan, WWJ 950 and WFDF 910, with their several hundred kilowatt "ERPs" in that direction, lose their digital signals on I-75, near Exit 181 near Pinconning, but are listenable to near their predicted 0.5 mV/m Daytime predicted signal contour in analog near Exit 215 near West Branch. According to V-Soft Zip Code, it is close to the M-3 predicted 1 mV/m contour where the digital signal is lost. In the Great Lakes region, that's about as good as it gets. Skywave is at best intermittent on any IBOC AM station, getting a digital ID and a few seconds of digital audio every once and a while, with greater than a predicted 1 mV/m 50% skywave.

 

[fybush]

I doubt that even digital only broadcasts could be heard below the 0.5 mV/m analog contour. Currently in Michigan, WWJ 950 and WFDF 910, with their several hundred kilowatt "ERPs" in that direction, lose their digital signals on I-75, near Exit 181 near Pinconning, but are listenable to near their predicted 0.5 mV/m Daytime predicted signal contour in analog near Exit 215 near West Branch. According to V-Soft Zip Code, it is close to the M-3 predicted 1 mV/m contour where the digital signal is lost. In the Great Lakes region, that's about as good as it gets. Skywave is at best intermittent on any IBOC AM station, getting a digital ID and a few seconds of digital audio every once and a while, with greater than a predicted 1 mV/m 50% skywave.

As I've noted frequently, my driving tests of WWFD's MA3 signal in 2018 and 2019 took me well past the 0.5 daytime contour with a very usable signal in the car. It was fairly solid (with occasional dropouts) in downtown Baltimore, in York PA and out by Andrews, all at around the 0.25-0.3 predicted contour, and it was locking at least sporadically in Harrisburg, at about 0.15.

 

[kenglish]

Digital TV signals only have to make the magic 15dB signal-to-noise number. The absolute signal level means nothing, as long as it can be boosted to what the receiver wants to see, without adding to the noise.
Does HD radio have a similar "magic" number?

 

[Kelly A]

Digital TV signals only have to make the magic 15dB signal-to-noise number. The absolute signal level means nothing, as long as it can be boosted to what the receiver wants to see, without adding to the noise.
Does HD radio have a similar "magic" number?

You can't compare the two. Completely different animals.

The difference between MA3 AM digital and DTV is available bandwidth, DTV uses 6 MHz per channel with enough headroom for redundant packets/Bit Error Correction. Plus noise floor at UHF frequencies is much-much less than Medium Wave.

Another thing to consider, is DTV reception has a standard assumption formula for average receive antenna gain and elevation: https://transition.fcc.gov/oet/info/documents/reports/SHVERA/SHVERA-FCC-05-199.pdf
MA3 has no such assumptions, because of a mobile/portable reception environment, and unlimited variations in antenna types and receiver gain with varying levels of environmental noise.

 

[kfbkfb]

Do AM[HD] broadcasts require non-omnidirectional format signals (now, due to interference into nearby analog AM, future, due to insufficient error correction in the AM[HD] signal, the overlap disrupting both the local and nearby signals)?


Kirk Bayne