XEEZ 970 Radio Palacios is broadcasting an AM HD Radio signal from the U.S./Mexico border town of Caborca, Sonora, using a Broadcast Electronics transmission system.

XHTY-FM 94.5 in Tijuana on the FM Side has installed a Nautel V10 HD Radio transmitter. The station is operated by Uniradio.

• Red – 3.0 mV/m – Generally the Sellable area of the station
• Purple – 0.5 mV/m – Rural protected service area, but nobody would buy ads.
• Blue – 0.1 mV/m – You might still get it on a car radio

For FM they are:

• Red – 60 db/uV or 1.0 mV/m – Protected service area for Class A and C stations
• Purple – 50 db/uv or 0.316 mV/m – A pretty weak Signal, nobody would buy ads.
• Blue – 40 db/uv or 0.1 mV/m – You won’t pick it up, except in rural areas

I determined this by comparing the plots of sample stations in Radiosoft’s Comstudy with their Radio-Locator maps. Hopefully this clears a few things up!

Official statement (translated):

“Considering the extent of the development and implementation of the IBOC system in the United States of America, Mexico is required to take decisive action so that [the country's AM and FM radio stations] in the zone located within 320 kilometers of the northern border of Mexico can transmit at the same technological level so that they can provide the benefits of quality service to the radio listening public.”

The NRSC also adopted a guideline for recommended bandwidth for AM transmission. NRSC-G100 provides guidance for operators who would like to decrease first adjacent channel interference by operating with bandwidth narrower than the 10 kHz limit. Using the full 10 kHz bandwidth is lost on most receivers, as nearly all receiver IF filters limit audio response to much less than 10 kHz. Benefits from this technique are limited to cases where the licensees mutually agree to bandwidth reduction of stations that interfere with each other.

This is one more bump in the road for digital Medium Wave Broadcasting, but I think that our neighbors south of the border are probably just reserving their places at the table. I have heard that at least one Mexican station has begun broadcasting in IBOC.

• The report finds: Internet radio listening has increased 50% in the last year
• Internet radio reaches 19% of 18-34′s weekly
• Both XM and Sirius are recognized by more than 60% of the public
• Satellite listeners are an upscale audienc: 27% have incomes over $100k
• There is confusion between podcasting, internet radio and downloadable music
• More than half of those who have listened to podcasts are under 35, and 20% under 17
• Interest in HD radio is up: 8% very interested, and 27% more are somewhat interested
• Most people report the desired price point for an HD receiver at $50 to $100
• 77% of listeners report that they expect to listen to the same amount of AM and FM radio as they do now
• Digital radio users have not decreased the amount of time they spend listening to AM and FM radio

The results showed that mutually reducing transmission bandwidth down to 5 kHz  is a big plus for speech.  There was either a benefit, or no change from the 10 kHz results when reducing the transmitted bandwidth to 7 kHz irrespective of format or first adjacent channel interference level.

The study was done with a selection of receivers, and used blind A-B testing to determine listener preference.  This methodology is superior when the sources are a selection of several transmission bandwidths.

This study assumed symmetry:  both the desired signal and the undesired signal were limited to the same bandwidth.  This implies a standard to be adopted by all stations within the AM band, which may or may not be a factor for stations that receive interference from stations in other countries.

Since stations broadcasting speech receive a big plus, there will probably be pressure by the “talkers” to adopt the narrower 5 kHz limitation.   This is also the bandwidth limitation required for medium wave HD radio’s analog signal.

The study did not include the effect of HD radio interference to first adjacent channel stations, and whether an analog station has any benefit from wider transmission bandwidth when an HD signal is the interferor.  In the end, HD radio’s medium wave “Digital Only” signal will be an excellent neighbor to other “digital only” and Analog stations, but I expect few stations will be moving to this mode in the next year or so.