FM HD Power

This topic contains 17 replies, has 8 voices, and was last updated by  nosignalallnoise 1 year, 7 months ago.

Viewing 15 posts - 1 through 15 (of 18 total)
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  • #33764

    mwdxer1
    Participant

    Is the FM HD power still limited to 1%? I was wondering as it seems certain FM stations get out better in HD that others. One example is KQOC 88.1 Gleneden Beach. Their FM signal booms into the North Coast in HD. The 2nd channel in Spanish is also good. 107.5 KXJM is the only Portland station that is in HD most of the time. No FM HD on the North Coast though. The best from Seattle in KJR 95.7 in HD. Locks in well. I wonder if the FCC with allow 100% HD power in the future? Would there would be too much interference? I have two HD Sony radios with a 9 element FM yagi.

    Thanks.

    #33765

    semoochie
    Participant

    I believe the figure that’s commonly authorized is 4% but stations can get up to 10% on a waiver. That’s plenty but there still might be dead zones in town.

    #33768

    cbaravelli
    Spectator

    FM-HD stations lose program channel(s) ERP levels and some program deviation bandwidth to prevent intra-cross channel modulation interference. 7-10% in accordance with DAB / Eureka Consortium rules and FCC regulations. Dual HD channels are limited to 4-5% each.
    True digital FM broadcast is extensive in most Northern European countries and did start to begin in Canuckland with up to eight program channels. Fever to sell new broadcast gear has cooled since coverage areas are dramatically reduced (see USA HDTV) and no cares to listen to CBC Franquois 2.

    #33773

    nosignalallnoise
    Participant

    Okay, good day, eh? As I know, DAB never really caught on in the Great White North. I don’t know if anybody’s still transmitting DAB there (CBC?) or if it’s just aboot gone the way of the wolly mammoth, eh? Lack of market demand essentially told the format, “take off”.

    FYI, Ibiquity (i.e. DTS) radio is not at all related to ATSC digital television. “HD” radio and the high-definition ATSC formats are NOT interchangeable!

    #33775

    Andy Brown
    Participant

    “Is the FM HD power still limited to 1%?”

    FM stations operating with ERP and antenna height above average terrain (HAAT) combinations that fall within the station’s class may operate with up to 4% of the authorized analog ERP without prior authority from the Commission. However, the station MUST electronically file a digital notification in the Commission’s CDBS filing system within 10 days of commencing such operation. Operation with digital ERP between 4% and 10% of the authorized analog ERP may only commence after the Commission has granted authority for such operation. Requests for increased digital ERP may be filed electronically in the CDBS system.

    Stations operating with facilities in excess of the station’s class (“super-powered stations”) have different permissible digital ERP limits and different filing requirements for increased digital ERP. For these stations, digital ERP is limited to 10% of the ERP which, for the station’s antenna height, would produce a 60 dBu (1 mV/m) contour distance equivalent to the reference facilities for the station’s class (see Section 73.211(b) of the Commission’s rules). In addition, for a few stations operating with very high ERP values, the digital ERP may be further limited to 1% of the station’s analog ERP.

    https://www.fcc.gov/node/34029

    “Their FM signal booms into the North Coast in HD.”

    Propagation of radio frequency signals is independent of modulation method. Signal strength is determined by the power to the input of the antenna, the gain of the antenna, and the height above average terrain. Don’t confuse propagation with how well a signal’s detected modulation sounds which is a function of much more then how well the signal has propagated. It includes primarily how much interference is at at the location under test as well as the receiving antenna and receiver.

    “I wonder if the FCC with allow 100% HD power in the future? Would there would be too much interference?”

    The interference problem is already out of control. HD radio causes interference to its own analog signal (which is required), causes interference to other digital and analog signals and receives interference from other digital and analog signals. In the current hybrid environment, digital power will never be 100% of analog power.

    Only when there are no analog signals (not anytime soon) can the grid be redesigned so that the digital power is maximized and it won’t be numbers like analog power now has. Digital signals need less power to work properly at the same distance as an analog one. However, having said that, the entire FM Class structure would have to be redesigned and interference studies done in the all digital environment to determine how many classes and what powers are needed to put the digital signal at the desired distance from the antenna. Only then and in combination with whether they want to cram more stations into the same grid, can new classes be created. The entire 60 dBu contour thing will have to be re-worked because that was all based on FCC 50,50 curves (received by 50% of the receivers being tested 50% of the time).

    #33776

    nosignalallnoise
    Participant

    to its own analog signal (which is required)

    As I understand it there’s supposed to be a full-digital mode it can use, which excludes the analog center channel and uses the full (?) 200 MHz channel for data, as opposed to the current hybrid method of cramming data sidebands in the channel along with the FM signals. I doubt anybody’s actually doing this in North America full-time if at all. Please correct me on either point if I’m wrong.

    #33777

    semoochie
    Participant

    Assuming that HD FM picks up steam and actually becomes popular, it’s unlikely that full digital FM will occur within my lifetime. It’s more likely that broadcast will eventually be replaced by streaming or some other yet to be invented technology. However, I think it’s possible that we will begin to see full digital AM within the next ten years, even five.

    #33780

    Andy Brown
    Participant

    “I doubt anybody’s actually doing this in North America full-time if at all.”

    Full digital mode is not legal in the U.S. yet (you must be either hybrid or analog) but they did run some tests somewhere when the hardware was being developed to test full digital mode. You can find some specs for that here: http://nrscstandards.org/SG/NRSC-5-C/1026sF.pdf sec 4.4.2

    There are four digital systems in use around the world that are recognized by the ITU:

    Two European systems Digital Audio Broadcasting (DAB) and Digital Radio Mondiale (DRM), the Japanese ISDB-T and the in-band on-channel technique used in the US and Arab world and branded as HD Radio.

    All Digital Radio Broadcast systems share many disadvantages which don’t exist for Analogue to Digital TV changeover: About x20 more power consumption, Digital Cliff effect for Mobile use, very slow channel change, especially for a different DAB multiplex frequency, high transmission cost resulting poorer quality than FM and sometimes AM due to low bitrate (64K mono rather than 256K stereo), higher compression is more distorted for hearing aid users, usually poor user interfaces and Radio audio quality, not enough fill in stations for portable / mobile coverage (like 1950s UK FM). The Multiplex & SFN concepts are advantageous to State Broadcasters and Large Pan National Multi-channel companies and worse for all Local, Community and most Regional stations. In contrast almost all the aspects of Digital TV vs Analogue TV are positive with almost no negative effects. TVs could be used with a Set-box. Digital Radio requires replacement of all radios, though an awkward DAB receiver with FM output can be used with existing FM car Radios.

    #33783

    mwdxer1
    Participant

    Thanks for all of the great replies. Interesting that 10% is now the max. I wonder if 107.5 or 88.1 Gleneden Beach are using the 10% level? Some strong signals pegging the meter from Seattle will not stay in HD or even lock, and others that are equal or weaker do lock. The ones are all on Cougar Mt, so I would guess some operate with more digital power. Anyway to know how much digital power an FM station is using?

    #33785

    lastday
    Participant

    I would wager that KLTH-HD is above 4%. It carries surprisingly well to Eugene.

    I’m curious about KRVM-FM. Their HD coverage also seems pretty solid. I can intermittently get an HD lock in the car when in Oadridge. KAVE in Oakridge is pulling KRVM-HD1 out of the air for rebroadcast with a modified Sony XDR-F1HD and it’s 100% solid. (Though KAVE has other issues)

    #33787

    semoochie
    Participant

    KLTH-HD is 3.84KW ERP.

    #33788

    mwdxer1
    Participant

    KLTH will on occasion pop in HD, but 107.5 is the one that is is the best here.

    #33789

    boisebill
    Participant

    Here’s a list of AM stations that have done full HD testing.

    All Digital AM Radio Testing

    #33791

    mwdxer1
    Participant

    Yes, I caught the KRKO/KKXA test. Even with some fading at 150 miles, KRKO stayed in HD most of the time. KKXA on the otherhand was in HD off and on, but too much KGDD 1520 interference. With 100% power in AM HD, no problem locking here. In fact I can hook up my Eastern Beverage, and KSL 1160 pops in HD often at night. So even at 550 air miles. KSL puts in a strong signal here at night.I am surprised I get “any” HD here as I was told by a CE that he felt it would be unlikely to get HD here, considering the low power.

    #33794

    Borderblaster
    Participant

    If you continue to have wet dreams about IBOCK, then dipshit move out of the hinterland, all you do is succeed in bringing out the usual shill suspects.

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