Radio World has an article about technical developments to preserve analog FrankenFM operations on digital Channel 6 facilities:
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Developments to preserve "FrankenFMs"
- Thread starter davideduardo
- Start date
FM radio services on 87.75 MHz ?
Just checked, my Sony HD radio goes to 87.6, my Sony Boombox to 87.5, my car radio to 87.7, none will properly tune in 87.75.
The block diagram late in the article does show 87.7
(the linked article about WNYZ-LD + FM mentions that a directional antenna is used for the ATSC 3.0 signal, but it seems to me that a directional antenna wouldn't be needed for the analog FM signal since that spectrum space in the [full power] Ch 6 in Philadelphia is empty)
Kirk Bayne
Just checked, my Sony HD radio goes to 87.6, my Sony Boombox to 87.5, my car radio to 87.7, none will properly tune in 87.75.
The block diagram late in the article does show 87.7
(the linked article about WNYZ-LD + FM mentions that a directional antenna is used for the ATSC 3.0 signal, but it seems to me that a directional antenna wouldn't be needed for the analog FM signal since that spectrum space in the [full power] Ch 6 in Philadelphia is empty)
Kirk Bayne
It is not. WPVI is on channel 6, both virtual and RF.
I hope Franken FM's do get a second chance, particularly Me-TV Radio in Chicago, however I don't know how long we are going to drag this out before the FCC decides to put FrankenFM's out of their misery altogether.
At the end of the article, there is a quote by Keith Pelletier that says that analog on FM would go away soon. IMO, when Norway implemented this in 2017, the citizens were arguably not happy with DAB's reception, so I suspect there would be some angst in the US (especially amongst the older populations) if FM ever turned off here. The younger generations might not even bat an eye, but most folks 35+ would be in an uproar, because plenty of vehicular radios would be rendered obsolete, or would need a converter box to pick up the IBOC HD1 main channel. (DAB just will not be adopted here, put I do think an all-digital version of our IBOC signals could take over, and supply up to 7 channels with reasonable bitrate, sort of like DAB. Imagine tuning to 88.1 FM, and hearing hash, but on an HD radio, you would get a Public Radio Package, like HD1 NPR, HD2 Classical, HD3 Jazz, HD4 Local Artists HD5 College Student-Run Radio, HD6 Adult Album Alternative, HD7 Reading Services.) So to say that FM would be converted to digital is a bit naïve in 2022, as opposed to, per se, 1999. I still think the likely pathway is to shut-down AM/FM in favor of just flat-out streaming, but I feel like a clipped portion of the AM/FM bands could remain as emergency relay tools.
True, WPVI is transmitting an ATSC 1.0 signal, the lower sideband of the WNYZ-LD Franken FM signal could interfere.
Kirk Bayne
No. ATSC 3,0 modulation won't work on VHF frequencies. Too much terrestrial noise.
The original plan was a 6-month testing period for these new ATSC 3.0/Analog FM setups to prove that they won't interfere and that there's a pop-up demand for FrankenFM's. I don't remember the FCC ever saying what would happen if these ended up being successful, however almost all of the current STA's have been extended recently. KXDP-LD Denver, WTBS-LD Atlanta, and KBKF-LD San Jose was extended in January 2022, WRME-LD Chicago in February 2022, and WDCN-LP Fairfax/Washington just submitted a major modification to their signal about a week ago. Although it feels like the FCC is stalling here, all the tests have been largely successful, so I imagine sometime in 2023 these ATSC 3.0/FrankenFM's could be approved entirely.
I plan to contact Jampro to ask if their FM Sidekick Combiner will combine an ATSC 3.0 signal and an FM+HD signal (there's currently a problem with their contact us page).
AFAIK, ATSC 3.0 is approved for use in the low VHF channels (error correction can be adjusted in the ATSC 3.0 signal so that more error correction can be used for low VHF broadcasts).
Kirk Bayne
AFAIK, ATSC 3.0 is approved for use in the low VHF channels (error correction can be adjusted in the ATSC 3.0 signal so that more error correction can be used for low VHF broadcasts).
Kirk Bayne
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Doesn't matter. The terrestrial noise level on that side of the band is too high for reliable ATSC 3.0 reception.
Here it comes everybody: FCC decision due in June. https://www.radiodiscussions.com/th...sal-placed-on-fcc-june-meeting-agenda.749637/
The answer is absolutely, yes. The combiner is listed as being capable of combining a channel 6 with an 88.1 FM signal, which means it must have enough bandwidth to accommodate HD Radio.
Whether any actual HD tuners would be able to decode the resulting signal is another question, for two reasons:
(1) AFAIK the Franken FMs are still broadcasting on the NTSC frequency of 87.75 MHz, which is not something the HD Radio tuners were designed to receive. Analog tuners will produce imperfect audio, but I suspect HD tuners will produce nothing.
(2) Would such operation be in regulatory compliance? Keep in mind, the FrankenFMs are technically, television stations, and HD Radio is authorized for radio stations.
My HD tuner at home tunes in 87.7 and 87.8, but not 87.75. Based on my testing with KUWR's signal on 91.9, and KOLT FM's signal on 100.7, it does not flash HD on the offset frequencies (91.8 and 92.0, for example), however it does 0.3 Mhz away from the HD signal for some odd reason (So in this example, I've had 91.6 and 92.2 flash). I wonder with how flexible the ATSC 3.0 signal is, if it can somehow accommodate the HD audio being moved to either 87.7 or 87.8?
This is because the HD radio has a wider bandwidth than analog FM. HD bandwidth is +- 200 kHz from the frequency you tune.
If you tune 92.2, your HD receiver is searching between 92.0 MHz and 92.4 MHz, and probably finding the HD sideband centered at approximately 92.05 MHz.
ATSC3.0 has no intrinsic support for analog audio. All the Franken-FMs are doing is running an ATSC 3.0 transmitter on Channel 6, and an analog FM transmitter at 87.75 into a common antenna. So the answer here is "very likely yes" - moving the audio carrier would likely have no impact
That would explain it, thank you.
I wonder what the implications of this would be?
I'm not sure that FM + HD would work with the FM Sidekick Combiner, the bandwidth (blue line) seems too low.
I'm a little surprised no one has mentioned using HD on Franken FMs.
Kirk Bayne
WNYZ 87.7 is most definitely directional. Back when it was Pulse 87.7 I remember it had trouble in Manhattan, Staten Island, and central NJ but it made it to Suffolk county and Fairfield county well.
Earlier this year WPGF-LD 6 in Memphis became the first station there to upgrade to ATSC 3.0, and they have restarted the Franken FM: https://radioinsight.com/headlines/223555/memphis-is-bumpin-for-the-third-time/
TV channel 6 analog audio has always been a sort of radio reception hack. It's off-frequency for most digital tuners. Some sound OK tuned to 87.7 or 87.8, others don't. The Franken stations used it anyway because that's the audio frequency allowed by the TV license and it worked well enough to get the job done on FM, even if it wasn't perfect.
If the FCC does decide to officially sanction it, would be nice if they allowed it to go on 87.70 so it would work properly on a standard digital FM tuner. WNYZ-LP always had a lot of hash-like distortion on my digitally tuned radios
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