I've read about stations doing that. How do they do it without the two signals interfering with each other? Transmit a physically "narrow" ~4.5 MHz ATSC signal that doesn't overlap the analogue audio carrier?
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FM Frequency of the week for Nov 12th: 87.75 and 87.9
- Thread starter ZantennaG1
- Start date
I've read about stations doing that. How do they do it without the two signals interfering with each other? Transmit a physically "narrow" ~4.5 MHz ATSC signal that doesn't overlap the analogue audio carrier?
The existence of WTTK is the only reason that CBS affiliated with them. Since that transmitter was moved to the northwest side of Indy, I'm not sure if it even covers Kokomo anymore.
From 1949 to 1957, WTTV was a network affiliate -- first as an NBC primary with CBS, ABC, and Dumont secondary (1949-54, in Bloomington on Channel 10), NBC only (1954-56, when they moved their main studio to Indy with the transmitter in Cloverdale, now on Channel 4), then ABC (1956-57, same setup). But whether the transmitter was in Cloverdale or Trafalgar, they couldn't cover the "money" areas on the north side of the market, which is why NBC left for Channel 6 and ABC for 13 when it signed on. It took Channel 29 to cover the wealthier parts of the market.
Part 15 devices are not allowed to use any frequencies assigned to TV. If one can operate on 87.7 or 87.9, it is blatantly illegal, but the FCC won't notice because the in-car units only have a range of a few feet, and of course, they're moving.
And/or it's so low-priority that they probably couldn't care less unless somebody's interfering with cell phone operations or 10kW NPR stations on 82-88.
Funny, I used to connect my VCR's RF output to the log-yagi on the roof and broadcast movies to the neighbourhood on channel 4 as a teenager like the subversive pinko commie scum I apparently was. Nobody gave me any grief about it, except my then-stepsister when she wanted to use the VCR. Few if any of those mid-late 1990s VCR RF modulators operated at power levels that could be considered "part 15" by any stretch of the imagination!
Yet we're all still here and the sun still rises in the east. Amazing.
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A dirty transmitter that could interfere with cell sites or other services certainly would attract their attention. No in-car transmitter will interfere with anything on the FM dial for more than a few seconds. Using one at home might be another story.
The power on those modulators had to be in the microwatts or less in order to prevent the TV it was connected to from overloading. I used to try connecting mine to a 1/4 wavelength (42 inches at 66 MHz) antenna and still couldn't pick it up in the next room. A cable modulator would run at higher power, but not those VCR things.
Where did you live at when you tried it?
I did that, But with a VHF Antenna with a Amp, Didn't go far on Ch. 3
In Massachusetts - this - covering much of the Boston metro area on 87.75:
B87FM – More Hip-Hop, More Dancehall, More R&B, More Urban Music
And soon to have competition from a legal low power TV station on ch 6 (WVCC-LD)...
B87FM – More Hip-Hop, More Dancehall, More R&B, More Urban Music
And soon to have competition from a legal low power TV station on ch 6 (WVCC-LD)...
The aerial may or may not have had an amp on it (seriously, I actually don't know). For a while it did but then it died -- Radio $hack, what do you expect -- so it was taken out of circuit and the TV just ran barefoot from then on. (Wish I could go barefoot but wouldn't dare with all the broken glass and other debris, so I live in sandals instead...) I don't know why he thought it needed one since local TV came in fine at that location; fools and their gold are soon parted, and perhaps some minimum-wage shlub at Rat Shack wanted to make an upsale. The 1994 Thomson RCA "Home Theatre" VCR we had at the time had a stupid-powerful RF output; out-of-the-carton, stock out-of-spec as obtained from Sears (not modded). Like, could receive it very weakly at the other end of the block on the battery-powered black-and-white strong. If I had to guess I'd say it put out at least a fifth or a quarter of a watt at the F-connector.
I did (maybe still do, somewhere?) have an old early 90s Scientific Atlanta cable modulator I got from my high school when they were upgrading the school's internal cable system in early 2002 before I graduated. The school's cable had been originally installed for a failled Channel One test project that the district cancelled early in its run because of controversy, and the cable infrastructure was left in place. It had 4 or 5 VHF channels. Channel 3 was where they'd run the morning announcements tape at the start of second period, filmed in the studio at the A/V room, and would repeat Educational Service District 112 Educational Television Consortium's "TV ETC" service the rest of the school day, straight off TCI/AT$T cable. Anyways, that modulator would put out a little more power than that into the same antenna, barefoot. Haven't powered it up in about that long; that might actually make for an interesting project to kill a Saturday when all the bike runs are rained out..... if I still have it and can get it working again after 20 years.
My mom's old house in Vancouver, WA. No coords or map links because she still lives nearby.
I was being borderline sarcastic with that comment. There are no cell services operating anywhere in low-VHF; it was intended as a political comment on where the F¢¢'s priorities (or lack thereof) are these days and whose hands are in whose pockets.
I did (maybe still do, somewhere?) have an old early 90s Scientific Atlanta cable modulator I got from my high school when they were upgrading the school's internal cable system in early 2002 before I graduated. The school's cable had been originally installed for a failled Channel One test project that the district cancelled early in its run because of controversy, and the cable infrastructure was left in place. It had 4 or 5 VHF channels. Channel 3 was where they'd run the morning announcements tape at the start of second period, filmed in the studio at the A/V room, and would repeat Educational Service District 112 Educational Television Consortium's "TV ETC" service the rest of the school day, straight off TCI/AT$T cable. Anyways, that modulator would put out a little more power than that into the same antenna, barefoot. Haven't powered it up in about that long; that might actually make for an interesting project to kill a Saturday when all the bike runs are rained out..... if I still have it and can get it working again after 20 years.
My mom's old house in Vancouver, WA. No coords or map links because she still lives nearby.
I was being borderline sarcastic with that comment. There are no cell services operating anywhere in low-VHF; it was intended as a political comment on where the F¢¢'s priorities (or lack thereof) are these days and whose hands are in whose pockets.
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I wonder if they could take the null out on WRME-LP toward WLNS-TV now that it's off of Channel 6, That would give better service to the Eastern Lake Michigan shoreline where a lot of Influential Chicagoans have "cottages". I don't imagine that Larry Langford would like it, but I don't know if WGTO and their translator come in well on the Shoreline anyway.
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Possibly. Hey, is it true that the digital side of WRME-LD now runs Jewelry TV?
It's quite possible.
I don't know about whether it was illegal or not, but I had several MP3 transmitters over the years and all of them could operate on 88.7 and 88.9, and I'd guess that most still do. But I'd guess that it wasn't a big deal with the FCC or they would have stopped it.
Also i ran my VCR through my parent's outdoor antenna and it would pick up in most of the house, but I never tried to see how far it would go outside the house. But I stopped doing it because of thinking it might interfere with WREG CBS 3 in Memphis in my area.
I just noticed I mistyped the frequencies. I meant 87.7 and 87.9. My dyslexic fingers struck again!
A dirty transmitter can transmit spurs and harmonics well into UHF. That could cause interference.
I bought one of those $15 car FM transmitters from Amazon for use with my phone. It was so dirty that it wiped out every signal on the band, except for the 100 kW stations on South Mountain, with hash. No way am I using it again.
Oof that's a bad transmitter. 🤣 Definitely only buy from brands you already trust (Sony, C. Crane, etc)
Nice! Some of those Chinesium transmitters are pretty dirty like that. You get what you pay for.
87.5 is the bottom end of the broadcasting band in many ITU region-1 areas (like Europe) and a valid frequency there. It's likely that your transmitter was programmed for the region 1 band plan, which is mostly compatible with region 2 (Americas) which starts at 87.9 (channel 200). The biggest difference, apart from pre-emphasis, is R1 uses 100 kHz spacing whilst R2 is 200 kHz so one needs to be careful they're on an odd-numbered frequency if they're going to operate one.
And since it was likely made in totalitarian China, you can bet that domination of the West is their ultimate design goal!
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Most "dirty" transmitters come from there.
🤣I've had some like that as well. There are several FM transmitters available at stores like Walmart now from major brands like Scosche, Monster, and Belkin that should be good quality now as well.
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