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You all remember the old AMPS networks

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Changes of FCC regulation, lack of market demand and general obsolescence. In 2008 when the FCC modified rules to make AMPS carriage optional, most telcos were really quick to get rid of their AMPS services. There wasn't as much money to be had in SCPC AMPS services as there is in multiplex digital services.

Funny thing though, depending where you are, if you are lucky enough you can sometimes find very small private (corporate?) AMPS base stations still in place. Usually corporate internal PBX patches I think. A friend and I came across one on a Moto brick fone a couple years ago that we believe was either at Boeing (Gresham, Ore.) or Wafertech (Camas, Wash.). What you can do with it (if anything) depends how the host PBX is configured, how big the company is and how far abandoned-in-place the base is. You'd probably stand a better chance of finding one at a huge multi/national headquarters or field office than a smaller local or regional-based company.

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Carriers couldn't wait to get rid of AMPS. It was a spectrum hog. They could compress a lot more GSM and CDMA calls in the same channel space.

 

In fact, AT&T finally got rid of 2G (TDMA) in January 2017. Again, lack of market share, spectrum hog, and everyone had finally moved on to GSM or LTE. In fact, 5G (actually not really a consumer standard) is on its way soon. More signals, less need for the older crap.

 

It was pretty amazing. In 2008 AMPS went away, in 2009 NTSC (analog) television went away. And in a few years, the current digital ATSC will go away (ATSC 1.0) because ATSC 3.0 is around the corner. And that will use even less spectrum because the FCC is giving that away to the cell companies. ATSC 3.0 uses more compression than the current ATSC 1.0 does.

 

And don't get me started on the landline side of things. I see huge changes in the next 5 to 10 years.

 

Ain't technology grand?

 

 

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Again, lack of market share, spectrum hog, and everyone had finally moved on to GSM or LTE.

 

Actually, they shut down the GSM network too; only T-Mobile provides large-scale GSM service in the US now. I'd argue that probably has more to do with AT&T's corporate politics than general obsolescence, but if T-Mobile follows suit, we'll definitely talk. But yeah - as others have said, by 2008, basically nobody made new stuff that spoke AMPS, and it used up a considerable amount of spectrum to boot. I don't think surveillance is a huge issue to most consumers judging by how the Snowden leaks have gone down, but A5/1, the encryption standard used in GSM, has been considered insecure for quite some time now. I dunno about UMTS and LTE, but you do hear about people devising attacks against them occasionally. To what degree though, I'm not quite sure.

 

EDIT: https://en.wikipedia.org/wiki/KASUMI

 

That being said, I think CDMA has been facing the axe as well. From what I understand, that has a lot to do with Qualcomm doing licensing on an annual (or monthly, I forget which) basis. Once they end of life the base station equipment, unless you can find some way to bypass the licensing (which would probably be a serious breach of contract. No established carrier would dare upsetting a big manufacturer like that), it's basically a paperweight; end of story. Someone who works with that sort of thing has remarked that a lot of recent carrier-side infrastructure is no longer made with the idea of longevity in mind.

 

Quote

 

Funny thing though, depending where you are, if you are lucky enough you can sometimes find very small private (corporate?) AMPS base stations still in place. Usually corporate internal PBX patches I think. A friend and I came across one on a Moto brick fone a couple years ago that we believe was either at Boeing (Gresham, Ore.) or Wafertech (Camas, Wash.). What you can do with it (if anything) depends how the host PBX is configured, how big the company is and how far abandoned-in-place the base is. You'd probably stand a better chance of finding one at a huge multi/national headquarters or field office than a smaller local or regional-based company.

 

Hmmmm! I wonder if I should start carrying something that searches for AMPS signals on long trips. Could you flip through FCC licenses to get an idea of who might be doing this?

Edited by ThoughtPhreaker
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From meetings I've been in, CDMA carriers are mostly planning to keep their 2G gear running for a while after they shut down their 3G networks in preference for LTE.  2G CDMA is comparatively narrowband (a pair of 1.5 MHz channels can serve a whole area), and keeping the 2G network active allows for 2G/3G phones to have a network to fall back on.  There are many 2G/3G only phones out there still; I assume each network is planning to keep at least one of these bands active to serve those customers.  There's probably also a regulatory angle involved.

 

GSM is distance-limited to I think like 50 km so it makes sense to keep UMTS but drop GSM, reducing the number of towers needed to serve the area, whereas CDMA isn't distance-limited in either 2G or 3G so it makes sense to use the narrower bandwidth one, freeing up spectrum.

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On 2/23/2017 at 4:00 PM, chronomex said:

...I assume each network is planning to keep at least one of these bands active to serve those customers.

T-Mobile came out and said a year or so they'll keep 1.5 to 3 MHz (can't remember exact numbers) for machine to machine users past 2021, Verizon will probably be at the point everyone can reliably use VoLTE by that time

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Forgive me for not knowing the carriers inside out, but wasn't AMPS using the signals similar to analog TV? 

 

I assumed this because the shutdown of AMPS was around the same time when analog TV was supposed to sign off (06, then early 09 then June indef of that year)

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Yes and no, AMPS was narrowband (+-30 kHz (15 kHz deviation)) FM when TV audio was wideband FM (~200 kHz IIRC) (mono baseband was around 20 kHz BW/10 kHz dev, then stereo difference and SAP was above that, similar to an FM radio station except the subcarrier offsets were different). The frequencies were in former TV channels 70-83 but those were reassigned for telephone and 2-way radio usage back in the mid or late 1980s. This is why many older TV sets and VCRs could monitor AMPS transmissions by playing with the fine-tuning controls when on those channels.

(Somebody please feel free to correct me on those bandwidths and deviations!)

 

Another bit of weirdness, I had a RCA "home theatre" VCR in the mid-late 90s that still had a full 82-channel broadcast tuner. You could only access the lower 68 (channels 2-69) via the channel up-down keys and it would only blind-scan that range, yet you could manually enter 70 through 83 and it would happily tune them. I suppose this is because it also had a 139-channel cable TV tuner (although advertised as only 125 channels!) since the cable ultra- and jumbo bands (channels 65-139) are mapped to UHF channels 14-83.

RCA (by that time a brand of Thomson (a.k.a. Technicolor), no thanks to the CED fiasco) was known for doing some weird shit with tuners back then anyways. For example most of their TV sets, especially the Proscan line, mapped the line inputs to pseudo-channels in the upper 90s.

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On 3/23/2017 at 1:03 AM, scratchytcarrier said:

Yes and no, AMPS was narrowband (+-30 kHz (15 kHz deviation)) FM when TV audio was wideband FM (~200 kHz IIRC) (mono baseband was around 20 kHz BW/10 kHz dev, then stereo difference and SAP was above that, similar to an FM radio station except the subcarrier offsets were different). The frequencies were in former TV channels 70-83 but those were reassigned for telephone and 2-way radio usage back in the mid or late 1980s. This is why many older TV sets and VCRs could monitor AMPS transmissions by playing with the fine-tuning controls when on those channels.

(Somebody please feel free to correct me on those bandwidths and deviations!)

 

TV Stereo used a different pilot for the L-R signal. Otherwise it was almost identical to FM Stereo. Yup, the 800 MHz band we know and love for cellular (the infamous "A" and "B" bands) were the old UHF channels 70 to 83.

 

With the advent of ATSC (now known retroactively as ATSC 1.0), channels 52 to 69 were removed in 2009 and those are now known as the 700 MHz LTE band.

 

With the upcoming ATSC 3.0 that's around the corner, UHF channels above 37 will be removed. That will become more bandwidth, probably for 5G wireless.

 

In addition, TV stations are volunteering turning in their licenses, which will free up even more spectrum. With ATSC 3.0, the 6 MHz channels will handle up to 4K video and you can compress the living snot out of 1080, 720 and 480 (tons of sub-channels). So the now pretty much empty UHF band will shrink once again and will be littered with wireless.

 

 

 

On 4/1/2017 at 4:38 PM, scratchytcarrier said:

Another bit of weirdness, I had a RCA "home theatre" VCR in the mid-late 90s that still had a full 82-channel broadcast tuner. You could only access the lower 68 (channels 2-69) via the channel up-down keys and it would only blind-scan that range, yet you could manually enter 70 through 83 and it would happily tune them. I suppose this is because it also had a 139-channel cable TV tuner (although advertised as only 125 channels!) since the cable ultra- and jumbo bands (channels 65-139) are mapped to UHF channels 14-83.

RCA (by that time a brand of Thomson (a.k.a. Technicolor), no thanks to the CED fiasco) was known for doing some weird shit with tuners back then anyways. For example most of their TV sets, especially the Proscan line, mapped the line inputs to pseudo-channels in the upper 90s.

Yup, CED killed RCA. Sadly. Had they foreseen that lasers would come into play, they could have taken the market away from Sony and Philips. But that's another topic!

 

As for upper cable bands - many people didn't realize that they co-existed with existing OTA stuff. Cable channels 14-22 were the infamous Air/Police band (and ITMS mobile phones back in the day!), and upper cable channels were mapped to UHF channels. Back in the 80s, I had an upconverter that converted cable channels 14-36 to upper UHF. Wonder if it can be repurposed in this day and age? :)

 

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FM pilot is 19 or 20 kHz and the BTSC pilot is somewhere around 15 kHz. The BTSC subcarriers IIRC are harmonics of the 15.something NTSC sync frequency which it used as a reference frequency and to avoid interfering with the picture signal. There are a few radios out there with adjustable pilot detectors and I had one a bunch of years ago, a Panasonic RX5030 boombox (1981-2011), which had a potentiometer buried inside near the cassette drive. I had set it to 15.something to pick up KOIN in stereo, which sounded very strange and out of phase on that rig. It did make a very effective "virtual surround" effect when external speakers were connected.

Yup, CED killed RCA. Sadly.



"Nipper's revenge". JVC also had a little-known CED-like system that I think they had wanted to market in the US but it never got too far out of Japan. They were also busy marketing VHS in the North American market and probably knew better than to get into another video format war, having already won one a couple years earlier.

As for upper cable bands - many people didn't realize that they co-existed with existing OTA stuff. Cable channels 14-22 were the infamous Air/Police band (and ITMS mobile phones back in the day!), and upper cable channels were mapped to UHF channels



And there are still others in shortwave (the "T" channels) and overlapping FM broadcast. I think it's also still possible to find cable monopolies here and there with FM service though ours was cutover to QAM simulcasts once Crapcast assimilated it.

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