Question: The mystery of Clear QAM


Am I receiving 75 channels of Clear QAM?

A while back Comcast announced a transition to digital and provided folks like myself with a free set top box so we could feed our old (but lovable) glass tube analog tv. Simple as pie: digital rf in, analog rf out (on channel 3) and one more remote to get kicked under the sofa.

Then, I buy a small, inexpensive digital tv for the bedroom and feed it off a splitter before the set top box. I just plugged it in and it gets all 75 channels. No Captain Midnight secret decoder box, no decryption of any kind that I can see, yet it gets all the channels including the ones I pay extra for. So, are they encrypted, or not?

Why do I care?

I would like to buy a new digital tuner/recordrer card for the PC. Right now I can can record analog with my old analog card, but look at what the signal has to go through:

In the set top box:
qam to the digital tuner/detector
digital to the d/a converter
analog video to the rf modulator​

In my present analog tv card:
NTSC rf to the analog tuner/detector
analog video to the a/d converter
digital to the hard disk​

Actually, the quality is not bad, considering. But I would like to record the digital without all that conversion. Is any way of determining which channels are clear? Can I expect a new digital tv card to just plug in and work like the new tv? I'm sure someone at Comcast knows, but the ones who answer my calls are clueless.



In the medium-term, you can generally expect that the only channels that you will be able to receive via clear QAM to be the channels that are offered on the very lowest tier of service, known in the industry as B1. This generally includes the local over-the-air broadcast channels, local public access channels, and maybe one or two "freebies". In my area, the freebie Comcast provides is Style.

For many people, this is already the case. For the vast majority of Comcast customers for whom this is not already the case, it will be the case by the end of the year, as Comcast brings its service offerings more in line with that of its strongest competitors, FiOS and DirecTV. This is already the case for FiOS, everywhere, and I believe DirecTV is even more restrictive.

If you have higher tiers of service, such as expanded basic cable, Digital Economy, Digital Starter, etc., then you will need to ensure whatever host device (television, PC tuner card, or DVR) you use is capable of supporting the standards that the industry put in place to comply with federal regulations for separable security. Your safest bet is to look for the following logo, which indicates a device that complies with the requirements:

More generally, you need to be sure that the host devices (television, PC tuner cards, or DVRs) that you purchase are at least CableCARD-compatible. That, at least, will ensure you can tune in all the linear cable channels that you pay for.

If you choose (chose) to economize, or to purchase before compatible devices were (are) available on the market, you run the risk of the devices you purchase being incapable of doing what you purchased them to do. Consumer electronics manufacturers will not warn you about this. They aren't required to, and it doesn't foster their revenues to effectively discourage you from purchasing their less-capable devices (especially when their competitors aren't warning their customers about such limitations).

If you've already purchased your host devices, you have to make do with your past selections, even if they end up being inadequate. Generally, this means augmenting your purchased host device with an external tuner (i.e., a set-top box, or a separate DVR), which has the capabilities you need.

I hope this helps.

Thomas G

I'm always curious why more information isn't available about Clear QAM on cable provider's websites. I used to be a Cox customer, and it was next to impossible to find any information directly on the Cox website. Their customer service was clueless too.


I'm always curious why more information isn't available about Clear QAM on cable provider's websites.
Basically because it is not required and it doesn't serve any productive purpose from the cable service providers' perspective.

Clear QAM is a support nightmare. The frequency allocations are often, but irregularly, switched, in recognition of problems with certain frequencies, perhaps due to variances reported in band-pass filters, etc. Unlike ATSC, QAM doesn't have anything built-in that is comparable to PSIP, and so channel mapping is provided via a separate signal. However, except for the host devices I mentioned above, those that are CableCARD-compatible, clear QAM tuners do not have any means of accessing the channel mapping signal provided. Therefore, channel mapping is necessarily a manual operation, and you could end up having to re-do it as often as weekly, as the mappings change.

Also, even if channel mappings didn't change often, you'd still have a significant amount of subscriber confusion, because all the channel lineups and program guide listings are expressed in terms of the virtual channel assignments (i.e., 508, 801, etc.) while QAM expresses channels only in terms of physical placement (i.e., 85.1, 85.2, 112.1, etc.)

So while clear QAM represents problems/cost, it offers little if any actual value to service providers. Usage of clear QAM typically results in bypassing the service providers' ability to offer pay-per-view and other revenue generating services. It also precludes the offering of even the "free" On Demand services, thereby meaning that those customers are getting less value, and therefore less likely to be satisfied with the price/value proposition offered by the service provider.

Beyond that, so few customers are willing to deal with all these complexities, that essentially making it the customers' own responsibility to figure out how to get clear QAM to work for themselves dissatisfies far too few customers for it to even matter.

So that's the deal in a nut-shell: From the service providers' perspective, clear QAM represents practically nothing but cost and trouble.


I just discovered Comcast's Clear QAM offerings tonight...I get about 100 channels unencrypted out of 325 or so total detected...and it is most definitely more than just the basics. I get the basics in crystal clear HD (local channels)...the rest are all digital but in SD. No tv package for me...just high speed internet over cable.

My TV has no issues detecting the channels...but a little digital tuner I had hooked up to my HTPC couldn't pick up anything. The little tuner was a tuner bundled with a laptop my dad bought...he didn't need it so he gave it to me.

I found out about it from a chatroom I go to regularly. They told me the channel lineups will probably change...but I'm willing to deal with it if I can avoid paying a TV package.
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Actually, it is likely to change pretty soon... Project Calvary is apparently just reaching the western suburbs, and that's why you're suddenly seeing a lot of channels in-the-clear. That happened here, as well, while they were moving things around, and then when they were finished with the work, everything was locked down, encrypted, except for the local over-the-air broadcast channels.

You can get more information about Schaumburg, in particular, from Andy Ross, who regularly posts here:
... and is pretty well-versed in these things.


oh long as I can get the local channels in HD like I get now I'll be happy...can't get all of those now with my even just the locals over comcast qam is an improvement.

Thanks for the link...good one to keep an eye on for me.
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