Smart Antenna Communications Modes

The CEA-909 standard calls out two different communications modes, A and B. Mode A is unidirectional, namely tv/convertor box to antenna only. Mode B is bidirectional, where in the smart antenna and tv/convertor box talk to one another. By far mode B is the best way to go… but nothing is ever simple.

The problem is, the standard left the details for mode B ambiguous as to what data is sent back and forth. Each smart antenna operating in mode B has a program identifier, such that the box/tv knows what types of data to send back and forth. As one might expect, as new mode B devices come on the market, unless the tv or converter box has a firmware upgrade, it wont know what data to send. Granted, some of this may be addressed in CEA-909A (being cheap, ie this is a home project, I got the old standard…)

However, all is not lost, if a tv or convertor box doesn’t know what to do with a given program identifier, it defaults into mode A operation… and the standard requires that ALL smart antenna devices must operate in mode A. Its not the optimum of course, but I can put a lot of intelligence in my smart antenna such that with the limited data available from mode A, I should be just fine. Also,being mode A is unidirectional, comms firmware is much simpler.

Mode A provides for the following data:

coarse direction/switching

fine direction


preamp gain

rf channel number

In many ways, even in the unidirectional mode A, this is pretty powerful. Of course, the question comes to mind as to how intelligent the tv/convertor box is. The standard calls out the capability to automatically set the parameters for optimum signal, or manual, where the user enters the data, or a provision for both methods. Until I get my AVR running, I wont know what my CECB is capable of…. the owners guide left that out, probably for good reason to avoid confusing the average user.

7 thoughts on “Smart Antenna Communications Modes

  1. I am using an RCA ANT2000 “smart antenna” which does help considerably in receiving over-the-air DTV signals here in Alexandria, Va. A “CEA-909 Mode-B” “super smart” antenna would likely reduce reception problems even further (but probably never down to an absolute resolution of all DTV reception issues such as dropouts, freeze frames, etc).

    My question is, why would they have an “open unspecified” standard for Mode-B data that would not allow for at least determination of the parameters required to achieve a minimum specified reception performance requirement?

  2. My Apex DT 250 converter box doesn’t recognize the Apex Smart Antenna SM 550. It says “no Smart Antenna found. Why is that? It is driving me nuts.

  3. Kman
    Having been on the side of writing standards when I was with ASTM, open ended standards occur when a deadline approaches and there is no consensus. My guess is the same occured at CEA.

    Thus manufacturers can still put the label on… but it can make it a royal pain from a compatibility standpoint. Future versions of the standard should address this, once an operating practice starts gaining a foothold. (Standards bodies meet often yearly or more frequently, even if many years may proceed between released revisions)

    Thus many manufacturers will often design to an unpublished gentlemans handshake type deal during the interim. Also, they discuss what works, and what doesnt… I must say meeting with all the major competitors in an industry, and discussiong successes and failures for mutual benefit can be a bit un-nerving at first, but all win out when standards work together for everyones benefit. *Plus we dont share everything, esp not the secret sauce that makes each one of us better than the other 🙂

    Its a bit hard to troubleshoot, unless you have a way to access the individual pins on the devices. Detection however should be pretty much fool proof, short of a bad cable. I would really doubt anyone would be shipping bad cables, but you can visually check to see if there are any cuts or really sharp bends in the cable, or even broken tabs or pins on the cable connector itself.

    What you might try, is to pick up a new convertor box at Walmart with a smart antenna connector. See if it finds your antenna. If it does, then the problem is likely resident in your DT250. If it doesnt, its likely in the smart antenna. I say Walmart, in that if it turns out its the smart antenna thats the problem, its easy to return the unit.

  4. Whoa, I got behind on this blog and site a bit… I am still here, have a few too many irons in the fire LOL

  5. The RCA ANT2000 does work well for me but requires an occasional reset as atmosphere and other conditions change from time-to-time. A “super smart” antenna which is continuously adjusting itself would likely largely eliminate even these minor resets. RCA discontinued the ANT2000 during the summer of 2009. The Apex SM620 looks to be a functionally identical replacement for those who wish to purchase a “smart antenna.”…… Apex indicated it is not yet available, but to call them back after the beginning of 2010.

    Apex SM620 Amplified HDTV Indoor Antenna with Smart Technology

    The most technically advanced innovation in terrestrial antennas! The SM620 Smart antenna receives digital signals from all directions and automatically self-adjusts to optimize performance of local broadcast reception.

    Apex introduces the SM620, a flat and decorative dual-purpose amplified HDTV antenna that is a perfect companion to any television or DTV converter box including those that feature the standard Smart antenna interface (EIA/ CEA-909). It’s the most technically advanced innovation in terrestrial antennas. The SM620 Smart antenna receives local digital signals from all directions and automatically self-adjusts to optimize the performance of your favorite local television broadcasts. Hang it on the wall, lay it flat, or stand it up vertically in its cradle

  6. There seems some inconsistence in the EIA/CEA-909 Sepcification. For example: the mode A requires the data should keep DATA at “low” when no transaction. However, the recommended circuits for “wire-OR” in mode B would keep DATA at “high” when waiting for reply from smart antenna.
    Am I right?

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