Analog TV to Digital Conversion, Can it be done ?

Discussion in 'General Electronics Chat' started by SteveHow, Dec 5, 2013.

  1. SteveHow

    Thread Starter Member

    Jul 2, 2012
    78
    2
    Hello all,

    Here in Australia our Analog TV will no longer be transmitting in 10 days time.

    I have an awesome analog portable TV that sites in our kitchen on the fridge.
    Whats so good about it? Well mainly it great reception with only its Rabbit Ear Antenna. (I live a far way out from the city and as you can imagine signal strength is not the best for indoor reception)

    I purchase a new flat screen, put it on the fridge, hooked up some Rabbit Ears (With a build in Amp) and got nothing but horrid reception. (Most channels were never even pickup.)

    Admittedly this was a no name brand LCD TV. However the Indoor Antenna was from a reputable company here is Australia called Antsig. I know I can hard wire a cable in but have wondered if this might work.

    This Analog TV (Healing brand) has NO external Video/Audio inputs. But it has a very good Antenna gain circuit.

    Would it be possible to get a Digital set top box, (I have a few laying around I can use) and mode this TV.

    My thinking is this, firstly find the Audio and Video line in and open this circuit. (Hence rendering the Analog reception redundant) I would then feed the output of the Digital Set Top Box in here.

    Secondly, I would also find the output of the internal rabbit ears circuit, break (Or cut this open, so its no longer being sent to the analog) but instead feed it to the RF input on the Digital STB.

    Can you see where I am going with this ? Essentially by doing this I have bypassing the Analog part. To write this in a block diagram it would be this.

    Before
    Rabbit ears Hi Gain circuit > Analog reception processing > Output/Screen
    To
    Rabbit ears Hi Gain circuit > Digital reception processing > Output/Screen

    Of course no one bothers? Well its a challenge, I think it can work.

    Only other problem, there are no schematics. But I thought you guys might know these old Analog TV sets like the back of your hands. :)

    Whats the verdict ?

    Thanks
    STeve
     
  2. Nykolas

    Member

    Aug 27, 2013
    87
    31
    Homeworx, Zinwell, Coby and others make them, about Can $60. Digital (ATSC) to analog (NTSC) pass-through converter box. E
     
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I'm surprised your "government" didnt cover this already as this what happened in the US..
    Analog TV went away BUT you could get a voucher for a conversion box if you have a TV thats still only analog and didn't have a set top box already.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    And because of the above program, there are now a LOT of boxes out there as people abandon their old analog gear and go fully digital. New TVs don't need the converter box, so they're popping up on the used market.

    I wouldn't bother to build a Franken-TV if that's what you're asking about. Just attach the box and be done. For one thing, you need to access it with the remote control, since it takes over the channel switching and volume control.
     
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  5. vpoko

    Member

    Jan 5, 2012
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    47
    It sounds like the OP already has a set-top digital converter box, but his TV has no inputs other than the ANT.

    You could always use an RF modulator to convert the output of your digital box into an RF signal that you can feed to the TV using a coax cable (with the signal usually on channel 2, 3, or 4). This is how video game systems were attached before TV's had AV inputs. Obviously, the quality won't be as good as it would have been with a baseband input, but it shouldn't be terrible.

    Opening the TV and trying to connect the digital box that way might be possible, but I have no experience in such things.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    Your right - I had to re-read his post. But my set-top box and many others have a coax output just for this purpose.

    The OP needs to shop for the right box. He needs high sensitivity (and/or an amplified antenna like I have) and a coax output. Plus whatever other features he wants.

    I have the Channel Master CM7000. I chose it primarily because, in addition to good reviews, it has an S-video output which my TVs can use.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Or just buy a new TV.. Something from the last decade ;)
    They are so cheap now.. practically giving them away..
     
  8. crutschow

    Expert

    Mar 14, 2008
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    He has a new TV. It just won't pickup the signals with his rabbit ears antenna.

    I think it would be easiest to bite the bullet and install a good outdoor antenna and run a cable to the new TV. Since the digital signals are likely on a higher frequency channel than the old analog ones, the digital signal may not be as strong as the analog (low frequency channels generally travel a longer distance than the higher frequency ones), thus the problem. Even the old analog set tunner may not adequately pick up the digital signal.
     
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  9. BReeves

    Member

    Nov 24, 2012
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    Along with this the old analog TV would still be viewable with a weak signal. Digital just drops out and quits working if the signal isn't strong enough.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I read it as his new TV is fine other than poor reception with the rabbit ears/current analog signals but that his OLD ancient TV can't get the new digital signals at all and this whole post is about getting that OLD one to work when the digital switch happens..
     
  11. wayneh

    Expert

    Sep 9, 2010
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    I wonder how much of the OP's problem is due to using VHF rabbit ears instead of a UHF loop antenna.
     
  12. SteveHow

    Thread Starter Member

    Jul 2, 2012
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    Is Digital TV UHF only/or all UHF ?

    If this is the case, I have been using the wrong Antenna on the LCD Digital TV. The Indoor Antsig Antenna (Rabbit Ears w/Amp) I tried is no doubt for VHS. I'm not sure if it has any UHF design in it ?

    Am I using the wrong Indoor Antenna. Doh!
     
  13. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    The reception using the dig converter box will likely be similar to what you get using the new digital TV which has a built in dig tuner. It is not the analog part which is the problem, it's the digital part. The new standard shoves nearly all the channels up into the UHF region. Typically, those signals do not carry as well as the older VHF band did.

    In other words: it probably won't fix your reception problems.

    When our country converted, we had horrendous reception problems. A couple of local channels got lost, and I am using a very powerful antenna to get good reception.
     
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  14. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Every converter sold here has the option of either feeding the signal in on the component inputs OR on the antenna input if the TV has only that input. You can adjust whether it goes in on analog channel 3 or 4. You just tune the old TV to that station, connect the RG-59 cable between the box and TV antenna in, and that's all.
     
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  15. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Agreed. Antenna field strength is measured in volts/meter..... however, the higher frequency signal means the antenna rods are shorter in length since they have to be 1/2 wavelength sets. That means that UHF is already at a disadvantage for reception and the transmitter has to be able to crank up a stronger signal.

    Also: every good UHF antnenna uses a stacked Yagi array to increase signal strength. BUT: if you convert to our standard, there are still some channels in the upper VHF (7-13) you must pickup. So the new "digital" antenna have a VHF/UHF combo to get both bands. You can get some REALLY good ones for about $60.

    Here is one:

    http://www.solidsignal.com/pview.as...tdoor-HDTV-Antenna-(HBU44)&c=TV Antennas&sku=
     
    Last edited: Dec 5, 2013
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  16. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The new standard still allocates the upper VHF band for use which is channels 7 - 13 along with the UHF band which is channels 14 up to about 83.

    The difference is that the UHF freq range is about 470 - 900 MHz.

    The upper VHF (7-13) is 175 MHz to about 215 MHz.
     
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  17. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,498
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    The are many sites that cover OTA TV and have designs for antenna's for your particular Freq's you are receiving.
    Depending where you are, you may be able to pull in a few more stations with the right antenna.
    I made an excellent one for the attic with foil covered ply for the reflector and copper tube for the elements.
    Max.
     
  18. SteveHow

    Thread Starter Member

    Jul 2, 2012
    78
    2
    Is that what the RF out socket was for. If I undertand what you are say?

    On a Digital Set Top Receiver, apart from having say Composite out/ S out they have a second RF out, are you saying this sends a modified digital signal which can be plugged into the RF Antenna socket on the Analog TV ?
     
  19. crutschow

    Expert

    Mar 14, 2008
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    Yes. It's been converted to analog TV RF format.
     
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  20. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    In Oz,Digital channels are on both VHF & UHF.
    We use a different transmission standard to the USA,so not all the comments directly apply.

    If you use a set top box & modify the old Healing (that is a very old TV) to accept video & audio inputs,or feed it with a PAL modulated RF signal from the box,you are not getting any benefit from the (maybe) more sensitive RF part of your analog TV.

    If the analog receiver's sensitivity is better,it is probably because of the performance of the tuner,rather than any of the passive circuitry.

    I sorely doubt that "bodging" the RF from the Healing's antenna into the set top box will give you any better results than with the indoor antenna.,especially,as from what I have seen,the "El Cheapo" set top boxes are less sensitive than a standalone Digital TV.

    If you can at all install an outdoor antenna,I would do so.
     
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