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DIY RF amp?

Discussion in 'Electronic Repair' started by David Nebenzahl, Oct 20, 2009.

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  1. Occurs to me that I could use a small RF amplifier to improve my DTV
    reception (it's marginal on some stations, PITA to constantly readjust
    my indoor antenna).

    So how about a reeeealy simple DIY amp? Anyone know any designs out
    there that would be suitable for DTV (VHF/UHF) signals? I'm thinking one
    transistor, battery powered.

    Could probably just buy one but it would be fun to build one instead.
     
  2. Like, maybe, this one? http://english.cxem.net/rf/rf37.php
     
  3. bw

    bw Guest

    That will work.
    It did for me, point to point wiring, using parts from the back of a
    scrapped VCR.
    Check eBay for a 1980s ARRL VHF manual.
     
  4. N_Cook

    N_Cook Guest


    Whatever it is has to go right up at the aerial, while there you may as well
    replace the existing aerial with a much higher gain one and new down lead.
     
  5. GregS

    GregS Guest

    More like produce noise, and with a low signal, you get that noise.

    I don't know the state of TV's and converer boxes as far
    as sensitivity. I heard its bad. I have made amps before
    using some small chips, and etched a board to form feedlines.
    It worked. Many of the old time amps used inductors and tunned
    circuits, and a spectrum analyzer was used to set the gain
    as flat as possible.

    I had problems at the old house and used a line amp
    to feed one drop. I also had to use the special one for
    the internet. The cable guy made me take it off, and
    the reseption was pretty good after he replaced the 30 year old
    feed from the pole.
    greg
     
  6. GregS

    GregS Guest

    Thats very correct in theory, but I have seen improvement for
    whatever reason.

    There is only one VHF channel thats broadcasting digital here and thats 13.
    There is no need for low VHF, but the FM trap is OK. When you need
    VHF at all may depend on location, as VHF high has some different signal
    paths, and is better in some locations.

    You can make or get a small directional UHF antenna that will
    work indoors. Receiving the digital channels is so much better with me with
    the requirment of longer elements and just using rabbit ears on VHF low.

    greg
     
  7. Something like this, perhaps?
    http://users.belgacom.net/hamradio/schemas/preamp_HF_VHF_UHF_SHF_wideband_MAR6.htm

    One problem is that this device (MAR-6/MSA-0685) cost something like
    $16-17, from what I've been able to find online. I was looking for a far
    cheaper solution. I think I'm just going to build that 1-transistor
    preamp and see how it works.
     
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