Dc volts on aerial socket

Discussion in 'General Technical Questions and Answers' started by G4REK, Apr 6, 2012.

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  1. G4REK

    G4REK Ham Member QRZ Page

    Ft897d which i thought i would connect to my Clansman atu tuning unit...all works fine ..but on switching off the radio the meter on the atu

    (which will only respond with a clansman radio 320 or 321 radio) flicks hard over full scale for a second same on switching set on.....
    with the clansman radios connected they send a dc voltage to the meter circuit so that it reads power out/tuning.....
    but why is there a dc voltage on the 897d aerial socket when it being switched off/on ???????and it must be a fair voltage to give a hard over with the needle.....sorry bit long winded but it puzzles me somewhat
    thanks Jim g4rek

  2. N0SYA

    N0SYA Ham Member QRZ Page

    I wonder if some cap in the yazoo is discharging via the socket on shutrdown?
  3. G4REK

    G4REK Ham Member QRZ Page

    Do not know but it does it on switch on as well......think i will put my ft 847 in its place and see what happens on switch on /switch off.....
    do not like the way the meter slams over full scale for a second........
  4. AB9LZ

    AB9LZ Ham Member QRZ Page

    A lot of rigs will put a DC "wetting current" on the tr relays to keep the contacts clean, two of my rigs do it, however, there is usually a blocking cap in there some where. Check the schematic.

    73 m/4
  5. G4REK

    G4REK Ham Member QRZ Page

    Have put my FT847 in line and there is not any needle kick at all now........be interesting if a ft897d owner could put dc volt meter across the hf socket and see if there is a brief needle movement on switch/switch off ,,,to be safe rf control at minimum setting and radio set to 7 megs band........ Jim g4rek
  6. N5USR

    N5USR Ham Member QRZ Page

    My assumption would be it's something to do with the ATAS-120 tuning circuit. When tuning it will put certain DC voltages on the antenna jack to control the ATAS. Of course I don't know why it would do so at power on/off...

    I have an 857D, same guts as the 897D, and mine does very briefly blip a multimeter when I turn it on/off. It's hard to get an accurate reading as the voltage is very brief and my digital meter doesn't register quickly enough. Most times it's only a few millivolts but on occasion I see 2-3V.
  7. G4REK

    G4REK Ham Member QRZ Page

    Right thanks that sounds as though your is behaving same as mine, as you say its so brief difficult to get a reading.......would not have normally noticed it but connected to the Clansman atu it kicks the meter hard across very briefly
    thanks for you help
    regards Jim
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