FT101ZD MkIII - S Meter adjustment question

Discussion in '"Boat Anchor" & Classic Equipment' started by VK7ADQ, Dec 24, 2016.

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  1. VK7ADQ

    VK7ADQ Ham Member QRZ Page

    Hi all,
    First post here.
    I bought this rig about a year ago and really love it. It's in very good condition and works well.
    Luckily there are a couple of amateurs locally who know a thing or two about this rig, but as it's Christmas and I've got the lid off it, I thought a question here, rather than annoying them at this time might be the better thing to do.

    Ok, on checking another rig the other day that had an obviously incorrect reading S meter on receive (which I fixed), I also ran a check on the 101 and found it to be a bit out as well.

    I've got a Sark 110 antenna analyzer and luckily it's got a sig gen that can put out the correct levels to calibrate this rigs meter.

    I've looked at the manual and it points to 3 particular pots on the 'IF Unit' board, ie, VR402, VR403 and VR405.

    Now on first tweaking these as per the manual, I just got into a mess, until I realised the pots VR403 and VR405 need to be set up in reverse to the instructions. - well it worked for me and finally brought order to chaos as I totally lost control over the S Meter initially.

    So it's now back in the ballpark, but, even though I can align a 50uV signal to an S9 spot on the meter and a 50mV to an S+60db spot on the meter, everything else in between doesn't quite track correctly when the correct sig gen levels are applied, ie, 158uV= (approx) +10dB, 501uV= (approx) +20dB, etc, etc.

    So am I stuck with this and it's an inherent problem with this/any analogue meter, or is there a particular way to line this sucker up to get it to calibrate correctly at each main dB marker, all the way up to +60dB?

    Any knowledgeable 101 hams out there been through this and know?

    And by the way, Merry Christmas (;->
     
  2. W1GCI

    W1GCI Ham Member QRZ Page

    At 50mv, which is -12 dbm, you're pretty close to, if not at, the output intercept point of the receiver and probably seeing some compression. I don't know the design of the s-meter for the 101zd, but I expect that it was designed for relative measurement rather than as a lab instrument. If you can get steps close to the 6 db per s-unit and something pretty close to accurate up to around S9+ 30, you'll probably meet the design expectations. Just my thoughts.
     
  3. VK7ADQ

    VK7ADQ Ham Member QRZ Page

    Thanks W1GCI,
    Yes, you're right I shouldn't be (and wasn't) expecting a 'lab instrument' (;->, I was just idly wondering if there was a particular relationship between these 3 pots that may have made the S9 to +60 calibration a little better than my fumbling around, but thanks for the reply, appreciated.

    Regards, Alvin VK7ADQ
     
  4. G0LQU

    G0LQU Ham Member QRZ Page

    I thought there was a pot on the rear panel to adjust the s meter. You shouldn't need to go inside.
     

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