FT-101E Intermittent Audio level/S-Meter level

Discussion in '"Boat Anchor" & Classic Equipment' started by KB3GWQ, Jun 26, 2018.

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: K5AB-Elect-1
ad: Left-3
ad: Left-2
ad: Subscribe
ad: L-MFJ
  1. HAMHOCK75

    HAMHOCK75 QRZ Member

    HS0ZED, you may be right that the PB1547 calibrator could produce 25/100 KHz harmonics at about the same level.

    This is PB1314A calibrator. Notice how the 100KHz is coupled to the buffer Q3 via C7, but the 25 KHz goes directly to pin 16 via C8 and does not get amplified by the buffer.

    [​IMG]

    Here is PB1547. The 100 KHz output at pin 5 of the 34024 divider is coupled directly to pin 16 via C23, but the 25 KHz output on pin 3 is amplified by Q5 then added to the 100 KHz output on pin 16. In the 25 KHz position the 25 KHz amplified signal is being added to the existing 100 KHz signal via C25 ( 7 pF ) which at 14 MHz represents about 1.6K impedance. Since the calibrator signal on pin 16 sees the antenna impedance which is normally pretty low compared to 1.6K, it would seem there would be little loading effect caused by Q5. In other words, you are seeing the same 100 KHz in either the 25 or 100 KHz calibrator position. Normally there might be cancellation of the two signals at the same frequency should one be out of phase but in this case, it does not happen because the two are synchronous being from the same divider and the frequency is not so high for enough phase shift to occur.

    [​IMG]

    Here is the pin out of the Fairchild 34024. Is has simultaneous 25 and 100 KHz outputs.

    [​IMG]
     
    Last edited: Jul 21, 2018
  2. HS0ZED

    HS0ZED Ham Member QRZ Page

    Thank you for that very interesting description. I must confess I had not resolved the signals to that level, nor indeed studied the specifics of the divider IC and buffer.

    Take a closer look at the diagram, C25, just right before the 7 there is a smudge that turns out should be a 2. I pulled the board and can confirm C25 is indeed a 27pF. C27 is indeed 39pF and C23 is a 5pF. Also on my board Q5 is a 2SC1675 as opposed to a 2SC784R. No suggestion that has ever been replaced, all the solder looks original.
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    That is all very interesting . . . and neither have I ever bothered studying the detail of that circuit ! (Never really had any reason to)

    However . . . on my FT101F the 25kHz Calibrator signals are about 10dB down on the 100kHz ones . . . just as with the earlier calibrator circuit designs.

    Not sure whether the board with the Calibrator on in my FT101F is the B version of PB1547 or not - will have a look sometime. I'm guessing it's the slightly earlier one, and on the later one they may have changed a couple of components to balance the 100kHz and 25kHz signals.

    That may also be why you see the output level as equivalent to 50uV, and not 10dB stronger (as on my FT101F.)

    (it seems like somebody at Yaesu was obsessed with all this!)

    Roger G3YRO
     
    Last edited: Jul 22, 2018
  4. HAMHOCK75

    HAMHOCK75 QRZ Member

    The change from 7 to 27 pF for C25 probably will have little effect on the outcome. That drops the impedance to about 420 ohms which is generally still much higher than the antenna impedance which is the primary load seen by the calibrator signal as it goes out pin 16.

    Not sure of the reason for the change from the 2SC784R buffer to a 2SC1675. The ft of the 2SC1675 is 150 MHz min compared to 250 MHz for the 2SC784R. The 2SC735Y used in boards prior to the PB1547 also has a 150 MHz ft. Two reasons for the change come to mind, cost or the higher ft device might have been more prone to instability.

    Its hard to say without a schematic of the PB1547B board what its expected performance might be like except I would not be surprised if they changed the device that the buffer might have been redesigned also. Another change from the earlier designs is the addition of D4.

    From the F manual describing the calibrator,

    [​IMG]
    This much work on the calibrator in the last version of the 101 is a bit surprising unless another Yaesu product from about that time period had a more current, less expensive calibrator design so it was borrowed by the 101. Maybe G3YRO knows.
     
    Last edited: Jul 22, 2018
  5. HS0ZED

    HS0ZED Ham Member QRZ Page

    I think it was a unique radio in many ways. The plug in modular concept was a pretty new idea and I think it must have been quite expensive as well, even back then. It certainly allowed them to change boards and as we know you can plug almost any vintage board into any other radio and it will for the most part work. It certainly allowed for module redesign and they clearly took advantage of that. I wouldn't be at all surprised if they had a "Mr Calibrator" striving through multiple iterations to achieve the ideal. It might be that our obsession is almost getting to the same level.
     
  6. HAMHOCK75

    HAMHOCK75 QRZ Member

    I was told it is the reason the Japanese radios came to dominate the world market in amateur equipment. The same method was used in other fields. They have a word for it "kaizen".

    https://en.wikipedia.org/wiki/Kaizen

    I first heard the term from an American CEO who had studied Japanese methods. Certainly looks like Yaesu continuously refined the FT101 concept. My interest in the 101 is mostly it's unique position in the history of amateur radio. For its time, it was closer to industrial rather than amateur grade.

    P.S. That CEO's attempt at kaizen met with surprising resistance. Buyer's were content with relationships with suppliers and balked at letting other suppliers bid. In the end, the buyer's had to be replaced. What was really bad was these buyers were used to buying MIL grade parts. In other words common op-amps where $30 when the commercial version was $0.50. They laughed at the commercial prices and joked if they were to look for the parts at dumpsters behind the distributors offices.
     
    Last edited: Jul 23, 2018
  7. HAMHOCK75

    HAMHOCK75 QRZ Member

    Here is an interesting side note about the "F" models sold here in the US. It was the only FT101 without 11M. 11M was removed at the request of the FCC. Apparently, 11M was included in earlier models not because 11M was once a US ham band but because it still was a ham band in Australia at the time.

    Also, to add to the mystery. There was not just a PB1547 plain and B. There was also an "A".

    https://www.ebay.com/itm/Yaesu-FT-101-PB-1547A-Unit-Fully-working-Rare-f-s/202372252096?hash=item2f1e5381c0:g:H88AAOSwueJbTeQx&_sacat=0&_nkw=yaesu+pb1547&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0

    The "B" version seems to be the prevalent version. There are currently eight "B's" for sale on eBay. No plains and one "A".
     
    Last edited: Jul 23, 2018
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Yes, I think the previous models sent to the USA just had the 11m band crystal removed.

    Yes, it was certainly much better engineered then the FT101Z series (which I have never liked), and the equivalent Kenwood rigs (which if you look at the history were just their attempt at "copies")

    In terms of construction, the FT301 was even better . . . but sadly it was breaking new ground, and had several design flaws. The engineering quality of Yaesu's rigs went downhill after that !

    Roger G3YRO
     
  9. HS0ZED

    HS0ZED Ham Member QRZ Page

    I never liked the 301 styling, or the 101z, 901/902 look, too mickey mouse military to me. I've got quite a bit of Collins S line kit, it's hard to walk into a back street Bangkok junk shop and not trip over the stuff. Not quite so much today but it's still out there. So I'm pretty up to speed on the various S line radios and it's hard not to draw parallels with the earlier Japanese rigs. I have a KWM2A kicking around here somewhere that was actually made in Japan when Collins opened a factory there and I have no doubt that's where some of the ideas came from. Looking at the earlier Yaesu rigs, FT400/401 etc and things like the FT200 which were all much more valve based you can almost see the Collins in them. The 101 through to 101E/F was probabaly the last radio they did before the accountants started to get excited. All those high quality edge connector plugs and sockets don't come cheap, they're full spec jobs. All the manual under chassis wiring that obviously would be quite hard to pre-do in a lot of parts of the chassis. It all adds up and I think by the time the 101z came along it was a much cheaper to make radio, and it shows.
     
  10. G3YRO

    G3YRO Ham Member QRZ Page

    Let alone the Jackson dial drives bought from Britain ! (plus they seemed to have used very high quality capacitors . . . I've never had to replace any electrolytics in any FT101 or FL2100)

    But the construction techniques is why these rigs are so incredibly reliable . . . most of the faults on other rigs are down to bad connectors or cracked PCB traces. And I would never mount a Valve on a PCB . . . and of course, Yaesu didn't on these rigs !

    Some people knock their use of Line Output valves in the PA . . . but in my experience (if you don't abuse them tuning up) they last much longer than 6146s. I also imagine Yaesu spent a lot of time trying different valves before they decided on the 6JS6C for this application.

    I've always said, that if I was going to be marooned on a desert island, an FT101 would be my rig of choice !

    Roger G3YRO
     

Share This Page

ad: chuckmartin