The Tempo One on CW

Discussion in '"Boat Anchor" & Classic Equipment' started by N2EY, Nov 5, 2018.

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  1. N2EY

    N2EY Ham Member QRZ Page

    In another thread on another forum, @W7UUU told of using the venerable Henry Tempo One (T1) (aka Yaesu FT-200/Sommerkamp FT-250) on CW. Here are some details of how it works - because the manual doesn't really tell the story well.

    The T1 was designed by Yaesu in the late 1960s. The rig is clearly a "bunyip design" - bits and pieces of all sorts, stuck together almost randomly:

    - Really nice VFO dial drive - better than almost anything Made In USA at the time. Linear, quite slow for the era (18 kHz/turn). btw, don't lose the tuning knob; the VFO shaft isn't 1/4 inch; it's a bit under.

    - Part PC board, part point-to-point

    - Mostly tube, part solid state

    - Many of the tubes are common, a few are not (7360 balanced modulator, 6BM8 audio)

    - Sweep tube finals (6JS6)

    - Some relays plug in, others don't

    - Some top quality parts, some real cheapies....

    - Features such as RIT, VOX and AM built in but full 10 meter coverage and CW sharp filter left out. You can add crystals to expand the 10 meter coverage but for CW you're stuck with outboard audio selectivity.

    - There are several versions of the T1 and power supply. The most obvious difference are that early ones are silver and later ones are black, but there are more variations than that. For example, the original balanced modulator was a 7360, and it was eventually replaced by solid-state because that tube was expensive. There may have been versions that used a 6JH8 but I am not sure. The power supply came in versions too; one had multiple HV taps; the other did not.

    The heterodyne scheme uses a 9 MHz IF, 5 MHz VFO, and a premixer arrangement on the bands other than 80 and 20. This means the dial tunes backwards on some bands and you have to know which numbers to look at.

    This heterodyne scheme wasn't new or unique; the main advantage was that it minimized the number of heterodyne crystals and coils needed. With just 3 heterodyne crystals you get 80/40/20/15 and part of 10. Full coverage of 10 meters required buying optional crystals at extra cost. When the T1 was designed, the US 'phone band on 10 started at 28.5 MHz, so it all worked out.

    The SSB filter is 2.4 kHz wide and there are two carrier crystals - one just below the filter passband (8998.5 kHz) and one just above (9001.5 kHz). They're both needed so that you can get the "right" (traditional) sideband on every band. Note that on some bands the sideband generated at 9 MHz is the same as the transmitted sideband, and that on other bands it is inverted. (The old myth about why we use LSB on 75 and USB on 20 is false, btw)

    For CW and "AM" (actually SSB-with-carrier), the T1 does a neat trick: the balanced modulator is unbalanced and the 9001.5 carrier crystal is "pulled" down just into the filter passband - but only when transmitting. This is necessary so that the carrier will pass through the IF filter. The pulling range of the carrier crystal is just enough to get it into the passband.

    However, they only did this to the one crystal, for simplicity. That's why on some bands you use the "normal" sideband and on others the "reverse" - so that you're always using the 9001.5 kHz carrier crystal. Forget to do this and it won't transmit right.

    The shift is only a few hundred Hz, though - much lower than most people listen to CW. So....another trick: turn on the RIT, and set for the tone you like best. The RIT control is even marked for it. Once you know how, it's no big deal.

    If one wants to be exactly precise about the RIT setting, a second CW receiver is needed, or a heterodyne frequency meter such as the BC-221. Here's the frequency meter way to do it:

    1) Warm up the T1 and the BC-221.

    2) Put the T1 in CW mode and tune up into a dummy load. Reduce drive so you are only putting out a watt or so. Key the rig as needed for steps 3 and 4.

    3) Find the transmitted signal using the BC-221 in "Het Osc" mode.

    4) Tune the transmitted signal for zero beat in the 'phones connected to the BC-221.

    5) Un-key the T1 and listen for the BC-221 heterodyne oscillator on the T1 receiver. Do NOT touch the tuning of either the T1 or the BC-221!

    6) Turn on the RIT and tune around with RIT until you hear the BC-221 heterodyne oscillator on the T1 at the pitch you like to copy.

    7) Note the RIT setting - that's the correct setting for that band.

    8) Repeat for other bands - you may find that the correct setting is different for some bands and the same for others.

    Yaesu did all that to avoid having a carrier crystal just for CW transmit, complete with switching and such. (!)

    Putting a CW IF filter into the rig is complicated because the 9001.5 crystal won't pull far enough. You'd need a circuit that would add another carrier crystal - and there's no space in that part of the PCB.

    Note that there is an audio oscillator for tuneup - it generates a tone of about 1500 Hz so you don't have to whistle into the mike. BUT - CW is NOT generated by the audio-injection method!

    All sorts of stuff like that in the rig.

    When introduced, the T1 cost about $350, with the AC power supply/speaker selling for $99. (That was expensive for the supply and cheap for the rig.)

    For that much money you could get an SB-101 with CW filter and power supply - but, you had to build the Heathkits; the T1 was ready to go out of the box!

    The T1 was quite popular in its time; lots of hams went for them. Then the FT-101 and TS-520 showed up and all heck broke loose.

    ----

    The finals in the T1 can be changed to 6146s; there's a QST article about how to do it, and it's not difficult nor irreversible. Some hams use xJS6 tubes with other heater voltages because they can get the tubes cheap.

    ----

    I have toyed around with the idea of modernizing the T1 to make it a real contender. Seems to me the best approach would be to make a new PC board that would be a drop-in replacement of the old one, but which would include a sharp CW filter, a CW carrier crystal, replacement of the 7360 and 6BM8 tubes with more-common versions, etc. Probably eliminate AM, replace the finals with 6146-family bottles, and a few other things.

    Trouble is, the project becomes almost as much work as building a whole new transceiver.

    73 de Jim, N2EY
     
    Last edited: Nov 5, 2018
    WA7PRC, KB4QAA, N2SR and 1 other person like this.
  2. KE4OH

    KE4OH Ham Member QRZ Page

    Jim, As someone who regularly uses a Tempo One on CW, I applaud your analysis!

    I for one think the worst "feature" of the T1 is how easily a loud adjacent signal wipes out the weak signal I'm trying to copy. If only I could either turn off the AGC or have a filter at the right spot in the RF/IF, or an adjustable passband, I would be a happy camper. All the other stuff just gives the thing character!

    The RIT tuning for CW is kind of a pain at first. but I have my little system for quickly setting it and it works well for me. I operate a variety of transceivers that all have different CW offsets, so I eventually learn what the "correct" pitch is for each. The T1 is my only transciever with RIT, so it's a treat to have it, even though there is a trick to setting it right.

    73 de Steve KE4OH
     
  3. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    Excellent writeup Jim. Thanks!

    Yes - once you have it down how CW works, it's a piece of cake. I just "know where to set the RIT" now to make sure I'll be in the narrow passband of the other station. No problem.

    My only complaints with that is the receiver is more stable in SSB, with the RIT turned off. On CW the received note is a tad "wobbly". I may look into the cap used for RIT and if it needs mechanical beefing or replacement with something beefier. The other thing being strong adjacent signal rejection - it's really horrible in a contest

    But outside of that, it's a solid runner and I worked everyone I could hear over the weekend

    Dave
    W7UUU
     
  4. N2EY

    N2EY Ham Member QRZ Page

    Thanks!

    The AGC can be partly defeated by turning the AF gain all the way up and using the RF gain for volume control. A simple switch can completely defeat it.

    Adding a narrow IF filter is a big job, because of the mod needed to the carrier oscillator. But it could be done. Besides the PCB replacement idea, maybe it could be done with "daughter boards".

    At least the T1 has the ability to tx and rx CW on the same frequency. Some "CW-SSB" transceivers, such as the National NCX-3 and 200, can't even do that!

    There is no capacitor used for RIT. It's a varactor - a special diode whose capacitance varies with applied DC voltage. (The Southgate Radio transceivers use an actual capacitor).

    One problem with varactor RIT is that it depends on having an extremely stable DC voltage applied to the varactor. Small variations in RIT voltage will cause warbling, "drift", etc. In your case there may be a bad resistor, bad potentiometer, dirty switch, etc. in the RIT control circuit.

    If the note is wobbly on transmit....couple other things to check.

    See above about AGC defeat.


    Sorry we didn't connect. I was mostly S&P on 40 meters.

    73 de Jim, N2EY
     
  5. G3YRO

    G3YRO Ham Member QRZ Page

    The FT200 was very much a cheap stop-gap rig, while Yaesu were developing the original FT101 . . . so as you say, there are LOADS of compromises in the design.

    It was coddled together using bits of circuitry from the FT401, as well as the PA components from the FT101 (which was already in development), and a simple Old School 9MHz I.F. single-conversion design with just a 6-pole crystal filter.

    But here's the thing . . . certainly here in Britain, you can buy a secondhand FT101 for about the same price as an FT200 . . .

    So personally, I would never consider using one!

    I could understand the attraction of using an FT200 from a nostalgia point of view, if it was many years older . . . but it only came out just over a year before the FT101 !

    You could spend a lot of time and money doing LOADS of modifications to it, and it still wouldn't come close to the performance and features of the FT101. (all the things you complain about simply aren't an issue in the FT101)

    Roger G3YRO
     
    Last edited: Nov 5, 2018
  6. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    All true enough. But sometimes we do things for reasons other than "performance and features". I wanted a Tempo One (black face) like crazy as a young Novice/General class. They seemed to me an amazing rig (despite their limitations and quirks) - and I never even touched one back then nor had any idea what the quirks and performance lacks even were. I just drooled over the ads.

    On the used market, kids my own age with wealthier parents, were picking them up and I would hear "RIG HR TEMPO1" in QSO, with me still on my Globe Scout 680 and SX-100 thinking "one of these days"

    So now, 43 or so years later, it's "that day"

    :)

    Dave
    W7UUU
     
    KE4OH and N2EY like this.
  7. K3XR

    K3XR Ham Member QRZ Page

    Purchased a new Tempo One when they were introduced and for it's time it was a good rig. Precision with respect to transmit and receive signals on CW was not always the order of the day and many recall separate transmitters and receivers where you called CQ and tuned the receiver slightly on one side or the other looking for a call.

    Also used the Tempo One along with a Yaesu FTV 650 6 meter transverter made for a very nice 6 mtr. set up. Again talking around the early 70s.
     
  8. G3YRO

    G3YRO Ham Member QRZ Page

    I suspect your Nostalgia was partly because they were re-badged to pretend they were made in the USA, and not a Yaesu rig !

    There seems to have been an inherent resistance to buy Japanese rigs in the USA back then . . . I never seem to hear about people with Mk1 or Mk2 FT101s over there . . . even FT101Bs seem pretty rare. (there also seems to have been less negative feelings about Kenwood rigs in the US back then, even though I don't think their rigs were in the same league back then)

    Over here, even though I worked for the Yaesu importers, I always talked customers out of buying an FT200, as the FT101 was only slightly more expensive, and so vastly better engineered and performing.

    Roger G3YRO
     
  9. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    No. Not at all. a 15 year old kid in 1976 would not have been thinking "buy America"

    That wasn't remotely a factor for me.

    Dave
    W7UUU
     
  10. K3XR

    K3XR Ham Member QRZ Page

    That might be the view from your side of the pond but it's not how I recall the interest in the Tempo line. If you were around at the time there was not much doubt that Henry Radio was importing the Yaesu rigs under the Tempo name. Likely the ads in the ham mags from that time would back up the premise. Later they imported the Tempo 2020 which was a Uniden product.
     

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