>gents
>
>Per my henry 8-K ultra manual, (I collect manuals), the "tuned
>input" consists of 2 un-uns back to back. They step the Z up
>with a 1:56 to 1 un-un and then back down again, same ratio
>in reverse, on all bands except 10m, on 10m they step up with
>one ratio, and down with a different ratio. (un-uns are relay
>switched)
>
> How they get any fly wheel effect at all is beyond me.
// They don't. Tuned circuits act as flywheels. Untuned/broadband
transformers have virtually no flywheel effect.
- Back in the days when Henry Radio did not build a 160m amplifier, a
friend dropped by the Henry Radio booth at a ham convention. He asked a
Henry engineer why they did not build a 3-500Z 160m amplifier. The Henry
engineer said that they tried it, but they discovered that 3-500Zs have a
cutoff frequency that's above 2MHz, so they don't work efficiently on the
160m band. (sic)
>This broad band input is a Henry exclusive used on the 8k ultra
and
>3-k ultra.
>
// "Exclusive". Chortle. No tuned-input on a g-g amplifier is
Looneytunes.
>The 8k manual also warns not to use the automatic tuner built
>into many rigs. It sez to leave the auto tuner offline, and
>just put up with any swr between xcvr and 8k ultra input.
>
// The trouble with auto-tuners that are built into radios (except the
TS-930S) is they run c. 1w during the autotune cycle. The sticky wicket
is that - unlike antennas - g-g amplifiers have a different input Z at 1w
than they have with high drive power. Thus, whan the tuner is adjusted
at 1w to a g-g amplifier, the SWR is sure to be feculent at 100w or so.
>I noticed on my homebrew 3CX-3000A7, with it's high C low L
>tuned input (consisting of a tapped 4 uh coil made from solid
>5/32" copper wire, and 2 x 4 section broadcast variables (padded
>on 160m), and with a network Q of abt 3.5, it works just
>fine.
// 'Tis indeed misfortunate that you don't design Henry Radio's g-g
amplifiers.
>
>However, when using a wattmeter like a drake W4 inserted between
>FT-1000D and input to amp, minimum swr on W4 wattmeter does not
>coincide with minimum swr on FT-1000D internal swr meter. I can
>tweak tuned input to read flat swr on either wattmeter, but
>can't get minimum on both at same time.
>
>I then replaced W4 wattmeter with my Bird -43, and now flat swr
>is indicated on both 43 and internal yaesu swr meter,
>regardless of length of coax cables between rig and wattmeter, and
>wattmeter to input to amp. Also maximum grid current
>coincides with minimum reflected power between xcvr and amp.
>
>The VFD wattmeter may be at fault. The henry "input" with it's
>back to back un-uns (all relay switched) may be creating some
>problems.
>
>-henry doesn't change the bias on cw/ssb. The bias consists of
>15-20 diodes in series in one block like a W2AW module. The
>idle current zsac goes up and down cuz of plate V difference
>between SSB V and lower cw V. Manual sez no load HV on ssb
>should be 5400V . Henry uses a 6kv plate xfmr with a choke
>input..... .9 x 6000= 5400V. They also suck a continuous
>300W of bleeder power all the time to make the tuned choke,
>look like a choke.
// A friend bought a 60-Hz custom tuned-choke L/C matched pair from
Peter W. Dahl. The amount of bleeder current needed was much less than
expected.
> If any of the 5 x 100 watt bleeders ever
>opened up, the HV would skyrocket to 8485V. And that's if you
>have the correct tap to start with.
>
// However, the filter capacitor could probably take the surge. When
the amplifier was keyed, the ZSAC acts as a bleeder current.
> The fil V should be below 7.5 V measured right at the
>socket. Life of tube is dependent on fil V. If the tube is
>lit, the clock is ticking. The tube won't last any longer cuz
>you are running it at 1500w out. If you had a 2nd amp. with
>just the tube fil lit, and no drive applied, and no HV, it
>would last just as long as your driven amp.
// Excellent points, Jim. Few designers seem to realize that the
emissive life of a thoriated-tungsten cathode/filament is cut in Half for
each 3% increase in filament voltage above what is needed to achieve full
PEP. Thus, the formula for emissive life vs fil. volts = (e1/e2)^23.4.
>
>The stock blower on the 8K ultra will not provide enough air
>for anywhere near 4kw of anode diss, more like 2500w tops. The
>stock straight up and down chimney puts quite a restriction on
>the airflow.
// A high-pressure blower from Kooltronics or Rotron would cure this
problem. Henry engineering is apparently clueless about manometers and
the effect of filament potential.
>
>The henry back to back un-uns are interesting though I don't
>understand the theory behind them. They operate from 1.8-30mhz
>continuous.
// But the SWR is somewhat less than satisfactory.
>
cheers, Jim
- R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
end
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