[TowerTalk] (Long) -- ATR-30 and AT4K Antenna Tuners
Jim Reid
jreid@aloha.net
Fri, 12 Feb 1999 11:25:54 -1000
Aloha to All,
Seems yesterday I initiated a thread on what has become a
controversial topic. In fact, I was convinced last night by
several postings that I had made a serious error in buying
the Palstar AT4K, and sent an email to both Tom, W8JI,
the ATR-30 designer, and to Gerald at Texas Tower
that I would order said unit from Gerald today. The
primary reason was the apparent use of a non-silver
plated copper inductor in the Palstar unit, smaller
capacitors and some other negatives surrounding
that situation. I am one who strives to have the best I
can afford, and the best performance given that I
can only have a triband beam, wire and vertical
antennas here at my QTH, small yard, fussy neighbors,
not really thrilled XYL, etc.!
So through the night I struggled with what I was about to
do in the morning, commit another $600 or so to
the rig, after all costs of getting an ATR-30 out
here to the island of Kauai. At last, I decided what
should be done first thing in the AM, was not call
Gerald and order the unit after all, but first, open
up the AT4K and determine the quality and suitability
of construction vs. the high price I have paid for it
along with air shipping to the island, and the several
comments made yesterday on this reflector.
So, that is what I did, and here is what I have found;
a unit not quite as either described on the Palstar
web site, nor as described by some yesterday.
Component parts:
Metering: Dual movement, cross needles, settable via a push
button to
either 3 k or 6kW full deflection, plus a 40
segment bargraph
pot adjustable to full scale deflection, peak
or average, for
any output power, 100 watts up to a full
6kW(!??!).
Capacitors Input and Output 6kVm 350 pf, with an added 350 pf
7.5 kV fixed doorknob C which can be switched in
in parallel
with the network output capacitor. This is said
to be necessary
when on 160 or 80 meters, and the antenna
impedance
is below 25 or 30 ohms; switching in the added
350 pf
will reduce the current within the inductor, and
thus losses
and heating therein.
Roller Inductor This is the surprise within my unit. The inductor is a
tape
would obviously heavily silver-plated unit,
using tape which
measure 3/8" wide, edgewound, with a tape of
0.062"
thickness, The inductor, per the manual, is
rated at 28 uHy,
5 kV and 30 amps. A large, maybe 0.75" or so
pinch
"wheel" rolls around inside the tape or the air
core unit
as shown in one of a neat series of photos of
the unit,
facilities, and of Paul Hrevnek himself
holding an AT4k,
at http://www.palstarinc.com/contact.htm
(takes a couple
of minutes to load pictures, then they appear
sequentially
one at a time).
The inductor in my unit appears visually to be
similar
in construction and color to the unit Surplus
Sales of Nebraska
illustrates on the back cover of their catalog,
8; that is
heavy, red plastic end plates, etc. However,
surplus
sales rates their inductor as 40 uHy, 12 1/2"
long,
but probably the same manufacturer, I would
guess.
Inductor in my unit is about 9 inches long.
As my unit was rcv'd, the bottom 14 turns of
the
inductor are shorted to ground; this can be
removed
if more L is needed down on 160 meters, but
should
be replaced, per Paul, when on 15 meters, as
the
full 28 uHy coil has an internal resonance on 15
meters.
If, for some reason use of 15 meters is not
anticipated,
the jumper may be removed permanently.
Appears completely unlike the obviously bare
copper inductor in
the AT4K photo appearing at the Palstar web site.
Which
is correct/newer, my unit or an indication of
cost reduction
viz. the photo at the web site??
Wafer Switches Two ganged, 6 position units, ceramic rated at 15kV/30 amps
these are equal in size to the heavy duty
switches within the
Antenna Mart 6kW remote antenna switch boxes,
maybe even
larger.
S)-239 Sockets are clearly silver/gold center
conductor/Teflon insulated
Case Chassis, brackets, and top cover are gold-chem film
coated
0.090 aluminum,
Hardware Bolts, nuts, washers are all bright silver plated (!)
and/or brass.
Balun for balanced antennas is at the front end of the circuit; all
capacitors, and the
inductor are insulated from the chassis with large standoffs, so the entire
unit
can appear as balanced to the output. Thus, the high output power of the
linear
is not seen by the balun, only the transceiver drive power is applied to
the balun
at the input when/if used and switched into the circuit by the large 6
position switches.
Based upon my visual inspection and findings this morning, I am beginning
to
feel better about my purchase from Paul at Palstar. So, for the moment,
believe I will do some more RF testing of the AT4K before I go ahead
and carry through with my announced intention to order an ATR-30.
Appears to me at least, that Paul has not been trying to collect unusually
high profit from his sales of the AT4K. I believe he does have some
pretty costly components and construction methods; e.g. lifting the
entire circuit off chassis ground to enable the balun to be placed at
the front end, rather than at the output as on all other antenna tuning
units, at least of which I am aware. He seems to have worked from
the beginning to produce a true QRO antenna tuner.
Some one posted yesterday that the AT4K appeared to be the same as
a Vectroics tuner. I have no way of judging that, but perhaps someone
else can advise based upon the info I have noted above. And, of course,
I also do not about the components within the new Ameritron ATR-30,
other than Tom, W8JI's information about the unit easily handling QRO
power to 3kW peak and even beyond depending upon mode, I suppose.
Not sure what I would gain by spending another $600 or so for an ATR-30,
and then trying to sell the AR4K; and probably also will offer the XMatch,
which is really optimally designed for 80 and 160 meter service, bands
which at the moment I am no longer able to use, as my big antennas were
invited off the property I had been using behind my QTH! (Someone
else, more clever than I, went to the Plantation and leased the land
out from under me for horse pasture.)
I plan some tests of output efficiency of both my AT4K and the XMatch
using Bird watt meters on both sides of the tuner. I plan to first put
both meters, alternatively on the same side, see how close they
agree in reading, note the deltas, then to opposite sides when
I hope to be able to read whatever loss in power has occurred in
travelling through the tuning units. Will have to do this vs. bands
and frequencies, and as I do not now have a dummy load will
do this into the antennas at times when the bands are dead, at
least as heard out here on Kauai. For each HF band, the AT4K
provides large tables of exactly what antenna R and +/- XL can be
tuned, and keep the losses less than 20 % of the power; impedance's
where the power loss will be more, if matched with the unit, are also
given out to 3200+/- j3200 ohms.
Well, this has become long enough, but wanted to get the info
out because of what happened yesterday, and my subsequent
actions.
73, Jim, KH7M
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