Jim,
Don't bother reposting. I already have forwarded this
reformatted text. Tabs are a bit iffy for email readers.
73, Eric N7CL
------- Start of forwarded message -------
From: "Jim Reid" <jreid@aloha.net>
To: "'Towertalk'" <towertalk@contesting.com>, <w8ji@contesting.com>,
<TexasRF@aol.com>, "Paul Hrivnak" <palstar@erinet.com>
Subject: [TowerTalk] (Long) -- ATR-30 and AT4K Antenna Tuners
To: <towertalk@contesting.com>
Date: 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 wound 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
------- End of forwarded message -------
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