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G8MNY > TECH 10.06.12 04:33l 120 Lines 5410 Bytes #999 (0) @ WW
BID : 45507_GB7CIP
Read: GUEST DK3UZ OE7FMI
Subj: Palstar AT1500CV ATU
Path: DB0FHN<DB0MRW<DB0ERF<IZ3LSV<I0OJJ<GB7CIP
Sent: 120609/2233Z @:GB7CIP.#32.GBR.EU #:45507 [Caterham Surrey GBR] $:45507_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Mar 11)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ FEATURES
³ ³/~~~\³ ø ø Þ ³ 4:1 Balun transformer for balanced output.
³ ³__ __³ /~~\ /~~\ ....... ³ Direct coax 1 & 2 & bypass outputs.
³ ÀÄÄÄÄÄÙ | () | | () | : ø\o: ³ Tuned coax 1 & 2 & wire outputs.
³ ::Ü:: \__/ \__/ : : ³ 300W & 3kW cross needle lit power meter.
³ '' '' :.....: ³ The T arrangement C L C has with vernier
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ drives & counter on the inductor.
Unfortunately this large 1500W QRO ATU flashed over & caught fire (smells of
burning), due to poor design of the QRO roller coaster coil mounting brackets,
flammable construction fibre board & inexperienced user (me) when tuning up
with only 400 Watts.
This unit is not fitted with the same sized capacitors or smaller rotary
ceramic & wire roller coaster as shown in the 2 Radcom articles below (*), but
it uses slightly smaller capacitors (still 4.5kV rated) & a large surface area
static silver plated flat spiral coil (very high Q) with a rotating internal
2 surface griping roller simular but bigger to the one used on the MFJ 989D.
_ _ INTERNAL LAYOUT SIMPLIFIED CIRCUIT
ÚÁÄÁÂÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ S ³ v Fire ³ Direct Via
³ W ³ ÜÜÜÜÜÜÜÜܳ oÄÄÄThu ATU
³ R ³ C1 C2 Þðððððððݳ TxÄSWRÄ>oÄÄÄCoax1ÄÄÄo<ÄÄ¿
³~~~ ======= ======= Þðð L ððݳ oÄÄÄCoax2ÄÄÄo ³
³ ======= ======= Þðððððððݳ WireÄÄÄÄo ³
³ SW ======= ======= Þðððððððݳ Via o¿ ³
³ ÜÜÜ ======= ======= Þðððððððݳ o´ RF HOT ³
³ º ======= ======= Þðððððððݳ ATU oÁÄ´ÃÄÄÄÂÄÄÄ´ÃÄÄÙ
³ º ======= ======= Þðððððððݳ C1 ³ C2
³ º ======= ======= ßßßßßßßßß³ L<¿
³ º ºÚÄÄÄÄÄ¿º º ³ ³ ³
ÀÄÄ×ÄÄÄÄÄÄ×ÁÄÄÄÄÄÁ×ÄÄÄÄÄÄÄÄ×ÄÄÄÄÙ ÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÂÄÄÄÄÄ
ßßß ßßßßß ßßßßß ßßßÝ ///
On the back coil insulator combs, there are 3 right angle brackets that have
sharp corners mounted only a few mm away from the RF HOT top of the tuned
circuit, a very high voltage point. They are mounted on inflammable thick fibre
board.
ROLLER COASTER
Flammable(³ ³] RF³³³³³³³³³³³ Silver Plated
Fibre ³ ³ HOT³³³³³³³³³³³ Flat Coil Spiral
Board ³ ³ END³³³³³³³³³³³
³ ÃÄÄÄÄÁÁÁÁÁÁÁÁÁÁÁFlammable
"L" ³ ³_ø_ø___________Support
Bracket ³ ÇÄÄÄÄÂÂÂÂÂÂÂÂÂÂÂ Combs
Screws (³ º] ^Sparks
(³ º] /Jump Earth
ÄÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄChassis
The Caps C1 & C2 are designed for very high voltage & should be the first thing
that arcs over not these sharp cornered brackets!
REPAIR.
The burnt fibre board & shaped mounting comb strip must be cleaned of any
charred material with a sharp knife. This may mean removal & part disassemble
of the roller coaster combs.
MODIFICATION
To stop reoccurrence of the RF flashover, the RF hot ends of the 3 "L" shaped
brackets were cut down in length & the redundant nuts & bolts left out of each.
__ ___ __ __ __
Screw³ ³
holes ORIGINAL MODIFIED
³ 4 HOLE ³ 2 HOLE
BRACKET BRACKET
³
Doing this mod to all 3 brackets (even the top on not near to ground), adds
about 1cm to the flashover arc distance! And has no effect on the sturdiness of
the roller coaster assembly.
LOOSE SCREWS
As this unit has been used for /P work, some screws had soon rattled lose,
despite locking washer nuts! These have been tightened up & threads painted.
IN USE
I use it for /P demonstration stations with a DRAKE L-4B PA & IC735 exciter,
on mains or of generator.
___________ptt+ALC
_____ ³ ³ _________ ______
³IC735ÃÄÙ ÚÄÄÄ¿ ÀÄ´DRAKE PA ÃÄ´ HF ³_ oÄ>1kW Dummy Load
MicÄ´ 12V ÃÄÄÄÄÄÄÄ´ATUÃÄÄÄ´_________³ ³Filter³ \oÄ¿ _____
³_____ÃÄÄÄ¿ ³ ³ ³DRAKE PSU³ ~~~~~~ ³ ³ QRO ÃÄ>80m Dipole
BatteryÄ´PSU55³ _³_ ³___ÃÄ¿ ~~~~~~~~~ ³_³1.5kWÃÄ>40m Dipole
~~~~~ ³BHI³ _³_ Topband 160m ³ ATU ÃÄ>3el Beam
HeadphonesÄÄ´LS ³ /// long wire aerial ³_____ÆÍ>G5RV
~~~
The small ATU after the Rig (VECTRONICS VC300LP) can select an internal dummy
load or the long wire. On the newer WARC bands the extra ATU is used to tune
out the DRAKE L-4B linear's bad SWR of its "out of tune" input matching
circuits, the PA output tank ciruit matches quite OK.
The HF filter is sometimes used to make sure there are no VHF harmonics, if
station is in a sensitive RF area & "direct" not ATU aerials are possible. With
the G5RV then the ATU's balanced output is used.
For public demos, a RF proof AF PA is used with mic audio from the AUX socket
of the IC735 & BHI noise reducing LS system, so that both sides of the QSO can
be clearly heard.
* RSGB Radcom Review Article May 2005 P26, & Comparative one to the MFJ 989D
Jan 2007 P30.
See also my Tech buls "HF ATU & SWR Bridge VC300LP/QT-1", "Drake WH7 QRO HF
SWR Bridge" & "QRO 1kW HF Metered Dummy Load".
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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