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G8MNY > TECH 02.04.21 08:21l 159 Lines 7821 Bytes #999 (0) @ WW
BID : 29558_GB7CIP
Read: GUEST
Subj: Palstar AT1500CV ATU
Path: IZ3LSV<I3XTY<I0OJJ<GB7CIP
Sent: 210402/0714Z @:GB7CIP.#32.GBR.EURO #:29558 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jan 19)
(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\ : ³ Tuned: coax 1, & 2, & wire outputs.
³ ::Ü:: \__/ \__/ : ø: ³ 300W & 3kW cross needle lit power meter
³ '' '' :.....: ³ 60W & 600W reflected.
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ The T arrangement C L C has verniers & a
counter on the inductor.
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 than the one used in the MFJ 989D.
_ _ INTERNAL LAYOUT SIMPLIFIED CIRCUIT
ÚÁÄÁÂÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ Direct Outputs
³ S ³ (\\\\\) v Fire ³ Wire xÄÄ¿
³ W ³ T ÜÜÜÜÜÜÜÜܳ Tx(ú)Ä[SWR]Ä>oÄÄÄ(ú)Coax1ÄÄÄÄ¿ ³ o<¿WAFER
³ R ³ ÞðððÛðððݳ oÄÄÄ(ú)Coax2ÄÄ¿ ³ ³ o ³SWITCH
³~~SW ======= ======= ÞðððÛðððݳ oÄÄÄ(ú)Thu ³ ³ ³ o ³
³ ÜÜÜ ======= ======= ÞðððÛðððݳ Via o¿ ³ ³ ÀÄo ³
³ º ==C1=== ==C2=== ÞðLðÛðððݳ o´ ³ ÀÄÄÄo ³
³ º ======= ======= ÞðððÛðððݳ ATU o´ RF HOT ÀÄÄÄÄÄo ³
³ º ======= ======= ÞðððÛðððݳ ÀÄÄÄ´ÃÄÄÄÂÄÄÄ´ÃÄÄÄÄÄÄÙ
³ º ======= ======= ÞðððÛðððݳ WAFER C1 ) C2 ÚÄÄx
³ º ======= ======= ÞðððÛðððݳ SWITCH L)<¿ _(|
³ º ======= ======= ßßßßßßßßß³ ) ³ ³ (|T
³ º ºÚÄÄÄÄÄ¿º [º] ³ ) ³ ³ ÀÄÄx
ÀÄÄ×ÄÄÄÄÄÄ×ÁÄÄÄÄÄÁ×ÄÄÄÄÄÄÄÄ×ÄÄÄÄÙ ÄÄÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÁÄÂÄÄx
ßßß ßßßßß ßßßßß ßßßÝ T ATU Á
SWR CIRCUIT
(ú)ÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄ>Switch Ref 60W +1k2
Rig === Cal (((() Cal === ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo<ÄÄÄÄÄÂÄÄÄÄ(M)Ä¿
6p8³ / ³16T³ \ ³6p8 ³ ÚÄÄÄÄÄÄÄÄÄÄÄo600W ===10n ³
ÃÄ´ÃÄÂÄ´<ô ô>ÃÄÂÄ´ÃÄ´ ³ ³ 300W Á ³
10p³ ) ³ ³ ) ³10p ³ ³ ÚÄÄÄÄÄo<ÄÄÄÄÄÂÄÄÄÄ(M)Ä´
=== )680 22 22 680) === ³ ³ ³ ÚÄo3KW === +1k2 Á
³ )uH ³ ³ uH) ³ CAL CAL CAL CAL For Á10n
ÃÄ´ÃÄ´ Á Á ÃÄ´ÃÄ´ 100K 100K 100K 100K
Á 10n³ ³10n Á ³ ³ ³ ³
³For Ref³ 6K8 47K 47K 100K
³ ÀÄBlackÄÄÄÄÄÄÄÄÁÄÄÄÁ´Ã´ÃÁÄÄÄ´
³ 10n Á 10n ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄRedÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
____ o
12V>ÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄWhiteÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄ´7810ÃÄo<ÄÄÄÂÄÄ>
=== 10n ===ÀÄÂÄÄÙ 10n=== Lamp
Á 47uÀÄÄÄÁÄÄÄÄÄÂÄÄÄÙ
Á
HI Q ROLLER COASTER
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.
On the back coil insulator combs, there are 3 right angle brackets, that have
sharp corners only a few mm away from the "RF HOT" top of the tuned circuit, &
are mounted on flammable thick fibre glass board.
_______________________1 of 3 Fiber Glass
³ ºo o Combe Support Bars
(³ º]____________________
Flammable(³ º] RF³³³³³³³³³³³ Contact
Fibre ³ ³ HOT³³Silver Plated ======H===Û= Wheel Rod
Board ³ ³ END³³Flat Coil Spiral Wheel Û
³ ³ OF³³³³³³³³³³³ÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÛÜÜÜAxil
³ ³COIL³³³³³³³³³³³
³ ÃÄÄÄÄÁÁÁÁÁÁÁÁÁÁÁÄÄÄÄÄ Flammable
"L" ³ ºo_o_________________ Support
Bracket ³ ÇÄÄÄÄÂÂÂÂÂÂÂÂÂÂÂÄÄÄÄÄ Combs Bars
Screws (³ º] /^Sparks
(³ º]v Jump Earth
ÄÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄChassis
The Caps C1 & C2 are designed for very high voltage & should be the first thing
that arcs over, but 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 support comb bars.
MODIFICATION
To stop reoccurrence at the RF hot ends of the 3 "L" shaped brackets, they 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 to all 3 brackets (even the top one not near to ground), adds about
1cm to the flashover arc distance! And has no effect on the sturdiness of the
roller coaster assembly as long as the bolts are kept tight.
OTHER BURN MARKS
The 3 combe supports bars can suffer. They are all different with the coil
slots all moved 1/3 of the pitch. But I have managed to reverse the top one so
the burnt RF hot end, is now the cold coil end.
LOOSE SCREWS
As this unit has been used for /P work, some other screws had soon rattled lose
despite locking washer nuts! These have been tightened up & threads painted.
IN USE
The "T" type ATU is easy to use, although it is not so good at removing Tx
harmonics as the ã (pi) type. But it does an excellent job of protecting the Rx
from DC static, & strong signals on lower bands, that some poorly filtered SRD
Rx can suffer from! (e.g. removing MW Broadcast signals as it is >-18dB for
each frequency halving.)
I use it for /P demonstration stations with a DRAKE L-4B PA or T500M PA & IC735
exciter, on mains or 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 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 circuit matches quite OK.
The HF LP filter is sometimes used to make sure there are no VHF harmonics, if
the station is in a sensitive RF area & "direct no ATU" to aerials may be used.
With the G5RV then the ATU's transformer 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 MFJ-904H", "HF ATU & SWR Bridge
VC300LP/QT-1", "Drake TC-3300-LP QRO LP Filter", "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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