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G8MNY > TECH 21.03.18 09:40l 230 Lines 12015 Bytes #999 (0) @ WW
BID : 13252_GB7CIP
Read: GUEST
Subj: RTT Comms Test Set
Path: IW8PGT<LU4ECL<GB7CIP
Sent: 180321/0725Z @:GB7CIP.#32.GBR.EURO #:13252 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Nov 16)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I bought this large test set in it's flight case, at a club junk sale. It
looked very smart & could do quite a lot. "Radio Telephony Test Systems" set
was made in Feltham UK in 1989. It uses PLL oscillators for the RF generator &
CTCSS tones. It came with an Operating Guide, but no service information.
(nothing on internet either) So I did a lot of reverse engineering of it.
___________________________________________________________
/ /|
/ / |
ÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜ/ |
Þ /__________________________________________________________/Ý |
Þ³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³Ý |
Þ³³ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿³³Ý |
Þ³³³ \ AF ³³ \SINAD³³ 5 6 0.0 0 0 0 0 0 ³³ \MOD ³³ \POWER³³³Ý |
Þ³³³__\____³³__\____³³___________________³³__\____³³__\ ___³³³Ý |
ÚÁ³³o _ _ _ _ _ ³³Á¿ |
³_³³ (_)_______(_) (ú) (_) o ø ! ! ! (_) o ³³_³ |
AF³³o _ ³________³ _ _ _ _ ³³ |
in³³o (_) o o (_) (_) ! ! =(_) =(_) (_) o ( ú ) ³³RF /
³³CTCSS SELCAL MOD _ GEN FREQ ú_ú _ _ _ ³³in/
³³1234 123456 12 (ú) 1 2 3 4 5 6 7 (ú) (ú) (ú) (ú)³³ /
³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ³/
~~Þ²Ý~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Þ²Ý~~
SO WHAT IS IT?
It is VHF/UHF RF Transceiver test set, with all of this in one Box...
Dummy Load.
Power meter.
Frequency Counter (9 decimal places, very accurate).
PLL RF Signal Generator (7 Decimal Thumbwheels). CW AM FM & PM
PLL CTCSS tone Generator (4 Decimal Thumbwheels).
Selcall ID Generator & Decoder (6 Hex Thumbwheels, but no PCB, so removed this)
AF Oscillator (Low distortion Wayne type, controlled by 2 Decimal Thumbwheels)
AM/FM/PM Rx (Automatic Scanning AM/FM Rx).
Modulation Meter, +/- Peak reading.
SINAD Meter (AGC & 1kHz Notch, for Rx Sensitivity & Distortion measurement/adj)
AF Volt & dB meter (level & frequency response checks).
IF Xtal Oscillator. (Xtal tester & IF reference Output)
SPECIFICATION
Power AC IEC Mains input 230V/115 @ 60W or 12V DC @ 4A.
RF Input N socket 50ê 40dB Load atten. 1kW peak, 50W continuous.
Power meter 1 3 10 30 100 & 300W (RF detection for Counter & Rx switch)
Frequency Counter 9 digit 1Hz-560MHz in 3 gate times & averaging to 1Hz res.
Freq Reference Accuracy < 1/10^7/month, internal Oven Xtal reference.
Signal Generator 100Hz steps 60MHz-560MHz, PLL type (OK down to 10MHz).
Attenuator 0-9dB +7x10dB steps gives 1.8uV-50mV before 40dB Load atten.
AF Meter 0.25mV - 10V FSD, with dB scale.
Pilot tone(CTCSS) PLL 10Hz-999.9Hz Mod Level adjustable & Counter Decoder.
Selcall 6 char, Mod Level adjustable & Decoder.(No PCB, so removed)
Modulation AF Osc 100Hz-9.9kHz or external, Level adj.(Mod to 15.9kHz)
AF Meter Bal/floating input 3,10,30,100,300mV,1,3,10V, 11Hz-27kHz -3dB
SINAD meter Auto level, 1kHz Notch, 0-20dB/0-100% Noise & Distortion.
Modulation meter Auto Rx. +/- peak, AM 50% 100%, FM 5kHz 20kHz, PM 2Rad 5Rad.
Rx AF Filters Comms 300-3kHz or HiFi 50-15kHz -3dB.
SCHEMAIIC (reverse engineered)
_______ ________ ________ _______________________
AF:ÄÄ´Bal AmpÃÄÂ>Ä´Range SWÃÄ´AF Meter³ MainsÄ´PSU +26,12,10,5,-12,-20³
IN ÀÄÄÄÄÄÄÄÙ ³ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ 12V__/ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
_______ ³ _______ ________ ___________
:ijIF Xtal³ À>Ä´AGC AmpÃÄ´Rej 1kHzÃÄ´Sinad Meter³
oÄÁÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ oExt Mod
__________ ________ link ___________ _________ ³ ____
RF ³Dummy Load³ ³ Relay Ão--oÄ<Ä´ Switched Ã<Ä´ PLL Sig ³_/ ÄÄÄÄÄÄÄÄ´ AF ³
IN o´AttenuatorÃÄ>´SplitterÃÄÄÄ¿ ³Attenuators³ ³GeneratorÃÄÄÄÄÄ<ÄÄ¿ ³Gen ³
OUT ÀÄÄÄÄÄÄÄÄÄÄÙ ÀÄÂÄÄÄÄÂÄÁÄ¿ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÂÄÄÄÄÄÄÂÄÙ mod³ ÀÄÄÄÄÙ
RF³ rly³ ³ ³ ________³_ _³_ ³
___________ _³____³_ ³ ÀÄÄ>ÄÄÄÄÄÄÄ´1/ö10 FreqÃ<Ä´Ref³ _____ ³ _______
³Power MeterÃÄ<´ RF ³ ³ Ex in o´ Counter ³ ³OscÃ>´CTCSSÃÁ´Selcall³
³ & Range SW³ ³Detector³ ³ ÀÄÄÄÄÄÂÄÄÄÄÙ ÀÄÄÄÙ ÀÄÄÄÄÄÙ ÃÄÄÄÄÄÄÄ´
ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ³ ctcss³ ³Display³
_________ _______ ÀÄÄÄÄ>ÄÄÄÄÄÄ¿ _____³_____ ÀÄÄÂÄÄÄÄÙ
³Mod MeterÃÄ<´ AF ³ ____________ À´ Automatic ÃÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄÙ
³+/-Switch³ ³FiltersÃÄ<´Range & ModeÃ<´Scanning RxÃ>ÄoRx Mod
ÀÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÂÄÄÄÄÄÄÄÂÄÙ
Ext RF In oÄ>Ù ÀÄÄ>ÄoIF Out
Auto RF switching changes the Rx & Counter over & disconnects the Signal
Generator, when the Power Meter detector sees Tx RF, so only the Tx signal is
measured. Useful, but confusing when I was chasing faults! (see /E)
FAULTS
Going through the maze of functions, I found several faults....
1/ Mains switch. The long push rod had come off the PSU switch deep inside, &
the button top had swollen & jammed in the front panel. I sanded the button
down & heat glued the push rod on the switch, & a rubber sleeve behind the
front panel captured it so it won't fall out again.
2/ Tx Load 40dB attenuator, presented 147ê not 50ê! It looked clean & not
smelling, so not burnt out? I stripped it down, to find it was all quite loose.
It had screw on ends that held large ally washers with spring washers in the
tube surrounding the RF resistors. There were no open circuits Rs or burnt bits
Put backs all together & did up tight, all OK now. (previous owner's been
playing?)
3 Small rod type Rs Þ Þ Þ Þ Þ Þ Þ Þ Þ Þ
/ | \ Þ Þ Þ Þ Þ Þ Þ Þ Þ Þ
(o)Ä8êÄÂÄ ÄÄ47êÄÄÄÄÂÄ39êÄ<SMA __Úßßßßßßßßßßßßßßßßßßßß¿
N³ ³ \loose ³ ³ N³ ³Ü._____±_____±_____.³Ä¿SMA
³ 139ê here 14ê ³ ³__³ß'~~~~~±~~~~~±~~~~~'³ÄÙ
ÀÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÙ ÀÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÙ
\ / Þ Þ Þ Þ Þ Þ Þ Þ Þ Þ
2 Disc type Rs Þ Þ Þ Þ Þ Þ Þ Þ Þ Þ
3/ FM deviation (Rx) range not right/un-calibratable. Stripping down the Rx
unit, I found a broken 10k preset. Replaced, but needed to be 15K to calibrate
the 5kHz range! Also the 20kHz range need a series preset on the range switch
to get that right too. Inside the Rx box there are also discriminator
adjustments that affect calibration & scanning stop ability! (previous owner's
been playing?)
4/ 12V DC input, uses a 2 transistor inverter had a NPN collector framing (OK
on isolated battery).
IEC 0.25A
LÄÄÄÄo-oÄÄÄÄÄÄÄ/oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
NÄÄÄÄÄÄÄÄÄÄÄÄÄÄ/oÄÄÄÄÄÄÄÄÄÄÄÄ¿ Mains ³ Transformer
+12VÄÄo-oÄ´>ÃÄÂÄ/oÄÄÄÄÄÄÄÄÄÄ¿ (((((((((((()
5A ³ ===========³====================
120 ()))) ()))))))))) ()))) ())) ())
³ ³ ³ ³ ³ 8-0-8v ³ Other
INVERTORÃÄÄ(ÄÙ ³ ³ ³ Secondaries
BIAS ³ ³101ÀÄ)ÄÄÄÄÄ¿ ³
³ ÀÄÄÄÄÄ)ÄÄÄ¿ ³ ³ The cure was to file some metal case away.
22 \³ ³ ³ ³/ This may have been from a bad upgraded
³ ÃÄÙ ÀÄ´ from small to large Tab transistors?
³ e/³ ³\e
0VÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ I also added 4700uF across 12V input.
On off switch stops inverter OK, but leaves bias load on the battery! Mains
lead must not be connected when the 12V is used !!
5/ PM un-calibratable. Something is wrong, had to change op amp gain R in the
Rx as a get around it. Same as FM for inside the Rx box. But I did learn that,
"1 Radian of PM occurs when FM AF Mod Freq = Deviation."
6/ Push button thumbwheel BCD selected AF Modulation frequencies were not very
accurate. I adjusted one of the Wayne C values (room for 4 caps on PCB for it).
The 2 BCD thumbwheels operated 8 relays to controlled the osc Rs. I also put a
CR (220 & n82) across the 150R (Thermistor to earth R) to frequency calibrate
the extended upper frequencies after my modification. (See G/).
7/ CTCSS Pilot tone poor shape @ LF. The output device is ICL 8038BC, so added
some LF frequency correction bias to the Set square 1:1 preset, as I have done
on these AF osc ICs before, but this correction DC had to come from decoded BCD
data line with Rs added them together this time.
MODIFCATIONS
A/ Made a set of test leads for it.
13A Plugð====================> IEC right angle Mains
DC + >ÄfuseÂ=================> XLR 12V
- >ÄÄÄÄÄÙ
3.5mm ÚÄ> Balanced AF & SINAD
Rig LSú-===================ÁÄ> Meters. 4mm plugs
PL259 -é]===================N> N Plug RF Dummy Load in
Both UR67
N Plug <N===================N> N Plug RF Dummy Load in
BNC <========================> BNC general patch lead
B/ I changed the Ovened Reference Oscillator's fine tune 10K preset (hidden)
inside the counter box, for a multi turn version, & drilled a hole to access it
with the top cover just slid off. This permitted the finest of tweaks when hot
without modifying it for an external off air Reference. I also made polystyrene
cover for the patruding hot oscillator box. This reduces the oven power & makes
the temp more stable (& hence Frequency) more quickly.
Warm up time.. Counter error of an air locked 500MHz reference.
Time min 0 1 5 10 15 30 40 50 60
Hz off -30K -1K +261 +122 +95 +69 +50 +42 +31
Error -6/10^5 -2/10^6 5/10^7 3/10^7 2/10^7 <2/10^7 1/10^7 8/10^8 6/10^8
C/ Max deviation measuring range changed from 20kHz to 100kHz. (E.g. now does
5kHz & 100kHz FSD), I put in a 10K series preset on the range switch. But
although usefull indication for broadcast work, the Rx is AF is asymetric @
>+/-50kHz dev!
D/ Added Meter illumination LEDs. Ground down 4 white LEDs to a thin square
sliver 4x4x2mm.
__
Original (__³== Ground []== ÚÄÄ´<ÃÄÄ´<ÃÄÄ´<ÃÄÄ´<ÃÄÄÄ220Ä<+12V
LED Down LED Á 4 under run white LEDS
Wired up all in series & glued on top of meters, making sure the top fascia
bezel did not foul, & feed them via a 220R from a +12V rail plug nearby Rx.
E/ Added a Rx mode LED (relay's +8V via 470R), so you know which mode it is in.
F/ Stripped out the Selcall thumbwheel bank from front panel & replaced it with
a small LS+Amp + Vol control & a Source switch. So AF in, Notched SINAD AF, Mod
or Rx AF, can be heard.
+12VÄÄ10ÄÂÄÄÄ¿+
SOURCE ³ ===470u
AF to SINADÄÄÄÄÄÄÄo<ÄÄ¿ ³\³6 Á
u1 ³ 2³ \
SINAD Meter AFÄ´ÃÄo 1M<ÄÄÄÄÄ´LM\ 5 +470u
Log ³386>ÄÄÄÄÄÂÄ´ÃÄ¿
MOD SwitchÄÄÄÄÄÄÄÄo Vol ÚÄÄÄ´ /¿7 10 ³
Pot Á 3³ / ³+ ³ ³_/³8
Rx Mod BNCÄÄÄÄÄÄÄÄo ³ ³/³=== === |_ ³LS
³ 4³ ³10u ³u1 ³ \³
ÁÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÄÁÄÄÄÄÁ
G/ I changed AF modulation BCD controlled Wayne Osc's "kHz thumbwheel", from
Decade type to Hex (from Selcall bank). This adds 6kHz more range, in 100Hz
steps from 100Hz-15.9kHz. But the thumbwheel types were not the same, the data
1 2 4 8 & C lines were rewired on ribbon to the PCB to make it work. The Wayne
Osc HF freq & gain were trimmed, so the AF osc is accurate (2%) see/6.
See my tech Buls on "Analyser Takeda Riken TR4122B", "AF Waveform Generator
(RS)", "RTT Mod Meter (100)", "Marconi Distortion Meter TF2337", "Marconi 2019A
Sig Gen"," Systron Donner 1702 Sig Gen", "198kHz Off Air Standard", "Comparing
Off Air Freq Standards", "Off Air Lock for Ref Osc", & "Scope RF Trick".
Why don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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