Message:19499 In: TECH.WW
From: G8MNYDate: Tue, 24 Mar 26 08:11:00 Z
Newsgroups: TECH.WW
Subject: RTT Comms Test Set
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Corrections Apr 24)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
At a club sale in 2014, I bought this large, heavy and rare test set, in its
smart flight case. It should be able to do quite a lot, but not seen working!
The "Radio Telephony Test Systems" test set was made in Feltham UK in 1987-9
and it would have cost >10K UKP back then!
Some of my repairs and modification information, which was much revisited
during the Covid lockdown, may be useful for other kit too.
____________________________________________________________
/ /|
/ / |
ÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜ/ |
Þ /___________________________________________________________/Ý |
Þ³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³Ý |
Þ³³ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿³³Ý |
Þ³³³ \ AF ³³ \SINAD³³ù 5 3 9.9 9 9 9 0 0 ³³ \MOD ³³ \POWER³³³Ý |
Þ³³³__\____³³__\____³³____________________³³__\____³³__\ ___³³³Ý |
ÚÁ³³. _ _ Oven _ _ Lock _ Rx ³³Á¿ |
³_³³ (_)_______(_) (ú) (_) o ù ! ! ! (_) ù ³³_³ |
AF³³' _ ³_______³_ _ _ _ _ .-. ³³ |
in³³o (_) o o (_) (_) ! ! =(_) =(_) (_) o ( o ) ³³RF /
³³CTCSS SELCAL MOD _ SIG GEN FREQ ú_ú _ _'-'_ ³³in/
³³123ú4 123456 1ú2 (ú) 1 2 3ú4 5 6 7 (ú) (ú) (ú)=(ú)³³ /
³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ³/
~~Þ²Ý~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Þ²Ý~~
SO WHAT IS IT?
It is a HF/VHF/UHF RF transceiver test set, with all this in one box...
Dummy Load & Attenuator
Power Meter with 6 ranges
Frequency Counter (9 digit, very accurate once warmed up)
PLL RF Signal Generator (7 Decimal Thumbwheels) with 90dB 1dB step Attenuator
Modulation modes CW, AM, FM, & PM
PLL CTCSS tone Generator (4 Decimal Thumbwheels) and CTCSS freq measure button
Selcall ID Generator & Decoder (6 Hex Thumbwheels, but no PCB, so removed this)
AF Oscillator (low distortion Wayne type, controlled by 2 decimal thumbwheels)
CW/AM/FM/PM Automatic wide band scanning Rx, tunes in and locks up in 3 seconds
Modulation Meter, +/- Peak reading, 2 AF Bandwidth filters
SINAD Meter (AF AGC & 1kHz Notch, for Rx Sensitivity & Distortion measure/adj)
AF Volt & dB meter (Level, Signal to Noise & Frequency response checks)
IF Xtal Oscillator. (Xtal tester & IF reference Output)
The RF generator uses 6 PLL oscillators and a PLL CTCSS generator. It came with
a brief Operating Guide, but no service information (nothing on net). So I had
to do a lot of reverse engineering.
SPECIFICATION
RF Input 50ohm N socket 20dB Load atten. 1kW peak, 50W continuous!
Power Meter 1,3,10,30,100,300W FSD, (RF detection for Counter & Rx mode)
Frequency Counter 9 digit 1Hz-540MHz in 3 gate times & 10s averaging to +/-1Hz
Freq Reference Accuracy < 1/10^7/month, internal Xtal Oven & warming LED
Signal Generator PLL 100Hz steps from 10 - 539.9999MHz, O/P -13dBm (50mV) BNC
Sig Gen Harmonics Better than -20dBc, Typically lower than -30dBc
Gen Attenuator 10x1dB & 8x10dB for 1.7uV-50mV, 40dB lower via Load Atten
Pilot tone(CTCSS) 4 Digit PLL 20-999.9Hz in 0.1Hz step, Mod Level, & Rx Counter
Selcall 6 char. Mod Level adjustable & Decoder. (No PCB, so removed)
Modulation modes CW, AM, FM & PM
AF Modulation Internal/External, Level Pot & 20dB Atten.
AF Osc Wayne type 100Hz-15.9kHz in 100Hz steps, not PLL
Ext Mod/AF out Needs >1V in, or 0-4V RMS AF out, 600ohm BNC
Xtal/IF 455kHz & 10.7MHz in built or ext Xtal socket & osc, O/P BNC
AF Meter Bal/floating 3mV-10V FSD, in 8 10dB ranges, 11Hz-27kHz @ -3dB
SINAD meter Auto level, 1kHz Notch, 0 to -20dB/100-0% Noise & Distortion
Automatic Rx Scans 2MHz->1GHz, <100mW to >300W Load input, up to 60dB S/N
RF & IF O/Ps Rear BNCs for RF & 450-470kHz IF
Rx AF Filters Comms 300Hz-3kHz @ -3dB, or HiFi 50Hz-15kHz @ -3dB
Modulation meter Auto Rx. +/- peak, AM 50/100%, FM 5/100kHz, PM 2/5 Rad
Monitor Amp & LS Vol & 1W for Listening to:- AF in, SINAD, AF Osc, & AF Rx
Power AC IEC Mains input 230V/115 @ 60W, or XLR for 12V DC @ 5A
Weight 24kg in it's flight case
SCHEMATIC I worked out.
Ext Mod/AF out oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ<>ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
__________ _________ link ___________ __________ Mod AM/ ³ ___
RF ³Dummy Load³ ³AttnRelayÃo--oÄ<´ Switched Ã<´6 PLL Sig ³FM/PM ³ ³ AF³
INo´AttenuatorÃÄ>´Splitter ÃÄÄÄÄ¿ ³Attenuators³ ³GeneratorsÃÄ<ÄÄÄÄÄÄÁ/Ä<´Gen³
OUTÀÄÄÄÄÄÄÄÄÄÄÙ ÀÄÂÄÄÄÄÂÄÄÁÄ¿ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÂÄÄÄÂÄÄÄÂÄÁÄ<ÄÄÄÄÄÄ¿ ÀÄÄÄÙ
RF³ rly³ ³ ³ ________³_ ³ _³_ ³
___________ _³____³_ _³_ ÀÄ>ÄÄÄÄÄ´1/ö10 FreqÃ<)Ä´Ref³ _____ ³ _ _ _ _
³Power MeterÃÄ<´ RF ³³Pre³ Ext o´ Counter ³ ³ ³OscÃ>´CTCSSÃÁ|Selcall|
³ & Range SW³ ³Detector³³amp³ in ÀÄÄÄÄÄÄÄÄÂÄÙ ³ ÀÄÄÄÙ ÀÄÄÄÄÄÙ |ÄÄÄÄÄÄÄ|
ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙÀÄÂÄÙ ctcss³ ³ |Display|
_________ _______ ÀÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ¿ __³___³____ À Ä Â Ä Ù
³Mod MeterÃÄÄÄ<ÄÄ´ AF ³ ____________ ÀÄ´ Automatic à - - - - -> - Ù
³+/-Switch³ Rx o´FiltersÃÄ<´Range & ModeÃ<Ä´Scanning RxÃÄ>-oIF Out
ÀÄÄÄÄÄÄÄÄÄÙ Mod ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ
_______ ________ ________ ________________________
AF:ÄÄ´Bal AmpÃÄÂ>Ä´Range SWÃ>´AF Meter³ ³PSU +26,15,8.5,5,-12,-20ÃÄMains
IN ÀÄÄÄÄÄÄÄÙ ³ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ\__12V
_______ ³ _______ ________ ___________ _______________
:ijIF Xtal³ À>Ä´AGC AmpÃ>´Rej 1kHzÃ>´Sinad Meter³ >Ä´AF Mon Amp & LS³
oÄÁÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
RF switching changes the Rx and Counter over, and disconnects the Signal Gen
when the Power Meter detects Tx RF, so only the Tx signal is measured. Useful,
but confusing when I was chasing faults! (see F/ mod)
INSIDE (top lid slid off)
PCB NEST DC INVERTER RF & IF
ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÁÁÄÄÂÄÄÄÄÄÄÄÄÄÄÄ¿
³ÚÄÄÄÄÄÄÄÄÄÄ¿³ RÝ SÝ CÝ S: ³ | |³WIDEBAND³ ³
³³ DOUBLE ³³ FÝ IÝ TÝ E: ³ | MAINS |³ ³ ³
³³ ³³ Ý NÝ CÝ L: ³ | TRANSFORMER |³ AUTO ³ ³
³³ SCREENED ³³ FÝ AÝ SÝ C: ³ |________________|³ ³ ³
³³ ³³ RÝ DÝ SÝ A: ³ ³ ³ _ _ ³ SCAN ÃÄÄ¿4 Way RF³
³³ BRASS BOX³³ EÝ &Ý Ý L: ³ ³ ³³ ³³ ³³ ³ ³splitter³
³³ ³³ QÝ AÝ Ý L: ³ o PSU PCB ³³ ³³ ³³ Rx IN ³ ³& Atten ³
³³ FOR 6 PLL³³ Ý FÝ Ý : ///
³ 5A 120R³ ³ ³ ³ 8-0-8V³ ³ ³ ³ ³ ³ ³ ³Secondaries
+12VÙ ÃÄÄ(ÄÄÙ ³ ³ ³ 26 17 7 0 7 17 26V
XLR INVERTOR³ ³1-0-1ÀÄ)ÄÄÄ¿ ³ Áct
0V¿ BIAS ³ ³ ³ ³ ³ The cure was to file some metal case away.
³ 22R ³ ³/ ³ ³/ This may have been from a bad upgraded
³FLOATING ³ ÀÄÄÄÄÄ´NPN ÀÄ´NPN from small to large 15A Tab transistors.
³DC ³ ³\e ³\e
ÀÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÙ I also added 4m7 Cap across the 12V input.
7/ Trying to reduce 12V hum and other rail interference, I lifted of centre
tap's (ct) high current 100Hz earth pulses off the transformer chassis, and
re-wired it directly to a newly isolated (2 nylon screws and insulation kit)
PSU PCB's 0V. So now the PSU DC earths only come from the PSU-module connector
plug and no more rectifier hum loops via the chassis!
Eventually to get the power rail interaction on the +12V rail right down, and
stop affecting the RF sig gen osc, I upgraded the PSU's 7812 reg to a 7815.
Then added 12V regs to both the RF osc box and AF meter PCB, for a proper job.
This gave no power rail interaction (seen as FM noise on 70cms internal or
external FM / SSB Rx). Then re-calibrated the Rx AM, FM, & PM on the new +15V!
8/ AF osc and SINAD circuits are on the 2nd card in the nest. The AF osc uses 2
push button BCD thumbwheels, to select the AF modulator frequencies, but they
are not very accurate, as measured on the counter with patch lead. I adjusted
one of the Wayne bridge osc C values (room for 4 caps on PCB for this). Each of
the 2 thumb wheels operates 4 relays, to control the 8 pairs of Wayne bridge Rs
that determine the 100 frequencies. I also put a CR (220R and n82 in series)
across the 150R (Thermistor to earth R) to frequency calibrate the extended
upper frequencies after my mod.(See H/ mod)
9/ CTCSS pilot tone had poor shape @ LF. It is 3rd card in PCB nest, the sine
wave osc device is a clock triggered ICL 8038BC function gen IC. So I added
some LF frequency correction bias to the set square 1:1 preset (sets balance of
+/- currents into the ramp Cap).
Preset Set Preset for best @50Hz & set SQ @500Hz.
ÚÄR21ÄÂÄÄ470KÄÂÄ100KÄ R1-7 I used this on these AF osc ICs before,
³ 4ÚÄÄÄÄ¿ ÃÄÄ47KÄ Resistor but this time the correction DC had to
VR1 ³8038³ ÃÄÄ47KÄ Pack come from set of Rs decoding some of
SetÃÄÄÄ6³ BC ³ ÃÄÄ47KÄ CTCSS the BCD data lines. (not in BCD order!)
SQ ³ ³ ÃÄÄ82KÄ Freq
ÀÄR15Ä5³ IC6³ ÃÄ390KÄ Data It now gives fairly good sine wave from
³ ³ ÀÄ180KÄ Lines 20.0Hz to 999.9Hz.
10/ The 1dB RF sig gen's stepped attenuator was dodgy. Leaning on the knob gave
different levels! Access to remove the atten unit was very difficult, the front
panel and PSU had to be removed. Tiny atten screws removed, showed it had 10
"fuse like" T atten in a cage turret construction, with sliding contacted at
each end with the in & out SMAs spring contacts & spring earthing contacts too.
SMA² ²SMA
ÚIJÂÄÄÄÒÄÄIJÄÄ¿ The fault was these weakened SMA gold plated
³ ÝßßßßßßßßßÞ ù³ springs, they needed a slight bend to fix. But
Shaft³ \[ atten ]/ |³Click also sliding SMA earths each end of the cage too.
±±±±±±±±±±±±±±±±±±±±±plate
³ [ atten ] |³mech
³ ÜÜÜÜÜÜÜÜÜ ù³ The middle of the cage is earthed with
ÀÄÄÄÄÄÄÐÄÄÄÄÄÄÄÙ greased silver braid wrapped around it
Cage with braid to mate with the outer cylinder case.
11/ A recent fault was hummy FM RF osc when cold, affecting all 6 osc and not
an external signal. This was not mains locked hum, as first thought, but from
the 100Hz phase locked loop RF osc system. Access was by removing top, bottom &
LH side panels, then strip down 2 brass pairs of nested covers that make the
dual RF Faraday cage.
ÚÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
SelectÚÄ<ÄÄ´ControlÃÄÄÄÄÄÂÄ<Ä´Control 1stÃÄ<Ä´7 Frequency ³
Osc ³ ³ EPROM ³ Freq³ ³PCB in nest³BCD³Thumb wheels³
³ ÀÄÄÄÄÄÄÄÙ Data³ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ
To ÚÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÁÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ ÚÄÁÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÄ¿
Rx<Ä´ AM Mod &Ã<´6 Osc Ã>´ ö100 Ã>´ö N Ã>´100Hz PhaseÃÄ<100Hz from
To<Ä´Level AGC³ ³HF-UHF³ ³Prescaler³ ³Freq³ ³Comparitor ³ Ref Osc
AttenÀÄÄÄÄÂÄÄÄÄÙ ÀÄÂÄÄÂÄÙ ÀÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÙ ÀÄÄÄÄÄÂÄÄÄÄÄÙ
³ ³ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³
AM >ÄÄÄÄÙ ³ ÀÄÄ<Ä´Buffered PLL FilterÃÄ<ÄÙ
FM >ÄÄÄÄÄÄÄÄÄÄÄÄÄÙ AFC ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Using freeze spray's long stalk and a hair dryer, it eventually turned out to
be on the PLL Filter Buffer, where an FET was not able to fully turn off a
2N2481 NPN AFC amp, on the plug in PLL control PCB inside the osc box. Changing
it for another NPN cured it, after a lot of testing.
+26V>ÂÄÄÂÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
=== ³ ³ 2K2 Pull up ³
33u Á ³ 22K ³ Current ³
³ ³ e\³ Mirror 2K7
\³ ³ s PLL Loop PNPÃÄÄÄÄÄÄÄÄÄÄÄ´
AFC NPNÃÄÁÄÄÄ>´ g Filter /³ ³
e/³ P chÃÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÄÄÄÄÄ´ ³
³ FETÚÄ´ 22K ===1u \³ 47u ³/
³ ³d ÃÄÄÄ´ NPNÃÄÄÂÄÄÄÂÄÄ´NPN
OSC ³ ³ 2u2=== === e/³ === 2K2 ³\e
AFC<ÄÁÄ10KÄÄÁÄÄÄÄÄÂÄÄÄÄÁÄÄÄÙ2u2 ³ +ÀÄÂÄÙ ³
DC Á 2K2 Á 2K2
The P type FET source follower ³Down ³Up
drives the NPN emitter follower. -ve 100Hz Pulses
Phase Detector IC
Later after reducing the 12V hum (see 7/), I reduced some of the RF osc wobble
for a better UHF CW note, by reducing the 1u to u47 and removing 1 of the 2u2,
Osc lock up time also reduced. But further C value reduction left unstable non
lock up!
MODIFCATIONS
A/ ADDED LEADS & BITS BOX. Set of useful trimming tools and test leads made up,
that fit in the flight case (small bits in a plastic box, so not to scratch the
4 meter fascia bezel or damage the lever-operated thumbwheels). Large leads are
stored between the feet and the manual above in the flight case.
13A Plugð===================> IEC right angle Mains (left in, in Flight case)
DC + >ÄfuseÂ================> XLR 12V @ 5A
- >ÄÄÄÄÄÙ
3.5mm 5T on ÚÄ> Balanced AF & SINAD
Rig LSú-(()===============ÁÄ> Meters. 4mm plugs
Ferrite
PL259 -]===================N> N Plug RF Dummy Load
Both low loss coax
N Plug
BNC <======================N> N Plug RF Dummy Load
BNC <=======================> BNC general patch lead
ÚÄ>
BNC <=====================ÁÄ> 4mm plugs & clips for AF testing
BNC to double banana plug adapter, for Sinad input testing
BNC T adaptor, to enable monitoring of signals
B/ FINE REF CAL TRIM. Inside the counter box, access remove top slide cover and
front strip then remove brass top sheet. I changed the ovened 10MHz reference
osc's fine tune "AGE" 10K preset (hidden), for a fine multi-turn version. And
drilled an access hole in the brass cover sheet, usable with the top cover just
slid off.
Unregulated Ú-----------¿ This permitted the finest of tweaks
+8.5V >ÄÄÄÄÄÄÄÄÄÄÄÄoOVEN HEATER| when hot, when calibrated with an
| | external off air reference.
+5V >ÄÄÄÂÄÄÄÄÄÄÄÄo+5V |
Local reg ³ | 10MHz REF | I also made a foam polystyrene cover
10K +10u | OSC MODULE| __ for the protruding hot oscillator box,
PreÃÄÄÂÄÄÄoAGE RF>oÄ)__ to reduce oven power and make the temp
set === | | ³ more stable (and hence frequency) more
ÄÄÄÄÁÄÄÄÄÁÄÄÄo0V GNDoÄÙ quickly.
À-----------Ù
Tracking down FM hum and drift, I found the original 6.8V reference zener and
1K8 were a poor regulator of the hummy +8.5V, and that gave a lot of long term
thermal drift. The fine tuning AGE voltage, only needed to be around 2.5V, so I
used the nearby 5V regulated rail with a 10uF on the pot slider. This was much
better for hum and much lower drift now too.
Also I added 6mm dia ferrite beads to the +5V rails feeding the 3 RF noisy
items in the counter box, and a 100uF 16V on +8.5V @ regulator, as it was now
an "osc" after I added the ferrites!
Warm up time is now a lot better..
Counter's error of an air locked 10MHz reference.
Time min 0 1 3 5 10
Hz off -41.9 +159 -2.6 +1 +1
Error -42/10^7 +160/10^7 -3/10^7 +1/10^7 +1/10^7
C/ REF OVEN LED. Inside the counter box, I also added an "OVEN" LED, to show
when the thermally controlled oven is still warming and freq not yet accurate.
+8.5V >ÄÄÄÄÄÂÄÄÄÄ4R7ÄÄÄÂÄÄÄÄÄo Heater
Unregulated ³ ³
ÃÄÄÄÄÄ´>ÃÄÄ´1N4001 The circuit and LED are placed inside
³ + ³ counter box and soldered to the +8.5V and
ÃÄÄÄÄÂÄ4K7ÄÙ 0V pins of the oven PCB for support,
e\³ === Â preset making sure they missed the lid's
PNP ÃÄÄÁÄÄÙ counter display and the LED is visible.
/³ 100u OVEN
³ // Adjust the preset so the LED lights,
ÀÄÄ180RÄÄÂÄ´>ÃÄÂÄo 0V and just goes out once the oven is
ÀÄ1K8ÄÙ fully warmed up (5-10 mins).
D/ DEV 100kHz RANGE. Max deviation measuring range I changed from 20kHz to
100kHz. (E.g. now does 5kHz & 100kHz FSD). I put in a 10K series preset on the
3 pole (mode) range switch. But the Rx AF symmetry (+/- readings) needs setting
up with a scope for full 100kHz dev with low distortion, with careful tuning up
of the Rx discriminator and AFC pot! (see CAL procedure in next bul)
E/ METER ILLUMINATION. After removing the top strip and front panel, I added 4
meter LEDs and ground down normal white LEDs, to a thin square sliver 4x4x2mm
to fit.
__ Smaller \\ \\ \\ \\
Original (__³== Ground []== ÚÄÄ´<ÃÄÄ´<ÃÄÄ´<ÃÄÄ´<ÃÄÄÄ220RÄ<+15V
Lensed LED Down LED Á 4 white LEDS
Wired up all in series and glued each on top of a meter, making sure the top
fascia bezel/strip did not foul, and feed them via a 220R from 15V in nearby Rx
relay box plug. For good measure I taped silver plastic foil (sweet packet)
around outside edge of the meters, to help even out the light.
F/ Rx MODE LED. Also after removing the front panel, I drilled a hole in it and
added a Rx mode LED, near the "Zero power" pot, on the Tx/Rx relay's +8V via a
470R from the nearby Rx plug.
Rx mode>ÄÂÄÄÄ¿
ÚÁ¿ 470R So I know which mode the test
RF³ ³ _³_ Gn LED set is in, when switched by
RelayÀÂÙ \_/ Rx Mode the Power meter zero control!
³ ³\\
0VÄÄÄÁÄÄÄÙ
G/ AF MON LS. Also after removing the front panel, Stripped out the Selcall 6
push buttons thumb-wheel bank (used in H/ mod), and replaced it with a small LS
(bent metal to fit), Amp, Vol control, and a source switch.
+15V>ÄÄ47RÄÂÄÄÄ¿+ Loud Volume is clipped
SOURCE ³ ===2m2 when the Volts drop.
AF to SINAD PCBÄÄÄo<ÄÄ´ÃÄ¿ ³\ ³6 Á
10n ³ 2³ \ So now the "AF in",
SINAD Meter AFÄÄÄÄo 1M<ÄÄÄÄ´ LM \ 5 + 220u "Notched SINAD AF",
Log ³ 386 >ÄÄÄÄÂÄ´ÃÄ¿ "Mod", or "Rx AF",
MOD Switch AFÄÄÄÄÄo Vol ÚÄÄ´ /¿7 10R ³ can all be heard.
Pot ³ 3³ / ³+ ³ ³_/³
Rx Mod BNCÄÄÄÄÄÄÄÄo ³ ³ ³/4³ === === |_ ³LS
³ ³ ³ ³10u ³u1 ³ \³8R
0VÁÄÄÄÁÄÄÄÄÄÁÄÄÁÄÄÄÄÄÁÄÄÄÄÁ
H/ AF OSC RANGE & LEVEL. Also after removing the front panel, I changed AF
modulation BCD controlled Wayne Osc's push button "kHz thumb wheel", from a
decade 0-9 type to a Hex 0-F type, recovered from the Selcall bank. This adds
6kHz more range (60 more) from 100Hz-15.9kHz. Unfortunately the thumb wheels
were not the same BCD data type! So 1 2 4 8 & C data lines had to be cross
wired with a ribbon to the wheel mounting PCB to make it work! The Wayne osc at
high frequency and gain were trimmed on the AF PCB, so the AF osc is now
accurate in level and frequency to +/- 1% see /8.
Also after the 15V PSU mod, I was able to greatly increased the AF osc level
(not clipping @ 4V RMS) to help the wide FM deviation I wanted, by replacing
the 56R with 680R in series with TH1 the regulating thermistor on the AF PCB in
the nest.
I/ OUT OF FREQ RANGE. The 100MHz frequency leaver operated thumb-wheel can be
set above 539MHz so I coloured RED the 6 7 8 9 thumb-wheel 100MHz number
options as a reminder!
See my tech Buls on "RTT Comms Test Set Cal & Use", "Analyser Takeda Riken
TR4122B", "AF Waveform Generator (RS)", "RTT Mod Meter (100)", "FeelTeck Dual
DDS Osc FY6600-60M", "Marconi Distortion Meter TF2337","Marconi 2019A Sig Gen"
"Systron Donner 1702 Sig Gen", "Marconi Counter Type 2432A", "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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