IW8PGT

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G8MNY > TECH 03.09.22 11:20l 484 Lines 27110 Bytes #999 (0) @ WW BID : 28723_GB7CIP Read: GUEST Subj: RTT Comms Test Set Path: IW8PGT<LU4ECL<LU9DCE<VA3TOK<VE3KPG<GB7CIP Sent: 220903/0910Z @:GB7CIP.#32.GBR.EURO #:28723 [Caterham Surrey GBR] From: G8MNY@GB7CIP.#32.GBR.EURO To : TECH@WW By G8MNY (Updated Jun 22) (8 Bit ASCII graphics use code page 437 or 850, Terminal Font) At a club sale, I bought this large, heavy & 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 & would have cost >10K UKP back then! Some of my repairs & modification information 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 6 ranges (Peak reading) 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) & 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) AM/FM/PM Automatic wide band scanning Rx, tunes in & 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, S/Noise & frequency response checks) IF Xtal Oscillator. (Xtal tester & IF reference Output) The RF generator uses 6 PLL oscillators & 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 N socket 50 Ohm 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 reference Signal Generator PLL 100Hz steps from 10 - 539.9999MHz, O/P -13dBm (50mV) BNC Sig Gen Harmonics Better than -20dBc, Typically -30dBc Gen Attenuator 10x1dB & 8x10dB for 1.7uV-50mV & via 40dB of splitter + Load 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) AF Modulation Internal AF osc or ext, Mod Level Pot & 20dB Atten. AF Osc 2 Dig Thumbwheel Wayne, 100Hz-9.9kHz (Now to 15.9kHz) Ext Mod/AF out Needs >1V in, or gives 0-4V RMS AF out, 600 Ohm BNC Xtal/IF 455kHz & 10.7MHz in built & ext Xtal socket & osc O/P BNC AF Meter Bal/floating 4mm, 3mV-10V & dBs 8 ranges, 11Hz-27kHz -3dB SINAD meter Auto level, 1kHz Notch, 0-20dB/100-0% Noise & Distortion Automatic Rx Scans 2MHz->1GHz, 0.1-300W Load input, up to 60dB S/N RF & IF O/Ps Rear BNCs for 450-470kHz & RF in/out Rx AF Filters Comms 0.3-3kHz -3dB, or HiFi 0.05-15kHz -3dB Modulation meter Auto Rx. +/- peak, AM 50/100%, FM 5/100kHz, PM 2/5 Rad Power AC IEC Mains input 230V/115 @ 60W or XLR for 12V DC @ 5A Weight 24kg in flight case SCHEMAIIC Ext Mod/AF out oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ<>ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ __________ _________ link ___________ _________ Mod AM/ ³ ___ RF ³Dummy Load³ ³AttnRelayÃo--oÄ<´ Switched Ã<Ä´ PLL Sig ³FM/PM ³ ³ AF³ INo´AttenuatorÃÄ>´Splitter ÃÄÄÄÄ¿ ³Attenuators³ ³GeneratorÃÄ<ÄÄÄÄÄÄÁ/Ä<´Gen³ OUTÀÄÄÄÄÄÄÄÄÄÄÙ ÀÄÂÄÄÄÄÂÄÄÁÄ¿ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÂÄÄÂÄÄÄÂÄÁÄ<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 Ã - - - - -> - Ù ³+/-Switch³ Rx o´FiltersÃÄ<´Range & ModeÃ<Ä´Scanning RxÃÄ>-oIF Out ÀÄÄÄÄÄÄÄÄÄÙ Mod ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ _______ ________ ________ ________________________ AF:ÄÄ´Bal AmpÃÄÂ>Ä´Range SWÃÄ´AF Meter³ ³PSU +26,15,8.5,5,-12,-20ÃÄMains IN ÀÄÄÄÄÄÄÄÙ ³ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ\__12V _______ ³ _______ ________ ___________ :Ä³IF Xtal³ À>Ä´AGC AmpÃÄ´Rej 1kHzÃÄ´Sinad Meter³ oÄÁÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ RF switching changes the Rx & Counter over & disconnects the Signal Gen, when the Power Meter detector sees 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 | |³ ³ 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 ³ ³& Atten ³ ³³ FOR 6 PLL³³ Ý FÝ Ý : ³ ßßßßßßßßßßßßßßßÛßß³ ÃÄÄÙ ³ ³³ ³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Ý ³ SCREEN ³ ÚÁÁ¿ ³ ³³ HF - UHF ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³ ³ ==========³ ³³ ³ ³ 5V reg ³³ BOX & ³ ===LOAD===³ ³³ OSCs & ³ OÚÄÄ´ ö10 PRE SCALLER ³³ ³ ==========³ ³³ ³ v³ ³Ref ³³ PREAMP ³ ==========³ ³³MODULATORs³ e³ ³OSC SCREENED BOX ³³ ³ ===ATTEN==³ ³ÀÄÄÄÄÄÄÄÄÄÄÙ nÀÄÄ´ ³ÀÄÄÄÄÄÄÄÄÙ ==========³ ³ÜÜÜÜÜÜÜÜÜÜÜ _____ ³ COUNTER PCB ³ _____ ÜÜÜÜÜÜÜÜÜÜÜ³ ³ ³ AF ³ ³SINAD³ ³ ON LID WITH ³ ³ MOD ³ =³POWER³==³ ³ ³METER³ ³METER³ ³ 9 DIGIT DISPLAY ³ ³METER³ =³METER³==³ ÃÄÄÁÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÁÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÁÄÄ´ ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÂÄÄÄÂÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÜÄÄÄÂÂÄÄÄÂÂÄÄÄÄÂÂÄÂÄÂÄÂÂ´ ³ Ext Mod Counter On Xtal Mod Gen ÀÄÙ RF³ /AF out in IF/Osc out out N Sample \\LINK// FAULTS Going through the many functions, I found several faults.... 1/ Mains on/off push switch's rod had come off the PSU switch deep inside, & the button top had swollen & jammed in the front panel. I sanded the button down, used a rubber sleeve behind the inner front panel to captured it, & heat glued the push rod on to the PSU switch, so it won't fall out again. 2/ Tx Load 20dB atten, presented 147R not 50R! It looked clean & not smelling, so not burnt out? Removed it (front & side panel off) & 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 5 special RF resistors. 3 rod type Rs Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý / | \ =Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý (o)Ä8RÄÂÄ ÄÄ47RÄÄÄÄÂÄ39RÄ<SMA __Úßßßßßßßßßßßßßßßßßßßß¿ N³ ³ \loose ³ ³ N³ ³Ü._____±_____±_____.³Ä¿SMA ³ 139R here 14R ³ ³__³ß'~~~~~±~~~~~±~~~~~'³ÄÙ ÀÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÙ ÀÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÙ \ / =Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý 2 Disc type Rs Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý Ý No open circuit or burnt bits found. Putting it all back together tightly, I now see 50R (previous owner been playing?) And on an analyser & tracking generator, it showed a constant 20dB atten to > 1GHz. 3/ FM deviation measurement range (used for the sig gen cal too) was un- calibratable! Rx access by removing top, bottom & RH side panel, then strip down the Rx Box's side panel with the Rx bolted on it. I found a broken 10K FM Cal preset. Replaced, but needed to be 15K to calibrate the 5kHz range! Rough holes had been drilled to access the calibration adjustments! The inner PCB is only soldered in place. The 3 nuts are just stand offs under the PCB, (used before soldering), & I soldered in the 2 loose captured screws for ease of assembly! ÚÄÄÄÄÄÄÄÄÄÄÄÄFMÄÄÄÄÄÄÄPMÄÄÄÄÄÄÄÄÄÄÄAMÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³( ) Cal Cal Cal /~~\ ³ INSIDE ³( ) \__/ ³ AUTO SCAN ³ Signal conditioning & AF meter PCB ³ Rx Box is ³ÚÄÅÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ this PCB, ³³ in Mixer IF[o] AGC IC AM [o] ³ ³ with a Relay ³³ [o]IF IF[o] Detect (o) ³ ³ & Preamp too. ³³ AM AGC³ ³ ³³Harmonic ³2nd³ ³³Multiplier (o) R x P C B (o) ³Screened ³³ Sweep amp STOP AFC ³Rx ³ ³³ ³Box³ ³³ ³ ³ ³³1.5-2MHz Limitor[o] FM ³ ³ ³³ [o]Osc rampIC 10HzOsc [o] Discrim 5V³ ³ ³³___________________________________________________³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Also the 20kHz range needed a series preset on the range switch to get that right too. (See 5/ Fault & D/ Mod) Inside the Rx box there are AM AGC & FM discriminator adjustments that affect calibration & the scanning STOP ability! (previous owner playing?) 4/ PM un-calibratable. (PM = 6dB/Octave treble lifted FM). Something is wrong, I had to change op amp's 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 (57ø) of PM occurs when the FM AF Mod Freq = the Deviation." So 2 Rad = 1kHz tone @ 2kHz FM Dev, & 5 Rad = 1kHz tone @ 5kHz FM Dev, & 2 Rad = 300Hz tone @ 600Hz FM Dev, & 5 Rad = 300Hz tone @ 1.5kHz FM Dev. 5/ A crackly Rx noise fault in the very wide-band 2MHz->1GHz automatic Rx. (see 3/) On testing I blew up its 78L05, & zapped a CMOS 10Hz osc hex inverter IC! In the end the noise was mostly from scratchy AFC preset pot. ÚÄÄÄÄÄÄ>ÄÄÄÄÄo)IF ÚÄÄÄÄÄ¿ ÚÄÄÄÄÄÄ¿ÚÄÄÄ¿ ÚÄÄÄÄÄÄÄ¿ÚÄÄÄ¿ ÚÄÄÄÄÄÄ¿ÚÄÄÄ¿ ÚÄÄÄÄÁÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ RxÄ´Ring Ã>´460kHzÃ´IF Ã>´460kHz Ã´AGCÃ>´460kHzÃ´IF Ã>´460kHzÃ´AM Ã´AF ÃÄ>AM in ³Mixer³ ³ LPF ³³Amp³ ³Filters³³ IC³ ³Filter³³Amp³ ³Filter³³Det³³Buf³ ÀÄÄÂÄÄÙ ÀÄÄÄÄÄÄÙÀÄÄÄÙ ÀÄÄÄÄÄÄÄÙÀÄÂÄÙ ÀÄÄÄÄÄÄÙÀÄÄÄÙ ÀÄÄÄÂÄÄÙÀÄÂÄÙÀÄÄÄÙ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄ<ÄÄÄÄ)ÄÄÄÄÄÁÄÄ>Lock LED ÚÄÄÁÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄ¿ÚÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄ¿ ³ ÚÄÁÄ¿ÚÄÄÄÄ¿ÚÄÄÄ¿ ³Harmonic Ã<´1-2MHzÃ´RampÃ<´256 RampÃ<´10HzÃ<ÄÙStop ³FM Ã´FM Ã´AF ÃÄ>FM ³Generator³ ³ Osc ³³Amp ³ ³ Counter³ ³Osc ³ ³Lim³³Disc³³Buf³ ÀÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÙÀÄÄÂÄÙ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÙ AFC ÀÄÄÄÙÀÄÂÄÄÙÀÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ<ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ The Rx has a wide LC tuned 460kHz IF, feeding AM & FM detectors. The front end is just a ring mixer, fed with highly harmonic rich 1.5-2MHz oscillator. This is tuned with a varicap in 256 steps, from a ramp gen/8 bit counter/analogue out IC. It counts a 10Hz osc, that is stopped when a good enough IF signal is detected by the AM (with AGC) detector. Then the FM discriminator's AFC takes over for fine frequency control, or unlocks it if it is a wrong side image. The Rx is fed from a wide band preamp, fed from the 4 way 20dB splitter that feeds the power meter, sig gen, frequency counter, & a diode switched preset Rx atten, all fed from the large 20dB load attenuator from transceiver under test. 6/ 12V DC PSU input option, uses a 2 NPN Tab transistor inverter on dedicated windings on the mains transformer, but there was a collector framing (OK on isolated battery). Only 6 screw to remove PSU. The way the On/Off switch is wired it stops inverter, but leaves bias load on the battery! The mains switch is cross-wired so when mains is off, the DC power option is on, this ensures there is no inverter bias when the mains is on, & the mains is disconnected in 12V mode! on off LÄÄÄÄo-oÄÄÄÄÄÄÄ/oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿Mains & Inverter NÄÄÄÄoÄoÄÄÄÄÄÄÄ/oÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ 115³ 230³Transformer IEC 2x 0.25A ÚÄ\oÄÄÄÄÄÄÄÄÄÄÄ¿ (((((((((((() ______ÚÄÄÄÄÄÄÄÄÄÄÄÂÄÄmains earth ³ ============³====================== Shield _³_ ÚÄo-oÄ´>ÃÄ´ ()))))) ()))))))) ())))))))))))))))) /// 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 & other rail interference, I lifted of centre (ct) tap's high current earth pulses off the transformer chassis, & re-wired it directly to a newly isolated (2 nylon screws & insulation kit) PSU PCB's 0V. So now the PSU DC earths only come from the PSU-module connector plug & no more 100Hz hum loops via the chassis! Eventually to get the power rail interaction on the +12V rail right down, & stop affecting the RF osc, I swapped the PSU's 7812 reg for a 7815. Then added 12V regs to both the RF osc box & the AF meter PCB, for a proper job, to give no power rail interaction (seen as FM noise on 70cms internal or external FM/SSB Rx). Then I re-calibrated the Rx AM & FM on the new +15V! 8/ AF osc & SINAD circuits are on 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 actually operates 4 relays, to control the 8 pairs of Wayne bridge Rs, that determine the 100 frequencies. I also put a CR (220R & 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 the 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 doggy. Leaning on the knob gave different levels! Access to remove the atten unit was very difficult, the front panel & 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 ÚÄ²ÂÄÄÄÒÄÄÄÂ²ÄÄ¿ It was these weakened SMA gold plated springs, ³ ÝßßßßßßßßßÞ ù³ needed a slight bend to fix. But also a Shaft³ \[ atten ]/ |³Click sliding to the SMA 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 & not an external signal. This was not mains locked hum, as first thought, but from the 100Hz PLL RF osc system. Access was by removing top, bottom & LH side panel, then strip down the 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 ÚÄÄÄÄÄÄÄÄÄÄ¿ ³ AM >ÄÄÄÄÙ ³ ÀÄÄÄ<ÄÄÄÄ´PLL FilterÃÄÄÄ<ÄÄÄÄÙ FM >ÄÄÄÄÄÄÄÄÄÄÄÄÄÙ AFC ÀÄÄÄÄÄÄÄÄÄÄÙ Using freeze spray's long stalk & 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 ³ ³ Current ³ ³ 22K e\³ Mirror 2K7 ³ ³ PLL Loop PNPÃÄÄÄÄÄÄÄÄÄÄÄ´ AFC \³ ³ s g Filter /³ ³ AMP NPNÃÄÁÄÄÄ>´ÄÄÄÄÄÄÄÄÂÄÄÄÂÄÄÄÄÄÄÄÄ´ ³ e/³ P ch³FET 22K ===1u \³ 47u ³/ ³ ÚÄ´ ÃÄÄÄ´ NPNÃÄÄÂÄÄÄÂÄÄ´NPN OSC ³ ³d 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 emmitter follower. 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 & 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. Set of usefull trimming tools & 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 opearated thumbwheels). Large leads stored between the feet. 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 <N==================N> N Plug RF Dummy Load 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 & 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 >ÄÄÄÄÄÄÄÄÄÄÄÄÄoOVEN HEATER| when hot, when calibrated with an | | external off air reference. +5V >ÄÄÄÄÂÄÄÄÄÄÄÄÄo+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 & make the temp set === | | ³ more stable (& hence frequency) more ÄÄÄÄÄÁÄÄÄÄÁÄÄÄo0V GNDoÄÙ quickly. À-----------Ù Tracking down FM hum & drift, I found the original 6.8V reference zener & 1K8 were a poor regulator of the hummy 8.5V, & 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 & much lower drift now too. Also I added 6mm dia ferrite beads to the +5V rails feeding the 3 items in the counter box, & 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 +16/10^7 -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 & freq yet not accurate. +8.5V >ÄÄÄÄÄÂÄÄÄÄ4R7ÄÄÄÂÄÄÄÄÄo Heater Unregulated ³ ³ ÃÄÄÄÄÄ´>ÃÄÄ´1N4001 The circuit & LED are placed inside ³ + ³ counter box & soldered to the +8.5V & ÃÄÄÄÄÂÄ4K7ÄÙ 0V pins of the oven PCB for support, e\³ === Â preset making sure they missed the lid's PNP ÃÄÄÁÄÄÙ counter display & LED is visible. /³ 100u OVEN ³ // Adjust the preset so the LED lights ÀÄÄ180ÄÄÄÂÄ´>ÃÄÂÄo 0V & 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 & AFC pot! (see CAL procedure in next bul) E/ METER ILLUMINATION. After removing the front panel, I added 4 meter LEDs & 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 & glued 1 on top of each meter, making sure the top fascia bezel did not foul, & feed them via a 220R from 15V in nearby Rx relay box plug. Then 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 hole & added a Rx mode LED, near the "Zero power" pot, on the Tx/Rx relay's +8V via 470R on the nearby Rx plug. Rx mode>ÄÂÄÄÄ¿ ÚÁ¿ 470R So you know which mode the RF³ ³ _³_ Gn LED test set is in, when switched RelayÀÂÙ \_/ Rx Mode by the Power meter zero control! ³ ³\\ 0VÄÄÄÁÄÄÄÙ G/ AF MON LS. Also after removing the front panel, I stripped out the Selcall thumb wheel bank, & replaced it with a small LS (bent metal to fit), Amp, Vol control, & a source switch. +15V>ÄÄ47ÄÂÄÄÄ¿+ Loud Volume clipped SOURCE ³ ===2m2 when Volts drops. 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_/³8R Rx Mod BNCÄÄÄÄÄÄÄÄo ³ ³ ³/ ³ === === |_ ³LS ³ ³ 4³ ³10u ³u1 ³ \³ 0VÁÄÄÄÁÄÄÄÄÄÁÄÄÁÄÄÄÄÄÁÄÄÄÄÁ H/ AF OSC RANGE & LEVEL. Also after removing the front panel, I changed AF modulation BCD controlled Wayne Osc's "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. But 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 @ HF frequency & gain were trimmed on the AF PCB, so the AF osc is now accurate in level & frequency to ñ1% 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 frequency thumbwheel can be set above 539MHz I coloured RED the 6 7 8 9 thumbwheel 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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11.05.2024 17:32:35l

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