G8MNY > TECH 08.06.25 08:30z 98 Lines 4617 Bytes #166 (0) @ WW
BID : 34345_GB7CIP
Subj: RTT Automatic Mod Meter (100)
Path: ED1ZAC<ED1ZAC<LU4ECL<VK4OT<VK6ZRT<GB7CIP
Sent: 250608/0814Z @:GB7CIP.#32.GBR.EURO #:34345 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jan 15)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I bought this meter at a recent SK sale. It came with an Operating Guide, but
no service information. (nothing on internet)
_________________________________________________________________
/ \
³ _____________________________________________________________ ³
³ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿% ³ ³
³ ³ ON ³ 8 8 8 . 8 ³kHz Vol ³ ³
³ ³ ( ) ³_______________³Rad ( ) ³ ³
ÚÄ´ ³ _______________ ³ ÃÄ¿
[³ ³ ³ (ú) ³ÜÜÜÜÜÜÜ________³ (ú) ³ ³ ³]
³Ú´ ³ MOD AM FM PM 3k 15K WB + - /2 AF TEST REM RF ³ ÿ³
³³³ ³ OUT [ ][ ][ ] [ ][ ][ ] [ ][ ][ ] [ ][ ][ ] IN ³ ³³³
³³³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³³³
³³³ RTT Series 100 Modulation Meter ³³³
³³ \_________________________________________________________________/ ³³
³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ³
\_____________________________________________________________________/
SO WHAT IS IT?
It is HF/VHF/UHF AM/FM/PM Digital Modulation Meter (Automatic scanning Rx).
SPECIFICATION
Power AC IEC Mains input 230V/115 @ 15VA or internal batt, rear SW
RF Input BNC socket 50ohm, Max 7V (1W)
Frequency range Scanning type 1.5MHz-2GHz (5-40mV input typical)
Modulation meter Auto Rx. +/- peak & combined Average. With 20 bit bargraph
Ranges Automatic AM 0-100%, FM 0-9kHz & 10-100kHz, PM 0-5 Radians (2% typical)
AF Filters Comms 300Hz-3kHz, HiFi 50Hz-15kHz & Wideband 50Hz-30kHz
IEEE 488 bus Remote control for measurements & reporting test result
Mod Out BNC & Volume control for internal rear LS
IF Out 410kHz at rear BNC
It was made in Feltham UK in 1980s. It has a comprehensive power on self check
that tests all the systems & basic calibration.
ERROR CODES
90 LEDs & Ram, 80 ROM Checksum, 18 Battery <10 or >14V, 5 +5V, 12 +12V, -6 -6V,
51 +ve detector, 52 +ve det 10x, 43 -ve Det 10x, 55 3kHz filter, 56 15k filter
57 Wideband filter.
INSIDE
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ( ) Front panel PCB [±] ³
³ o o ³
³________________________________³
Rx Converter & IF modules
below Digital PCB underneath.
_____________________________mod out PRESETS
³ 1 Wide 2 .. ³ 1 Bar Graph
Å Filter :³_FM Rx 2 PM Cal
³ Filter :³_AM Rx 3 Cal test tone 1
Å SW HiFi ³ 4 10x gain Cal
Å 3 Filter 5 ³ 5 FM Cal
³ 4 Mode 6 ³ 6 AM Cal
Å 9 SW Comms 7 ³ 7 Cal test tone 2
Å 10 Filter 8 ³ 8 AM/FM/PM Gain Cal
Å____________________ ³ 9 DC A-D cal (batt,12v)
Upper Analog PCB ³ Det ³ 10 DC A-D offset (+5V,-6V)
³. 11³ 11 +Det gain
LS³: LS ³ 12 Set +12V
³ amp ³
³___________³ Calibration is a VERY long winded
________________________________ round robbin if you upset A-D converter
³12 | | | | | ³ (gain & offset?) presets 9 or 10!
³ Mains XF| | | | | charge ³
³ | Batteries | regulator³
³PSU under| | | | | ³
³_________|__|__|__|__|__________³
[LS]
.ú' 'ú. Rear Panel IEC
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
FAULTS
It internal 12V (10x AA 0.5AH) Nicad battery was missing, so I added 4
recovered 4AH Li cells to make a 12-16V pack. A voltage doubler & constant
current is used for battery charging with cpu controlled boost if low.
One of the 2 diodes in the 12V PSU was high resistance & caused the toroid to
overheat. The Logic card has it's own 5V reg & there is a -6V PSU somewhere.
AF Wideband 4 opamp filter, components changed to give 10Hz-60kHz
If anyone has more info one the unit I would appreciate it.
See my tech buls on "RTT Comms Test Set", "DYMAR Mod Meter Type 1785",
"FeelTeck Dual DDS Osc FY6600-60M", "FM Deviation Calibration", &
"FM Stereo Radio Principles".
Why don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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