Message 28189 in TECH.WW
From: G8MNY
Date: Tue, 18 Aug 26 06:49:00 Z
Newsgroups: TECH.WW
Subject: RTT Automatic Mod Meter (100)
Message-ID: <2593_GB7CIP>
Path: N2MH4|GB7BED|EI2GYB|GB7CIP
R:260818/0652Z 35614@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260818/0652Z 16098@GB7BED.#21.GBR.EU LinBPQ6.0.25
R:260818/0651Z 57808@EI2GYB.DGL.IRL.EURO LinBPQ6.0.25
R:260818/0649Z @:GB7CIP.#32.GBR.EURO #:2593 [Caterham Surrey GBR] $:2593_GB7CIP
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)
_________________________________________________________________
/ \
\_____________________________________________________________________/
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
Rx Converter and IF modules
below Digital PCB underneath.
_____________________________mod out PRESETS
________________________________ round robbin if you upset A-D converter
[LS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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 and caused the toroid to
overheat. The Logic card has it's own 5V reg and 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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