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RDDS Information Updated January 2013
Reverse DDS Phase Lock Loop Kit for use with existing OCXOs
As described in Scatterpoint February and March 2010 issues
More details here including information about encoding JT4 signals
The G8ACE MKII OCXO Kit - Gold
Updated January 2013
This OCXO using a 5th overtone crystal typically around 96-125 MHz and has been developed to provide improved frequency stability when operating on all the microwave bands. PCB is 35mm square with aluminium heater block to the rear side which holds the crystal (HC49/U) at the temperature provided by the attached heater transistor typically at 60C and adjustable by preset potentiometer top centre
Larger are pads provided for installing a fine tune ceramic piston trimmer replacing the red smd trimmer when fine free running frequency adjustment is required without using electrical fine tuning.
The varicap frequency control is used for fine electrical frequency adjustment or for connection to a PLL such as the RDDS above
A kit is available for this OCXO, more information.
Multiplier module for 23cms
1152 MHz LO or as a 1296 MHz signal source additionally 1276 MHz LO for Hydrogen Line Rx
Multiplication is x12
Also as a Multiplier for 13cms
2176 MHz LO 2320 MHz signal source or 2556 MHz for further multiplication to 3cms or 24GHz tuned to 2390.4 MHz LO or 2404.8 MHz for signal source
Multiplication is x24
Suitable for use with the MKII OCXO Kit
Output frequency can be tuned to 2176, 2320 2556 MHz ie. 3cm LO 10224 / 4 for further multiplication
Using four semiconductors the output power of the module shown is a minimum of 20mW for 1mW drive. The Output Filter is located at the top of the PCB. The on board 9v regulator on the underside.
Module size is 110 x 55 x 30mm.
UK Radio Amateurs Set New Distance Record on 76GHz
A new distance record of 129km was achieved on 76GHz Saturday 23rd November 2013, contacts between Brown Clee Hill in Shropshire (IO82QL) and Winter Hill, Lancashire (IO83RO).
Operating on three mm-bands, 24, 47 and 76GHz, were Ian Lamb G8KQW and John Hazell G8ACE at Brown Clee Hill and also on the three bands at Winter Hill was Roger Ray G8CUB with John Wood G4EAT who was operational on 76GHz.
Contacts on all three bands were made using NBFM, signals on 76GHz were exchanged for one hour with some QSB at time primarily due to changes in atmospheric conditions along the path.
This tremendous success follows closely after the previous distance record was set by Ian Lamb and John Hazell on 14th September 2013 with a contact of 102km. Earlier in 2013 the existing 79km distance record had been bettered 3 times, this reflecting the increasing level of interest in mm-band operating in UK and the culmination of much hard work on-going to improve system performance.
By calculating the link budget and path loss of this path it was possible to predict what environmental conditions would potentially give sufficient margin for success. The weather forecasts (specifically the dew-point temperature) were carefully monitored during the preceding week to ensure the conditions on the day would allow the possibility to establish contact over the distance.
The team are indebted to Jim G8UGL and the Telford and District Radio Society, without their kind assistance in arranging access to Brown Clee and support on the day this would not have been possible.
Pictures left and right and video below are the previous record distance of 102 Km and first G - GW contact on 76 GHz Distance shown in the video title below has now been increased to 129 Km for a new record as above
Above and below 76 GHz equipment of G4EAT
and G8CUB at Winter Hill Lancashire IO83RO
G8KQW above and G8ACE below at Brown Clee Shropshire IO82QL
Picture below G8KQW equipment 24GHz top
47GHz below 76GHz Tx & Rx left and right
Picture below G8ACE 47 GHz left 76 GHz Tx centre 76 GHz Rx right