DISTRIBUTION AMPLIFIER FOR Z3801A BY JWM ENGINEERING
The most important tool in the workshop is the HP Z3801A GPS disciplined 10 MHz oscillator. It was acquired on E-Bay for about $350 since most cellular phone sites were upgrading to newer frequency and time control equipment. There is a lot of information on the web concerning the conversion from RS-422 to RS-232 and building a 48 volt power supply for it. The best site for information is owned by K3CU where he also has many links. The unit came with a GPS antenna/preamp where the Z3801A supplies 5 volts through the coaxial cable. The antenna was placed on top of a piece of schedule 40 one inch pipe inside a larger end cap and waterproofed. It came with software and had to be setup to learn it's new location and discovered it was originally used at a cell site in Fargo, North Dakota. An unregulated power supply was made using a 36 volt @ 1 amp transformer from MOUSER which gives the needed 52 volt boost when turned on, then settling down to it's required 48 volts. The Z3801A has it's own internal voltage regulators since most cellular sites had varying voltages from it's battery bank and the emergency generators. For my Flex Radio, microwave JWM oscillators and test gear using an external 10 MHz reference, a commercial 6 channel distribution amplifier was purchased from JWM Engineering. When the GPS antenna is removed after a 24 hour learning period, the Z3801A will go into holdover mode making it possible to use it in the field as long as 48 volts is available. The Z3801A and JWM distribution amplifier remain on 24 hours a day since a reference is now used for the Flex Radio gear upstairs in the radio room. A second Z3801A was obtained for future 10 GHz operations while roving. Living at almost sea level makes it difficult for microwave work but by using rain and snow scatter, many hams have made great contacts. High accuracy time is not my bag but this unit can also display time on a computer screen making it as accurate as WWV or CHU in Canada.
So far the Z3801A references my HP5340A frequency counter, HP8640A signal generator, and locks in a JWM oscillator which acts as a beacon in the workshop on 1296.00000 Mhz. It makes the frequency counter as accurate as any laboratory counter which guarantees radio gear and other equipment will be right on after calibration. The HP8640A signal generator required 5 MHz as it's reference which was easily acquired using a divide by 2 chip. New software was found on E-Bay named GPS Control that works well with Windows 98 through XP.
