[time-nuts] Z3815 receiver transplant now fixed

[Morris Odell]

Hi all,

Well I've got it working absolutely perfectly now. My thanks to Dave Brown
of this list who sent me a manual for the GT-74! The problem wasn't the
receiver output message but the unusual antenna feed situation in the Z3815
that baffled me for a while. Briefly, GPS receivers feed the antenna
connection with DC for the amplifier in the antenna and sense when it's
under or over current for a software message re antenna health. In the Z3815
the receiver interface 5V antenna power pin is supplied with 5 V but the
antenna cable from the receiver is capacitively isolated and possibly loaded
(haven't checked yet) on the mother board and the antenna is fed from an
independent 5V antenna supply which is monitored on the mother board, hence
the alarm situation. I had an antenna directly connected to my new receiver
and put a suitable load on the antenna power pin of the Z3815 connector but
that didn't solve the problem. It wasn't till I loaded the (non-functional)
Z3815 antenna connection that the alarm was cleared. 

The u.fl antenna lead connector that comes with the receiver would, I think,
fit the connection on the mother board. Unfortunately the Chinese u.fl to
SMA connector that I wasted $1.60 on was perfidiously the wrong size so I
cut off the tiny connector in a fit of pique and terminated it on a BNC. No
matter, I can salvage the cable from the old receiver as I'm going to
butcher it anyway for the unusual 2mm pitch interface connector. Now that I
know what's what I'm going to make a new interface board on which to mount
the new receiver and then put it all together again.

If anyone here wants to go down the same route, let me know and I'll send
you the PCB pattern and schematic. I still use DOS based Easytrax to make
PCBs but print to a file which you can output to a printer if you can
remember how to drive a DOS window :-)

Morris VK3DOC