[time-nuts] Z3805 utility, Was: AW: (no subject)

Rex rexa at sonic.net
Sun May 23 11:24:48 UTC 2010


I can't say for sure if the Z3805a will automatically initialize itself 
from a power-on with no monitor on the serial port, but I think it 
should. I got mine from China over a year ago and I don't recall telling 
it to do a survey, but maybe I did. One thing that has been mentioned 
here is that it could take many hours to initialize the first time and 

But even if you CAN run it without a monitor and sending it commands, I 
think you should try to figure out what is up with the serial port, 
because it will make things so much easier than shooting in the dark. If 
your serial interface is really not working, that indicates something is 
very wrong with your unit even if it does lock to GPS eventually. If you 
are going to be a certifiable time nut, you will definitely want the 
ability to see what is going on inside the box.

I have both a Z3805a and a Z3816a. They have both been running for a 
long time and I don't plan to power cycle them just to remember how the 
initialization process works. Many people have a PC monitoring the 
serial port all the time and tracking the EFC, holdover, etc. I only 
connect to the monitor port occasionally, but I know the serial port on 
both do work (or at least have worked) when needed or desired.

I did a little experimenting and memory refreshing tonight. Maybe 
something in this description will help.

First, I know my Z3805A came with the bottom 25-pin connector supporting 
RS232. As far as I know, that is all it can do, unlike the Z3801 which 
can be configured as either RS232 or 422. I am not absolutely sure about 
that on the Z3805, but I think so.

Here is how I make the connection between the Z3805a and the PC. -- I 
have a DB25 to DB9 adapter plugged into the bottom DB25 on the box. Into 
that adapter I plug a standard DB9 serial cable. At the other end of the 
DB9 cable I have a 3-wire 'null modem' adapter I made. [It has a ground 
wire between pins-5 of the two connectors and it has pins 2 and 3 
crossed-over between the two connectors. No other signals besides tx, rx 
and ground, but with the tx/rx crossed.] Then that adapter plugs into a 
serial port that is actually a serial DB9 to USB dongle.

Much of this chain could be replaced by making your own 3-wire DB25 to 9 
cable that connects the ground pins and crosses tx and rx. I think that 
is pins 2, 3 and 7 on the db25 and 3, 2, and 5 on the db9, but I'm not 
going to take the time now to check.

I'm running XP on the PC. I checked in the Hardware Manager to make sure 
what COM port the serial dongle is mapped to. You need to know the COM 
port to configure a terminal emulator program or any of the monitor 
programs like Z38XX, GPSCon or SatStat.

The Z3805 serial port defaults to 9600 8 N 1 but I proved tonight that 
all of these serial parameters are configurable, so it is possible that 
your box has the port configured to something other than 9600 8 N 1. If 
you have a serial terminal monitor program that you are familiar with, 
I'd start with that. The windows-supplied Hyperterminal will work but 
it's a bit odd to configure. To use it, as it starts give the 
configuration a name like 9600. On the Connect To window on the 'Connect 
using' field use the drop-down to select COM1 (or whatever COM port 
connects to the Z3805) Then you will get a window that allows 
configuring the baud, etc. You should set flow control to 'none'. When 
the empty terminal window displays, anything you type should be sent.

If you just hit Return to send a CR to the Z3805, the Z3805 should reply 
with a prompt of either 'scpi >' or 'E-nnn>'. If it does, you are 
communicating. If not, try a different COM parameter configuration.

You could also just try the Z38XX program. If it is communicating, you 
should see some ID info in the lower-right corner of the window (status 
bar) that has Z3805A in it. You could also select 'Debug Window' from 
the top menu to see what is being sent/received on the serial interface. 
To configure the serial port parameters, select Parameters from the 
top-left of the menu bar.  If 9600 baud doesn't work, I'd try at least 
1200 and 19200 baud. I doubt very much that someone would have 
configured the Z3805A port with other than 8 N 1 ( 8 data bits, no 
parity, one stop bit).

Hopefully there is something in this write-up that will get the serial 
interface sorted out for you. The other suggestions you have received 
about monitoring signal levels on the RS232 could help too, but the 
Z3805 doesn't send stuff out by default -- it replies to commands sent 
to it, so getting it to reply with anything if the port parameters don't 
match could be problematic.

If you do get some serial communication happening, you may then need 
more guidance on commands or interpreting what you see, but we can save 
that for later.

I have never seen any documentation specific to either the Z3816A or the 
Z3805A, but there are some docs for the Z3801A and the 58503B that are 
close enough to guess most of what is needed. If you haven't found them 
yet, I could try to search where I found what I have used.


Robert Benward wrote:
> Thank you all for these inputs!
> Most importantly, the big question is:  Regardless of RS-232 or 422, 
> will the unit do ANYTHING without communications? Do I need a computer 
> to get anything beyond the "power" led?
> I bought this at the Dayton convention ham flea market, and the guy 
> told me it was already modified for RS-232.  The board inside says 
> RS-422 near the connector.  Without the other LEDs blinking, I'm 
> worried I bought a dead unit.  I had a GPS antenna on it, but it never 
> locked on.  Do I need a computer to enable this thing?
> Thanks,
> Bob

More information about the time-nuts mailing list