[NLRS] W9FZ's Z3801A GPS standard now on the air...

[Doug Reed]

At 08:13 PM 3/2/2003 -0600, Bruce wrote:
>My question to those of you in town who have also been down this road, did
>any of you spring for the GPSCon software?  I bought the BD Systems software
>for about $20 and it's fine, but it doesn't have the graphing and web-page
>building features of GPSCon.

I installed a Z3801A at work for a 10 MHz distribution system. And I did
buy the GPScon software because it makes nice graphs. What I'd like to see
is a good discussion of exactly what the graphs MEAN. For instance, the
Z3801A runs along fine and then gets some spikes in the EFC graph. I
haven't a clue what caused them. The graphs make it easy to see anomalies
at a glance but nothing tells you what caused them or what it means. 

My original antenna was a $30 hockey puck mounted on the roof with RG174
and RG58 coax. It gave poor receive amplitudes and didn't pick up well
overhead. On Friday I replaced it with a $60 Motorola Timing antenna
designed for the purpose. I went overboard on the coax and used LMR400. My
signals are all near maximum and it hears overhead as well as lower to the
horizon. I'll watch it for a few weeks to see if those spikes come back. 

>Did any of you build a distribution amplifier?  I will eventually but other
>projects are higher on the priority list.  Getting this box on the air was
>the top project on my to-do list and it just took 9 months to get to it.
>Bruce Richardson - W9FZ

Bob W0AUS said he found a cheap video distribution amplifier on Ebay and is
using that. The N8UR site suggests a Maxim 6 output video distribution chip
and the demo board costs $70. Another source suggests a high power buffer
amp and splitters. At work I'm suggesting a $4000 distribution amp because
it will switch between two sources. For home, I've got an old 3M video amp
I'll probably use. Even a single channel baseband video amp could probably
drive a 4 to 8 output TV signal splitter and give enough output for most
equipment. 

If you have any sort of AC power problems at home, be sure to put isolation
transformers in line too. At work, the Z3801A is at one end of the building
and I'm at the other end. With the scope hooked up to check stability of a
local crystal oscillator, triggering off the Z3801A signal, the display
lines are slightly thick and fuzzy. If you watch for a bit you'll see the
lines puff out and wiggle for a fraction of a second. When I put an
isolation transformer in-line the trace becomes sharp and crisp, the wiggle
goes away. I was watching power line noise and glitches effect the
triggering level at the input of the scope..... If you are building stuff,
one source of isolation transformers are the transformers you'll find on
old computer network Ethernet cards. If you don't have any I'm sure you can
find a box of them at the next hamfest for $1 or less. 

One of my long term projects is to take a nice stable 10 MHz OCXO and make
it into a portable source. I intend to put it inside a simple outer oven to
improve stability, with dual regulators and internal batteries, and a lot
of foam insulation. All that gets me up to about the size of a 50 caliber
ammo can for a project box..... I know I'll want a buffer amp on the box
but after that it begins to get hazy..... One of the web sites has a nice
project idea that uses a PIC chip as a programmed divider to generate 100
KHz and down from a 10 MHz source. Cute for the work bench at least.... 

73, Doug Reed, N0NAS.