If you've come here to find another (?) exciting, sexy weblog full of observations both witty and meaningful, you've come to the wrong place. I don't have any reason to believe that you'd find anything in my life very interesting.

This blog has one simple purpose: to be my on-line logbook for data from my experiments in ham radio and time/frequency measurement. If you want to know when I last adjusted the frequency of my Rubidium standard, then this is the place to be. Otherwise, forget it.
jra on 08.03.03 @ 10:11 AM EST [link]

28 Volt Battery System Details

I am using two 100AH AGM batteries in series. using an IOTA DLS 27-15/IQ4 15 amp charger. The IOTA is an intelligent charger with three modes:

LED steady on -- float charge at 2.266V/cell -- 27.192V total
LED slow blink -- absorption charge at 2.366V/cell -- 28.392V total
LED fast blink -- bulk charge at 2.466V/cell -- 29.592V total
jra on 02.26.12 @ 06:44 PM EST [link]

Voltage Regulator for BVA

I'm using an "ALWSR" low noise voltage regulator to power the 8607 BVA. It is designed by Andrew Weekes and is based on Walt Jung's "Super-regulator". Andrew's web pages about the regulator start here: http://www.andrewweekes.talktalk.net/potentially_positive.htm.

The board has a pre-regulator stage but using this requires significant headroom above the output voltage -- abiout 4 - 4.5 volts. Since the oscillator wants 24 volts and the system is run off of 2 "12V" AGM cells in series connected to a float charger, this doesn't allow for much drop if the power goes off and the batteries start to run down. The main advantage of the pre-regulator is to improve the dynamic stability of the system (ie, reduce the output voltage change when there is a sudden change of input voltage). That's not a major issue for this application since the OCXO will draw nearly constant power once it's warmed up. So, I am bypassing the pre-regulator stage to reduce the headroom requirement.

With a 28.8V input, the output voltage is 24.023 volts. Reducing the input voltage shows a very pronounced loss of regulation at about 24.5V, with about 0.1V reduction of the output over less than 0.1V change of the input. The voltage has been stable within +/-0.5 millivolt for 12 hours after initial power-on.

The circuit uses an LED which glows when the circuit is operating properly. The LED extinguishes at about the same point as regulation is lost, so it's a good reference point -- if the LED is fully lit, there's enough voltage to maintain regulation.

As a last bit of data, at 28.8V input, the regulator draws about 32ma with no load other than the DVM.

jra on 12.28.11 @ 03:03 PM EST [link]

GPS Antenna Cable Delays

VNA measurements of the delay from each GPS antenna to the output of the splitters:

Antenna 1 -- Aeroantenna choke ring to HP 58517A 8-port splitter: 140 ns

Antenna 2 -- Motorola Timing2000 to HP 58535A 2-port splitter: 165 ns

Details at http://www.febo.com/pages/lab_documentation/gps_cable_delay/

jra on 12.27.11 @ 11:57 AM EST [link]

Z3801A self survey result

For comparison to the M12+ survey results, this is what Z3801A unit #1 came up with after doing its (shorter) self-survey:

33 52 43.214 N
84 02 29.041 W
325.20 M MSL

jra on 12.24.11 @ 02:37 PM EST [link]

GPS Coordinates

A 48 hour survey using a Motorola M12+ receiver shows the coordinates of the Aeroantenna GPS antenna to be:

Latitude: 33.8786812 N
Longitude: 84.0414157 W

Latitude: 33 52 43.252 N
Longitude: 84 2 29.097 W

Latitude: 33 52.7208720 N
Longitude: 84 2.4849420 W

Elevation 331.97 M MSL, 300.91 M GPS

jra on 12.24.11 @ 02:31 PM EST [link]

Restarting the Blog

After packing up the lab in Dayton, Ohio in late 2009, I'm finally getting things running in our new Atlanta-area basement.

jra on 12.24.11 @ 10:45 AM EST [link]