Electronics – Page 15 – anderswallin.net

Frequency Distribution Amplifier - first tests

Update 2015-12-18: Things improved quite a lot by simply wrapping the board in aluminium foil!

The amplifier phase noise floor is now at around -156 dBc/Hz while the 6502 is at -163 dBc/Hz. The AM noise numbers are similar.

Original post 2015-12-17: I put together a first prototype (only one output channel) of my TADD-1 inspired frequency distribution amplifier. Preliminary schematic here.

I compared the prototype board to two commercial distribution amplifiers: an SRS FS710 (quite awful) and a Symmetricom 6502 (very good). I also compared my new data with John Ackermann's measurements from 2007.

The new board showed ugly spurs at 50 Hz and harmonics using an el-cheapo wall-wart 12 VDC SMPS, so I also tried it with an "ultra-low noise DC-source" a.k.a 12 V lead-acid battery.

First distribution amplifier prototype. No soldermask. Only one output channel for now.

Comparing John Ackermann’s data from 2007 with my data.

Phase noise of distribution amplifiers at 10 MHz.

Difference between 12 VDC SMPS “wall-wart” and 12 VDC battery.

Not all probes created equal?

These two RP3300A probes came with a Rigol DS2072A scope. One is specified as DC-350 MHz and the other as DC-300 MHz. Go figure.

0.5mm pitch SMD parts with solderpaste

I soldered some quite small SMD parts today using solderpaste and a Hakko FR-810 hot-air rework station.

The smaller part is an 8-pin 2.0 mm x 2.0 mm MLF-8 packaged logic buffer. 0.5mm pin pitch. See page 17 over here.

The large part is a 14-pin 2.5mm x 2.5mm UQFN-14 packaged op-amp. Also 0.5mm pin pitch. Dimensions and footprint available here.

I had to rework one chip manually with a soldering iron because I applied too much solderpaste. Otherwise things seems to have gone smoothly. I applied the solderpaste manually using two disposable scalpels - getting the amount and location of solderpaste right took quite a long time. I then positioned the chip on the footprint and applied hot air. On the FR-810 I used the lowest air-flow setting "1" and a temperature of 290 C. When the solderpaste melts it pulls the chip into position if things go well.

chip3, the one that required rework. In hindsight there is too much paste on the pads.

chip5, the last for the day. Note how I’ve learned to apply a minimal amount of paste to the pads.

Hakko FR-810 hot air station. I used +290C and the lowest air flow setting of “1”.

KiCad footprints now on GitHub

I've created a GitHub repository for my KiCad footprints

https://github.com/aewallin/awallinKiCadFootprints.pretty

Maybe some day schematic symbols will also follow this foolproof convention of

directory <-> library
file <-> part

ToDo: polish up some of the footprints, check if they adhere to the Kicad Library Convention, and try to get them included in the official libraries.

PSU electrolytic cap fix

This is the PSU from a Symmetricom SyncServer NTP-server. The same capacitor has failed previously. The installed one was a 3300uF 10V cap and I replaced it with a 2200uF 16V one. Let's hope it works for a year or ten.

SMPS Fail

Hmm, what happened here?

12V 1A SMPS for Cisco EPC3000 cable modem. Worked for many years but suddenly blew a fuse and died today. Replaced for 8 euros from Biltema.

DIY DSOXLAN

Let's say you have a DSO-X 2000 or 3000 series oscilloscope and you're not super keen on paying about 300 euros for the brand-name DSOXLAN module to enable the Ethernet port it already essentially has on board? No worries, just build yourself this DIY DSOXLAN module! The most expensive part of this build is the 8 euro magjack Ethernet connector.

The 2×40 pin connector at the bottom of the DSOXLAN module opening at the back of the scope.

DIY DSOXLAN installed. Needs some vertical support.

Sources: https://github.com/aewallin/DSOXLAN

In other news this blog has been updated to WordPress 4.1. Hope everything works OK.

SMD R/C kit

Inspiration and labels from: DIY SMD Resistor Capacitor Kit. I enhanced the labels with tolerance and wattage/voltage infromation as well as color-coding.
Boxes: www.shenzhen2u.com
Components: Digikey
Resistors 1x, 2x, 3.3x, 4.99x over 5 decades from 10 Ohms to 100 kOhms. All 0805 size.
Capacitors: 4.7x and 10x over 7 decades from 1pF to 10uF. Smallest 0603, mostly 0805, and largest 1206 size.
Bugs: X7R is misspelled as XR7. One printed label was lost in production. My choice of components uses 36 out of 40 boxes - still room for 4 more components.

Agilent DSO-X 3034A

I got a 4-channel 4 GS/s 350 MHz Agilent DSO-X 3034A scope on ebay!

Options are available for free for 30 days (maybe 60?), after which you are supposed to pay a ridiculous amount of money for them.

So far I've just explored the Easter eggs built into the firmware 🙂

TREK screen-saver
'matrix' style name-list under Utility / Options / 6-6-6-6
etch-a-scope under Utility / Options / 5-5-5-5
LOST countdown enabled by 16-23-42. Seems very boring from looking at Dave's video.

op-amp PID controller

Here's an old-school PID controller based on simple op-amp circuits that I put together a week or so ago.