DIY RF Adaptor Set

So I was looking at commercial RF adapter kits and the prices shocked me so I decided to make up my own. The commercial ones I saw used a weird connector to join the adapters to each other. I decided I would use female BNC as the interconnect that way i could use male to male adapters to make short connectors or BNC patch leads for longer cables. Here is a commercial kit from element 14 it is pretty limited and is more than US$200.42421688

I put together a much larger kit with two of all the adapters as well as to 50 dummy loads just small ones to use to match the load when connecting to a scope to match the impedance, you use a BNC Tee piece. Anyway here is my kit… It has double of each connector and should cover all my needs it cost me about 120 bucks Australian to put it together.

rfadapt

Dust PC from Hell

So I rebuilt a friend of my sons PC. It was a mess it had water cooling and the radiator was hanging lose. It was overheating from all the dust and when he brought it over in the car the radiator ripped the CPU out and bent dozens of pins.

emp

It was one of the worst PC’s I had seen in a long time for dust and if it had gone to a shop they would have thrown the CPU in the bin and it was an AMD FX 8 core worth 300 bucks

Nearly an hour under a stereo microscope with tweezers that are so fine they are like needles was spent getting all the pins straight.

I pulled it all apart except for the motherboard, blew all the dust out, mounted the radiator to the top and put a HDD cage in as the hard drives were just hanging by the power cables.

emp_2

 

It took Angus and I about four and a half hours to get it from the first photo to the finished product in the last two photos, one of the back which has a case cover over the cables and one of the front side which is missing the cover.

Some people might think it is to much to repair a PC like this and rebuild it but I actually enjoy this type of work, I just wish I could actually do this as a full time job but my health wont let me

IMG_20160114_222123 IMG_20160114_222142

Geek

Okay I was a geek at school, .. Nothing has changed… Just ask my wife
I run Linux
I am a licensed Ham Radio operator
I Own 4 Oscilloscopes
I also own 8 calculators including 3 graphing
3 slide rules
I have a glass world globe on my desk
4 Ham Radios in my shack
3 Radios in the car
2 Handheld ham radios
5 Multimeters
My phone and tablet run custom android roms
My bookshelf in my man cave has the following books…
Machine Tool Operation Book 1
Machine Tool Operation Book 2
Taps and tapping by sutton tools
The Australian Amateur lapidary handbook
Meters for measuring water
RCA receiving tube manual
108 uses for an oscilloscope
Audio Handbook No2 “Feedback”
Phillips Valve data book
Electronics Made simple
Oscilloscope equipment
101 ways to use your signal generator
99 ways to use your oscilloscope
Aquariums
How to use grid dip oscillators
101 uses for your Vacuum tube volt meter
Transistor radios Circuits and servicing
The casio PB100 Computer manual
RCA Tube Manual
WIA Handbook Vol 1
Summary of lectures Automatic control systems
Faber castell slide rule manual
Hemi 40RK Sliderule manual
Icom ICT90a Manual
Transistor Transmitters for amateurs
Radio Data Reference book
Program Design
The boys book of crystal sets
ARRL radio Amateur handbook
Electronics Principles Integrated and discrete
GIMP Graphics Package User Manual (Linux)
Tech topics radio handbook
Radiotron designers handbook
High quality sound reproduction with valves
Temperature measurement
Novice Operators Theory Handbook
Tektronics Scope 314 Service Manual
1972 Melways (Street Directory of Melbourne) from my birthyear
The ARRL handbook 1995 (Theory)
Sourcebook of electronic circuits
Yaesu FT707 Service Manual
Ford Falcon EA-EF Factory Manuals (We own 2 falcons)
Running Linux
Linux Sys Admin
HEMA World Atlas
Oh and I own two domains, twistedsouls.com and hamshack.org
Geek and proud

Low Cost 10Mhz Frequency Reference

I was looking at a low cost way to build a 10Mhz frequency for my electronics lab. I had a few options that I could pursue, these were…

  • GPS Disciplined Crystal Oscillator (GPSDO)
  • Rubidium atomic standard (RbXO)
  • Caesium atomic Standard
  • Oven Controlled Crystal Oscillator (OCXO)

So to make a choice on what I should use I had to come up with design parameters for my frequency standard, these were as follows.

  • Had to be low cost
  • Had to be portable
  • Had to work inside of a building
  • Had to be stable, better then +/- 0.5 hertz drift over 2 minutes

The preceding criteria ruled out a GPSDO as that requires an antenna that has a view of the GPS satellites, this would be ok at home but I didn’t want to have to make sure I had a outside view of satellites if I was taking it to someone else’s shack or like the club shack with no windows this would have been impossible to get a GPS lock.
I next looked at atomic standards. The Caesium standards were out of the question due to the cost, second hand you could expect to pay upwards of USD$5000 for one, certainly not low cost by any measure. The rubidium standards were a lot cheaper at around USD$200 so that was an option. This raised the question, did I need the accuracy of a Rubidium or could I get away with a cheaper option ?
This led me to investigate OCXO’s to see if they would suit my needs. First was to see if they met my stability requirements. A typical 10Mhz OCXO has a stability of 5×10-10 This is ±5 mHz drift per second on a 10Mhz signal, well within my requirement of 0.5hz over 2 minutes. The reason I need this stability is for WSPR digital which requires a very stable clock signal.

What about the cost of an OCXO ? Well a quick search of eBay led me to a Double Oven OCXO from a Russian company called Morion. I could get a second hand unit for less than $40 delivered. This particular unit listed stability of better than 2×10-12 over 1 second which is 0.005 mHz and stability of ±5×10-10 per day at 10Mhz. These figures were well within my requirement’s so I ordered two units from eBay.ocxo
I now started to put some thought in to the design and construction of the complete unit and what I would need.

I had an old car computer case that I could use for the project so I ripped out the old motherboard and found some rubber feet in my junk box to put on it, this gave me an idea of the size case I had to work with so I grabbed a ruler and measured it up to see if the OXCO would fit. It would fit with heaps of room for an internal 240 to 12 VDC power supply and a battery.
I was thinking about the power requirements for the unit and how I was going to power it. I needed about 1.5 amps for the oven while it is warming up with that dropping to about .5 amps once warm. Wrapping the oven in insulation should drop that even lower. I had an old 4 amp 12VDC power supply from a computer monitor that I could use so I dug that out as well.
At this stage I put the project aside for a couple of weeks while I waited for the OXCO’s to arrive in the post. When they had arrived I put one in the case with the power supply and soon realised I actually had the space for both of the OCXO’s.

top view
I had originally bought two so I had a spare but I quickly decided at the cost of them I could just run both so I would have two units that I could compare against each other to make sure they were still within specification and also It meant I could connect it to more than one device at once. The signal quickly attenuates if you are splitting it.
I then got all the other stuff together to assemble the unit this consisted of the following.

  • Trimpot’s to adjust the OXCO
  • SLA 12V Battery
  • Switches to switch power and outputs
  • Veroboard to mount it all on
  • LED’s for status indicators
  • Volt Meter for battery level
  • IEC Socket for Mains input
  • DC Barrel plug and socket for 13.8VDC to charge battery
  • DC-DC Buck/Boost converter to level out battery voltage
  • BNC Sockets for the output
  • Current limiting resistors for the LED’s

veroI soldered the two OCXO’s on to a bit of veroboard and then connected 25 turn 2KΩ trimpot’s with the wiper to the calibration pin with one side of the trimmer to GND and one to the 5VDC reference output on the OCXO, this forms a voltage divider to calibrate the oscillators. I measured the output of the power supply I was going to use and it was 12.3VDC which is within the spec of 12VDC ±5% that they require.

The next problem I would have was to power it while travelling, I didn’t want a huge battery so I used a 1.3AH SLA battery that I would charge off the car while travelling. I needed to keep the battery voltage at 12VDC into the oscillators while I would see between 14.2VDC while charging and 11VDC if the battery was a bit flat.

dcdcTo get the nice 12VDC I used a cheap $2 buck boost DC-DC converter from eBay. They wont supply the 3 amps I need to warm up but it would handle the .5 amps that I had measured once warm. I had managed to get the 400mA current per OCXO down to around 500mA for both once warm by wrapping the ovens in neoprene foam from a stubby holder.

I adjusted the DC-DC converter to output 12.3VDC so it was the same as the mains power supply, this prevents instability of the 10Mhz signal due to supply differences.

I have each oscillator feeding a DPDT switch, one pole switches the signal the other switches an LED on to show the output state, I can feed either the A or B signal to a common N Type connector or to their own BNC connector. A cheap LED volt meter was added to the front panel to show the battery voltage, these are available on eBay for a couple of dollars.

frontIf you were building the unit with one OCXO and had to buy everything instead of raiding you junk box for parts you would need to invest around 80 to 100 dollars. This includes a case the OCXO and the needed hardware. It took me around three hours to assemble.

Freq ref FLIR 02So what is it useful for ? Well some of the things you can use it for are as a stable reference to calibrate test equipment like frequency counters and signal generators. With a divider board to generate a one pulse per second signal to sync your PC time. This is useful for the digital mode WSPR that requires no more then ±1Hz drift over two minutes. With a general multiplier/divider DDS you can produce signals from 1 hertz to around 100Mhz from the 10Mhz input. This is useful for calibrating rigs to see if they are on frequency.

All in all I am very happy with the resulting unit and it makes a nice addition to my test bench.

Jaycar MP3086 30 Volt PSU Teardown and testing

Old MP3086

Okay so I bought a 30VDC Variable 3 amp PSU from Jaycar a few weeks ago. It is model MP3086 with CV and CC modes. I was expecting the one shown above with 3 pots, one for amps, and coarse and fine ones for volts.. Instead I got a new improved model, unless you like the coarse/fine pots!

New MP3086
So of course with anything new you need to follow Dave from EEVBlog’s advice.. Don’t turn it on tear it apart so that’s what i did..
Cover off, transformer looks nice doesn’t it ?
Okay so first impressions from the photo above.. Nice secure soldering on the mains connections, shake proof washers on the earth wire and extra covering on the mains feed, see that black rectangle on the right centre ? Here it is closer up…
Switch Close-up
It is a real clunking power switch on the mains, so no standby current usage, Yay a thumbs up..
IEC socket with integrated fuse holder, nice one !
Shake proof washer a point for Jaycar
Spring washers on transformer mounts with intake vent for fan, there is also vents on the sides with exhaust at the rear of the unit
Terminal block for permanent connections say a bench Multimeter and banana sockets

Okay now for the close-up internal shots, there are five boards

  • Rectifier board Power transistor board with Relays to switch taps from transformer to transistors
  • LCD Display board
  • Keyboard Board for buttons
  • CV/CC Control board
  • Connection board for front panel outputs with current shunt for amps readings

Rectifier Board with room for two more transistors


Is this a real Japanese Rubycon or a copy ? 
The Main Power board looks like it has a real Rubycon capacitor, the screen printing looks good and it does not look like a rip off

LCD Control Board all SMD, the bodge wires on the right run to the back light, keyboard board bottom left with ten turn pot for volts selection underneath
The Voltage and Current control board, there is nothing on the other side apart from a few through hole caps and a voltage regulator on a small heat-sink, notice the flux residue on the through hole hand soldered joints, not good how hard is it to clean a a board ? Here are some close ups of the cruft left behind after soldering. But hey the Ningbo QJE company gave us their phone number if you want to call and complain to them about it :p

NXP Chips a counter IC and a logic gate, some more quality parts to go with the Rubycon cap…

Nice SMD soldering, re-flowed not hand done ! This is one of the trimmers to calibrate it all
Nice thick bus bars to the connections on the front panel with shake proof washers as well, excellent job.
Thermal switch for the fan, wired in series with fan it is rated at 5 amps and 50 C cut in temperature but cuts in before that, 
Okay now for some testing…. 
The test set-up consisted of the following.
  • RS232 connected DMM logging temperature
  • Galaxy Note 2 Smartphone for dB readings (Not real accurate but okay) 
  • Incandescent 12V globe as resistive load
  • Digitech QC1932 25MHz DSO
  • Supply set at 6.9 Volts, this just switched to the second tap (6.8V) so max heat from transistors

12 Volt Light globe pulling 1.33 amps at 6.9 volts, this tested at about half of the maximum amps and the second tap on the transformer had just switched in at 6.8 volts so I was dissipating the most heat for this amperage in to the heat-sink. 
The test set-up, I connected the scope probe to the terminal block on the front directly, I just hadn’t done it here yet
Below is the capture of power on unloaded, there is a small HF ripple at power on then ramp up to full voltage (5VDC) with no overshoot, there is a small amount of ringing when it reaches the set voltage, from power on to stable voltage is about 10 milliseconds.
This is a close up of the spike at power up unloaded, about .5-.75 volts lasting 206 microseconds
Here is a capture of a loaded supply at 7VDC from turn on to full output is 76 milliseconds with no overshoot to speak of.
1.6mV ripple at 7 volts under loaded conditions
dB levels with phone acting as meter with smart tools app. The first bump is me pressing the power switch, the second is the mechanical temp switch clicking in, then you can see the fan ramp up to 69dB. the phone was sitting 10cm behind the PSU with the microphone sideways to the fan, the power switch click is quieter as it is at the front while the temp switch was closer to the rear. The ripples in the graph is just background noise in the shack.
If you look between the cursor marks on the timebase below you can see two little ripples lasting about a second, this was when the fan switched in but was brief and low in amplitude. It may have just been induced noise from the arcing in the mechanical temperature switch for the fan as its contacts closed.
Here is the temperature run at 7VDC 1.33 amps from cold (I did this test first after leaving it off overnight) Starts at about 26c the shack temp, ramps up to 43.9c in about 2 minutes then settles to around 34c and stays there. I ran it longer then this graph loaded and the temp was stable and didn’t run away at all which it shouldn’t pulling 9 watts from a 90 watt supply.

 All in all for the price I am very happy with it, well built steel case, the front panel is plastic but has steel rails running from it to the back panel for support.

So what don’t I like ? Well not much the only things are as follows.

  • Earth Connection is in the centre, so I cant plug a standard spaced dual banana plug adaptor in to the – and + rails, I may re arrange the banana sockets and move the earth to one side.
  • You need to short the rails to set the required amperage for CC mode, I am going to put a NO momentary switch on the front so i don’t need a lead to do it
  • Switching on CC mode is a bit hit and miss, I dont know if it is key bounce or a slow micro but you have to press the CC button a few times before it locks in to CC mode, it is a soft switch
Apart from that i really like it and it actually goes to 31.5 Volts
MP3086 Regulated lab Power Supply 30VDC at 3 AMPS
List price $199 AUD

Photos of the shack all setup

The Twisted Shack
The twisted Professor

Shack mascot Tux and Mr Bean teddy
My Pulse Jet

Tools in filing cabinet

Power tools in Filing Cabinet

Close up of my books

More books

Even More Books

Bits and bobs on display

A few more knick knacks and a dummy load project DC-1GHZ 250W

VIC Royal mail Service Morse Key circa late 1800’s

Small hand tools

More Small hand tools

Pocket Digital Scope and Function Gen from Velleman

Keyboard and mixinf desk at workstation side

Fishtank and tablet

Loose tools behind Drillpress

Storage bins

12VDC Shack battery backup

Gas storage Mapp/propane

Microscope, ultrasonic cleaner battery Charger, Pestle & Mortor and telescope optics

Flatbed scanner I get out as needed and storage draws

Breadboarding

Labeller, tacho and camera

Dremel and Hot Snot

Gaming PC in old 19inch Rack case and Fan/heater on top under the desk 
Air COmpressor Oiless with water trap for dusting electronics

Tool Bag for field work

Inside tool bag, I add the pocket scope and sig gen when i go out with the bag

Swing out lead rack

Test leads for field bag

Network cable tester and resistor/capacitor sub boxes

2nd Dremel and drillpress stand

Air tools

Measuring and scraping draw

Spanners

Metal Working, files snips reams

Screwdrivers

Drillpress

Hammers clamps and random tools

larger pliers, side cutters allen keys

Sockets

Handmade clock from old 240VAC clock that had broken glass and burnt out Mistral Desk fan

More Sockets Taps/Dies Drifts Wad punches

Under workbench storage and solder dispensper Atten Digital iron and Compressed air outlet

Digitech 2 Chan DSO, Powertech 30VDC 3A PSU Tek 314 Scope GW Freq Counter DMM with Cap/Ind/Tran test and cordless power screwdriver

Main Shelving with video feed from driveway and frontdoor so i dont miss the postie with goodies from eBay

Atten Iron (Base under desk) Digitech SMD rework station (air and iron) and small PCB hand tools in old makeup case with USB outlets to left and Power fail torch (Comes on when power goes out)

Drill press and visitor chair with storage bins, resistors in drawers to left

Asst small parts Caps/Semis/Screws etc

Overview of workbench side

Panning to left of workbench

Workstation, Desktop PC at top laptop with 2nd screen center and tough book laptop right, all linked with synergy remote software to use one keyboard and mouse to run it all as one virtual PC

Ham radios Mindisc recorder, 10 band graphic equalizer transmatch and 13.8PSU with 24VAC for weller iron (So I can solder power etc at radio side)

Sign my son made me for Christmas, just hung it up for the pics 🙂

The entry to the shack

Old fridge outside shack to use for chemical storage

The 2.4×2.4Mt (8×8 foot) garden shed that is the shack

The wire bin for scrap wire

Around the back of the unit is bins of larger parts and some tools