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Monday, 31 December 2018

TS-890 Again

Well,

I've been asked to put a video together on why I love the TS-890; well here it is:


Sunday, 30 December 2018

OCXO Update

Well,

You may recall back here where I built a VE2ZAZ GPS disciplined OCXO as a frequency reference for my shack. This was back in 2013 and the unit has pretty much trundled along, doing its thing ever since.

My recent fiddling here resulted in my realisation that a more accurate 1PPS signal is achievable by putting certain GPS receivers into a fixed location mode for timing applications.

So, I decided to invest in a decent enclosure and re-build the frequency standard. I have effectively swapped the PSU, GPS receiver and the OCXO itself.

This is the internal gubbins of the new unit:


This is the main PCB - the wire you can see from a PIC pin is to a reset switch on the back panel which clears the alarm condition manually. A firmware mod included this but the PCB is prior to this change.


This is the MAX232 device and regulator which converts the PIC comms into RS232 levels for the PC.


This is the PSU board and the OCXO itself:


And finally this is the GPS receiver parked in the corner:




The config of the system is fairly complex, but for those playing along at home, these are the settings I used to get the system into a stable state. I first forced the DAC value to be close using my test gear and manually adjusting the value, then I left the device running overnight with these parameters:


Then now the unit is settled, I have changed the config to be thus:


The unit itself looks like this at the front, there are two 10MHz outputs plus a selectable 1 or 5 MHz output:


The rear of the unit has two further 10MHz outputs:



I have more than enough "bits" here to make another one of these; anyone want one?

Friday, 28 December 2018

Stationary Mode - Really?

Well,

I've been fiddling quite a bit this week with frequency standards (man with two watches never know correct time et cetera). All of the GPS based frequency standards rely on the 1 PPS signal from the GPS receiver, and the accuracy of this can be improved by putting the GPS receiver into "Stationary" mode i.e. not moving. This mode is intended for timing applications and is clearly the correct mode for any fixed GPS being used as part of a frequency reference.

I have recently bought a couple of GT-U7 GPS modules from Amazon. They are as cheap as chips and the documentation for the chipset can be found online. This documents the process of squirting a bunch of data down the serial comms link to the GPS module to put the receiver in "Stationary" mode.

So, in order to do this I have stolen some C code and modified it a bit (the Syncronisation command being looked for wasn't correct) and stuck it on my qsl.net webspace.

I've connected the GPS module to a Raspberry Pi:


Its just the TXD and RXD lines of the Pi Serial0 connected to the GPS TX and RX serial lines.

You need a bit of jiggery pokery on the Pi before you can use the Serial Port in the way we want:


  1. Edit the config.txt file in the /boot directory and make sure you have the line enable_uart=1
  2. Edit the cmdline.txt file in the /boot directory (make sure you keep only one line in this file) and remove the text "console=serial0,115200" - this removes the need for a login when you connect to the serial port
Once you have done that, reboot your Pi and then from the comand line:

>sudo gcc Stationary.c -o StationaryMode
>sudo chmod +x StationaryMode
>./StationaryMode

And the software should respond with a message to say the configuration has been updated and saved correctly.

What could be simpler?


Wednesday, 26 December 2018

Arduino Nano - Upload Issues

Well,

For some time I have been having issues with my cheap eBay sourced Chinese Arduino Nano boards. These are not genuine and are completely ripped off by the Chinese - really we should all be supporting the genuine Arduino hardware.

Anyhow, when connecting to try and upload to these boards I keep seeing:


Using Port                    : COM4
Using Programmer              : arduino
Overriding Baud Rate          : 115200


avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xf6
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xf6

avrdude done.  Thank you.


Now, I had always assumed this was something to do with the driver or other compatibility issue; possibly related to the FTIGate.

BUT NO !!!!!!!!!!!!!!!!!!!!!

Arduino has recently changed to using a different bootloader on their official Nano boards that communicates at 115200 baud rather than the previous 57600 baud.

Support for these new boards was added in Arduino AVR Boards 1.6.21. The new Nano board definition is not compatible with old Nanos and likely most 3rd party Nanos.

Backwards compatibility is provided via the Tools > Processor > ATmega328P (Old Bootloader) menu selection.

And BINGO.

Here is our lovely Pepper doing what cats do best:


More Counting with Nixies

Well,

As part of my TEAS which I described previously, I have acquired a further HP Counter/Timer as "spares" for the one I already have (yes, this is part of the condition it seems).

So, I started with the normal replacement of the electrolytic capacitors in the PSU and then did some debugging of the electronics itself. I found one of the 4 bit latches to be suspect so I removed it:


It didn't work out well for the poor thing, but removing DIL devices from through hole boards can be quite tricky at times. I did manage to remove some working parts from another board I have:


although removing the Nixie socket was extremely challenging, and I ended up prizing off the top plastic part and removing one pin at a time.

So, in the broken unit we now have:


A socketed replacement for U9 - this was the chip I suspected of being bad.

I have also inserted sockets for the "Option 001" which is the addition of the extra digit and then used parts from the spare board above to create this option. You also have to move a resistor that drives the Overflow electronics to that it does this one decade higher.

You have to admire the design and build quality of these units, they certainly don't come like this anymore:


The unit has had a good clean and everything now seems to be working:


The top unit is the newly repaired item, the one on the bottom is from last time.

Now, what next?

Monday, 24 December 2018

Curve Tracing - using an Octopus?

Well,

Some time ago, I built an experimental curve tracer attachment for an Oscilloscope using an "Octopus" design. You can find many such examples on Google.

I was very much inspired by this excellent video by Alan, W2AEW:


You are basically creating a voltage vs. current graph on the 'scope in X-Y mode.

Now, I have recently discovered the most excellent You Tube channel of Mr Carlson; lots of very informative videos there. However, he also has a Patreon channel and it is here I have found a much better design of a Curve Tracer.

I will 100% respect the fact that the design is only available to his subscribers, but for $2 per month (thats a cup of coffee) you can join the subscription and get access to this design plus a hole lot more. There is also a very excellent capacitor tester that I am building at this time.

My build looks like this:


You will note that I still can't cut out rectangles in metal and get them flat and also that I have tried to paint the front panel and made a bit of a mess there too!

But this is a great project, and I recommend you check out the Patreon site above.

Friday, 21 December 2018

Test Equipment Anonymous

Well,

My name is Mark and I suffer with Test Equipment Acquisition Syndrome (TEAS).

It starts quite mildly but soon creeps up on you; symptoms are said include:


  1. Buy some broken test gear cheap
  2. Buy service manuals for the broken test gear (often costing more than the gear)
  3. Troubleshoot broken test gear
  4. Seek obsolete components to repair the broken test gear
  5. Buy more test gear to help with the repair of the test gear you are working on
  6. Build shelving and storage for test gear
  7. Buy second and third same items as "spares" and find they are better condition than that you already have
  8. Go to 1 and repeat
You get the idea.

There is help available here, but the condition is quite hopeless.

My latest acquisition is a Tek 466 "storage" scope.

Its in very good condition for its age and notably has "LEDs" instead of "indicator lamps" so is a more recent one of these models:





I've fiddled about with it and given it a good clean, replaced some caps and transistors in the PSU and also a (socketed - thanks Tek) IC regulator and bingo:


There seems to be very little wrong with this. Now all I need is another for spares....

Miss Luna cat is become slightly less timid, but not much:

Sunday, 16 December 2018

And for my next trick...

Well,

You will remember back here where I was talking about a complete waste of time?

So, I've persisted with the referb and finally I have a working unit. It's now permanently installed in the pile of test gear.

Apart from the repairs, I have replaced the electrolytic caps in the PSU:



And bodged together "Option 001" which is the extra digit:




Works rather well:


Not bad, is it?

Sunday, 2 December 2018

Yet more Nixies!

Well,

My TEAS (Test Equipment Acquisition Syndrome) condition seems to worsen; I have acquired another Nixie frequency counter from that great auction site.

I've fiddled around with it considerably to get the internal clock to stabilise - some bright spark, maybe even the designer, has stuck a block of polystyrene (Styrofoam) over the crystal to try and maintain some temperature stability - but alas its all over the shop.

So, I've basically hacked two holes into the back of the unit and added an external reference clock input - this can be supplied by my ever faithful shack frequency reference.

So this is the unit; albeit on its side:


And here the small modification I've made:


The circuit forces whatever signal is on the input to be +ve DC - I've built it dead bug style on the back of the input BNC socket:


This is where I was poking about to find the clock output:


Using some of my other ancient test gear acquired through my TEAS condition:


Here's the result:


Lovely Jubbly.