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Curve Tracing - using an Octopus?

December 23, 2018, 11:35 pm
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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.
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More Counting with Nixies

December 26, 2018, 12:19 am
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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?
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Arduino Nano - Upload Issues

December 26, 2018, 8:02 am
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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:


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Stationary Mode - Really?

December 28, 2018, 4:57 am
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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?


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OCXO Update

December 30, 2018, 12:43 am
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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?
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TS-890 Again

December 31, 2018, 4:24 am
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Well,

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


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TS-890 and Data Mode Configuration

January 4, 2019, 11:08 pm
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Well,

Following my video last time, I have been asked by a few folk to do some more. Here is a video on Digital Mode configuration for the rig:


and another one with a few more bits 'n' bobs:


Enjoy.
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A collection of FT990s - A gaggle?

January 11, 2019, 12:27 am
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Well,

I've had an old Yaesu FT-990 for quite a while; its a delightful analogue radio with very few modern bells and whistles.


Now, I've previously opened up and admitted I suffer with TEAS; I suspect the diagnosis may be wrong and actually it's GAS that I have got (Gear Acquisition Syndrome) it seems to be more far reaching that just test equipment.

I've got myself another FT-990.

There is some logic behind this madness, the ROM version in mine was 1.2 and that doesn't allow CAT control from my logging software. The second radio I have is at version 1.3 which does.

This is the inside of the new rig, which is extremely clean and tidy.


It has two filters fitted, one is an Inrad SSB filter and the second is the wider 500Hz CW filter.


The image below is the "control board" and this contains the CPU and ROM with the software version:


So, all I have done is simply swap these boards between the two radios. I also notice that the one I use on the bench is much dirtier inside. The case on the latest acquisition is a little scruffier so I guess we will stick as we are. I also notice my existing rig has this modification at the back. It's clearly switching am RF path, bit I haven't tried to figure out which one or what it does. There's a relay on the underside of the bit of veroboard and it is doing something under certain unknown conditions. I need to investigate further.


Anyone know what that mod might be?

I'd also be interested in anyone who wants a FT-990 V1.2 ROM fully working. It's only going to gather dust here.

Local conditions.
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FT-990 CAT Interface

January 13, 2019, 12:12 am
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Well,

Very much in line with what I did back here; I have today knocked together a PC interface for my FT-990 with its new control board from here.

I've included a audio interface and RTS driven PTT just for good measure - I don't think for a minute I'll use it though.


The construction is very simple on veroboard, and it allows me to read the transceiver frequency automatically from Logger32.

Here's Miss Pepper Cat and Miss Florrie Cat doing what they do best:


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Es'hail-2 - really?

February 17, 2019, 7:48 am
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Well,

I've just lashed together a first attempt at receiving the downlink from Es'hail-2.

If you have been asleep, the is the first ever Geostationary Amateur Satellite and is a bit fab 'n' groovy!

I'm just using an Amazon sourced LNB:



I've stuck it on a dish I had lying in the hedge and attached it to an Azimuth and Elevation rotatormabob - you may remember that setup from here.

There's an LVB tracker with computer driven elevation and azimuth control.

I pointed the dish in very roughly the right part of the sky and then tuned around where I expected the signals to be, with the narrow band transponder downlink at 10489.550 - 10489.800. I've subtracted the 9750 local oscillator in the LNB.

I then found some signals and used the rotator controller to peak the signals - I've ended up at 149 degrees to the south and 18 degrees elevation - there will be many, many errors in my setup at thus time.

I'm a bit off frequency, and also drifting a touch. I need to add external frequency lock to the LNB. I've also started to setup an uplink based on the system we made here.

But I've certainly found it:


So the lob beacon on the narrow band transponder is sending:

5i 5i 5i de qo-100 BK dl50amsat

and I am receiving this at a constantly drifting down frequency, currently at:

739.306 MHz on my SDR. So I add the 9750 MHz Local Oscillator and we get 10489.306 MHz

If should be between 10489.550 and 10489.555 MHz so I am a bit out of bonk and drifting.

Next job - lock the LNB to a frequency reference!

Much more to follow on this topic!
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Portsdown - again?

February 24, 2019, 10:41 am
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Well,

I've been building myself another Portsdown DATV transmitter.

This is the Portsdown 2019 - instead of the Filter Modulator board in the last version, this uses a LimeSDR Mini.

I'm rather pleased with this new build, it's a lot neater than the 2018 version I made:


You can see the LimeSDR in the picture above, its in a 3D printed case - that's now got a 20mm square fan fitted.



The front panel is a lot better than the last build, if I had got the holes for the LEDs upright it would have been even better.


I wanted this second Portsdown so I can take it portable without destroying the shack to remove the 2018 version.

I'm rather pleased with this.
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es'hail-2 dish feed

March 10, 2019, 11:04 am
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Well,

Very much inspired by the fun back here, I figured it would be great to try and make a better single feed for the dish for both bands.

This seemed to be just the ticket.

Not this needs to be plumbing, not electronics!

I paid a visit to fellow ham and insane constructor Ian, G4EVK; who has some amazing model making equipment and a good plumbers blowtorch!

Here's some photos of the build:






I'm waiting for a "rocket" LNB that I hope will fit on the end of the waveguide (read 22mm pipe) using a compression fitting, I have also used the trick from here to check the 2.4GHz return loss - after a little bit of bending it's now looking spot on.

Yesterday I very nearly mowed the lawns, today we woke up to this:


Let it snow.....
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ADSB Receiver - Really?

March 17, 2019, 12:49 pm
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Well,

For some time I've run an ADSB receiver here called PiAware - It's by flightaware, runs on a Raspberry Pi and uses an RTL dongle and a short bit of wire wedged in the shack window as an antenna - not the best.

Today I've been making a better antenna, a masthead amplifier and checking for improved reception. I recorded my musings as a video:



Fun, egh?

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SSTV - though a Satellite?

March 22, 2019, 2:10 am
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Well,

Been playing some more with my Es'Hail-2 setup.

I noticed yesterday some SSTV signals on the band from Mauritius; I've not used SSTV before so I installed MMSSTV and have since had some QSOs.


I've annotated some images and created some templates in the software to enable reports and the like to be exchanged:



It's really quite fun!
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Digital TV - really? QO-100 again!

April 1, 2019, 5:30 am
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Well,

Over the weekend I have been playing with the software KG-STV.

This is a kind of digital TV; its slow scan TV that's digitised on TX.

It took me a while to get the software to key the radio - eventually I figured out it doesnt seem to work if the selected COM port is > 9. Hey ho, as my PC Is COM port city, I had to shuffle some stuff about.

Here's two instances of the software running at the same time; the top one is my TX signal going up on 13cm and the bottom is my RX of the signal on 3cm.


And here is the same image as received by CT1BYM, Miguel:


and here some more images Migual has been kind enough to share. This is his RX setup:


How cool is that?
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70cm DATV - Portsdown again!

April 6, 2019, 10:41 am
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Well,

You may remember a while ago I built a Portsdown 2019, well today I've been thinking about how to get that on the air on 70cm (437MHz).

John, G4BAO does a nice driver amp kit for this frequency, and I have built one here today:


I've built and tested it as per his instructions, and then built a fairly simple circuit to switch the bias line which needs +12V on PTT. The schematic below is built on the veroboard you can see in the image above and takes a ground on TX line from the Portsdown and uses that to switch the VCC to the amp, turn on an LED and also provide a ground on TX line out (to go to the PA perhaps).


I've done some very initial tests and the spectrum analyser image below is created with a 30dB attenuator in line:


Without the driver amp in line, the output was measured at -29dBm (so about +1dBm without the attenuator) and then -6.59dBm with the driver amp in line. I make that a gain of about 23dB which seems bang on the money.


The driver amp is now completed in the box you see atop the Portsdown.

Good, egh?

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A Portsdown Conundrum

April 20, 2019, 12:33 am
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Well,

As part of my Es'hail-2 experiments, I am now preparing a DATV TX system for the satellite. I've ordered a Spectrian linear amplifier which seems to be the way to go, it looks like this but isnt here yet:


But in the mean time, I have been playing with an eBay sourced "wi-fi booster":


I have modified this to be permanently in TX by shorting pins of the op-amp as per many published explanations:


and simply connected this between the 23cm output port on the Portsdown and the Wi-Fi antenna that came with the amplifier.

Firstly, to test all is well with the setup, I have set the Portsdown to:


  • Frequency 146.5MHz
  • Modulation: DVB-S
  • Encoder: MPEG-2
  • Output to: Lime Mini
  • Source: TestCard
  • SR 1000
  • FEC 7/8
  • Lime Gain 88
This feeds from the 2M output port of the Portsdown to the linear I made back here and then to the 2M beam on the mast.

I have connected a "white stick" antenna thats on the house somewhere to the input of the MiniTiouner from here and these are the results:

Perfection!

Now, I change the Portsdown TX frequency to be 2407.75 MHz, change the antenna on the MiniTiouner to be a 2.4GHz patch on the bench:


and this is the result:

With a suitable piece of wire shoved into the front input socket on the spectrum analyser I can see the 2.4GHz signal I am transmitting:


So I am really not sure why I can't decode the TV signal on the MiniTiouner - any ideas anyone?


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Es on 4 - really?

May 28, 2019, 7:15 am
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Well,

I've always found the 4M band quite a challenge, but also very interesting. I don't really know how well the 'parasitically' fed antenna works I built here, but I certainly put out some RF.

The linear works on 4M, but is rather pants - very inefficient - not much RF out for an awful lot of current consumption.

There's been some sporadic E on 4M yesterday:


and today:


Yesterdays hop over to LZ2WO in Bulgaria is a reasonable distance at 2149.15 km (1343.220 miles), at a bearing of 109.3 degrees.

Good, egh?
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IC-9100 or the new fangled IC-9700?

June 2, 2019, 4:21 am
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Well,

I've been using a Icom IC-9100 as by base station 2M/70cm and 23cm rig for a number of years. The radio cost a small fortune but now, due to the release of the IC-9700, is worth about 3 bob and a conker.

My friend at LAMCO has lent me a IC-9700 (their shop demo model) to play with so I thought I would document my findings.

The IC-9700 is a modern rig, a "twin" if you like to the IC-7300 - the later has proved an extremely low cost SDR radio which has sold extremely well.


So here are the things I see as an advantage over the IC-9100:
  • Modern SDR architecture on 2M and 70cm
  • Accurate power out setting (on the IC-9100 you turn the knob and put it about where you want it - the IC-9700 has a %age power setting display)
  • Accurate CW pitch setting - as with the power out on the IC-9100 you have to turn the knob until it sounds about right. or alternatively you can use a CAT command but that's a bit bonkers too.
  • lower noise floor on 23cm - listening to the Martelsham beacon on 23cm I am sure the noise floor is lower on the 9700 than the 9100 - I may have just made that up though as I cant have them both running at the same time.
  • The SWR meter on the 9100 is a load of Dingo's Kidneys on the VHF/UHF/SHF bands, it seems to work on the 9700.
  • Accurate ALC - the AC meter on the 9100 on 23cm is inaccurate but the 9700 seems to work OK.
  • Bandscope/Waterfall - hadn't been invented when the 9100 was made.
And here are the things I already dislike:
  • It drifts! When you TX and the PA fan kicks in the TCXO clearly drifts - that's bad, and I mean that's really bad. I have measured 5-6Hz drift on 23cm.
  • There is no RCA PTT or ALC jacks on the back for linear amplifier interfacing - you have to use the 8 pin din ACC socket - which in itself is OK but I want to connect my MicroKeyer to that socket so I can have multiple CAT ports and other gubbins. Seems quite an oversight.


So, in conclusion the lack of RCA jacks is annoying; but the drift is unforgivable. I will need to make an adapter so I can connect both the MicroKeyer and the linear to the same socket at the same time - some diodes might be needed as the MicroKeyer will use the PTT (ACC pin 3) as an INPUT to the rig and my amplifier wants to use it as an OUTPUT from the rig. According to the manual it's both.

Just for the record, I'm planning to have a bonkers bash at EME on 23cm; I will be using the transverter from here to go from 28MHz IF to 144MHz, then have a remote 23cm transverter.

The TS-890 can do this:


and I've even installed a garden based enclosure thingy to house the 23cm transverter and VLNA remotely:


As ever, I don't really know what I am doing so we will see.

Been a bit of tropo on 2M today:


Local conditions.
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More Sequencing Secrets

June 8, 2019, 2:01 am
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Well,

I've been making another sequencer with a bias-t included; it builds on the stuff I did back here. This time I ordered some kits from the very excellent W6PQL.

The basic schematic for the sequencer is this:


Here's the build:


You can see the sequencer, a FET switch (which is used to turn off the power to the Bias-T during TX) plus the bias-T itself.

The bias-T is the sequencer event 1, events 2, 3 and 4 are ground on TX and available on the back panel as RCA sockets.

I've added some LEDs to the front panel to show the events switching and also a control to adjust the delay timing of the sequencing. The case is recycled from an old project:


I plan to use this to control the Transverter(s) and other gubbins I mentioned related to EME last time at the bottom of the post.

Local conditions.
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