30 July 2021

Winding QCX toroids as left-handed

The other day I resumed building the QCX transceiver kit I bought a couple of years ago in 2018. I had left it to the point of winding toroids.

All seemed fine for L4 (the red one), a bit loose but can be moved to match the PCB silkscreen.

Then comes the middle one from the output filter (L2) and ... I realised that winding toroids is another thing that left-handed people do differently! Loose ends of the winding end up on the opposite side vs. what is expected on the PCB and the inductor sits diagonally.

QCX toroids by a left-handed
QCX toroids by a left-handed builder.

When winding L1 I paid attention to the position of the wire and it matches better the silkscreen. Since I've had to remove L3 I might fix L2 as well so that these coils are perpendicular to each other as designed by Hans Summers.

Regardless the toroid is done with the right-hand or with the left-hand in the direction expected by the PCB, it really goes against the left-handed nature!

05 July 2021

From Tortona 2021, Nixie and CRT

The picture shows part of the spoils from Tortona June 2021 flea market.

On top is the original box containing a DP7-32 CRT. The letter "P" in the name means "long persistence, dual color". It has been opened to check the content presence and integrity, and that's all.


On the lower part of the picture is the display board from R&S receiver, showing a nice algorithm of hand routing PCB traces. Something had burned in this board because a resistor had been replaced but another one has a different [lower] impedance which causes lots of current to pass into a Nixie and the associated 74141 driver, which, in turn, is not functional any more. So the board gives 7 sockets, probably 6x 74141 and 5 good ZM1182 Nixies.


01 July 2021

Testing the equipment by testing other things

I found myself stuck in a testing loop while learning on-the-field how to use the Hantek oscilloscope: I was creating test cases for the oscilloscope that dubbed into test cases for accessories.

See this. The scope has a -3dB 150 MHz bandwidth, so I picked up my 14 MHz Marker Generator and tried to visualise the output terminated on a 50 ohm dummy load. The marker generator creates a short impulse in the time domain, which results in many peaks in the frequency domain. The short square impulse should be 10 ns long inside a period T of 71 ns at 14 MHz.

Grab all the probes in the lab and see which one renders better the impulse train. Don't forget to set the probe to 10x.

Probes were tested in this order:

  1. P6100, 100 MHz
  2. P6100, 100 MHz
  3. PK-8150, 150 MHz
  4. PP150B 150 MHz, Hantek
  5. 88025, 250 MHz, Greenpar

The first stitch below shows 4 periods of the test signal, while the second image is a zoom-in on one impulse.

According to the screenshots (wow!), all five probes behave almost in the same way! Even the input square wave show ringing.

Well, I do want to see an impulse train so I will either change the XTAL in the marker generator or use the arbitrary function generator embedded into the scope. Or both.

When time allows I will repeat the experiment with a 200 MHz Siglent oscilloscope (not mine).

 
 



29 June 2021

Hantek DSO2D15 first impressions

Holding the box with one hand.
The delivery of the Hantek DSO2D15 oscilloscope was really fast ("EU Direct Shipping" by AliExpress from Spain), just 3 days.

The very first positive remark is the overall weight: 2.3 kg, vs 13+ kg of what I owned until last week.

Once you power it up it feels like interacting with a computer through a "usual" oscilloscope interface with menus, settings, updates, resets, ... I had to read the manual to get a feeling of what the device is capable of.

For example, take "trigger modes": Edge, Pulse, Video, Slope, Overtime, Window, Pattern, Interval, Under Amp, UART, LIN, CAN, SPI, IIC. Some of them have options, too. Well, once you implement trigger in software, imagination is the limit. And you need to read the skimpy manual to understand how they operate. In most cases the default "Edge" and the trigger level knob do the job.

Another positive note is the absence of a fan. If you disable key-press beeps, the DSO2D15 is totally silent. But if you press the "Default Setup" button, it will beep again.


25 June 2021

Gone is the Tektronix oscilloscope, welcome Hantek

For a number of reasons I needed to relocate the Tektronix 7000 series oscilloscope: large, heavy, noisy, at times unreliable, stuck in an uncomfortable operating position. It also needed some thorough inspection, which would have meant being unable to use my lab desk until the work would have been over.

So I found a new owner, with other Tek 7000's, and it will keep showing signals.

I cannot live without an oscilloscope and the market is now offering compact and powerful devices, probably as reliable as the old unserviced Tek, at very affordable prices. I studied the market, read reviews on eevblog and finally clicked the trigger for a Hantek DSO2D15.

It is a digital storage oscilloscope, 2 channels, 150 MHz and includes an arbitrary function generator up to 25 MHz. This is quite an upgrade with almost twice the bandwidth, storage function, protocol decoding and a signal generator.

I must admit that when you look at the current offer of DSO's, even if you set a budget, there is too much choice! I opted for a product that has received firmware upgrades, has more than 4k sampling memory (as cheaper Rigol's do) and has no big issues or community-documented design flaws.

Time will tell.

23 June 2021

Tortona, 20 giugno 2021

Last Sunday I attended a ham/electronics flea market after 9 months of lockdown, with the open-air location taming the smell of dust, vintage gear (materials, components, grease, ...) and the occasional (unintended) lack of personal hygiene caused by the very hot days. The whole feeling was very positive!

A side view of the location. We were trying the optical QSO on the grass.

For the second consecutive year I have been able to attend the fair in Tortona, which is held in a parking lot under the June Sun. There were approx. 20 tables, with lots of space for chatting, moving around, digging into the boxes. I could recognise a couple of "new entries" amongst exhibitors, that are heirs of SK, which sold some stuff unseen in previous editions.

I went there to meet friends, attempt an optical QSO with Mauro IK1WVQ and deliver the heavy and bulky Tektronix R7603 oscilloscope.

I came home with a N.I.B. Philips DP7-32 CRT (dual color, dual persistence), the Nixie display board from a Rohde&Schwarz EK47 receiver (7 sockets for six ZM1182 tubes, five of which still working), a new 250 MHz probe (for the no-oscilloscope that I have :)), some coax connectors, few large VFD and a board with LED displays.

It was not possible to complete the QSO because my optical transmitter used inefficient LEDs as opposed to Mauro's blindingly TX head, and I had not built the FM modulator. Too bad, because we had a whopping 100 metres in full daylight and his setup had a lot of margin!



16 June 2021

10 GHz WBFM activity 2021

The yearly 10 GHz "old mode" FM Contest was last Saturday. That is the only chance to play with WBFM, Gunnplexer, HB100 and show your presence in some official documents.

LNB over a tree.
Three operators managed to arrange three points with mutual visibility in NW Italy, max distance above 100 km. My setup was HB100 on the TX side and LNB+RTLSDR+laptop on RX side.

Since my spot was 15 minutes hike from the car I had to minimize the weight: everything you see in the pictures was carried on my shoulders (except for the tree).

Having skipped the year 2020 contest because of the pandemic, we operators have forgotten some details of our setup, like the correct orientation to match TX and RX polarisation which caused some confusion when looking for each other when we knew we had to be heard.

In the end we all managed to work each other without using the parabolic dish boost, which is a good achievement thanks to modern sensitive LNB. The 2 MHz waterfall view does help to locate unstable transmitters, even if my HB100 constantly under the Sun moved just some 200 kHz on 2 hours.

As planned I worked the two operators at 35 km and 99 km. Once you sort out the correct polarisation, HB100, Gunn and LNB antenna patterns are wide enough to allow very comfortable beaming, to the point that my LNB was waving at the wind on the branch and there was no QSB at all.


TX head on a lightweight tripod.


It was a pleasant afternoon on the field. Too bad the season already calls for family/vacation trips and it is hard to involve more operators.

PS: my distance record on the same setup is 144 km from the same contest in 2019.