26 September 2022

Almost working circuit with 6LO1 CRT

A square little 6LO1 CRT and associated circuit.
A square little 6LO1 CRT and associated circuit.
 

The are a few reasons why I bought this homemade circuit originally meant to display the two ellipses when tuning an RTTY signal:

  • it has a small CRT, probably 6LO1
  • it has a proper transformer with filament and HV
  • it might not work right out-of-the-box 

I was three times right! The CRT lights up and responds to both X-Y inputs but

  • it is out of focus
  • the beam doesn't reach display ends
  • something overheats

At closer inspection I saw that a resistor has suffered some form of heat shock. One resistor is floating and the wiring is close to a nightmare, let alone the routing and crossing of high voltage lines.

I do have the schematic diagram which matches the PCB (oh, BTW, it is double sided but the magazine showed only the bottom side). But schematic and component placement (not shown here) differ with values especially in the CRT bias network.


The schematic diagram: it's a starting point!
The schematic diagram: it's a starting point!

Well, it is not a complex circuit and with some extra parts I should be able to get it running... one day. I should also add a Z-axis control if this is going to become a clock.

 

 

17 September 2022

A simple way to 77 GHz

The Italian government has approved a new frequency allocation document, so I checked which changes would impact the amateur radio world. I also looked at "our" bands in the GHz range and I saw we share 77 GHz with many other users.

Since I was "lucky" with 24 GHz radars, I hopped to the usual Chinese online marketplaces to see what they sell on 77 GHz.

It turns out that 77 GHz are currently used in automotive radar sensing and of course there are modules for sale.

Looking at pictures I identified a product name: Continental ARS-408-21 Radar. There is documentation on the Continental Engineering website (they also have other 77 GHz radars), so it could be adapted for a simple HAM RTX without too much "guessing". They claim to be able to detect objects at 1200 meters, much more than my 24 GHz radars.

So, probably simple but not cheap, though! These modules are currently (2022/09) selling at 80€ each, so I will just observe how the market evolves and prepare in case their price drops.

 


11 September 2022

Italian RAI has stopped medium wave service.

As of today, Sunday September 11th, 2022, the Italian national broadcast RAI has stopped all its medium wave transmissions. 567, 657 and 999 kHz have gone silent.

In most of the Italian territory there are no signals to be received in MW during the day with a domestic receiver.

Time to put into service those 1.000 MHz canned oscillators?

28 August 2022

Summer 2022 PCB Collection

In order to reduce the impact of returning home from holidays, this year I prepared a small present that would make me want to get back: not one, but three PCBs!

In July I designed the PCB for a secret project (it will be a birthday present). Then I added a board to simulate the spin of the WE6167 dekatron. And at the last minute I designed a board that would modulate either an HB100 or a CDM324 radar transceiver.

Each design is packed separately.
Each design is packed separately.

All the design was done in KiCAD 6 and each board had some challenges to learn something new: proper Net spacings for HV, new component footprint that includes a large "hole", adding an ICSP connector.

I chose JLCPCB as fabhouse, but I needed to slow them down so that the packet would arrive once I am already back at home, not before.

First of all, I chose three different colors for the three designs, and these colors take two extra days for production.

I submitted the order on a European Saturday afternoon and it went in production almost immediately: I didn't check that JLCPCB respects business hours, but they are open 7 days a week! Little mistake on my side, I lost one day, but otherwise I would be tempted to make more changes to the boards.

Then I paid for the slowest shipping option.

Why all this trouble? I didn't bring a computer with me on holidays, so I had to submit my order before departing.

Who came home first? PCBs, of course! They beat me for 2 days, shipping was too fast.

The secret project has passed the hardware smoke test and is now in the hands of the firmware development team (it's always me).


Three designs, three colors.
Three designs, three colors.



26 August 2022

A request to my German (speaking) readers

At Friedrichshafen fair last June 2022 I bought some stuff from the seller at table A012 (https://youtu.be/BH29tY4Sjyc?t=154 and next 30"). I would like to get in touch with him to ask if the has more (not complain about something broken! HI).

Is there a German forum where I could ask if someone knows him? If you asked me for the Italian scene, I would answer "ARI Fidenza forum".

Please let me know with a comment or via email to ik1zyw@yahoo.com .

Thanks!

05 August 2022

Using KiCAD on dual screen on Ubuntu

When I tried ordering a PCB from a manufacturer in 2017 my choice for generating the Gerber files was KiCAD, version 4 back then. All home computers run Ubuntu (no young boys that need Windows for videogames), so it was KiCAD on Ubuntu. With a couple of good tutorials and memories from OrCAD for DOS at high school (past century), the experiment was successful.

Fast forward past pandemic, I need again PCBs. This time I swapped the work PC on the remote working table with the lab laptop that runs KiCAD gaining an external monitor, keyboard and mouse.

Now, THAT IS a productive way to design PCBs!!

KiCAD 6 on Ubuntu on two screens. Unfinished circuit.
KiCAD 6 on Ubuntu on two screens. Unfinished circuit.

Schematic diagram on one screen, PCB on the other, with KiCAD (now version 6) you can make changes on the fly on either side and reflect it on the counterpart with a keypress. I needed to change quite a few pin assignments on the microcontroller to have a simpler routing once the general layout was done, and the dual screen was the way to reach the goal without endlessly swapping windows. And if you memorize keyboard shortcuts, it's even faster.


21 July 2022

SGS integrated circuits H100/H200 series

Shortly after posting about H 257 and H 258 never-seen-before(-by-me) ICs, I tried different search keywords and a datasheet popped up from the back of Internet.

According to that document SGS-ATES produced a series of High Level Logic I.C.'s designed specifically for applications in areas where noise is a hazard. The supply voltage is from 10.8 to 20V and they are compatible with MOS technology:

 

From the datasheet you learn that the suffix D1/D2/D6/B1 distinguishes between voltage+temperature range and case material. I think it was 1970-1975. Afterwards SGS should have adopted the standard naming for their IC line-up.

As already stated, contact me if you need those chips (H 257, H 258, H 202, H 203).