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?