30 June 2022

Tune-a-Lite gas filled tuning indicator

I learned about gas filled tuning indicators in the last month, as I started reading through an Italian forum packed with information on restoration of old radio receivers ("Elettroni al tramonto"). They were used before the introduction of magic eyes, so approximately from 1930's to 1940's. It is like a shorter IN-9 or IN-13 tube. On radiomuseum there is some documentation: look for Tune-a-Lite. Of course it ended up in my "to look for" mental list.

I was very lucky as I found one at Friedrichshafen Ham Messe 2022 on the stall of a German seller that deals with vacuum stuff. I tested the component for leaks with my magic wand neon tester, which surprised two more sellers in the same day. Given the presence of neon inside, it came home with me.

On the mentioned forum there are few diagrams showing how to wire the indicator so I tried the setup while swapping the three terminals, since the pinout was unknown. Moreover, since it behaves like a Nixie, as long as the current is limited (to 1 mA) you cannot damage it.

So it did light up. The picture shows a zero, middle and full indication, plus the look from behind the slotted metal window/support.


tune-a-lite gas filled tuning indicator  

Zero, middle, full extension.


And this is the wiring layout of my specific part. You may use it as a starting point in case you come across a similar indicator mounted on its base:

tune-a-lite wiring diagram
Wiring diagram.


 

 

 

 

26 June 2022

My Ham Messe Friedrichshafen 2022

Yeah! I managed to be in Friedrichshafen ham fair 2022! We traveled on "day -1" so we were not in a hurry and we could be at the gates at the opening time. Also we could enjoy the evening in town.

Like most of these events, even the self-proclaimed #1 in Europe is shrinking. The side with commercial operators and associations was full to 2/3rds (my estimation), while the private sellers area was one hangar and 1/3rd (my estimation). Hint for the future to organisers: unless we will fit in just one hangar, keep tables further away so it's easier to move around.

I walked from 9:45 to 17:00, had lunch and an extra rest-drink, and I saw every stand.

What I bought at the Ham Messe 2022.
What I bought at the Ham Messe 2022.

 What I bought this year:

  • 3 boards with red-coated Nixies (12 pieces OK)
  • another board with 9 Nixies
  • a "Tune-a-Lite" gas filled tuning indicator
  • a probably 2AP1 CRT (got it for free actually)
  • a board with eight HP 5082-7300 displays
  • a 40m band RTX "Frog Sounds", kit, assembled
  • 2 aero DME units because of their Minitrons (13 pieces OK of out 14)
  • machined-pin IC sockets (if they're the wrong length, I will cut them)

What I haven't bought:

  • "kostenlos" (free) Telefunken E 104 Kw receiver torn apart, more than 70 kg of stuff!
  • a large device with CRT, looking heavy too!
  • some cheap '80s oscilloscopes, in the range of 20€ each, for clock conversion
  • more aero DME units, now I regret

I found out that being even slightly social helps getting discounts, as I helped the Italian seller from whom I bought the red Nixies to interact with a German person that bought a (overpriced IMHO) calculator. I also realised I considered German sellers as unavailable to haggle the asking price, while it isn't true.

Our travel schedule did not leave me time to listen to the talks and because of the queue I couldn't greet Hans G0UPL as his booth.

As usual the organiser advertised next year dates: 23-24-25 June 2023. Of course nothing will be certain until next Spring, I dare to say.

17 June 2022

The James Knights Co. JKTO component - 2

What was inside.
What was inside.
From part 1, the circuit either had no output or produced a signal on 10 MHz. When I plugged in the oscilloscope, there was no output. The cylinder did warm up, always. Curious as I am, I couldn't resist but look inside .... to find a surprise!

A previous owner has replaced the innards with a 10.000 MHz crystal oscillator and used the heater to give it a form of ovenised stabilisation.

Ingenuity in pure state. A true hack. 

I wonder if the XTAL was actually cut for ovenised operation, otherwise it would have operated in a steep area of the f/T curve. Today we can achieve better performance with a GPSDO, and it will consume less power so the circuit has been dismantled giving: a 220/9V 300mA transformer, a large 10000 kHz XTAL to play with penning (lower freq) or grinding (higher freq), an experimental octal socket and an extra cool hand warmer. 

If I will ever get to it, if the XTAL can be pulled up to 10.100+ MHz it will be part of a valve transmitter on 30m. One more project in the to-do list!

Tightly build oscillator.
Tightly build oscillator.

 

 

14 June 2022

The James Knights Co. JKTO component - 1

In Marzaglia last May I picked up an anonymous circuit (click to zoom):

I was intrigued by the large metallic cylinder on the octal base. Just an AC power cord, on/off switch and a BNC output(?). The cylinder carries the message seen here:

JKTO 4.0 KC
JKTO 4.0 KC

Built in 1957 by the James Knights Company from Sandwich, Illinois. I don't know why, but I think it is amusing. It should be a 4.0 kHz (KC) oscillator, resonator, crystal and given these labels

Average Temperature 57°C, 6.3V thermostat.
Average Temperature 57°C, 6.3V thermostat.

the letter "T" in JKTO stands for "Temperature". Under the external cylinder there is another metallic cylinder and a wire wound at its base:


Since it did not smell or look burned, I powered it up. The cylinder got warm (not 57°C outside) and there was no output. At one point I picked a 10 MHz signal at the BNC on the frequency counter, but it did not convince me.

So probably the JKTO is/was the crystal element of a temperature controlled oscillator. Something could be broken in the circuit even if voltages are OK. I drew the circuit around the octal base and it might look like a Colpitts oscillator.

Since I don't need a OCXO at 4000 Hz I will look inside the cylinder, in part 2.

 

11 June 2022

Low VHF OIRT band - June 2022

Living far away from those Countries that use(d) the FM OIRT band (65.8-74 MHz), it is hard to tell if it is still used nowadays. But with the help of Sporadic-E propagation you should receive few stations if you are lucky.

The video below shows my unscientific band scan on 2022-06-10 at 1705Z, while the path had been open for an hour or so. The antenna was the humble 4 element beam on the balcony facing East.

The language sounds Russian. I patiently waited for advertisements and I could grab the word "Bielorussia", White Russia. I am not sure of the frequency because my 706 is getting old and a bit off, plus I might have heard several transmitters of the same station in different locations.

If you can identify the stations please leave a comment.


 

 

05 June 2022

Marzaglia maggio 2022

Marzaglia true spirit!
Marzaglia true spirit!
YES! I managed to me in Marzaglia meeting in May 2022. In my opinion it is THE place to be if you like old radio-electronics stuff. You need to get there by 7 a.m. (if you're a buyer/visitor). Bring a hat a sun lotion!

I brought home:

  • a couple of Nixies
  • two unknown large vacuum tubes
  • an unknown circuit
  • a valve radio skeleton to build my ideas on
  • a high-impedance headphone

Nothing really big because I've run out of space in the shack, even if some prices were quite right. Now planning for Friedrichshafen 2022. See you next May, Marzaglia!

A picture with vacuum tubes
Need valves?


 

 

 

22 April 2022

Milliwatt meter with AD8318 inconsistent readings

First of all: I do not own a calibrated generator in the frequency range of the AD8318 chip. The closest approximation is a Kenwood handheld that emits about 50 mW at 450 MHz. That is my source.

With 30 dB attenuation I could bring that signal down to about -13 dBm that the AD8318 reads as 0,904V, which is in the ballpark of -16 dBm according to figure 4 of the datasheet.

What I could confirm is the -0.025 V/dB slope by adding and removing attenuators. This let me compute the 0V intercept, but the Arduino firmware does something weird and tells me I am feeding a much higher power.

There also is a dependency on impedance matching at the AD8318 board input, since swapping my attenuation chain changes the detected value, appreciably. 

The NanoVNA did help to confirm my attenuation chain value and impedance mismatch.

For the time being, since I lack too much instrumentation to turn the circuit into something precise, I will use its output voltage to peak an RF signal and I will not care of its actual Wattage (trimming 10 GHz filters on PLL modules).