baltic: M2 (M 2); Crystal Receiver

I have a receiver that looks exactly like the M2 although I cannot find any number on it. I have some remarks on this model:

I do not beleive it is as late as 1930. Baltic merged with AGA in the summer 1928 to form AGA-Baltic AB, a receiver marked Baltic would then be made before this. Baltic made advanced valve radios already in 1925-26, so even if they may have produced these crystal receivers in parallell with the valve ones, I believe it is an earlier product, my guess is as early as 1924-25.

My receiver has capacitive tuning, the condenser consisting of two copper plates with glimmer isolation between them, one fixed to the panel and one "spring loaded" that can be pressed against the fixed one by means of a threaded screw on the tuning knob axis. The frequency range is aproximately 270 to 550 kHz, the selectivity is quite bad and of course also the sensitivity as there is no amplification. The receiver would obviously need a strong local station to work reliably.

I enclose photos of my receiver and a wiring diagram.

Attachments:

• Baltic crystal receiver (70 KB)
• Baltic M2 wiring (15 KB)

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I would say, such a knob is hardly before 1928, which also matches the sets appearance and style.

Are You sure that the tuning capacitor is connected to the coil tapping?  A1 doesnt make much sense, if the resonant circuit impedance is stepped up again to experience even more damping from the antenna plus remarkable detuning.

- What kind of antenna did You use?
- How distant is Your closest BC station, and what is its power? 
- Have You ever tried to input at A2 through a small fixed capacitor of ca 100 pF?
- For tests dont use the crystal but a Germanium diode. The crystal is too unreliable and unstable. 
- Once the hook up is running with the diode, then it is time to put the crystal in action for comparison.

Good luck!

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Hello Konrad,

Thanks for your remarks on the Baltic M2. I agree with you on that the wiring looks odd. I had drawn it the other way first, but this is how it is actually wired. I think that the former owner may have tampered with it!

I have not attempted to listen with it, I used a signal generator to find out frequency and selectivity first.  I will test it more thoroughly later, now I am concentrating on restoring my R1082 which is dead due to some faulty components.

I used to listen to the close by and very strong Motala/Orlunda on LW with old sets, but it is no longer operative.  The only Swedish MW transmitter is Sölvesborg with 600/300 kW on 1179 kHz which is certainly strong but outside the frequency range of the M2. I believe the strongest station would be Kalundborg in Denmark on 243 kHz or some station in northern Germany.

Why do you think the knob could not be before 1928, it looks like many early knobs to me?

It was really nice to have your opinion on this set. Best collector regards to you, Konrad!

Bo S.

 

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Hi Bo,

my dating is based on comparison with numerous models, mainly British, German, and US in original and in literature. The center part and the rim inside the dial scale I could only find from ca 1928 onwards. But it is just an educated guess.

For test using a signal generator You should also feed via a series cap of max.50 pF in series with ca 500 Ohms (not critical, can also be discarded). Try A2, it could be the better choice.

Good luck,
KoBi

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