Question about self oscilator mixer

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Re: Question about self oscilator mixer

Post by Admin on Sun Jan 22, 2017 12:14 pm

Hello Densil,
The self-oscillating mixer I think you mean is like this:


The turns ratio you need is (rule of thumb) 1E : 4C : 20Tune
That is to say for every one turn in the emitter, you need four turns in the collector and 20 (or more) for the tuned winding.

There are three big disadvantages to the Reinartz oscillator when used as a mixer:
1 - The two feedback windings have to be small compared to the tuned winding if using "normal" coils. You can use strip-line (and cavities) for other frequencies.
2 - If the input frequency from the antenna is close to the oscillator frequency then the oscillator can snap to the input frequency, especially if the input is strong.
3 - The input needs to be tuned to reduce 2) above.
If you go back through the older questions you will find a short discussion about it.

I used a self-oscillating mixer in one of my projects, but I used crystal or ceramic resonators to keep the frequency stable.


(note that G1 and G2 signals can be reversed if the biasing remains the same)
Yes, denco did some ready-made coils for home constructors, then a company called Q-max took over.

Yes, Q-max is another company that make chassis punches, but Qmax is yet another company who also make super-tankers (shortning of Qatar maximum). There is also a Qmax wrist watch. Commercial Companies seems to love inventing new (re-used) company and product names. Tid you know that American Express was formed in the 1800's? After a year of trading they changed their name to Wells Fargo. The NY in nylon stands for "New York" after the product was presented at the 1945? science fair. But as long as there is money in it, there will be "new" names reused, such as Mazda (the name of God in Zoroastrianism). Hope they never make the Toyota "Budda" or the Nissan "Alla". They would be a bit OTT.

Best regards from Harry - SM0VPO

Bet you are not religious.
Wrong! I believe that there is something, but I do not believe in an old man in white robes, sitting on a cloud, eating cottage cheese. Call me an "evolutionist". I don't want to take this further on this forum. Discussions about religion more than a couple of words in passing will be blocked - off topic. That is why members can send private mails. By the way, your e-mail keeps bouncing back.

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Question about self oscilator mixer

Post by Densil on Sat Jan 21, 2017 11:52 pm

Hi harry, yes yo did answer my question and some. I like the way you think. Bet you are not religious.

But i have a question about the self oscilating mixer that used to be used in the old vintage transistor radio (sorry, wireless set). The one with three coils on a single can - emitter - collector - tuning.
It is a simple device but what are its limitations?
If it is so good then why dont we use it more instead of other nogain mixers?
Do you have any ideas about the turns for the coils?
I saw your posting about denco coils but i didnt see any info. can you please share it with me?

btw - q-max, did they make coils? I thought they made hole punchers?
73 /D

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