Looking for Paul S / Ferrite in SE CT- FARMERIK


Rik
 

If I remember correctly, you used to DX with simple one active device radios. I just won a Miller Hi Fi crystal AM tuner on Ebay, and wondered if the germanium crystal could be replaced with something more sensitive or a detector/amp solid state device I could power with a battery. I don't want to permanently modify the antique tuner. Here is a page with links-

http://fmamradios.com/XtalTuner.html

Yes, I know it is not an ULR, but could be built small enough.

All are welcome to answer this, not just Paul S.


radiojayallen
 

I don't have any info for you on this but just wanted to comment that this looks like an interesting and fairly unique device. Good luck with it!

Jay


Paul S. in CT
 

Miller made these pretty good in the day. More modern individual components would make it better using ceramic caps and tighter tolerances.

For a start the manual suggests using a 15pF cap on top of both L1 and L2, this is advisable, 18pF looks OK if two are handy. I'm not sure what the Audio Output is intended to be, but I presume 2K headsets of the day (50's). These are coil-wound (inductive type) headphones. Tough to find in new condition and working well.

Modding this with my low power amp requires two crystal earphones in parallel (a great idea no one talked about in the modern day) to be directly driven by the transistor. This would not need any part of the Miller circuit from the diode to the right, substituting the amp. I'll email the small diagram of the whole radio I built, you would not need my "front end". In your case, the 68pF cap that is input cap can to be lowered to 56 or 47pF. Some trade off of final volume for select-ivity, but OK to use 68pF (not any higher though).

Regards
Paul S. in CT fn31nl


Rik
 

Thanks Paul.

I saw your email before I saw your message here.

I will use a microphone or phono input on a tube Hi-Fi amp made in the 1950's. I have a collection of them to try. It is mentioned in the Miller literature.

Also I expect the 20 Kc. wide selectivity will be too wide, and would want to change the caps to the values recommended by Miller to increase sensitivity and narrow selectivity some what.

I will be choosing from four sharply directional BOGs so adjacent 'channels' will be less common on the dial, and signal strength from the antennas will be high.

They connect into the house via co-ax so low impedance compared to just an inverted L wire directly connected. I may need a matching transformer at the Miller?

-FARMERIK


radiojayallen
 

If the output is too low for a Line level input I would try a Mic input rather than a Phono input as the phono;s RIAA equalization will give very unflat frequency response.


Rik
 

Thanks Jay
Some of my tube amps have tape head inputs too. I can't remember what the NAB equalization is like for those. Perhaps you know.
Most all with mag phono inputs have equalization choices to try. [RIAA, Lon, EUR, Columbia etc.]
-FARMERIK


radiojayallen
 

The NAB (formerly referred to as NARTB) equalization is very severe and only slightly different than the RIAA Phono eq...neither is suitable for a nominally "flat" input signal and will give a huge bass boost and treble cut compared with a "flat" mic input. But have you already determined that a Line level input is not sensitive enough for this application? If not, I would try that first.


Rik
 

MillerĀ  report- Just as it arrived the crystal tuner got 20-30 stations at night on the West BOG which included WWVA-470 miles, WTAM-440 miles and WJR-565 miles. Audio is suburb, there is some fading with out an AVC at night too. Day time locals have even better audio. One pair of stations only 10 KHz. apart can not be completely separated, but I could favor either one. I plan to send it into the shop later for more modern fixed caps and to have other diodes compared for sensitivity. It really hears more than I expected as it is. -FARMERIK