Tracker IV Tx circuit

[Carl-NC]

The Zener is 11v and added to the VBE of Q1 gets close to 12v and with a low tempco. The rail splitter effectively gives you a +/- 6V analog supply.
The speaker driver is a PNP and the emitter is connected between the batteries.
U4a is not used.
The U1-pin8 and R32 connection is also tied to analog ground.

Here's the complete power supply:

Here's the audio:

You have an R4 in the audio but also an R4 in the demod stage.

[dbanner]

Thank you Carl.
I've updated my schematic.

[dbanner]

final

[dbanner]

The fixed ground balance could be what's keeping things back a bit. Maybe dialing back the ground balance may improve performance a little. And also a revamped Rx amplifier.

[dbanner]

Looks like another Tracker variant. MD-318.

[Skippy]

"The fixed ground balance could be what's keeping things back a bit."

I think the truth is : there are many things holding it back. They aren't going to make a machine with numerous good aspects, and spoil it with a couple of 'low spec' features/lack of features. Everything is made to a design budget. The coil won't be so well nulled, it may have cheapo shielding, the pre-amp isn't low-noise, and a pile of other things.
Adding ground balance may increase it's raw all-metal depth, but whether there would be much improvement in motion-mode disc is unknown.
I'm not sure what good coils would benefit it, the bi-axial DD that fits the Fisher F4 may be the 'best' , but the Tr4 may not work well with DD coils, only CC's. In which case the F2's round coils, that are really Bounty Hunter ones, would be worth a try.

Re: the pre-amp. Perhaps decreasing all the resistor by a factor of 20, and increasing all the C's by 20 may lower the noise, especially if the '064 opamp was replaced with a quieter one. Eg. 220n, 4n7, (75R + 100R // 100R pot ) ,2k7.

[dbanner]

Final 1.0
MPSA63 is PNP Darlington Transistor.

[dbanner]

The passband gain of the post demod motion filters(first derivative) for both channels seems very high. Fc is around 4Hz, which is kind of low. 8Hz - 11Hz would be more typical.

[dbanner]

I found a mistake in the scheme.

here is corrected version
[ATTACH]n428571[/ATTACH]