No more tuners please [read]

[pebe]

I think capacitors are a benefit to my design. I just added another one between base and +ve of the NPN transistor driving the push-pull pair.
there was already one between base of the same transistor and ground.

This is what I mean by 'random changes', you appear to have no idea what the capacitor you've added is supposed to do, nor if it should be there or not?.

In actual fact it's simply in parallel with the lower one!, depending on it's value it's probably giving treble cut?.

Isn't there a special name for people who keep asking questions in a thread - just for the sake of it? :?

 

[JimB]

I just think of him as the "Entertainments Manager".
He has me in stitches with every post.

JimB

 

[Jay.slovak]

heh

I hope I caught your attention with the title haha.

ANYWAYS, I have a question.

I managed to make my superregen (see my 1/2 completed schematic on the superregen revisted thread) work. I can pick up the local TV station.

Here's the interesting part. As soon as I try modifying the amplifier portion of the radio, it seems that I'm getting an extra tuning control with my hand. As soon as my hand is at most 2 inches away from the actual tuner, the stations automatically change on me. I don't want this to happen.

Welcome to the world of super regen radio receivers!.

Basically, my amplifier design is quite similar to Rick anderson's own version of the "Radio Shack powered amplifier". found at this link: **broken link removed**

BUT I have made a few modifications.

Why?, I hesitate to use the term 'random changes' again, but this appears to be what you have done again?.

The amplification stage on the left is eliminated.

Fair enough!, if you only need low gain you can remove that stage.

the 0.47uF is changed to 100pF because the results are clearer and sound less distorted (and less volume).

BAD MOVE - 100pF is FAR too small, 0.47uF should be fine, leave as 0.47uF!.

the 390K in the 2nd stage (of his circuit) is changed to a 1.5M. Another 1.5M is placed between base and ground.

BAD MOVE, the 390K provides local negative feedback, your change will reduce the quality and upset the DC conditions of the stage.

Both 4.7K resistors are changed to 20K resistors, and the capacitors connected to them in parallel are removed.

Sounds another BAD MOVE, why did you do this?, and what is the collector voltage now?, an dwhat was it originally?.

the 0.47uF capacitor between Q2 and Q3 is changed to 0.1uF and the 27K resistor is shorted because I dont want to lose too much volume.

SERIOUSLY, SERIOUSLY BAD MOVE! - the 27K resistor is one of the gain setting components (along with the 390K) - you should refit the 27K, and I see no reason to change the 0.47uF, all it will do is reduce your bass response.

the 390K connected to Q3 is changed to a 470K.

Again WHY?, you've already ruined the operation of the stage, so it can't really make it any worse!.

the two diodes are changed to one diode and its part # is 1N4007

Again WHY?, they set the idle current of the output stage, doing this will give MUCH higher distortion at low volumes.

the 2.2K on the right is changed to 4.7K.

Why?.

the 1K between Q3 and ground is changed to 12 ohms.

Another BAD MOVE - presumably for no good reason?.

Transistors Q2 and Q3 are now BC547's instead of 2N3904's.

No problem with that.

Transistors Q4 is now TIP-31 and Q5 is now TIP-32.

Or that!.

My power source is 6VDC.

Probably NOT a good move, more voltage is always better, 6V is pushing this type of amplifier a bit.

So is there anyway I can improve the signal quality without losing a great amount of volume? and is there any way to minimize or prevent the stations from continuously changing as my hand moves anywhere within two inches of the tuning capacitor?

I think I need another capacitor.

You need to build a 'proper' radio, rather than a regen, or fit it in a screened metal box, plus rebuild the amplifier as the original circuit was (not that it's great?, but your changes have made it greatly worse!).

Nigel I LOVE this reply. Maybe I will save it and look at if I feel bad :lol:

 

[mstechca]

Me an entertainer, LMAO!

Actually, I'm building a radio from scratch. I'm just asking so many questions so that I can optimize it without significantly changing the design.