Sunday, May 9, 2021

Using a piezo element

The High Z element will require a high voltage low current drive. To control the frequency response we must adjust the coupling caps and the load resistance. The high R high C circuit gives good low frequency response but drops off on the high end.

Lowering the load resistance flattens the response.
Lower coupling caps cause the low end response to drop off. This will make a 'tinny' sound.      

Thursday, April 15, 2021

Turret board amp upgrade.

 

I will use the double row layout. First step is to layout the components.
 
 

I laid it out in spice so i could test the circuit. The sim works so I didn't miss any jumpers or cross fed any points.
 

My first build worked very well but left room for improving the layout.



I may want to put it in a box. The components on both side and the transformer mounted on the turret pins will not fit a box well.


This will install in a box much easier. The transformer on a separate board will allow it to be placed so the jack is accessible.


The little amp works nicely with a DBM.
I wound 9 turns of 3 strand wire. One coil is the primary. The other 2 form a tapped secondary. The taps are the AF output. RF and LO feed the primaries.
The platform is a pill bottle cap. The base is a piece of press board. I used turret pins to mount the diodes. I had the terminal strips on hand so I used them for the I/O connections. Turret pins would work just as well for the I/O.
This setup received a station in Texas and one in Tenn.
The 80 meter ham band was active.
WWV on 5Mhz.
Several shortwave stations around 6Mhz.
This was using my bench signal generator as the LO. Next step would be to build a generator.

Monday, April 12, 2021

Amp, Coil, Turrets, Board

 Had a little shop time. (rainy day) 

Took the lid off an ice cream carton and made a coil form.

I squared the material, Wrapped it around a suitable round mandrel. When heated the material melts and is sticky. (Think hot glue) I used a heat gun (hair dryer) to fuse one end. Pushed the form off the mandrel so it didn't stick to it. Fused the other end in like manner. Then fused the seem length wise.

I wound the coil with the wire on the bench. Then finished the coil with a dope made from ping pong balls and finger nail polish remover.   

The plan was to make a turret board for the amp build. This material is readily available and perfect for the job.

Look familiar? You will see it in the kitchen and bath. (If you do not have stone counters tops.) Formica was invented to be used as an insulator. It also makes some fine counter tops.


The plan is to use a turret board, These are ok but a little pricey. The formica is left over from a kitchen rebuild. The turret pins are 1 - 2 cents each.
Here are some examples of the turrets.

Here is the drawing for my amp. I used the scrap which was about 1" wide. I made 3 rows of pins. In the future I will spread the circuit out more. But I just used the piece which was already cut.




The pins were double ended so I put parts on both sides of the board. The little amp sings. It drives my earbud with the output of my AF generator all the way down and the 20db attenuator on.

I added a V cap and diode with test leads and it picked up a station which IDed itself as being 600 miles away. The prototype performs well. I will likely make another on a bigger board.

It may be worth looking into the formica. Last I bought was about $50 for a 4' by 8' sheet. Less than $2 a square foot is not bad?


Tuesday, April 6, 2021

Adding a pot to spice.


 symbol file .ASY

*************

Version 4
SymbolType CELL
LINE Normal 0 -36 0 -48
LINE Normal 0 48 0 36
LINE Normal -20 -3 -9 0
LINE Normal -20 3 -9 0
LINE Normal -20 3 -20 -3
LINE Normal 9 -36 0 -36
LINE Normal 9 36 9 -36
LINE Normal -9 36 9 36
LINE Normal -9 -36 -9 36
LINE Normal 0 -36 -9 -36
LINE Normal -32 0 -20 0
CIRCLE Normal -6 32 1 25
WINDOW 0 16 -32 Left 0
WINDOW 3 17 -1 Left 0
WINDOW 123 16 26 Left 0
SYMATTR Value R=10k
SYMATTR Value2 T=.5
SYMATTR Prefix X
SYMATTR SpiceModel pot
SYMATTR ModelFile ..\sym\EXTRA\Misc\pot.lib
SYMATTR Description Potentiometer
PIN 0 -48 NONE 0
PINATTR PinName A
PINATTR SpiceOrder 1
PIN 0 48 NONE 8
PINATTR PinName B
PINATTR SpiceOrder 2
PIN -32 0 NONE 0
PINATTR PinName C
PINATTR SpiceOrder 3

*******************

Model - .lib file.

 

 .SUBCKT pot 1 2 3
.param tap=limit(T,.001,.999)
R0 1 3 {R*(1-tap)}
R1 3 2 {R*tap}
.ENDS

******************

 

*NOTE.

The ASY file defines the lib file location. Spice will look for the lib file in your lib directory. To allow spice to find the file either place it in the lib directory or modfy the line in the ASY file to locate it.

 

 


Monday, March 29, 2021

Sunday, March 28, 2021

The amp response


 


Click EDIT
Click SPICE Analysis
Fill in the 4 blanks to define the sweep.