Amateur Radio Tuning Analysis

[GWS]

Here's a little program to analyse the tuning range for a parallel coil and capacitor circuit.

It uses complex number values and includes subroutines for multiplication, division, addition and subtraction of complex numbers.

It's probably only of interest to radio amateurs as a tool for checking the tuning range of a given coil and capacitior arrangement, but the code might be of use in other applications ..

all the best,

Graham

[aurelCB]

Excellent Graham,i just love this types of programms.
zlatko

[tbohon]

Great job, Graham!  I'm going to mention this to our local ham group at our meeting next week.

73,

Tom / KE7EJJ

[GWS]

You're welcome Tom - I didn't realise there were so many amateurs around .. 

I presume you've seen the other amateur programs I did:

World Callsigns:

http://www.ionicwind.com/forums/index.php/topic,2058.0.html

Morse Code:

http://www.ionicwind.com/forums/index.php/topic,2139.0.html

They seemed to work quite well ..

best wishes,

Graham G4EVW

[tbohon]

You're welcome Tom - I didn't realise there were so many amateurs around .. 

I presume you've seen the other amateur programs I did:

World Callsigns:

http://www.ionicwind.com/forums/index.php/topic,2058.0.html

Morse Code:

http://www.ionicwind.com/forums/index.php/topic,2139.0.html

They seemed to work quite well ..

best wishes,

Graham G4EVW

I have now ... 

73,

Tom

[aurelCB]

Hi GWS...
Why is L induction limited to minimum 0.1 uH?
For example if i want to simulate FM from 88-108 MHz
then i need small coil with few ( 4 turn / dia 7mm / Cu wire 0.75mm )
so i need inductance about 70-90 nanoHenry right?

all best
Aurel

[GWS]

Hi Aurel,

It was only a demonstration program, so I chose values I thought would cover most needs.
Very small inductances will also need small tuning capacitances, and I doubt the usual calculations would be accurate enough at the frequencies involved.

In a practical case, it mostly comes down to trial and error - in the past, I've made inductances from half a turn of silver wire, and capacitances of small air-spaced strips of a printed circuit board.  I wouldn't say any of that could be calculated with any accuracy.

The bit of code that limits to 0.1 uH, is ..

Code Select Expand


if (L < 0.1)
L = 0.1
setcontroltext win,5, using("#.#",L)
a$ = "Tuning coil inductance set to 0.1 microhenry minimum."
messagebox win,a$,"Data Value Error"
return
endif


You could change the test to say 0.01 uH - but how accurate the results would be I don't know.

Best wishes,

Graham

[aurelCB]

Hi GWS..

Hmm so there is a catch..LC resonance currently looks fine to me.
What i need is from 88-108 Mhz ,so
minimum capacitance must be cca 3->5pF and maximum cca 33-35
and from this capacitance range will be 30pF for FM band..right?
Mid frequency will be on 98MHz..well in most comercial FM tuners this mid freq is
on 96MHz.
Yes i agree with you that without experiment there is no fine tuned freq-range.
As you maybe remember i like to build this small radios - regens or superregens
so this type of programs are very useful to any home-builders.

Another small question ...did you maybe try to create program for coil to calculate coil
inductance from specific coper wire?
i know that there are some programs around but i am not quite happy with them
and are not created in Basic ( read Creative Basic   )..

[GWS]

I'll look into some code for small coils .. but right now is not a good time for me ..

I need some time ..

Best wishes,

Graham

[aurelCB]

Hmm well it looks that Creative have some limitation with such a small values and
return error as i try to devide with zero which is a nonsense..
look into quick program:

Code Select Expand

'quick program to calculate resonant frequency
'with random colors
def win:WINDOW
def L,C:double
def freq:double
'open window
window win,0,100,640,400,@SIZE|@CAPTION,0,"Resonance LC -> paralel...",wndproc
setprecision 14
'inductance in nH
'L = 90*(10^-9)  : '90nH 0,000 000 000 000
L = 0.00000009
'capacitance in nF
'C = 50*(10^-9)   : '50pF
C = 0.0000000001
'-----------------
move win,10,10:print win,"inductance(nH):",L
move win,10,30:print win,"capacitance(nF):",C

'freq = 1/2*3.14*SQR(L*C)
freq = 1/(6.28*SQRT(L*C))
move win,10,60:print win,"ResonantFreq(Hz):",freq

'-----------------------------------

run = 1
'show a 'wait' cursor while we are drawing

waituntil run = 0

closewindow win
end

'our windows handler subroutine
'this is where all the messages
'our window receives will be sent to
'the only one we care about is @IDCLOSEWINDOW
sub wndproc
SELECT @CLASS
CASE @IDCLOSEWINDOW
run = 0
ENDSELECT
return

'this subroutine is just an example
'of how parameters can be passed
'we could have just used CIRCLE
'without the sub
sub docircle(x,y,size,colora,colorb)
circle win,x,y,size,colora,colorb
return 1


[aurelCB]

After some thinking i have decided to use my small interpreter and try
to calculate resonant frequency and it looks that work