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First use of LTSpice (For tests filters 45mhz)

 

Hello,

This is the first time I use LTspice and as at the beginning with Kicad I struggle...
Maybe you have already done this test in LTSpice, that¡¯s why I go through the Ubitx forum at first.
What I want to do is simulate the 45MHZ filter
I have two drawings to do, the one for the Ubitx V6 and the one for MOTHY.
If I can place the selfs and capacitor, where can I find the 45MHZ filter.
1)??It¡¯s a silly question, but I didn¡¯t find the manipulation to rotate one components.
The manipulation?

2)There is a section "Components", but there is no quartz, nor 45MHZ filter.
I have 2 type of filter: Motorola 20J26 and UN-1 45R15AZ filters.
Maybe we should download these components?

Here that i want to do

cdt
 

Hello,

watching this video, I realized that in fact the quartz and 2-pole filter components don¡¯t seem to exist in LTspice
they have to be simulated? (Theoric shematic), which complicates things.?


Not easy to do if you don't have specifications of the filter

cdt
 

While you do not have the dataset for them you do have the filters.

The solution is the empirical method, measure them.

Allison
--------------
 

You can try calculating the values for a simple filter or use the digikey calculator here

There are several calculators around that will give you several poles depending on the accuracy you want.
Then draw the appropriate Inductor /Capacitance in LTspice with a voltage source and a 50 ohm load.? Don't forget the ground. Right click on the voltage source and put a 1 where it says ac amplitude. Then go? to simulate, edit simulation card and select ac analysis.? Select type of sweep: Decade. Start freq 100, stop freq 1 Meg.? Be sure to type Meg because M will give you 1000.? ?Now run and it should draw a bode plot of the filter.
Andy KM4TRT
 

Hello,

Yes, thank you
As with Kicad, I need time to figure out how LTspice works.
Fortunately, there are plenty of videos to explain all this.
I even saw that we can also simulate in Kicad.
So many things to do with the net.
I was wondering if anyone had done a LTspice diagram of a complete Ubitx. A school case to test. LOL
See you soon
 

Hello,?
Allison an all

Do you think that I can find the characteristics of my filters (45R15AZ and 20J26) by applying the method of diagram 5 with a NanoVNA.
I think I put 2* 2K variable resistor? and 2 * 0/ 10pf variable capacitors and look for the best response curve.? --> 2 pole filter
Then depends on the values taken:
Is the acouplement point (black dot) related to these values? Because no dot on my filters.
If I want a filter 4 poles? ---> I can connect 2 filters on the side where these have identical resistance and capacitance following the measurement. (Basically what is the method to align the 2 monolytic filters)


cdt
 

hello

I made a small model on the shown on diagram 5.
I spent 2 good hours trying to have a correct setting to display with the Nanovna a correct curve.
For me, variable resistors only have the effect of decreasing gain, only capacitors modify the curve a little.
So pretty much a test.
Maybe you have a better test schematic? that works better.
I think, It may be necessary to serialize 720nh inductors with resistors or something other
Your feedback is welcome.
cdt
 

So for the diagram 5 test circuit, you should be adjusting for the desired filter shape and nothing else. When you increase the R, the gain WILL decrease, but you don't care, since you are looking for the best filter shape, not anything to do with gain. The R value on each side should be the same, adjusted together. Same with the C value, adjust them the same on each side. Figure 3 on the datasheet shows the shape, two peaks with a small dip in the middle. Only one peak? No dip in middle? You have the wrong settings. Can you post a picture of your best result? Or some various results? Can you post a picture of your setup? We really can't help without seeing some of your results.
 

Hello Dave,

I have also open a message on nanovna iso forum
I think have a good method to test the filter

see here:??[email protected] | 2 poles filters teminaison impedance

cdt

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