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A 2.4GHz to 1.5 GHz down converter layout, and VCO internals.

A 2.4GHz to 1.5 GHz down converter layout

This is basically a VCO, mixer, and voltage stabilizer:

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The screw in the trimpot will allow fine adjustment of the output frequency from outside the box.

After using this 964 MHz VCO in several projects, finally a pad (VCO in) broke off. Had to open it... removed the cover:

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This time I did take a picture of the internals:

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The little 3 turn coils is the main oscillator. The big SMD is a varicap I think. There is only one transistor, active component.. And a mysterious zig zag coupling to the 50 Ohm output on the left.

BTW: their 2.4 GHz VCO coil only has 2 turns.

So now you know how to make your own...

The LM317 makes an excellent voltage stabilizer. Now need to solder that cap back on, and add come capacitators and resisisters.

As this is only a 'monitor', to check what I am sending upwards towards the sky (satellite), and that will be many Watts, there is no need for any gain.

The output goes into the DVB-S satellite receiver's LNB input. Any cheap WiFi antenna will do for the input.

It so happens the VCO output is just the right level for this mini-circuits ring diode mixer.

Of course all still has to be tested, I am using that mixer out of spec.

Reply to
Jan Panteltje
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A 2.4GHz to 1.5 GHz down converter

Its working!

This is basically a VCO, mixer, and voltage stabilizer.

Added the resisistors and capacitators, some not wireless connections too:

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Note the disconnected coil, its basically a protection for DC coming back via the LNB cable from the sat receiver in case a SMDcap blows, its soldered back in now.

The screw in the trimpot will allow fine adjustment of the output frequency from outside the box.

here: One problem when you do not have the right test equipment is how to do without. And the other in digital is, that if something does not work then there can be a thousand things wrong, and unless you can check everything in the 'chain' of processing (have the tools), you have to be either clairvoyant, or be able to win the lottery on command, or just be plain lucky.

My rtl_sdr spectrum analyzer only goes to 2.2 GHz. My frequency counter with prescaler to 3. So by measuring the frequency of the VCO in the transmitter to be 2,404,474,000 Hz, then setting the down converter VCO to mid range (it has no prescaler for easy measurement), and looking at the mixed down output on the rtl_sdr based spectrum analyzer, found the spectrum at 1,441,474,000 Hz:

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Cool, now tune the sat receiver to 10,600,000,000 Hz higher because it assumes a LNB LO, makes 12041,474,000 Hz, we should see a signal:

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indeed, and recording works too.

It is not completely clean as the other sat receiver shows (that one one has lock problems on this):

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look at the constellation, that should be 4 dots at right angles... Looks like some noise, will have to find if it is the transmitter or the down converter, or both, what causes it, maybe decoupling; goto here.

:-)

Next to make some holes in the box for that converter,

Close up:

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Reply to
Jan Panteltje

A 2.4GHz to 1.5 GHz down converter

A whole new range of interesting frequencies opens up with this litte converter, here now in box with antenna:

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Modified my rtl_sdr based xpsa spectrum analyzer software to allow for a local oscillator setting: I found a peculiar very strong intermittent signal around 2432271360 Hz, it turned out to be my Logitech wireless mouse ;-)

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The more I mouse the more constant the signal.

Where is the upper limit? Around 3.2 GHz with this VCO I think. No reason one cannot use a higher frequency VCO, then the mixer is the limit.

Nice new tool added!

Reply to
Jan Panteltje

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