Electronics > RF, Microwave, Ham Radio

Easy way to create hairpin filters?

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rwgast_lowlevellogicdesin:
Ive been working on a 0-4ghz transverter for RTL sticks for quite a while. Ive finally got most of the harmonics and spurious noise the dongle creates cleaned up whith a few tricks I plan to release later a long with results. Part of this project is also adding a pre selection filter. I think using a bunch of home etched hairpin filters may be a fairly easy route to go. Is there any software out there that work about as simple as elsie but designs hairpin/lumped element pcb based filters by entering a few parameters? Something thats not 1000 of dollar either

Nuno_pt:
I would be interested in that mods, to get rid of the harmonics and birdies out of the dongle.

I've seen some mods, of replacing the crystal by a better one and remove some other components of the board.

I think there was something from Anasoft for that or HP, for designing, not sure if they are pay.

rwgast_lowlevellogicdesin:
well i plan on sharing everything in a blog. Basically im working on a 2 though 4ghz transciever based around the dongle as the heart. Right now i plan to remote control it via wifi and pi from a remote location eventually id like to turn it in to a full on tranciver running gnu radio with a 7 inch screen.

As far as noise mods im not done. I still need to add the new power supply, the txco with lp filter and sheilding. When i get time ill post a picture of what ive done with a spectrum scan from 27mhz to 1700mhz. Ive managed to knock out over half the spurs without even filtering the LO yet

KJDS:
The filter wizard in AWR suite will do what you need, to a reasonable first guess approximation. It's also not $1,000s, but that is because, added in with the rest of the suite it's $10,000s

Alternatively you could spend a few months calculating them from first principles, checking them with Sonnet lite and going from there, but it will be hard work.

Nuno_pt:
That looks good.
Something's that I've seem include, replacing the 1.2V supply of the RTL2832U, for an low noise one with LT3042, replace the 3.3V supply from the USB for the dongle with 2xLT3042, removing the 28.800 crystal by an better one with decoupling filter, adding USB common mode filter, etc.

Did your experiments improve the noise figure in the circuit?
How is the thermal drift?
Is the dynamic range improve?

Will wait for your news on your blog.

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