Bandpass filter needed for 434mhz

[Shax]

Hi all,

does anyone have a schematic for a 434 mhz (70cms) bandpass filter?
It only needs to be able to pass 100mw or so, so no huge power requirements needed!!

 

[Nigel Goodwin]

TRy the VHF/UHF Manual from the RSGB, or the RSGB or ARRL Handbooks, you should have at least one of those if you're interested in radio.

 

[Shax]

TRy the VHF/UHF Manual from the RSGB, or the RSGB or ARRL Handbooks, you should have at least one of those if you're interested in radio.

The only filter designs I can find seem hell bent on allowing 400watts thru.. I only need 100mw MAX.. Lugging a filter designed to pass huge wattages is an absolute no no for tracking a downed rocket!

 

[Nigel Goodwin]

Same inductor values, same capacitor values, just lower power components.

 

[Shax]

Same inductor values, same capacitor values, just lower power components.

Maybe, but the schematics / articles I have show the inductors made from copper tube!

I'm after a quick fix, not a complete redesign..

Oh well, never mind, back to Google!!

 

[on1aag]

Hi Shax,

Google for helical filters.

**broken link removed**

**broken link removed**

on1aag.

 

[Hero999]

Maybe, but the schematics / articles I have show the inductors made from copper tube!

I'm after a quick fix, not a complete redesign..

Oh well, never mind, back to Google!!

Just make the coils with the same dimensions from thin copper wire.

Alternatively, the schematic should list their inductance values and you can easilly calculate how many turns of normal copper wire to use. Google for coil winding formulae.