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lpf

ron mcmurray All Messages By This Member #110829 has anybody made one for 432Mhz. i need one for a homebrew vhf-uhf radio. ron, kc0tdj
Ryuji Suzuki AB1WX All Messages By This Member #110832 It’s best to do it on microstripline with SMD capacitors. Lumped element inductors are best avoided. If it’s just for one amateur band from direct freq synthesis rather than old fashioned freq multiplier stages, the LPF shouldn’t be too difficult.
Tony Scaminaci All Messages By This Member #110844 Hi Ron, Here's an LTSpice model for a filter I designed at 431 MHz that you can easily tweak for 432 MHz. This is only a model using ideal components and hasn't been built. If nothing else, it'll give you an idea of the inductances needed for a microstrip or stripline implementation. Tony AC9QY toggle quoted message Show quoted text On Mon, Sep 25, 2023 at 11:08?AM Ryuji Suzuki AB1WX <ab1wx@...> wrote: It’s best to do it on microstripline with SMD capacitors. Lumped element inductors are best avoided. If it’s just for one amateur band from direct freq synthesis rather than old fashioned freq multiplier stages, the LPF shouldn’t be too difficult.
Barb WB2CBA All Messages By This Member #110846 I use these: Zyyini Low Pass Filter Module, Power Distribution Control Equipment, Wide Operating Frequency Range， for RF Signals These have a pretty good response on 70m. 73 Barb WB2CBA
Tony Scaminaci All Messages By This Member #110847 Here's an alternate differential 431 MHz design using a 1:1 transformer to handle the differential drive. Tony AC9QY toggle quoted message Show quoted text On Mon, Sep 25, 2023 at 11:48?AM Tony Scaminaci via <tonyscam=[email protected]> wrote: Hi Ron, Here's an LTSpice model for a filter I designed at 431 MHz that you can easily tweak for 432 MHz. This is only a model using ideal components and hasn't been built. If nothing else, it'll give you an idea of the inductances needed for a microstrip or stripline implementation. Tony AC9QY On Mon, Sep 25, 2023 at 11:08?AM Ryuji Suzuki AB1WX <ab1wx@...> wrote: It’s best to do it on microstripline with SMD capacitors. Lumped element inductors are best avoided. If it’s just for one amateur band from direct freq synthesis rather than old fashioned freq multiplier stages, the LPF shouldn’t be too difficult.
Tony Scaminaci All Messages By This Member #110849 Wow, you can't beat the price! Barb, have you scanned these for harmonic rejection? I'd like to pick up some of these if they meet FCC specs. Tony AC9QY toggle quoted message Show quoted text On Mon, Sep 25, 2023 at 11:58?AM <wb2cba@...> wrote: I use these: Zyyini Low Pass Filter Module, Power Distribution Control Equipment, Wide Operating Frequency Range， for RF Signals These have a pretty good response on 70m. 73 Barb WB2CBA
ron mcmurray All Messages By This Member #110850 thanks . i will try the Zyyini Low Pass Filter Module. ron kc0tdj
Barb WB2CBA All Messages By This Member #110852 On Mon, Sep 25, 2023 at 10:03 AM, Tony Scaminaci wrote: Wow, you can't beat the price! Barb, have you scanned these for harmonic rejection? I'd like to pick up some of these if they meet FCC specs. ? Tony AC9QY On Mon, Sep 25, 2023 at 11:58?AM <wb2cba@...> wrote: I use these: Zyyini Low Pass Filter Module, Power Distribution Control Equipment, Wide Operating Frequency Range， for RF Signals These have a pretty good response on 70m. 73 Barb WB2CBA ? ? Tony, Couple of years ago I built cubesat ground stations with these. They worked pretty good. They are kinda hit and miss but not that off from FCC parameters. It’s easy to tune them just by playing with inductors, sqeeze or extend, using a vna or spectrum analyser. I didn’t even have to try cap replacement.? 73 Barb WB2CBA ?
Tony Scaminaci All Messages By This Member #110870 Thanks for the info Barb. I ordered one today and will do a VNA scan when it arrives. Can’t expect perfection at that price point.? Tony toggle quoted message Show quoted text On Mon, Sep 25, 2023 at 12:27 PM <wb2cba@...> wrote: On Mon, Sep 25, 2023 at 10:03 AM, Tony Scaminaci wrote: Wow, you can't beat the price! Barb, have you scanned these for harmonic rejection? I'd like to pick up some of these if they meet FCC specs. ? Tony AC9QY On Mon, Sep 25, 2023 at 11:58?AM <wb2cba@...> wrote: I use these: Zyyini Low Pass Filter Module, Power Distribution Control Equipment, Wide Operating Frequency Range， for RF Signals These have a pretty good response on 70m. 73 Barb WB2CBA ? ? Tony, Couple of years ago I built cubesat ground stations with these. They worked pretty good. They are kinda hit and miss but not that off from FCC parameters. It’s easy to tune them just by playing with inductors, sqeeze or extend, using a vna or spectrum analyser. I didn’t even have to try cap replacement.? 73 Barb WB2CBA ?
Tony Scaminaci All Messages By This Member #111251 For anyone interested in the Zyyini 70cm LPF module, here’s the VNA scan of the module I just received. As Barb previously indicated , it’s a bit off meaning too low of a cutoff frequency as well as having only ~30 dB of return loss. Hopefully, playing with those tiny inductors I can barely see might make it usable in the 431-433 MHz range. How much effort before I toss it in the trash is unknown. Tony AC9QY toggle quoted message Show quoted text On Mon, Sep 25, 2023 at 4:17?PM Tony Scaminaci via <tonyscam=[email protected]> wrote: Thanks for the info Barb. I ordered one today and will do a VNA scan when it arrives. Can’t expect perfection at that price point.? Tony On Mon, Sep 25, 2023 at 12:27 PM <wb2cba@...> wrote: On Mon, Sep 25, 2023 at 10:03 AM, Tony Scaminaci wrote: Wow, you can't beat the price! Barb, have you scanned these for harmonic rejection? I'd like to pick up some of these if they meet FCC specs. ? Tony AC9QY On Mon, Sep 25, 2023 at 11:58?AM <wb2cba@...> wrote: I use these: Zyyini Low Pass Filter Module, Power Distribution Control Equipment, Wide Operating Frequency Range， for RF Signals These have a pretty good response on 70m. 73 Barb WB2CBA ? ? Tony, Couple of years ago I built cubesat ground stations with these. They worked pretty good. They are kinda hit and miss but not that off from FCC parameters. It’s easy to tune them just by playing with inductors, sqeeze or extend, using a vna or spectrum analyser. I didn’t even have to try cap replacement.? 73 Barb WB2CBA ?

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