A BP filter for my next QRP Transceiver

I came across this YU1LM interesting side a time ago. Really interesting result. I build tree of this filter to check the performance, and get very close to the description but I don’t use so accurate values, that’s way I think it is worse loss in the passband. But I will go for this type.

 I has also tested pin diodes and other diode to use as switch, BAT18, BAP70-3, BAP51-02, BA592, BAP50-04 and 1N4148, I chose BAP70-03. I have read that some has problem with IM product when using diodes my test don’t show up worse with diode compared to without.

 I use 2 generators and a hybrid combiner a generator G1 in passband -12 dBm and G2 to different frequencies to test for IM -70 - +17dBm. If there is IM product it is worse without filter, so I can’t blame the diodes for that.

dokument http://yu1lm.qrpradio.com/INPUT%20HF-6m%20BP-LP%20FILTERS%20FOR%20SDR%20TRANSCEIVERS%20-%20YU1LM.pdf

The Measurment.

Stay tuned I working on PA for QRP. 

de SM4HNG