A band-pass filter for 144 MHz

To cure our severe RFI issue described in one of my recent blog posts I decided to order an 144 MHz BPF. Found it on Ebay first but finally ordered from the seller’s Italian web shop directly and saved another 10%. 😉 What sold me on this one is the 3 cell helical design promising excellent attenuation data. It arrived within 4 days, ufb service!

The JG-BPF2M atop of my FA-NWT ready to be swept

Before installing it in the station today I made a few measurements with my FA-NWT network analyzer (an improved version FA-NWT2 is for sale by BOX73 if you ever need one). It does not quite meet the promised -100 dB @ 98 MHz but still is very good. It surpresses all of the amateur radio HF bands by at least 65 dB (at some frequencies even more than 80 dB).

Full sweep from 0 to 200 MHz

Zoomed into the HF spectrum only – at least -65 dB on all amateur bands 😎

Flat passband across the whole 2 m band

The measured insertion loss is still acceptable although it could certainly be further optimized as the filter’s low of 0,2 dB loss is just below the 2 m amateur band

Integration into the station went smooth. Nothing to take care of, it works both ways. 😀 It’s now connected between my trusty HA1YA transverter and the 2 m amplifier. Extensive structured testing confimed that all RFI from high power on the HF bands is gone now. 😎

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