144 - 146 MHz High Selectivity, High Q, Low Loss Bandpass Filter BPF
Bandpass Filter BPF uses high Q coils with unloaded Q of more than 1000, and capacitors with Q more than 1200. Low loss of filter achieved with careful design and adjustment.
Here are presented measured results with HP8753ES network analyzer full two port calibrated.
Return Loss (S11)
Insertion Loss (S21)
Achieved results on a built Bandpass filter:
50 MHz = -68.4 dB
88 MHz = -45.6 dB
108 MHz = -31.5 dB
144 MHz = -0.21 dB
146 MHz = -0.21 dB
432 MHz = -75 dB
These excellent results were achieved by careful selection of components and design of the filter. This type of filter is necessary when you have near by strong 50 MHz, 432 MHz station or FM transmitter (88 - 108 MHz).
Filter characteristics zoomed:
Filter characteristics zoomed again:
At the end of the test we connect VLNA2m13 Low Noise Wideband Amplifier with SPF-5122Z.
And measured again characteristics. Only amplifier:
And amplifier with band pass filter:
Positions of connectors are selected so that the filter can be directly connected to the coaxial relay as shown. Band pass filter enclosed in strong 1mm sheet brass box. Strong mechanics will ensure stability and longevity.
This type of filter will almost nothing disturb noise performance of preamplifiers which is especially important in terrestrial and EME (Earth - Moon - Earth) communications. It will further ensure smooth operation in the presence of strong signals.
Finished Band Pass Filters:
What others say about Bandpass filters and preamplifiers.
"LNA test: Two LNA have the same behavior. Gain at 144MHz 25.96 dB, NF 0.68, LNA only Gain 25.73 dB, NF 0.88 dB, LNA + filter. Results seems cosistent and confirm the 0.2 dB loss of the filter.
-1db compression point happened with -3dBm input signal level."
73 Franco I2FAK"
"Many thanks, good news today all staff well arrived ! I made DUTs on test this PM to the VNA HP 8510C and to the noise analyzer, congratulations all specs are very well respected ! NF it is a bit better 0.28dB on 144MHz, for the others bands as you say.
73 Sylvain F6CIS"
Outdoor variant can be found here: