2m Low Noise Preamplifier with Band Pass Filter 144-146MHz
If you want to hunt super weak DX signals, MS, EME, or multiband contesting, this 2m Low Noise Preamplifier with Band Pass Filter is for you. Super low noise, input bandpass filter that will prevent overloading from stations on different bands, and high IP3 of the preamplifier are the keys to successful contesting, DXing, or EME.
The most important question. Why “N” male connector is on the input side of the 2m Low Noise Preamplifier and not the “N” female as everybody put it?
If you want the lowest possible NF and accordingly the best receiving performance you must pay attention to every 0.1 dB of loss on the input side of the preamplifier. Every patch cable has a loss. Even the best ones. So how to prevent that loss of about 0.2dB? Simply by eliminating the patch cable and connecting the preamplifier directly to the coaxial relay. Like this:
In that way with virtually no loss and accordingly the best possible receiving performance will be achieved.
The second most important key to the best receiving performance is input filtering. Nowadays, almost all manufacturers do not put any filtering on the input side of preamplifiers – the way to trouble. Thanks to input filtering this preamplifier and bandpass filter combination are much more immune to interference from strong out-of-band signals. The ultimate input bandpass filter inside the 2m Low Noise Preamplifier will eliminate all out-of-band signals from 6m, 4m, 3m, or 70cm stations.
This ultimate 2m Low Noise Preamplifier with Band Pass Filter consists of:
Measured results of 2m Low Noise Preamplifier with Band Pass Filter with HP8753ES network analyzer:
7 MHz -79 dB
14 MHz -68 dB
21 MHz -53 dB
28 MHz -47 dB
50 MHz -39 dB
88 MHz -18 dB
98 MHz -12 dB
108 MHz -5 dB
144 MHz = +25 dB, NF=0.7 dB, Input RL -10dB
288 MHz -42 dB
430 MHz -38 dB
432 MHz -37 dB
440 MHz -36 dB
IP3out > 37 dBm
Power consumption +12 V / 100 mA.
Connectors: “N” Male / Female.
Measured Return Loss (S11) and Insertion Loss (S21) of 2m Low Noise Preamplifier with Band Pass Filter
Measured HF and 6m attenuation of the preamplifier
Measured FM attenuation of 2m preamplifier
Measured Harmonic and UHF attenuation of the 2m preamplifier
Positions of connectors are selected so that the filter can be directly connected to the coaxial relay as shown. The Bandpass filter is enclosed in the strong 0.8 mm sheet brass box. Strong mechanics will ensure stability and longevity.
What others say about Bandpass filters and preamplifiers.
“I received the 2 x BPF144 filters and they work very well. They have resolved my out-of-band RFI problem and made my 2M EME station more sensitive to weak signals. The small O.2 dB insertion loss is more than compensated by having the preamps operating in their linear region and not in compression caused by strong local FM broadcast and Aircraft radio systems. It’s a pleasure to do 2M EME now.”
73 Paul W2HRO
“LNA test: Two LNAs 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 seem consistent 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 arrived well! 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 is a bit better 0.28dB on 144MHz, for the other bands as you say.”
73 Sylvain F6CIS
Link to all low-noise preamplifiers