BPFILTERHF-QRPRADIO

2023年12月24日發(作者：楊錦文)

TUNABLE BANDPASS FILTER FOR ALL HF BANDS (160m-10m)

Ing Tasic Sinisa –Tasa YU1LM/QRP GQRP10091

At the beginning of 80 I worked with stations which have rious problems with

IMD products such as FT101B, this was very noticeable on lower bands 7 ,3.5 and 1.8

MHz . In literature I saw very simple tunable bandpass filter designed by M. Martin

DJ7VY in CQ-DL 7/84 which cure IMD problems substantially. Filter have 3 coils ,

double variable capacitors and few toggle switches for the frequency and bandwidth

lection. Filter behaves as a tunable peak filer and inrtion loss is changing very much

with changing operation frequency from less than 1dB to 15dB. Bandwidth and

lectivity is changing very much with operating frequency and becau of that it was

not suitable for u in transmitting systems. When you like to build HF bandpass filters

especially for 50Ohm system problem is how to design them that the realization have to

be a simple as possible. Without appropriate measuring equipments adjustment will be a

nightmare especially with unknown coils or coils with taps. I designed simple tunable

bandpass filter for whole HF and it is one of my favorite RF BRICK-s for design on the

table. It was designed and realized with the next design goal:

1. All HF frequencies (1.8-30MHz)

2. Inrtion loss in range to max 3dB

3. Selectivity at harmonic related band in range of 30dB

4. input/output impedance 50 Ohm

5. coils with fixed inductance without taps

Tunable bandpass filter realization is very simple and compact made in one box bad on

PCB soldering ,it is important to notice that double variable capacitors(both connection)

are isolated from the ground. Inductors are made with toroid core but I tried BP filter

with fixed molded chokes and results are similar except little bigger inrtion loss (e

example diagram for filter 3.5 MHz). It is possible becau working Q in banpass filter is

small and nsitivity to component values is small too. It is possible to realized HF filter

with only 2 coils (for example toroid T50- ) with taps but it is not recommend for un

experienced builders. Filter schematic diagram is at the picture below , toggle switches

S3,S4 is possible to change with one SPDT with one neutral position. It is possible also to

u fixed values for C and L to make filters according to given component values.

0-10-20-30-40-50-600.001BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf0.028485 GHz -1.1395 dB0.014056 GHz -31.83 dB0.0110.0210.031Frequency (GHz)0.0410.05FILTER 28MHz

L=1.8uH Q=100

Cvar=20pF

C1=150pF

0.024941 GHz -0.61642 dB0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-10-20-30-400.01248 GHz -28.149 dB-500.0010.0110.0210.031Frequency (GHz)0.0410.05

FILER 24MHz

L=1.8uH Q=100

Cvar=25pF

C1=150pF

0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf0.021089 GHz -0.23435 dB-10-20-300.010191 GHz -24.194 dB-40-500.0010.0110.0210.031Frequency (GHz)0.0410.05

FILTER 21MHz

L=1.8uH Q=100

Cvar=36pF

C1=150pF

0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphf0.021138 GHz -1.7125 dB-20DB(|S[2,2]|)bphf-40-600.010424 GHz -35.04 dB-800.0010.0110.0210.031Frequency (GHz)0.0410.05L=1.8uH+1.2uH Q=100

Cvar=21pF

C1=150pF+100pF

0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphf0.018047 GHz -1.1095 dB-20DB(|S[2,2]|)bphf-400.0090646 GHz -32.08 dB-60-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILTER 18MHz

L=1.8uH+1.2uH Q=100

Cvar=28pF

C1=150pF+100pF

0BPHF0.014061 GHz -0.41101 dB-20-40DB(|S[1,1]|)bphf0.0070685 GHz -24.946 dB-60DB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILTER 14MHz

L=1.8uH+1.2uH Q=100

Cvar=50pF

C1=150pF+100pF

0BPHF0.0101 GHz -0.48722 dB-20-40DB(|S[1,1]|)bphf0.0050027 GHz -20.898 dB-60DB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILER 10.1MHz

L=1.8uH+1.2uH Q=100

Cvar=88pF

C1=150pF+100pF

Alternative value

0DB(|S[1,1]|)bphfDB(|S[2,1]|)bphfBPHF0.018123 GHz -2.2242 dB-20DB(|S[2,2]|)bphf-40-600.0090255 GHz -35.189 dB-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILTER 18.1MHz

L=1.8uH+1.8uH Q=100

Cvar=24pF

C1=150pF+150pF

0-10-20-30-40-50-600.001BPHF0.014055 GHz -0.87851 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf0.0070925 GHz -29.837 dB0.0110.0210.031Frequency (GHz)0.0410.05FILTER 14MHz

L=1.8uH+1.8uH Q=100

Cvar=39pF

C1=150pF+150pF

0BPHF0.01015 GHz -0.90293 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-200.022247 GHz -35.701 dB-400.0050426 GHz -24.79 dB-60-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILTER 10.1MHz

L=1.8uH+1.8uH Q=100

Cvar=70pF

C1=150pF+150pF

0BPHF0.007 GHz -0.45532 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-200.014232 GHz -21.976 dB0.0035061 GHz -17.473 dB-40-60-800.0010.0110.0210.031Frequency (GHz)0.0410.05FILTER 7MHz

L=1.8uH+1.8uH Q=100

Cvar=155pF

C1=150pF+150pF

0BPHF0.0070111 GHz -4.2313 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphf-200.0035332 GHz -46.794 dBDB(|S[2,2]|)bphf-400.010104 GHz -44.312 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 7MHz

L=1.8uH+15uH Q=100

Cvar=32pF

C1=150pF+680pF

0BPHF0.0035647 GHz -1.8523 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-400.0070538 GHz -40.816 dB0.0018054 GHz -30.237 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 3.5MHz

L=1.8uH+15uH Q=100

Cvar=130pF

C1=150pF+ 680pF

0BPHF0.0035647 GHz -3.5791 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-400.0070538 GHz -40.857 dB0.0018054 GHz -30.274 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02Filer for 3.5 MHz same as previously but Q=50 typical value for molded chokes

0.0018054 GHz -1.6957 dB0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-200.0035647 GHz -20.266 dB-400.0070538 GHz -44.471 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02FILER 1.8MHz

L=1.8uH+15uH Q=100

Cvar=500pF

C1=150pF+680pF

0.0018054 GHz -1.9647 dB0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphf-200.0035647 GHz -22.993 dBDB(|S[2,2]|)bphf-400.0070538 GHz -46.409 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 1.8 MHZ

L=1.8uH+1.8uH+15uH

Cvar=500pF

C1=150pF+680pF

0BPHF0.0035647 GHz -1.9616 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-400.0070538 GHz -43.063 dB-600.0018054 GHz -30.109 dB-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 3.5MHz

L=1.8uH+1.8uH+15uH Q=100

Cvar=127pF

C1=150pF+680pF

0BPHF0.0070538 GHz -1.8931 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-400.0035647 GHz -40.551 dB-60-800.00010.00510.0101Frequency (GHz)0.014023 GHz -51.781 dB0.01510.02FILTER 7MHz

L=1.8uH+1.8uH+15uH Q=100

Cvar=29pF

C1=150pF+150pF

0.0035647 GHz -2.3348 dB0BPHFDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-200.0070538 GHz -32.297 dB-400.0017989 GHz -26.343 dB-60-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 3.5MHz

L=1.8uH+1.8uH+15uH

Cvar=118pF

C1=150pF+150pF

00.0035647 GHz -38.926 dBBPHF0.0070538 GHz -1.7349 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-40-600.014115 GHz -50.222 dB-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 7MHz

L=1.8uH+15uH

Cvar=32pF

C1=150pF+150pF

0BPHF0.010107 GHz -1.6923 dB0.0050506 GHz -39.563 dBDB(|S[1,1]|)bphfDB(|S[2,1]|)bphfDB(|S[2,2]|)bphf-20-40-600.02 GHz -53.847 dB-800.00010.00510.0101Frequency (GHz)0.01510.02FILTER 10.1MHz

L=1.8uH+15uH Q=100

Cvar=18pF (some variable capacitor can reach this value)

C1=150pF