prophecyTUNABLE 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
猪的英文
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:
研讨会英文
1.All HF frequencies (1.8-30MHz)
2.Inrtion loss in range to max 3dB
清华大学总裁培训班3.Selectivity at harmonic related band in range of 30dB
4.input/output impedance 50 Ohm
参数英文
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
leadsS3,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.
FILTER 28MHz L=1.8uH Q=100
Cvar=20pF
miffy
311是什么意思FILER 24MHz L=1.8uH Q=100 Cvar=25pF
C1=150pF
善良的小峓子在线观看中文翻译
FILTER 21MHz L=1.8uH Q=100 Cvar=36pF
C1=150pF
L=1.8uH+1.2uH Q=100 Cvar=21pF
小样本C1=150pF+100pF
