EME209 HF Low Pass Filter Kits
The Mini-Kits EME209 Low Pass Filter modules are part of the M1 series building blocks to construct a high performance M1 HF Transceiver. The filters have been designed to be able to be used on the output of 100 Watt amplifiers, and cover all the 160M to 6M bands excluding the 30M band. The PC Board has been designed to fit two separate relay switched low pass filters so that a number of bands can be covered with each module board. This allows constructors to just purchase the filters for the bands that they want to transmit on, and the boards are also stack able which saves space. The rejection up to 50MHz is greater than 50dB, and decreases to 30dB at 100MHz which is probably due to capacitance when stacking the module boards.
The LPF-4M1-7M3 band module has a 4.1MHz low pass filter for the 80M band, and also a 7.3MHz low pass filter to suit the 40M band. The LPF-19M-30M band module has a 19MHz low pass filter for the 20M/17M bands, and also a 30MHz low pass filter to suit the 15M/12M/10M bands. The LPF-2M-54M band module has a 2MHz low pass filter for the 160M band, and also a 54MHz low pass filter to suit the 6M band. The basic filter designs are 5 or 7th order Elliptical designs, and have been optimized using the Elsie Filter software and tested using a DG8SAQ vector network analyzer. The filters input and output impedance have been matched for 50ohms, and have low RF loss in the filter pass band for low heat dissipation when used with 100 Watts CW. See the M1 Transceiver Block diagram for the connections to this module.
The M1 HF Series Kits have been designed to allow easy construction due to the use of mainly leaded components for those that don't like surface mount devices. Larger 1206 size SMD components are used for the filters as they are more easily obtainable in high voltage NPO type. RF modules are all designed with a 50ohm impedance making it easy to interconnect with the other M1 series modules, and your own home brew circuit designs.
1/ There are no current alerts.
The images below show both sides of the board. The module uses a number of SMD capacitor that could not be avoided as it makes the module more compact and offers better performance. The capacitors used for the filters are all 630v NPO 1206 size SMD types for low loss and for RF power handling. The inductors for each filter need to be wound with the correct number of turns as per the Kit construction notes to work correctly. There is some minor issues when stacking modules that increases the capacitance on the RF input and output connections to ground, and this can affect the return loss above 100MHz with the 54MHz LPF. It appears that the modules can be stacked in any order without any issues with coupling of the toroids between filters that could affect the filters response.
1/ The module that is used in the middle of the stacked modules is called the first filter module and has SMA connectors and a right angle 16 way header connector for the logic control fitted.
2/ M3x12mm nylon spacers are used to stack the module boards. There has been no measured difference with RF losses or impedance mismatch when nylon spacer are used to save cost.
3/ The modules extended headers will require and extra header stacked when using the longer 18mm nylon spacers. The pins on the extra stacked headers will need shortening by cutting around 2mm from the pins so that when stacked are then flush.
The LPF-4M1-7M3 contains two low pass filters to suit both the 80M, and 40M bands. The 80M band filter rolls off at around 4.1MHz, and the 40M band filter has a 7.5MHz roll off. These filters have been designed to be used on the output of 100 Watt amplifiers, and use low loss 630v NPO ceramic capacitors and wire wound high Q inductors to reduce RF losses.
The LPF-19M-30M contains two low pass filters to suit both the 20/17M, and 15/12/10M bands. The 20/17M band filter rolls off at around 19MHz, and the 15/12/10M band filter has a 30MHz roll off. These filters have been designed to be used on the output of 100 Watt amplifiers, and use low loss 630v NPO ceramic capacitors and wire wound high Q inductors to reduce RF losses.
The LPF-2M-54M contains two low pass filters to suit both the 160M, and 6M bands. The filters are a combination of Chebychev and Cauer ( Elliptical ) design, which are tuned to reduce the second harmonics to a lower level compared to conventional designs. 160 Meter band filter is a 2MHz 7th order Chebychev rolls off at around 2MHz, and has a tuned notch at 4MHz. The 6 Meter band filter is a 5th order Chebychev with a 54MHz roll off, and has a tuned notch near 100MHz. The 160M Band filter has been designed for 100 Watts, and the 6M Band filter is probably OK to 50 Watts maximum. Both filters use low loss 630v NPO ceramic capacitors and wire wound high Q inductors to reduce RF losses.
1/ There are currently no issues with these Kits.