114 MHZ High-Pass Filter - DIY KIT
Good to 500 MHZ
Handles 100 W on TX
DIY KIT complete with box, N-type connectors and all parts
It eliminates strong broadcast FM transmissions at 88-108 MHZ from coming into a 2 m/70 cm transceiver.
It helps lower receiver noise and IMD products so receiving weak wanted signals is much more possible. On Tx, it is transparent up to 100 Watts.
Since it is easy for hand soldering, it is offered as a DIY KIT of parts which includes all the components, the box (80x25x25 mm) and the N-type connectors, one male and one female.
The capacitors are rated at 630 V or 1 KV and the square formed inductors at 4.5 A. A high quality PCB is also supplied which fits inside the box perfectly just between the two connectors.
Two ground connections to the PCB from each connector is only required and this is done using a high power soldering iron and copper braid (supplied).
This filter KIT is offered in two variations, the first with the cut-off at 114 MHZ and the second at 134 MHZ. The main difference is the rejection of the FM Broadcast band which is -7 dB at 108 MHZ and - 50 dB at 88 MHZ for the 114 MHZ filter, while it is -36 dB @ 108 MHZ and - 50 dB at 88 MHZ for the134 MHZ filter. The rejection is deeper for the 134 MHZ filter. Another difference is that the insertion loss at 144 MHZ is about half a dB lower with the 114 MHZ filter. So depending of how much attenuation is required of the FM broadcast band the user can make his choise which also affects the maximum power handling. An insertion loss figure of 0.5 dB at 145 MHZ or at 435 MHZ, means that if transmitting with 50 W then 5.5W will turn into heat.