Introducing the HAMtronics.uk Band Pass Filters, which are based on a 3 section Butterworth bandpass filter. This design minimises insertions losses, produces a flat response across each band and maintains close to a 50 Ohm impedance. Each one is built by hand in the UK by myself, tested and tuned to ensure correct frequency filtering for each band. All the cores are then secured in place with hot glue once tuned to ensure the odd knock and bump does not alter their frequency response.
I use high-quality components sourced from Italy. T68-6 Torrid cores and number 20 enamelled wire for the inductors and all capacitors are 500v(or higher) 1% Silver Micra Caps, which are not cheap! This allows continuous 100Watts of power to be used safely without any significant heating of the cores.
The cases are aluminium die-cast boxes providing good solid protection and rf shielding of the components inside which are all mounted on a proprietary custom-designed PCB board.
Connectors are SO239, allowing connection with standard PL259 feeder cable. These should be placed in between your Radio and any external ATU. If no ATU is used then simply place in between your radio and antenna (at the radio end!).
These are perfect for your portable setup, ensuring that there are no more “20m is wiping me out” shouts across the field when multiple stations are operating together at a field event.
Currently available for 20M & 40M Bands, (80M to be launched shortly) other bands will be added over the coming weeks once I have tweaked the production process.
Here are some of the charts showing the filter frequency sweep and the VSWR of at the centres of the bandpass.
40M VSWR & Bandpass chart
20M VSWR & Bandpass Chart
Units can be purchased with an optional premade patch lead, simply add to your basket before checking out. Please note I try to keep a stock of pre-built units ready to ship immediately, however as these units take time to build and test, it may take a few extra days from time of order to ship units to you(you will be notified at the time of order if they are on backorder or in stock ready for immediate dispatch).
All units are sent 1st Class Signed for delivery via Royal Mail, please note currently I only ship these units to the UK.
As these units require parts shipped from both Europe and China, HAMtronics.uk will donate £1 from the sale of every unit to a tree-planting charity in order to offset some of the carbon footprint from making these units.