I've recently resumed my interest in radio technology after seeing the "SDRPlay RSP" device featured on a popular electronics website. I bought one and then proceeded to be puzzled by the black magic that is Antenna Design.
A few small breakthroughs in understanding and I'm well on the way to taking the UK Foundation exam. More on that in the coming months hopefully.
In the last few weeks I decided to build a band pass filter for my portable receiver and antenna to attempt to improve my reception of the spectrum between about 100MHz and 160MHz by suppressing everything outside that range, which contains Airband and some interesting Ham traffic.
The schematic and a photo of the finished article ...
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To make this filter I used DipTrace to draw out the schematic which had already been tested using LT Spice software.
I then used DipTrace to generate a simple PCB design which I simply printed 1:1 scale on paper and used a scalpel to cut out the bits of paper where the copper pads would be (rather like a paper solderpaste stencil).
Then I taped that paper stencil to a piece of double-sided copperclad board and used a marker pen to draw the copper pads onto the copper.
Removing the paper stencil, I then drew a set of lines on the copper that showed the copper areas that needed to be removed in order to separate all the copper pads from the surrounding areas.
With this pattern finished, I clamped the copperclad to the table of my milling machine and used a small abrasive grinding bit to cut away the copper.
Once that was done I removed it from the mill, cleaned it with acetone and then soldered all the components on and tested it for short circuits. There was one short where the grinding bit had left a tiny fragment of copper hanging over a pad but that was removed with a pair of tweezers.
Then I drilled a pair of holes in the copper board and mounted it into a die-cast aluminium Hammond enclosure to provide good RF shielding. To finish off, I added some panel-mount RF connectors and coax to feed the signal in and out.
And happily I can report that it does behave exactly like LT Spice said it would!
A few small breakthroughs in understanding and I'm well on the way to taking the UK Foundation exam. More on that in the coming months hopefully.
In the last few weeks I decided to build a band pass filter for my portable receiver and antenna to attempt to improve my reception of the spectrum between about 100MHz and 160MHz by suppressing everything outside that range, which contains Airband and some interesting Ham traffic.
The schematic and a photo of the finished article ...
To make this filter I used DipTrace to draw out the schematic which had already been tested using LT Spice software.
I then used DipTrace to generate a simple PCB design which I simply printed 1:1 scale on paper and used a scalpel to cut out the bits of paper where the copper pads would be (rather like a paper solderpaste stencil).
Then I taped that paper stencil to a piece of double-sided copperclad board and used a marker pen to draw the copper pads onto the copper.
Removing the paper stencil, I then drew a set of lines on the copper that showed the copper areas that needed to be removed in order to separate all the copper pads from the surrounding areas.
With this pattern finished, I clamped the copperclad to the table of my milling machine and used a small abrasive grinding bit to cut away the copper.
Once that was done I removed it from the mill, cleaned it with acetone and then soldered all the components on and tested it for short circuits. There was one short where the grinding bit had left a tiny fragment of copper hanging over a pad but that was removed with a pair of tweezers.
Then I drilled a pair of holes in the copper board and mounted it into a die-cast aluminium Hammond enclosure to provide good RF shielding. To finish off, I added some panel-mount RF connectors and coax to feed the signal in and out.
And happily I can report that it does behave exactly like LT Spice said it would!