Hedghog L is a homebrew standards converter. From a 625 line input it will generate 405 line or 819 line standards . It is coupled with a versatile programmable modulator that uses two MC44BS373.

This converter uses the Lattice iCE40HX1K FPGA. When compared to the FPGA's used in previous Hedghog's it is very small. The standards converter had to be heavily pruned back in order to get it to fit within the iCE40HX1K. While the standard of the output isn't up to the standard of previous Hedghog's it still gives a reasonably good conversion. In order to get more functionality multiple program images are stored in flash memory and loaded as required.


On this page you will find the files required to build it.

 All material including Downloads on these pages are provided 'as is' without warranty of any kind, either expressed or implied.



  • 405 line standards converter with 4:3 => 4:3, 4:3 => 5:4, 16:9 => 4:3, 16:9 => 5:4 aspect ratio conversion.
  • Selectable equalising pulses when converting to 405 lines
  • 405 line Test card
  • 819 line standards converter



  • Frequency coverage 28.5 to 900 MHz in 5 ranges
  • Frequency ranges and step:

        28.5   to 56.25 MHz  step 15.625 KHz

        56.25 to 112.5 MHz  step  31.250 KHz

        112.5 to 225 MHz     step  62.500 KHz

        225    to 450 MHz     step  125 KHz

        450    to 900 MHz     step  250 KHz

  • Selectable negative video FM sound or positive video AM sound
  • Selectable vision/sound carrier separation of 4.5, 5.5, 6.0 and 6.5 MHz  or when in positive video AM sound mode the video and sound carriers can be set independently(Variable mode)
  • Selectable picture/sound carrier ratio of 12 and 16 dB  or fixed at 6dB when in Variable mode
  • Can be used as a stand alone modulator


All Resistors, Capacitors and Inductors are 0805 size.

All Capacitors are ceramic multilayer types.

Where given manufacturers part numbers are given as examples alternative parts may also suit.

The PCB is double sided and measures 100 mm X 89.5 mm.

Link to uploaded Gerber files on PCBWay.




Menu description (.pdf)

Circuit diagram (.pdf)

Component list (.pdf)

Component layout top (.jpg)

Component layout bottom (.jpg)

Front and rear panel legends (.pdf)

FPGA program file (.mcs)

Microcontroller program file (.hex)



Hedghog L thread on Golborne Vintage Radio Forum


Hedghog II PCB top

Hedghog II PCB bottom