BATC Forum

I use the term QRO loosely - I have a 20 watt Stealth amp for 3.4GHz and was planning initially on using a small Log periodic built on FR4 PCB pointing into a small BSB offset dish...that is until it was pointed out to me that more than a couple of watts would quite likely let the magic smoke out out of the PCB.
Having had success with various Bi-quads in the past I used an on-line calculator to derive the relevant sizes https://www.changpuak.ch/electronics/bi ... signer.php and I then designed and printed a plastic jig to help get the wire bends in exactly the right place. A scrap of PCB as the reflector and a short stub of rigid coax to sma produced a solution. With minimal tweaking it showed as a 1:1.15 match on my nanoVNAV2, so I fitted it to the dish. Quite how well it illuminates the dish I can only guess, but allowing for the offset angle its definitely directional. How well it works in practice remains to be seen, but at least there's no FR4 in the RF path.
Comments welcome, especially if I can improve on it.
As it stands the dish needs using on its side for horizontal radiation but its easy to mount and line up.
Gareth

Looks good. The feed will probably over-illuminate the dish. A few directors would help but possibly not worth the effort. Is it vertically polarised?

Mike

This website https://martybugs.net/wireless/biquad/ (scroll down) suggests a -3dB beam width of around 50 degrees and as shown in my picture, its vertically polarised, hence in use |I'll rotate the dish 90 degrees which suits the mounting method - it came with a 90 degree bend pipe for mounting vertically.
A year ago I built a double bi-quad (detailed here https://martybugs.net/wireless/biquad/double.cgi) and that seems to be a good match. Field testing next to see if either are any good. https://martybugs.net/wireless/biquad/double.cgi
Gareth