I bought a new SdKfz 250/3 from Heroics & Ros to replace the one which was first painted in Afrika Korps Airfix desert yellow (that's how long ago it was!) and the new one came with a frame aerial so I decided to have a go at making some for the SdKfz 223s & 263's. The workbench photos were taken on my phone, sadly.
I've got loads of single strand wire (probably steel) from out of telephone cabinets for model railway wiring (the multicoloured insulation makes it easy to trace it under the layout). About 0.5mm in cross-section it was the thinnest I had.
Some square jawed pliers made it easy to get good corners by simply pulling the wire tight
I tried putting in the slight angle towards the front of the frame but it was difficult and just looked wonky, so I just bent the sections into rectangles, butting together on a short side and a blob of superglue bridged the gap.
A 1mm drill bit was the smallest I had so I used that in a pin drill to make locating holes for the supports.
The supports initially stuck out perpendicular to the body panels. I realised that if I left the insulation on, the supports fitted the holes better but the wire needed supergluing in place or it could twist within the insulation.
Supports were bent to the vertical for the 223s or at suitable angles for the 263s and reglued where it had come loose.
A good way to get the supports on the SdKfz 223s level for the reasonably horizontal frame was to upend them and snip off the excess.
Frames were perched gingerly on top and half droplets of glue applied (I didn't have the gel variety). (The insulation was a bit long in places but once painted, it disappeared).
The aerials for the 8-rads started off rectangular, then a longitudinal central section was dropped in & glued. Cross pieces between the vertical supports were omitted as they were only about 3mm long and were too fiddly for me. The whole was bent slightly over the curved handgrip of a pair of pliers, balanced atop the support and glued.
They all got 2 coats of Humbrol 27, an ink wash (1 drop black Windsor & Newton + 8 drops water + drop of washing up liquid) which was dabbed off, Humbrol 26 highlighting.
Trafalgar Models balkankreuz from Heroics & Ros were added where possible