Dan, AC6AO, has built a toroid version BPF using the existing STAR PCB's.

Adapter PCB's for this project, see end of page

Dan fitted the trim caps under the PCB on his STAR P1 build.

Expanding on this idea of using Toroids in the BPF, VK3PE has made available some small PCB's using Toroids in the BPF filters and then fitted over the appropriate band position on the Combo boards BPF section. NOTE: this is essentially experimental as VK3PE has not fitted a full set of these PCB's to his own STAR builds, but it is very similar to the Toroid version by Dan, in the link above. In fact, the winding information will be based on Dan's good work.

Below, is a 'modular' way to add Toroid type BPF sections to your STAR. This may be desirable if you are having difficulty in obtaining Toko or Lodestone formers for the original BPF.

These are small PCB's one per band, designed to stand vertically over the area where the Toko coils would have been fitted originally. You could in theory mix these PCB's with some bands still using Toko coils although for best results, the boards should be tilted over a little to get a lower profile and also to allow easier access to the trim caps.

There are some small solder areas on the top of each of the adapter PCB's which are intended to to be linked together across the top of a set of these PCB's in STAR with some tinned copper wire, to mechanically 'stiffen" the resulting boards. Input and output connections are made by wire links to the BPF section. It might be best to also hot melt glue the Toroids to the PCB for mechanical stability also.

The values for each BPF are identical to that in the documentation for PICASTAR BPF's. But in this case, the Inductors are fixed and trim caps used to tune the filters. You could of course spread turns on the Toroids to achieve tuning but it would be tedious to do, especially if you do not have a means to sweep the filter, like a VNA for example.

The sample below is a home etched PCB made by VK3PE and set up for the 40M band. In this case, the trim caps are the only series 'C' value. In practice, one would select a fixed capacitor and use a trim cap in parallel, to allow a small (fine tune) adjustment of the total C value.

The proto 40M filter for example. 'Yellow' caps were used, other values may be more

appropriate. Sweep of this 40M band filter. Tuning not final.



Dan also made one of these PCB's to try on 10M, see below. Dan used some SMD trim caps but the PCB is designed to use the Murata type of trim caps as these seem to be available all over the world to hobbyists. The pig tails at the bottom are intended to mount through the Toko can ground points. On top of the PCB you can see the three little pads intended to be linked across to other boards with tinned copper wire, to stiffen them up. i.e. mechanical stability. This may or not be required.



PCB availability. VK3PE will be doing a small once off, group buy of a set of 10 of these little PCB's. (approx. 1.1" x 1.5")

Approx. AUD$21 including postage

Contact VK3PE for more information. (Link on other pages.)

June 7th, 2013:- This is how the 'Pro' made pcb's look. The group buy was a panel of 10 of these little boards. ie some spares included.

The component reference numbers are NOT those from PICASTAR.


DRAFT Winding details. [Thanks to Dan, AC6AO]

Wire size needs to be determined. Usually, the size should allow the winding to be made without winding over any already wound section. ie avoid scramble windings.

Inductance values should be measured and adjusted to the values given in the PICASTAR BPF schematics.


1.25 ?H 19t T37-6 270 degrees
1.67 ?H 23t T37-6 300 degrees
7.15 ?H 42t T30-6 Full core
16.7 ?H 58t T50-2 Full
24.5 ?H 69t T50-2 Full
0.25mm wire
25 ?H 69t T50-2 Full
0.25mm wire
12.5 ?H 50t T50-2 Full
41 ?H 88t T50-2 Full


Murata™ Trim Caps are the suggested type of trimmer to use.


6.2 - 30pF Trimmer Capacitor - Green

3 - 10pF Trimmer Capacitor - White

6.8 - 40pF Trimmer Capacitor - Yellow

9.8 - 50pF Trimmer Capacitor - Brown



Page created by VK3PE on 21st April 2013