BATC 8-band RF output switch - preliminary Version 3 parts list

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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M0JUR
Posts: 5
Joined: Wed Jun 08, 2022 2:40 pm

BATC 8-band RF output switch - preliminary Version 3 parts list

Post by M0JUR » Wed Jun 08, 2022 3:21 pm

Hello,

Since the relevant Wiki page still only provides the parts list for version 2.2 and older in spite of the BATC Shop only selling V3 PCBs for quite a while now, I have attempted to update the spreadsheet for the new version using the board layout and G8GTZ's hand-drawn circuit diagram as reference. Unfortunately I have run into two snags in the process, in any case I would very much like someone who knows what they're doing to double-check my revisions!

Anyway, as far as I could tell the simple changes are as follows:
  • changed resistance of R1 and R2 from 68 to 100 Ohm
  • changed resistance of R3 from 220 to 68 Ohm
  • changed capacitance of C16 from 1 to 2.2 pF
  • new resistors (presumably with the same package and power requirements as the old ones, given they are in the same circuit): R6/R8 - 150 Ohm, R7 - 36 Ohm
  • new capacitor (ditto) C17 - 1 nF
Does this make sense?

The snags on the other hand are as follows:
  • what, if anything, should the capacitance of C11 and C12 (which in version 2.2 ground, in parallel, the "top" terminal of L1) be in this version? In spite of being highlighted on the revised board layout they are not pictured in G8GTZ's diagram; this makes it somewhat unclear as to whether they should be left as-before like R5 (which the diagram simply pictured as a short), removed altogether, or something else;
  • the diagram doesn't mention the inductance of L1. Should it still be 220 nH? On the one hand, unless I've completely misread the documentation L1 is simply an RF choke on the amplifier's supply-voltage line so there should be no pressing need to replace it. On the other, if C11/C12 have changed then perhaps so should L1... Figured I'd better make sure.
Many thanks in advance for your feedback.

edit: clarify what the potential problem with C11/C12 is

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