v9.0 and switched BPF module - 6m option
- Hi all,
Several weeks ago a question was raised about using the switched BPF module for the v9.0 when built with the optional 6m filter in the band 1 position.
There is a serious problem with the current build instructions and filter order. Fred PE0FKO and I discussed the problem, and whether it was worth looking into modifying the firmware to cope, however as there was not a single response to the message I posted, we assumed that it was not worth bothering and it appeared very few had tried or were interested in using this option.
The 'problem' is that using the 'ABPF' mode in the firmware (to give compatibility with Rocky), the filter cross-over switching points must be in ascending frequency order, currently defaulting to 4, 8, 16MHz.
As it stands the firmware will select the band 1 (6m) filter for frequencies up to 4MHz.
The current build instructions use band 1, for the 6m option, which causes the problem.
By far the simplest solution is for the circuit diagram and build instructions to be modified, and re-order the filters such that band 1 = 80/40 and the rest in order, with band 4 = 6m.
That solves the problem and means no messing about to produce a new version of the firmware (filter cross over points can be set at 8, 16, 30MHz), and all will work fine.
The only other option open to anyone who has already constructed their filter module is to use the 'BPF' mode and set the start and end frequencies for each band via the Winrad firmware set-up screens. That will provide a solution, however you will loose the ability to use Rocky.
So my advise to any constructors wanting to use the 6m option, ignore the current build instructions and make the filters:
Band 1 = 4 - 8MHz
Band 2 = 8 - 16MHz
Band 3 = 16 - 30MHz
Band 4 = 50MHz
73, Bob G8VOI