I'm quite pleased with the multi and single-channel filter/combiner design and flexibility this gives you. I've had my prototype BB-6 running on four bands (80/40/20/10) using the 4-band combiner, since I've got an antenna that works on those bands (an off-center-feed dipole). And yesterday I put up another off-center dipole for 30 and 15 meters (the OCF Dipoles resonate on even harmonics, rather than on the odd harmonics of a normal dipole). I used my single-band filters for 30 and 15, connected the outputs together and fed the new antenna from that. So now I'm transmitting FST4W simultaneously on 80/40/30/20/15/10 meters (that's six bands)., one Watt on each band, using two antennae.
These filters are designed to have high input and output impedance out of band, which allows them to operate in coupler mode without significant interaction. You couldn't do that with a traditional pi-LPF. The filters also include a deep 3'rd harmonic notch, which lets you transmit a clean signal when driven by the Digital One-Watt Amplifier. To allow the use of standard surface-mount components and still maintain low-loss, the combiner filters are broad, and the combiner needs to have the channels spaced by an octave or more. It is certainly possible to hand-build narrower filters (toroids, etc.) should you want to combine closer bands.
Yes, this system is almost entirely digital -- the GPS and reference-clock inputs, and the clock-generator chip are semi-analog, but most of that's hidden inside those off-the-shelf chips. All ham band frequency-sensitive components are external to the box, these being the filter/combiners. This gives us maximum flexibility, and there is no customization needed inside the BB-6 box.
Here is Phil's obit: https://rumsey-yost.com/2023/06/philip-phil-norman-anderson/
Steve, thanks for this nice mention!
I'm quite pleased with the multi and single-channel filter/combiner design and flexibility this gives you. I've had my prototype BB-6 running on four bands (80/40/20/10) using the 4-band combiner, since I've got an antenna that works on those bands (an off-center-feed dipole). And yesterday I put up another off-center dipole for 30 and 15 meters (the OCF Dipoles resonate on even harmonics, rather than on the odd harmonics of a normal dipole). I used my single-band filters for 30 and 15, connected the outputs together and fed the new antenna from that. So now I'm transmitting FST4W simultaneously on 80/40/30/20/15/10 meters (that's six bands)., one Watt on each band, using two antennae.
These filters are designed to have high input and output impedance out of band, which allows them to operate in coupler mode without significant interaction. You couldn't do that with a traditional pi-LPF. The filters also include a deep 3'rd harmonic notch, which lets you transmit a clean signal when driven by the Digital One-Watt Amplifier. To allow the use of standard surface-mount components and still maintain low-loss, the combiner filters are broad, and the combiner needs to have the channels spaced by an octave or more. It is certainly possible to hand-build narrower filters (toroids, etc.) should you want to combine closer bands.
Yes, this system is almost entirely digital -- the GPS and reference-clock inputs, and the clock-generator chip are semi-analog, but most of that's hidden inside those off-the-shelf chips. All ham band frequency-sensitive components are external to the box, these being the filter/combiners. This gives us maximum flexibility, and there is no customization needed inside the BB-6 box.