Some good developments here over the weekend. On Friday afternoon I added new elements to a 20m dipole in the loft to give me a multi-band parallel-fed dipole covering 20m, 17m, 15m and 10m bands. This is in addition to the ~25m horizontal loop I have around the perimeter of the loft coupled with my SGC SG-211 battery ATU at the feed point. The current setup looks something like this:
The dipole elements have been spaced away from each other to minimise the interaction between them but with no particular attention to orientation – experience from the 20m dipole over the last month or so doesn’t show much of a dipole pattern so I expect the shallow-V profile and the unavoidable loft clutter (wiring, light, water tank, etc…) to make it broadly omni-directional.
Dipole element lengths have been adjusted (with the help of a borrowed MFJ-259B analyser) to suit the low end of the bands for data modes and it’s fed by coax to a 1:1 balun. Performance looks reasonable so far and some QSOs have been made on all four bands including my furthest yet, 5500km deep into Russia on 17m.
Interestingly I changed some connections around to have a look at the level of co-site interference between my transceiver and the loft SDR receivers now I have two multiband antennas and noticed SWR on 20m and 17m rise above 2:1 on the dipole. Reconnecting both antennas back to the transceiver (through a 2-way coax switch) restored SWR to below 1.5:1 on all bands, as before. This had left one of the coax feeds unconnected and running close to the 20m and 17m elements so the dipoles appear to be very sensitive to their surroundings!