It’s been a long slow process but today I finally finished installing the G4DDK 23cms VLNA at the masthead. The extended timeline was partly due to some other improvements that needed to be done to the 2m EME setup and the availability of some reasonably priced right-angle N-type connectors for LDF4-50. With the assistance of Roger, EI8KN I was able to complete this initial work.
Ideally to minimise the losses the box housing the VLNA and TX/RX relay would be mounted right at the driven element (DE) on the Wimo 67 element long yagi. I know of one EME station that has done this but a lot of extra support was needed to keep the yagi boom straight and to not have the antenna break in strong winds.
My solution has been to mount the box on the support brace and have a 2.15m length of LDF4-50 between the relay and DE. To keep the losses to a minimum the LDF4-50 passes through the wall of the box and connects directly to the relay also the input to the VLNA connects directly to the relay using a high quality SMA<>N-type adapter. The calculated loss for this arrangement is ~0.6dB. I used a large (25mm) plastic cable-gland to weatherproof the entry of the LDF4-50 into the box. This has the advantage that the N-type connector will pass through the internal securing nut which allows the complete VLNA box to be removed from the mast for servicing.
The VLNA box is secured to the 15mm square section brace with two short lengths of aluminium angle that sit either side of the brace.
The system uses separate TX and RX feeders. Currently Ecoflex 15 is used for the loop round the rotator and down to the base of the mast. I’m not sure on the use of this foil+braid type of cable for this part of the system and only time will tell.