Latest Backpack Build September 2021
2 min read
The Latest HF backpack set up was initially constructed from a very rusty ex Military Clansman backpack …
The rusty metal backpack was rubbed down and rust treated and then given two coats of hammerite black paint and replacement webbing straps were fitted …
Lightweight brackets were made to support the Alinco DX-70TH transceiver to a 3mm aluminium plate that was fastened to the frame and significant cross structure bars were added to strengthen and support the set up …
A 12V 22Ah lightweight lithium polymer battery was chosen to power the system and this is strap mounted in the centre of the backpack in order to retain a good weight balance, the DC output to the radio is fed via a resettable 20A breaker…
The ground tuning unit (GTU) is mounted under the antenna base and is a toroidal version of my previous tuning units to provide necessary ground coupling…. The mirror mount 3/8″ antenna base is clamped but insulated from the Clansman frame, twin headphone sockets were added to the lower part of the metal backing plate.
More information re ground tuning https://www.g4akc.co.uk/ground-tuning-units-gtus/
The antenna is a stainless steel sleeved MFJ-1979 full sized quarter wave vertical which is adjustable in length to be resonant for all bands from 10 to 20M inclusive at its full length for 20M it is 17ft long.
A parallel charging socket was added to charge the LIPO battery and an LDG Z100 plus auto ATU was added to facilitate impedance matching over differing terrains.
The total weight is around 20 pounds and is easy to carry and feels well balanced.
The 22Ah battery provides several hours of solid operation on 50W
The charger is a dedicated LIPO charger and is fed via an IEC type connector.
The backpack will also fit on my tricycle for transportation purposes and removed for backpack operation.
Dave G4AKC
