12 volt battery, Redback 30, 30th March 2017

Front view showing voltmeter

The photo above shows a front view of my Redback 30 ‘thumper’. Andrew, VK1AD, requested a picture and description of this battery which can be seen on the ground in a photo (of me holding the squid pole) of my post about Scott Conservation Park. Here is a link to that activation:

https:///vk5bje.com/category/scott-conservation-park/

I activated this Park on two days early in March while attending a wedding at Port Elliot. The battery pack is made at Mount Barker SA and contains two gel cell 12 volt batteries wired in parallel to provide a 33 amp hour battery. It is very well made as you can see from the photos. It is all held together by substantial screws and rivets. It has a handle on the top which makes carrying the battery quite easy, and as it is a mere 33 amp hour pack, it is not too heavy. Paul, VK5PAS, told me about the shop at Mount Barker and the business has a good range of 12 volt equipment. I use my battery to augment but not replace my LiFePO4 batteries. On our interstate holidays it is not always possible to charge batteries where we stay, particularly if I miss charging them for a day or two. The ‘thumper’ can be charged while in use using solar cells, providing of course that the sun is shining!

input end 75 amp hour Anderson connector

The photo above shows the input end or charging end. 75 amp Anderson Power pole connectors are used and I simply grip each connector with a cable equipped with alligator clips observing correct polarity. I use a five amp hour smart charger which is quite small and easily packed in my gear.

end view showing 50 amp hour Anderson connectors

The output end is equipped with double 50 amp hour Anderson Connectors. I have made up adapters which I add to the 30 amp hour connector when I use this battery rather than a LiFePo4 battery. I usually set my radios to 20 watts and this battery will last a full 44 contact activation for WWFF at a park. The other advantage of this battery is that I can, and occasionally do, operate at 40 watts on the 20 metre band and it does this well. Having a volt meter on the front of the battery is of great assistance. I never take the battery below 11 volts: hence my reminder on the front panel. 11 volts is slightly higher than the manufacturer recommends so I have a safety margin.

Advertisements

My equipment

In recent times I have renewed my interest in portable operation specifically using QRP radios. My equipment is an FT817 and a Ten-Tec Argonaut VI. My antenna is a home made linked dipole for 20 and 40 metres together with a light weight SOTA linked dipole from England.

My linked dipole is rugged and great for parks use and probably alright for a summit as well. I use Mark’s (Tet-Emtron) dipole centres and the Kevlar centred wire. This wire is very strong and light and does not kink. Its construction is similar to coax. There is an outer plastic insulating cover, a mesh conductor (braid) like the shield in coax and the centre contains the Kevlar. My approach to soldering this wire is based on a few experiments. Where the wire goes inside the Power Pole lugs I stripped the outer insulating material off to the correct length, then pushed the braid back and very carefully, using side cutters, trimmed three millimetres of Kevlar off allowing me to then twist the braid into a point or spade shape. I lightly tinned this and then placed the Power Pole lug over the wire and applied a hot iron to that point on the lug where the cylinder containing the wire gives way to the spade. The solder flows through the cracks. I then run the iron down the join on the cylinder to complete the assembly. You will notice that the soldered joints are not load bearing. To erect the antenna slide the dipole centre hole over the squid pole ensuring that the SO239 is facing down. Attach the coax before pushing up the squid pole.

I have two ways of mounting a squid pole. The first is to use a PVC plastic sleeve slightly larger than the base of the squid pole and lash the sleeve to a post, rock, fixed picnic table or something similar. The sleeve protects the base the squid pole from being crushed. The second method is to mount the squid pole on a tripod (in my case a speaker tripod from Jaycar). You can see this approach in some of the pictures. I have made a bracket that fits over the top of the tripod and this contains two baluns for antenna experiments. On occasions with light winds I do not need to guy the tripod or squid pole, but if the winds are reasonably strong I guy the whole assembly. You can see this in the picture of the Cooltong CP activation.

Tet-Emtron dipole centre

Tet-Emtron dipole centre

Front side of dipole centre

Link assembly (20 & 40m)

Link assembly (20 & 40m)

Well you might ask, what’s the difference between an FT817 and a Ten-Tec Argonaut VI as far as portable QRP operation is concerned? The major differences between the two transceivers are as follows: the receiver in the Argonaut is better and less prone to suffer from strong signals near by (5 KHz or less)  and second, the Argonaut has a splendid variable width SSB filter, which is really effective. There are many other differences, but the ones that count are the Argonaut has a speech processor, the current drain is less for receive, the display is larger and visible in bright light (using the default colour of blue) and the DSP is excellent. However, it is a little larger than the FT817 and, while it is rugged, it is not as suitable as the Yaesu as a back pack radio. I have fitted the 2.4 KHz SSB filter to my FT817 and it does improve receiver performance. I like both radios and will admit my comments are entirely subjective!

Front view of Argonaut & FT817

Front view of Argonaut & FT817

Side view

Side view