Clever piece of engineering or not? (Battery Tech)

ModCD posted the following on Element -14.

An ongoing project at my local radio club, the Ripon and District, has been to try and sort out the LF antenna. This is an end fed one, from the end of the bunker and it goes up to the eaves of the Town Hall. On the end is one of those “smart-tuner” units that’s been playing up. So whilst we were doing our 30th club birthday event, we let loose the menders.

We did find that the connection to the wire wasn’t very good, the connection for the 12V supply neither, and that the bolts holding it to the wall were siezed up. With those two little bits sorted it’d tune, but then the SWR would creep up even on low power. No it wasn’t the tree the wire goes through, after all the club is definitely a stealth affair, located in a bunker underneath the Town Hall lawn. After much messing the box came off the wall, and we had a look inside.

Possibly we’d like to introduce SGC to a product called threadlock and a device called a lock washer. These two items would be very good additions to the main antenna terminal, as tightening the terminal outside had allowed the threaded section to turn and not hold the nuts and tag on the inside end. The blob of silicone on the nut we found is not enough!

Using this antenna with a 9:1 balun and the rig’s tuner meant the noise level was S7 and very difficult to work anything.

Also done in the day was to make a copy of my own 80m antenna. It has loading coils about 2.5m each side of the dipole centre to make it a lot shorted than a full sized dipole as I’m kind of short of room. Even so this does escape the garden and attached to the drainpipe of the other block. It used to go to a tree, but after the incident with the neighbour’s dish, I relocated the VHF mast. I also added a pulley to the fitments, making putting the loaded dipole up a ten minute job rather than a complete takedown job. The coil was put on the LC meter and came out at 48uH, a tad less than the 55uH I thought it was, but then I did adjust the tuning (ie length) to nip it to best at 3.600MHz.

Using a shortened antenna and low down (20ft/6m up, inverted V) gives a lot up into the sky, and being 80m straight back down. Just the job for the RSGB 80m Club Championship in which we came 8th – not bad as we don’t have a vast number of members or ones that can do all of the modes. Being “up north” does not help either as it seems the majority are “down south”. If you do check the calendar, you’d see there are CW, SSB and data sessions, and it all goes mad for the time, then goes quiet again.

I have discovered that all this high-tech battery technology doesn’t like cold weather. The ones that keep going are the alkaline and the SLA ones, all these fancy Li-ion ones don’t like getting chilled. Anyone else found this?

Chris Pinter responded with:

You bring up a good point that I think many amateur radio buffs forget to think about; the consideration of the environment in which the radio needs to work in.  Battery technology is not created equal.   You need to look at the environment and the intended application before you select the battery technology.

The reason why Lithium -Ion batteries were developed was to solve a very specific problem.  The first cellular telephones would develop a memory of a charge as the battery was used.  Many people would charge a battery when it was convenient to do so not when the battery really needed a charge.  They would come home after the days activates and plug in their phone.  This would change the chemistry inside the battery and degrade the level of charge the battery could hold.

You cannot blame Lithium -ion batteries for the issues you are describing.  The applications you are describing need a very specific battery for the intended purpose.  You need to look into cold weather batteries.   These are often military specification batteries however they are available to consumers as well.

A good lithium cold weather battery is the made by Tadiran or Saft.

http://www.tadiranbat.com/

http://www.saftbatteries.com/

Both manufactures have many different sizes and typically have potentials of 3.6V to 4.1 V and can hold a charge typically double that of a standard lithium battery.  This is often the first battery I look to when I am designing a small or portable radio for industrial and military applications.   The AA (3.6V) batteries are available at Radio Shack if you want to test one to see how it works.

http://www.radioshack.com/product/index.jsp?productId=3145893

Hope this helps.

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