I previously posted about monitoring how long my vx8-dr would last on different types of batteries. One of the things that I noticed was that there is a relationship between battery voltage level and the output power but I had no way of watching what was happening. So I invested in a Diamond SX-600 SWR & power meter along with an MFJ-261 dummy load and re-ran parts of the battery test.
2,000 mAh lithium ion w/ power
This is pretty much what I would expect. As the power available from the battery goes down, the output power on the radio goes down.
AA alkaline w/ power
This, ladies and gentlemen, is utterly ridiculous! Starting with fresh AA alkaline batteries, the output is less than 1 watt and it quickly deteriorates from there.
I swapped out the AA alkaline for AA lithium ion and found a similar output power level. Since it started with less than 1 watt output power, I didn’t bother running through the whole test. This was not at all what I expected, The input power voltage level is critical for the vx8-dr to perform well.
My original intention was to use AA lithium ion and / or AA alkaline batteries as a backup power source for the vx8-dr in the event of an emergency. This now looks like a bad plan. Running on anything less than the lithium ion battery packs has a detrimental effect on output power. It might do as a backup to the backup power but I don’t think it’s a good idea to count on it.
Right now, I’m thinking multiple 2,000 mAh lithium ion battery packs, a charging dock and perhaps a solar panel to charge it all. Plus an automotive plug adapter. And a plug w/ anderson powerpole connectors.
This was an interesting experiment!
I was asked about the discrepancy between the maximum measured power out of 4.2 watts with the battery voltage of 8.2 and the published maximum of 5.0 watts. I have a couple thoughts on that though they’re not based in much more that aether.
- The published specs may be coming from theoretical maximums.
- The published specs may be coming from values measured in a lab under ideal conditions.
- Maybe the battery’s just not quite fully charged.
- The SX-600 power meter may be off calibration.
I did plug the radio into the wall wart that comes w/ the charger. The voltage showed at 10.8v and the output power at 4.3 watts. Using the automotive cigarette plug, the voltage shows at 12.8v and the output power was measured at 4.5 watts.
BTW, the manual for the vx8-dr has specs for the supply voltage maxing out at 12v.
From all this, I take the maximum output wattage as being 4.5 with a more typical of 4.0 to 4.2.