I only have a few years of rove experience but have found the following
issues to be important concerning DC supply systems:
1. I chose not to power radios off the vehicle starting system battery. I
wanted to concentrate on filling the log without the paranoia of wondering
if my vehicle would start! I did allow the vehicle charging alternator (100
amps) to charge my station secondary battery system. I kept the starting
battery system separated from the radio battery system using a solenoid
switch which performed better than the solid state switches (isolators).
2. I chose a pair of 6 volt flooded lead acid golf cart batteries and
placed them in series. These batteries are seriously heavy duty and have a
deep reserve. I used a number of high power TE Systems amplifiers which
typically drew 54 amperes. I blew a few fuses but never ran down those
golf cart batteries.
3. After years of resistance (no pun intended) I was finally convinced to
use a battery booster. My resistance was overcome once I realized that the
value of the battery booster was not to boost voltage but to regulate the
DC bus voltage to a 13.8 volt value. I found that much of my gear, and
particularly the amplifiers mentioned above were much more sensitive to
fluctuations in DC supply voltage than I thought. They produced about half
rated output power when the DC supply dropped from 13.8 to 12.0 vdc. This
was not just caused by the amplifier itself but everything in the transmit
chain: IF radio, transverter and power amplifier. The effects combined
because the DC supply fluctuations cumulatively affected drive levels at
each stage. Without the battery booster the drop in supply voltage
occurred just at the wrong time too: When I had turned off the engine to
reduce vehicle noise so I could work the weakest and most distant stations.
4. It's important to fuse each load with an appropriate protection fuse
but not to place fuses in series. Each fuse has a voltage drop, and
several in series can produce a serious deficiency in the supply voltage.
In my experience, most short circuits do not occur inside the equipment
chassis but are commonly caused in DC supply wiring. If you use a secondary
battery system fuse both the positive and negative leads
5. Use a single point DC ground on the vehicle chassis.
Hope this helps. Bill W7QQ
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|