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--- blog:2020-04-12:power_cable_resistance [2020/04/12 23:14] – created va7fi
+++ blog:2020-04-12:power_cable_resistance [2020/08/07 13:03] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== Power Cable Resistance ======
-At home, my radio station is all crammed in a very tight space so the main battery bank is in the container about 55 ft away.  A few weeks ago, I purchased a [[blog/2020-03-28/n8xjk_super_booster |N8XJK Super Booster]] to keep the voltage at the radio constant when the battery voltage drops too low.  So far, I'm very happy with it.  The main advantage for me is that the booster helps get around the voltage drop in the 55 ft long cable between the battery bank and radios during transmit.  Here's a schematic of my setup:
+At home, my radio station is all crammed in a very tight space so the main battery bank is in a detached container about 55 ft away.  A few weeks ago, I purchased a [[blog/2020-03-28/n8xjk_super_booster |N8XJK Super Booster]] to keep the voltage at the radio constant when the battery voltage drops too low.  So far, I'm very happy with it.  The main advantage for me is that the booster helps get around the voltage drop in the 55 ft long cable between the battery bank and radios during transmit.  Here's a schematic of my setup:
 {{  :blog:2020-04-12:radio_diagram_20200328.png  }}
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 </WRAP>
-The slope of the line is the resistance since: $R = \frac{\Delta V}{\Delta I}$, which in my case is 0.09 Ω.  Note also how much power is loss in the cable.  The booster helps maintain a constant 14V at the radio, but the total power used can be much higher because of the loss in the line.
+The slope of the line is the resistance since: \$R = \frac{\Delta V}{\Delta I}\$, which in my case is 0.09 Ω.  Note also how much power is loss in the cable.  The booster helps maintain a constant 14V at the radio, but the total power used can be much higher because of the loss in the line.
+A trick to help reduce this power loss is to add a smaller battery in the house.  The idea is that during transmit, some of the current will be drawn from that smaller battery.  Since less current will flow through the longer cable and the voltage drop will be reduced, the power loss will also be reduced.  Here's the same table again when the small battery is connected:
+<WRAP indent>
+|<10px >|
+^ ^Current (A) ^Voltage Drop (V) ^Power Loss (W) |
+|5W    |2.8	|0.5	|1.4 |
+|12W   |4.8	|0.6	|2.9 |
+|25W   |5.2	|0.6	|3.1 |
+|50W   |7.3	|0.6	|4.4 |
+|100W  |10.8	|0.7	|7.5 |
+|>100W |16.7	|0.8    |13 |
+</WRAP>