Topband: ZJ Electronics Beverage Box and Power Supply - Help Needed

[Pete Smith N4ZR]

I am trying to repurpose a ZJ Beverage Box's DC power coupler to support 
a Beverage hub with remote preamp, and have run into a problem.  The DC 
supply is extremely "un-stiff."  With no load, it delivers close to 25 
volts, while under minimum load it quickly drops to only about 9 volts.  
Add a little more load (one relay) and it goes to 7volts and relays 
start not actuating.

I looked inside the box and find a 240 ohm 1-watt resistor in series 
with the 12 VDC wall-wart supply, and a 2200 uF electrolytic from the 
output side of the resistor to ground.  There is an additional 22ohm, 
1/4 watt resistor in line before the DC gets to the antenna port.

I thought that the two crucial components of such a "bias tee" were a 
capacitor to keep the DC out of your receiver and an RF choke to isolate 
the RF signals from the DC supply.  The cap is there, but there is no RF 
choke, and if Dr. Ohm was right, the big resistor is dropping the output 
voltage much too much.  I'm guessing maybe ZJ put it in there to protect 
the antenna-end electronics by dropping the voltage as soon as any load 
was applied, but it seems like a sloppy way to do it.

I'm thinking of substituting a little regulated Radio Shack 12v supply 
for the wart, deleting the big resistor, and feeding the DC to the 
antenna port through a 1 mH RF choke.  Any reason not to do that?  Is 
the big capacitor still indicated?

-- 
73, Pete N4ZR
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