In the previous post I elaborated on the design of Beverage transformers.
When using several Beverages ‘out in the field’, sometimes several hundreds of meters
away, they have to be switched inside the shack.
A popular method is to use LED bar drivers (i.e. an array of comparators) in ‘single dot mode’.
The Bavarian Contest Club (BCC) published a design in CQ Contest in 1997 using the LM3914.
Although this design is very straight forward and built by many, imho it lacks one of the
most important features which is important ‘out in the field’: powering the switch box from the shack
with a phantom power supply.
I changed the design so that the switch box is powered and switched inside the shack through the RX-coax.
A W7IUV-preamp is included to compensate likely cable losses, as I will use thin (light weight) RX-coax in 7Q.
The circuit diagram is depicted below, your mileage may (of course) vary (click to enlarge in a new tab):
The idea is to use the range 12 – 24V to switch the Bevs, as I will have 50V in my PA.
Proper voltages to select specific Beverages are adjusted with the potmeters (1 – 2k each),
also to compensate possible voltage drops due to RX-coax lengths.
Below a picture of my Bev switch box (click on image to enlarge in a new tab).
Yes.. I use RCA connectors, it’s light weight .. and only <10 MHz for 1.5 cm ; -)
Note: in this picture I erroneously soldered the zener to the RX-coax.
It has to be connected to the other end of the choke of course.