Ken,
I would avoid any attempts to do relay switching by supplying voltage
down a coax cable but rather use two coax runs. The relay, blocking
cap, diode and associated circuit in my case with two DXE boxes have
deteriorate within less than a year to be useless, mostly due to
electrolysis and zillions of ants attracted apparantly by the voltage or
relay coil vibration when pulled in. (Yes I covered all the edges with
silicon sealant) DXE refuses to send me a print to repair the board
for what reason I don't know, thus making repair very difficult. They
worked well when I got them but are useless today. Another
disadvantage of having a blocking cap in the signal line is that you can
not determine the coax run continuity through the windings of toroid
back to the shack with a common VOM. This is an easy troubleshooting
tool that is not possible via the DXE system.
Herb, KV4FZ
On 3/23/2012 11:10 AM, Kenneth Grimm wrote:
> I'm in the process of building a new two wire beverage control box to
> replace the one that Thor destroyed the other day. Fortunately the coax
> lead in was disconnected at the time! The top of the box has not been
> recovered and much of the contents vaporized. The inside of the box has
> lots of scorch marks...and not much else. The reflection transformer, some
> 580 feet away, appears to be unaffected as does the 450 ohm twin lead.
>
> I plan to do a PC board for the new control box and so I had a look at how
> the DX Engineering box was laid out. I also had a look at the board made
> by RA6LBS. Both of these boards appear to have an electrolytic capacitor
> installed. On both boards the electrolytic appears to be associated with
> the direction switching relay. None of the two wire beverage diagrams that
> I have seen have such a cap and I wonder what its function is and how it is
> connected in the circuit. I am told that the value is 100 mfd @ 50 volts.
>
> Apparently the cap isn't necessary, but since I have a few in my junk box,
> this might be an opportunity to put one of them to use!
>
> 73,
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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