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, > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
