On January 11, 2007 at 19:02, Ridenour said...
Just curious, I have been out on yet another service call
for possible RF on an older (about a year) MRF-300 with
the RFX-150 reciever (not narrow band). The runs of Cat5e
to the two RFX-150s are about 80 feet long each. I tested
the voltage on the MRF-300's phoenix terminal and it showed
5 volts. At the RFX-150 I got 4.8 volts off of the mini
plug. Do you think that just adding a 5volt power supply
to the recievers would be enough? Or would I still need
the caps? The system is wired with two MRF-300s: on has
both of the cat5e wires from the recievers wired into
the phoenix connector with a mini from the "RF out" to
the "RF In" of the other. So would the caps have to be
in the same phoenix that the cat5s are in or would they
be effective in the other, which does not have any wire.
It is important to point out that your devices are quite differnt than mine. I have no idea if the same problem exists on your models of UR equipment. Presuming they are the same. you should absolutely include the capacitors as well as the external supply. As outlined in my original post, I had a signficant improvement in operation when I added the cap to my external supply.
Also, make sure you disconnect the +5V wire at the RFX-150 and the MRF-300 devices.
Finally, please understand that you cannot truly measure voltage with a VOM in this instance. VOMs cannot record brief changes in supply voltages. When the RFX-250 goes active, it draws several ma of additional current. It takes time for the power supply to react to this change through wire. The longer the wire, the longer the reaction time. Use a fast oscilloscope if you want to measure. You'll also need to carefully connect the scope lead tip and ground to avoid distorting, or misrecording transients like this.
