RCA Selector Switch Build

Discussion in 'General Electronics Chat' started by Zatarra64, Jul 21, 2014.

  1. Zatarra64

    Thread Starter New Member

    Jul 21, 2014
    I've seen a similar topic on here (via a Google search), but the questions I have were not answered there, and I didn't want to derail the topic.

    I'm building a multi radio desk for student training. I chose to go with a RCA selector switch for ease of use as it can select between several 6 wire inputs and output to a single output. Descriptions below.

    I have 8 radios, 6 wires each... Two wires for each of the three types of signal I need to pass through. . (Rx signal/Filtered ground, TX signal/Filtered ground, and Push to talk(Key line)/Filtered ground). I bought 2 Sony 4:1 RCA switches (SB-V40S). My original plan was TX to red, Rx to white, PAT to yellow.

    After it arrived, I messed around with it and found that the 3 unselected yellows all shorted together when the 4th was depressed. This makes the yellow unusable for PTT as it will send a key signal (ground to key in) for the three radios that are not in use (hot mic).

    This problem did not happen for the Red/White legs of the box. I decided to move the PTT to Red, the TX to white, and the Rx to the yellow. It seems to work, but I don't have a viable method to test if there are any problems with my unselected radios.

    My questions:
    1. Why are the Yellows(video) shorted and not the Red/White(audio)?
    2. Are there any problems with line level audio outputs being shorted together?
    ----A line level audio signal shorted to its own ground. Ie. A RCA cable tip to its own sleeve.
    3. Same question, but now with three different outputs.
    ----4 line level audio outputs plugged into yellow RCA. 1 is selected and connects to the output. The other three are all shorted together.
    4. Do you know of a better method of making 4 (or more) 6 wire signals selectable by an idiot?
    ----Assume the user is a rabid monkey with a hammer attached to his hands.
    ----The signals should all be disconnected (break before make) prior to changing, or I could have a radio stick in TX mode.
    5. I saw a suggestion in another thread for a M5 - Series 3 pole, 12 position make and break selector switch, but I'm unsure if that would work for my needs.
    6. If the M5 would work, is there a way to build something similar with push buttons?

    Any help/suggestions/clarifications would be appreciated.

    Ps. I have a Visio/PDF of my current setup if needed.

    Rob Lloyd, TSgt USAF
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009