How does a Voter work ?
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A voter is not a particularly complicated device. Descriminator audio is an AC voltage as it passes through the radio circuits. This AC voltage is fed into the inputs of the voter. A high pass filter is used to remove the low end noise and a series of op-amps equalize the audio levels before voting . Then the AC audio voltage is rectified into DC voltage. The voter then measures the voltage of the signals. The signal with the lowest DC voltage is the one that is selected and sent to the controller as the voted signal. The more the noise, the higher the voltage, and likewise, the less noise, the lower the voltage. This is a continuous process as long as two or more receivers are receiving a signal. You can check the voltage of audio by hooking an AC volt meter to the speaker leads of a radio & then transmitting to the radio from another radio. A fully quieted signal has nearly 0 volts, but as noise appears on the signal, the voltage goes up. That being said, let's discuss some of the problems associated with voting. I use UHF links to connect the remote receivers back to the main repeater. If the link is not fully quieted, that receiver will have noise on it as far as the voter is concerned. This may cause the voter to vote a signal from a site with poorer reception even if the receiver with the noisy link is full quieted. If the audio is not matched well before voting (i.e. one receiver is louder than the other), the voter will more than likely vote the receiver that is not as loud because it will seem less noisy to the voter, regardless of the signal quality. If a receiver has a lot of background noise like an over deviated CTCSS or AC line noise, the voter may see it as noisy and not vote it verses a noisier signal from another receiver. If a user has their mouth too close to the mic, is talking too loud, or has the deviation of their radio set too high, the voter will be unable to determine which receiver has the best signal. It will jump around between the receivers rapidly and will probably vote a site that has a poorer signal because there will be less overall audio. The audio from all the receivers should be carefully matched and at the same level so that the users cannot tell the difference between the individual receivers. This way no one can tell that the system is voting. There should be a subtle improvement in signal quality, but no change in the audio level, volume, or tone. This is also important for the passing of DTMF commands as a noticeable change in the signal will cause the DTMF decoder on the controller to fail. It is not uncommon for the voter to change receivers while receiving DTMF tones. On a voted system, you want it set up so that the receivers have overlapping coverage in case one fails. This also helps to remove some of the mobile flutter and picket fencing because you might be a little noisy into one receiver, but you could be DFQ into another at that particular moment in time. By continuously evaluating all the inputs, the voter can piece together quality audio to provide your system with what sounds to be one super receiver. The voter automatically picks the quieter one & makes your signal sound good. Problems arise when the audio levels don't match or there are quality issues with the link. The way to get the most out of a voted system is to keep your voice low so that there is less noise for the voter to deal with. Wind noise from riding around with your car window rolled down can cause artificial noise for the voter. Running lower power levels will actually help the voting system because it will increase the noise level of the sites you are not getting into very well anyway. Always key your mike and count to one (to yourself). This gives time for the system to come up. There are unavoidable delays in linked & voted systems because you are bringing up several components. If you find that you are having your first word of your transmission cut, this is why. Visit
the Repeater
Builder's Technical Information Page for more information about
voting and voters. Return to my homepage or technical info. |