RE: [Repeater-Builder] Re: LDG Voter RVS-8 Mystery
Skipp, I appreciate your suggestions. I will follow your advice to see whether input level is causing the erratic behavior. Many thanks for your analysis and advice. John >-Original Message- >From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >buil...@yahoogroups.com] On Behalf Of skipp025 >Sent: Saturday, November 07, 2009 9:52 PM >To: Repeater-Builder@yahoogroups.com >Subject: [Repeater-Builder] Re: LDG Voter RVS-8 Mystery > > >With a constant test tone into the Voter, you should be able >to adjust the pots while watching the proper voter input >metering point with an AC Volt Meter or even better a scope. > >I doubt the pots are bad out of the starting gate, but >who knows with maybe the use of low cost parts, with >the corresponding lower quality. > >My first guess is you might have way too much input signal >or if there are adjustable gain stages, they are set (maybe >with a gain set resistor strapped) for max gain. If >you don't already have one, a Spray Can of Caig Labs DeOxit >is a must have for anyone working in electronics. A very >small shot of DeOxit or ProGold G5 Spray to the pot should >be a big help to most any cranky control pot. > >If it is a case of junk pots... the Caig Labs Spray would >help resolve the issue... or at least hopefully tell you >yes/no if the pots are the real problem. > >> So my question is, "Is there any way something external >> to the voter could cause the voter POTs to behave this >> way?" > >Yeah, really excessive input levels and op amps with improper >gain set resistor values. > >Test time: > >Get a 100K Linear Taper Pot, you can use an Audio Taper if >you can't find a linear taper version. Connect the receiver >output to the high side of the pot (one end of the pot becomes >the "high side", the other end is grounded and becomes the >ground side). Ground the other end of the pot as mentioned >above "ground side". > >Solder a wire from the center tap of the 100K pot to the >input of the LDG Voter. Be sure the common ground from the >receiver audio to the ground side of the pot is also connected >to the audio input ground on the voter. > >Set the Voters internal Audio Input Level Pot to 1/4 best or >1/2 rotation. Set the external pot about 1/4 rotation from >the ground (totally off) position. > >Apply the receiver audio test tone input... measure and/or >look at the value of the tone inside the voter input at the >test point. > >Rotate the test pot up and down to reduce the inside voter >test tone down to almost off. Then rotate the LDG Voter Audio >Input Gain Pot up and down to see if the tone still jumps >in large block (amount) values. > >Yes - The same big audio value jumps... Then I would next >try the Caig Labs Spray and test again. > >No - The audio seems to rise and fall in a more controlled >ramp... Then you're hitting the input with way too much >signal. > >Miller Time... >s. >
[Repeater-Builder] Re: LDG Voter RVS-8 Mystery
> We added an LDG RVS-8 voter... Very nice... I have three or four in operation and I'm very happy with them. > Now we have a problem. When I set up the voter, the > POTs that I must adjust seem to have step functions, > i.e. I can adjust to, say, 500 mV, then the next > slightest adjustment will immediately take me to, say, > 3 V. With a constant test tone into the Voter, you should be able to adjust the pots while watching the proper voter input metering point with an AC Volt Meter or even better a scope. Got Scope? I doubt the pots are bad out of the starting gate, but who knows with maybe the use of low cost parts, with the corresponding lower quality. My first guess is you might have way too much input signal or if there are adjustable gain stages, they are set (maybe with a gain set resistor strapped) for max gain. If you don't already have one, a Spray Can of Caig Labs DeOxit is a must have for anyone working in electronics. A very small shot of DeOxit or ProGold G5 Spray to the pot should be a big help to most any cranky control pot. > I put the two receivers on channels 1 and 2 and found > the step occurred in both channels. This was perplexing. > I called LDG tech support and was told that maybe a POT > was just dirty even though the voter is brand new. So I > tried again with the same result. Then I switched the > two receivers to channels 3 and 4. These POTs had the > same characteristic. There are two POTs per channel, so > the problem is there for eight POTs! At first blush, > this looks as though LDG has a large supply of defective > POTs. If it is a case of junk pots... the Caig Labs Spray would help resolve the issue... or at least hopefully tell you yes/no if the pots are the real problem. > So my question is, "Is there any way something external > to the voter could cause the voter POTs to behave this > way?" Yeah, really excessive input levels and op amps with improper gain set resistor values. > I don't want to charge LDG with using bad components if > there is any chance that the problem is caused by our > receivers or controller. I don't see any way the receivers > or controller could cause the problem. What do you all > think? I try not to think too much... Test time: Get a 100K Linear Taper Pot, you can use an Audio Taper if you can't find a linear taper version. Connect the receiver output to the high side of the pot (one end of the pot becomes the "high side", the other end is grounded and becomes the ground side). Ground the other end of the pot as mentioned above "ground side". Solder a wire from the center tap of the 100K pot to the input of the LDG Voter. Be sure the common ground from the receiver audio to the ground side of the pot is also connected to the audio input ground on the voter. Set the Voters internal Audio Input Level Pot to 1/4 best or 1/2 rotation. Set the external pot about 1/4 rotation from the ground (totally off) position. Apply the receiver audio test tone input... measure and/or look at the value of the tone inside the voter input at the test point. Rotate the test pot up and down to reduce the inside voter test tone down to almost off. Then rotate the LDG Voter Audio Input Gain Pot up and down to see if the tone still jumps in large block (amount) values. Yes - The same big audio value jumps... Then I would next try the Caig Labs Spray and test again. No - The audio seems to rise and fall in a more controlled ramp... Then you're hitting the input with way too much signal. > A further problem is that the maximum audio output of the > RVS-8 is not adequate to modulate the BaseTech II transmitter > (through the RC-850) to any deviation above 1.7 kHz. I can > solve this with an audio amplifier or a change to the RC-850, > but I would rather that the voter did the job. Most of the Midland Radios require much higher level audio drive (input), meaning there's a pretty decent gain preamp inside the mic. You can steal the mic preamp from a Midland mobile mic or "roll your own" by copying the preamp circuit available in the files section of the Yahoo Midland Group. http://f1.grp.yahoofs.com/v1/ICb2SlwP7ymoenfK1fs-4D1RA-D22chUd8U2c8e_Tc0BrqZP8RIqtJVbq6wSewZj9HeE8BW2pBQEahLvlu_UNMd5LRD2/hand%20mic%20preamp.jpg Otherwise Email me direct and I'll send you a copy of the circuit. You can buy and install an LM-386 type of amplifier stage from the output of what ever type of device (the controller or the Voter) you drive the Midland Transmitter with but it will be a lot more noisy than using the original Midland circuit, which works very well. I'll throw out the generic statement regarding driving one of the classic Midland Syntech, XTR and ST2 Radios. The tx audio drive requirement is so high... I can and have put two radios back to back in repeater service using speaker audio direct to the tx input of the repeater transmit radio and it works very,
RE: [Repeater-Builder] Re: LDG Voter RVS-8 Mystery
>-Original Message- >From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >buil...@yahoogroups.com] On Behalf Of Randy >Sent: Saturday, November 07, 2009 10:59 AM >To: Repeater-Builder@yahoogroups.com >Subject: [Repeater-Builder] Re: LDG Voter RVS-8 Mystery > >John is the inputs Capacitor coupled? And or are the RX sources DC >coupled? > >Randy > Randy, The receivers are AC coupled to the voter, and the voter is AC coupled to the controller. John > > >This message was checked by NOD32 antivirus system. >http://www.eset.com
[Repeater-Builder] Re: LDG Voter RVS-8 Mystery
John is the inputs Capacitor coupled? And or are the RX sources DC coupled? Randy --- In Repeater-Builder@yahoogroups.com, "John Transue" wrote: > > Our club recently added a remote receiver and RF link to our club > repeater. We are using an ACC RC-850 controller at the repeater site. > We added an LDG RVS-8 voter so we would not have to use PL and to make > life easier for mobile users. > > Now we have a problem. When I set up the voter, the POTs that I must > adjust seem to have step functions, i.e. I can adjust to, say, 500 mV, > then the next slightest adjustment will immediately take me to, say, 3 > V. I put the two receivers on channels 1 and 2 and found the step > occurred in both channels. This was perplexing. I called LDG tech > support and was told that maybe a POT was just dirty even though the > voter is brand new. So I tried again with the same result. Then I > switched the two receivers to channels 3 and 4. These POTs had the > same characteristic. There are two POTs per channel, so the problem is > there for eight POTs! At first blush, this looks as though LDG has a > large supply of defective POTs. > > So my question is, "Is there any way something external to the voter > could cause the voter POTs to behave this way?" I don't want to charge > LDG with using bad components if there is any chance that the problem > is caused by our receivers or controller. I don't see any way the > receivers or controller could cause the problem. What do you all > think? > > John > AF4PD > > PS: The repeater receiver is in a Midland BaseTech II and the link > receiver is an Icom IC-F221S. > PPS: A further problem is that the maximum audio output of the RVS-8 > is not adequate to modulate the BaseTech II transmitter (through the > RC-850) to any deviation above 1.7 kHz. I can solve this with an audio > amplifier or a change to the RC-850, but I would rather that the voter > did the job. This problem, too, could be caused by a bad POT. I am > sorry to say I did not measure the audio voltage out of the voter. >
