Introduction

A "voter" is a device used in a LMR base station, or better yet, a repeated station. Several remote (input) receivers at various remote locations pick up a user's weak signal, and then are transported them back to a Master Control Point (MCP) by means of dedicated RF, wireline or IP channels for each of those remote receivers. At the MCP the voter "decides" which of the "best" user signal will be heard by the control station, or better yet, sent back out to the remoted (supported) system output transmitter for all to enjoy the best reception possible. This can provide superior reception and user coverage over a conventional single-Tx/Rx repeater station at one remote site. This comes with a price, starting with cost (equipment, sites, etc.) advanced experience, understanding and very high maintenance discipline and standards by the supporting technicians. Voters come in two basic types; time domain or signal-to-noise quality (S/N). The latter is more popular and effective for best LMR communications,

Two manufactures are known to produce a S/N voter for Amateur Radio repeaters. Doug Hall makes a 4-channel, while LDG Electronics makes an 8-channel. Both are the S/N type and neither require a status tone, like the Motorola and GE comparator shelves (voters) do. By not needing a status tone the remote links don't have to be active (keyed-up) before or after the user activity. For this article we will discuss the LDG voter, model RVS-8.

 

Vintage-Versions	Manual	Board	Schematic	Firmware & 2
Original	?	?	?	?
Before 2001	?	?	?	?
2001	2.1	2.1	2.0	2.1
2005-2007	1.0	3.4	3.2	?
2008-	who knows?	who knows?	who knows?	who knows?

History

The author ordered the RVS-8 on August 21st, 2005, through the U.S. mail and received the unit Sept 10th, in great physical condition. They pack the unit well and attempt good communications. If you're a slow-western-er "county hick" like the author, you'll need to get up to "speed" on the East coast's way of talking and doing things. They operate at a much fast pace however, do provide a quality product. This unit was slated for the 147.20 repeater, however was returned shortly afterward. This was due to a few reasons that's beyond the scope of this documentation. The short reason is it did not work. A later version was obtained on April 12, 2007. Here's SRG's web site , in case your not already there.

The unit's fairly simple in design and construction. Being that this is the first micro-processor based piece of equipment on the SRG system, this is out of the "comfort zone" for the Author. The author's been studying the documentation on their web site , which, the manual is down loadable with no obligation. That's a real nice touch. If other companies for repeater equipment could offer that, we (honest) Amateurs could study what we are interested, so we don't waste a lot of time and frustration and end up shipping something back, to our expense. By seeing what the product does makes easier selection to your needs. More on the documentation at the bottom of this page.

Here's some pictures of the unit, which is an earlier version, should you be considering buying one for your repeater. For larger version of the picture(s) just click on the images. If you do that, it's better if you have a high-speed connection, since some of them are rather large.

The unit........

The front panel........

The rear connection points.......

Here's the main board. On the right is an area the author was working with on the COR inputs.

Here's a sectional of the board in third's, for a closer view of each section. Reminder: for a larger version click on the image(s).

The "disclaimer"

The author designs, builds and operates several pieces of equipment, such as antennas, duplexers, controllers, and yes, voting units. Unfortunately, the voter units built were "cheap and dirty" with very simple time logic and did not actively audio (quality) vote signals. This product was found and to save lost of precious time it was decided to give it a try for the 147.20 repeater. There are possibly other repeaters that might use this product in the future, after proper operation and evaluation takes place.

As with any product, it's not a "perfect world". This page is NOT to stir up things, nor make trouble for anyone. Let's make this perfectly clear. SRG and the author supports this product. There are some things to be aware of; about the unit which should be known to both the manufacture and the general customers, to avoid wasted precious time and created frustration, and unnecessary "venting" to other news groups, forums and discussions on the air waves. These people produce a quality product. The reason this page is published is because..........

WE CARE. Read that again...... WE CARE.

If we did not care, we would send the unit back and buy something else, and join the brain-dead masses and that do not (positively) complain with constructive criticism to help a product get better. This is the classic case where, an unhappy customer just stops coming to a store. Sometimes, the management does want to hear about any problems to correct, as to stay in business. It's assumed, here, this is the case. The author is attempting to avoid (twisted) readers turning the truth around, making the "nice guy" who cares and trying to provide quality communications and getting the bad rap. Having said that (yes, a rant) here's what the author found with the RVS-8.

The critique

This section is about the version obtained in 2005, for you to be aware of, should you have this. Most of the "problems" and errors have been corrected as of 2007.

SRG's repeaters are all pretty much designed with "buss" type control lines, normally, active going logic "low" for DC lines such as COS and PTT signals from and to various type of equipment, making up a system. Most audio paths are lower impedance and at a -5 ~ -10 dbm TLP. What's a TLP? Explain more....

Therefore, there was an issue with incompatible COR inputs with the system's design. This was determined after several hours spent. A phone call to the factor confirmed this. It's imagined the unit could be modified with "real" pull-up resistors, say, in the 1-10K range. Here's a list of issues currently, to be watchful for:

• COR (COS) inputs are not "open collector" "active low" compatible. However, pull-up resistors can be added for this mode. Recommended value 1 ~ 4.7 K.
  
  
• Disagreement with the board layout on manual ver 3.1 with board ver. 3.2; there are corrections provide, here, below.
  
  
• The LEDs are a little on the bight side, because they are driven hard with 470 ohm resistors- might consider changing them out with 1K resistors.
  
  
• It would be nice to replace those LEDs with colors more meaningful, such as green for Power and Yellow for COR activity. Red is for alarms and decodes, normally. The LCD screen is fine.
  
  
• Would be nice if the inside (or even outside) was painted white, making it easier to find something dropped into, at the site at 2:30 in the morning.
  
  
• The schematic is nicely PC generated and all, but a little distracting with all the coloring; a BW version would be nice; and larger, say at least 11 x 17". A quick visit to the local copy store fixed that issue.
  
  
• Upper and lower case could be improved on; Upper is fine for parts ID, lower for Explanation, etc (no shouting), however, a couple of items should be upper case, such as Q1's "2n3904" and the k's on all the resistors. Appropriate casing per the industry standards (if there's such a thing).
  
  
• Using a relay (come-on; give us a break!) is not really the 21st century. Very few types of equipment would need such a mechanical device. Thank goodness from what the physical board shows a "COR OUT" eyelet is provided for such an occasion. Rip that relay out of there !! (well, un-solder it, man) And, of course, jumper the output, etc).
  
  
• The schematic shows several "NC" 's,(NC16, NC15, NC9, NC8, NC7, NC4, to name most of 'em) however, do not seem to go anywhere. This was the issue (NC15) while troubleshooting the "cor" inputs as active (open collector) problem with the system.
  
  
  
  
  

  The documentation issues/corrections have been provided (with lots of TLC and time) by the author, as found, so far. There are two versions, one in BLUE and one in ORANGE. In the event your color blind in one of those colors, this might help. Reminder: for a larger version click on the image(s).

  Board layout corrections.....in BLUE..........................

  

   

   

   

   

   

   

   

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  and in ORANGE..............

  

   

   

   

   

   

   

   

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  And here's some corrections for the schematic in manual ver. 3.1, for board ver. 3.2. Sorry, no time to make 'em in blue. Orange only..........

  

   

   

   

   

   

   

   

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  This is the end of the earlier version evaluation

   

   

  This next section covers the later version as of 2007. This for version 3.1 hardware, with schematic version of 3.2. The silk screening on the board has a version, as well. Most of the "problems" have been corrected, including:

• The disagreements with the board and manual have been corrected.

• One of the (incorrect value) resistors (R7) have been corrected, as not to over drive the power LED indicator. The COR resistor (R1) is still the (too low) 470 ohm.

• Both LEDs are still red in color. It would be nice to replace those LEDs with colors more meaningful, such as green for Power and Yellow for COR activity. Red is for alarms and decodes, normally. The LCD screen is fine.

• Would be (still) cool if the inside (or even outside) was painted white, making it easier to find something dropped into, at the site at 2:30 in the morning.

• The schematic is nicely PC generated and all, but a little distracting with all the coloring; a BW version would be nice; and larger, say at least 11 x 17".

• Upper and lower case on the schematic has been corrected and appears much better. It's still way too small for the older folks, so you'll need to visit your copy store and blow it up to a 11"x 17", or larger.

• They are still using a relay for the PTT (COR) output. Reminder - this is the 21st century, folks! Click-clack, Click-clack (yea, right). They have improved on the available eyelits to bypass that ancient device, so you can rip that thing out of there. (un-solder it). And, of course, jumper the output, etc).

• The thing about the schematic's "NC" was finally figured out to mean "No Connection". That was a thoughtless part of the Author- sorry about that! The later version's schematic now has an "X" by the non-connections for dummies like the Author. Thank you, LDG Electronics.

• COR (COS) inputs are still not "open collector" "active low" compatible. However, an external interface, consisting of eight 1K resistor on a barrier block corrected this problem.

• The manual's setup section is a little misleading. It talks about setting each input level for "1.0 volts peak to peak", etc. Then with noise (input) from the receiver it talks about setting each channel (different pot) for 3.5 volts. One would assume that's 3.5 volts, Peak-? Nope, what they "meant" to say is "3.5 volts, positive D.C.". The manual could stand for that clarification. Once this was discovered after significant bench time, the alignment was a breeze. The rest of the (small) manual is adequate for operation. The pictures are a nice touch, as well.

• There is a problem with excessive levels into the unit, per the manual. This causes bad voting and squelch tickles leaking through. More on this below.

• The 2-year warranty is excessively generous. These people produce a fine product and mean it.

  Just to remind the reader most of these listed items are personal preferences of the Author. You may be just "fine" with everything about this unit. This is just to help particular technicians from hours of frustration, re-inventing "the wheel". It's the opinion of this Author that LDG Electronics makes a good product and recommends this unit for most any repeater.

  

  In 2007 SRG's system inputs were set for a TLP of 0 (dbm), for each channel. Per the factory manual specs the level too high. This may cause bad voting on noisey channels. To solve this problem the Author did extensive research and troubleshooting and came up with an alternative alignment procedure. It's pretty the same, except the levels are a little different. You can view or download it HERE.

  After running the unit for a year or so this way it was still noticed when a station is good into one or more channels (and voted) there still was a sputtering noise. After more considerable research and troubleshooting it was determined and best described that trickling squelch from noisy path are not muted out properly from the unit. In the spring of 2008 the Author decided to try lower TLPs to the unit's eight inputs even further from the first step a year earlier. The way the manual calls it, turns out about a +5 dbm, which was suspected to be way too high. After lowering the spec another 5 db; ending up with a -5 dbm TLP and performing the alignment the unit started to act more like a normal voter; ignoring (and muting) noisy, squelch tickles from distant receivers that a high-powered station working the system. The (above) alignment procedure reflects this latest development. Just for laughs a port (4) was picked to plot the noise/logical value graph as show above. It's enlargable by clicking on it (large file).

  It was (future) planned to make some of the changes from the features, listed earlier. In January of 2009 most of them were done. That includes:

• Installed (little) 1/8w resistors on the COR inputs 1~8. These were nicely soldered on the surface mount 100K resistors, with the commond buss going to the 12v source. This cleaned up the MCP installation.

• Pulled that silly PTT relay; ran a jumper from Q1 collector to the PTT output's terminal labeled "NO".

• Changed out the front panel LEDs to something more meaningful; Power is now green and COR is now yellow.

  Here's a couple close-ups on those modifications

  
  

   

   

   

   

   

   

   

   

   

   

  Here's an overall view of the entire board, with the latest modifications.

  
  

   

   

   

   

   

   

   

   

   

   

   

   

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  It is hoped this page will help both the manufacturer and the customers. You can contact the Author for any input or run over to the main web site, by clicking on the icon, below.

  
  

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