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,
Voters in General
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.
One other note as of June 2013, it was learned of the possibility the DHE voter will no longer be made. That's a tragedy however, the Author understands the economics of that decision.
The RVS-8 VoterThe model probably went through some changes and versions since it was introduced over a decade ago. A comparison chart is started, here, but not completed due to time for research. Two rows of "fields" are left blank, possibly, to be filled in at a later time.
|Vintage-Versions||Manual||Board||Schematic||Firmware & 2|
|2008-||who knows?||who knows?||who knows?||who knows?|
History and Service
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 attempted 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.
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 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 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..........
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.
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:
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, 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 "issues" have been addressed, including:
Just to remind the reader most of these listed items are personal preferences of the Author. You may be just "fine" with the original setup. This document 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 curiosity 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:
Here's a couple close-ups on those modifications
Here's an overall view of the entire board, with the latest modifications.
It is hoped this page will help both the manufacturer and the customers. In 2013 lighting damaged the unit. Also was discovered the possibility of LDG no longer making this unit, however there may be some "old-new" stock out there. In mid 13 one was found and put in service. Also extensive R and D was done during this period.