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RATS Repeater System FAQ
Here are answers to some of the most common questions we receive about our FM repeaters. Also see our DMR FAQ for DMR-specific topics.
- Where are the RATS repeaters located?
- How do I access the autopatch?
- What happened to IRLP?
- Can I access the RATS repeaters over Echolink?
- What's all that noise on the 146.88 repeater?
- Your coverage map for the repeater seems to be a bit too generous. Why?
- Can I use a "crossband repeat" function to extend my handheld's reach to the RATS repeaters?
- Do the RATS repeaters have backup power?
- I kerchunked the repeater a few times to test my radio, and now the repeater doesn't seem to respond. What happened?
- Why isn't anyone responding to my "test" or "radio check" transmissions?
- I think there's a problem with one of the RATS repeaters? Who do I contact?
- Why does the repeater's transmitter sometimes cycle on and off repeatedly?
- Can I have a tour of the RATS repeater site?
- I heard something about a RATS 900 MHz repeater? P25 digital?
- I heard the 146.88 repeater supports DMR. Is that true?
- How much does it cost to operate the club's repeaters?
Where are the RATS repeaters located?
All three RATS repeaters are located at the Virginia Public Media (VPM) studios and transmitter facility on Sesame Street in Chesterfield County, near Chesterfield Town Center. The 146.88 and 442.55 repeaters transmit from antennas at around 680 feet, and the 443.5875 DMR repeater is at about 580 feet. The RATS repeater systems are just under 10 miles west of downtown Richmond.
How do I access the autopatch?
RATS discontinued autopatch in early 2021. Our current repeater equipment does not support this feature. We think we had the last functioning autopatch in central Virginia. In early 2024, our repeater coordination will be updated to de-list this feature, which should stop it from appearing in most repeater directories.
What happened to IRLP?
RATS discontinued its IRLP (Internet Radio Linking Project) services in early 2021 due to equipment incompatibility and aging IRLP hardware. The closest IRLP systems as of 12/31/2023 are:
- Node 4943 on the KB4ZIN 147.105 MHz repeater in Williamsburg
- Node 8373 on the WT4RA 147.195 MHz repeater in Smithfield
- Node 3510 on the W7VOA 446.925 MHz repeater in Widewater (Stafford County)
- Node 8561 on the N4WFU 146.745 MHz repeater in Roanoke Rapids, NC., which is often linked to several other repeaters in southern Virginia
Can I access the RATS repeaters over Echolink?
No.
What's all that noise on the 146.88 repeater?
The intermittent RF noise issues are a fact of life on our VHF system due to extremely high noise levels in our part of Chesterfield County. The RF noise issues and the club's efforts to diagnose them are described on our VHF repeater page.
The Technical Committee recommends the use of C4FM digital input (Yaesu Fusion "automatic mode selection") into the 146.88 repeater as a way around the noise. Testing has indicated that this works quite well.
The RF noise level has trended gradually higher since around 2018.
Since sometime in 2018, a specific recurring burst of noise has been heard on signals repeated through the 146.88 machine exactly once every 64 seconds, nearly 24/7. A few local hams call this the "noise fart." We have not been able to figure out what it is, but we believe the origins to be broad-band in nature (that is, impacting a large swath of the RF spectrum, vs. one discrete frequency). If you have any ideas what that might be, please give us some hints.
We are confident that the RATS repeater equipment is in good working order, and it's doing the best that it can given all the sources of interference in that part of town.
Your coverage map for the repeater seems to be a bit too generous. Why?
The system used to generate the coverage maps is Radio Mobile Online by Roger Coudé VE2DBE. This tool does an excellent job of estimating transmitter coverage area when fed accurate details about the transmitter (frequency, power, exact location, height above ground, antenna gain, feedline specifications, and equipment insertion losses, etc.) and receiver (antenna height, gain, feedline losses). It does not, however, take into consideration the effects of propagation changes, or the high RF noise level on the repeater. Thus, the coverage maps may appear to be somewhat exaggerated.
Our maps assume a receive antenna at 2 meters (6.5 feet) off the ground, with 2 dB gain, 4 dB receiver feedline losses, and 70% signal reliability.
It's important to understand that the maps show the areas where the repeater can be heard, not necessarily where it can be used. Your ability to access the repeater will depend on your transmitting antenna height, output power, band conditions, and the RF noise level impacting our repeater at that particular moment.
A good interpretation of our maps is that the typical full-power (50-ish watts) mobile station with a properly installed 5/8-wave VHF antenna should have little trouble using our repeater while mobile in most areas shaded in green. Mobile stations may have success in the yellow areas while sitting stationary. Well-engineered home stations using a modest rooftop (or higher) outdoor antenna such as a J-pole or vertically-polarized Yagi and high-quality feedline (LMR400 or better) should have little trouble using our repeater in the yellow shaded areas.
Coverage maps are not reliable predictors of performance for handheld transceivers, stations with indoor antennas, or low-power transmitters such as HT's connected to mobile or home base station antennas. In particular, HT users with any type of device-mounted whip or "rubber duck" antenna should not expect reliable performance more than 8-10 miles out from the repeater.
Can I use a "crossband repeat" function to extend my handheld's reach to the RATS repeaters?
Yes, provided that you follow some common-sense guidelines:
- Use a PL/CTCSS or DPL/DCS/DTCS tone on the RF path between your mobile radio and your handheld to reduce interference.
- Remain in control of the crossband system at all times. That means being aware of what your crossband repeater is doing, what it's transmitting back to RATS. It also means being able to shut down the transmitter quickly in the event of a malfunction.
- Operators of crossband systems are reminded of FCC identification requirements, which apply to all frequencies on which the crossband system is transmitting -- both the RF path between the crossband system and the RATS repeater, and the RF path between the crossband system and the handheld radio user(s). Crossband operators must configure their controller in a manner which ensures any automated identification does not interfere with other transmissions through the repeater. This may require the use of an external repeater controller.
Do the RATS repeaters have backup power?
All equipment at the RATS repeater site is protected by two levels of backup power. A pair of 2 kVA uninterruptible power supplies provide instant backup power for the repeater radios, Fusion control PC, and networking equipment. This is capable of running our stuff for several minutes, although it only takes a few seconds for our host TV station's large diesel generator to kick in.
I kerchunked the repeater a few times to test my radio, and now the repeater doesn't seem to respond. What happened?
(Kerchunks are short transmissions without accompanying voice traffic made without intent of two-way communication with another station. Briefly pressing the PTT button without saying anything just to see if the repeater responds is called kerchunking.)
RATS considers kerchunks to be unidentified transmissions made in violation of FCC Part 97, as well as a nuisance to other users, and thus a double violation of the RATS repeater usage guidelines. By request of the RATS Board of Directors, the Technical Committee maintains a "zero tolerance" policy for deliberate improper operation on our repeaters. When kerchunking flares up and occurs so frequently that it becomes a nuisance to other users, or any time persistent improper operation or QRM is impacting the repeater, we may remotely power off the system for as long as we feel necessary. Our direction-finding team will deal with repeat offenders. On the rare occasion that you need to make a test transmission, simply announce your call sign and "testing" or ask for a radio check.
Why isn't anyone responding to my "test" or "radio check" transmissions?
There could be several reasons. For starters, you simply might not be reaching the repeater.
A test transmission, such as "AB1CDE testing" usually doesn't call for a response. By use of the word "test" you're implying that it's a one-way test transmission, and you're presumably making some sort of measurement of your signal. Do not expect a reply to "test" transmissions.
A "radio check" transmission does invite a response, but you still may not get one. The number of requests for radio checks on the RATS system has increased sharply over the last few years. Our control operators generally will not respond to these requests, and some other stations now ignore them as well.
Repeaters should never be used for regular testing or tune-up of your transmitters, and there is no reason to ask for a radio check on a repeater unless you have made considerable changes to your station or some reason to suspect a problem. If you need to test your radio on our repeater's input frequency, use a dummy load. Here's one of many ways to make a homebrew dummy load.
I think there's a problem with one of the RATS repeaters? Who do I contact?
System performance concerns and reports of interference to our systems such as jamming or other malicious activity should be reported to the RATS Technical Committee. The entire Technical Committee has access to monitor and control the RATS repeaters. Send an e-mail to techcomm@rats.net for fastest response.
Why does the repeater's transmitter sometimes cycle on and off repeatedly?
This is usually an indicator of a very weak signal trying to come through the repeater. Because our repeater uses a single feedline and antenna for simultaneous reception and re-transmission of signals, special equipment is used to isolate the repeater's input and output frequencies from one another, preventing the signal coming out of the repeater's transmitter from going directly into its receiver. It is difficult to 100% isolate the two with this antenna and feedline configuration. As a result, a small amount of "de-sense" occurs in the repeater's receiver while the transmitter is on the air. The de-sense causes the transmitter cycling.
- A distant user transmits to the repeater while the system is idle.
- The repeater's receiver can hear the weak signal just fine, so it activates its transmitter to rebroadcast the distant station.
- The moment the repeater's transmitter activates, it begins de-sensitizing (de-sensing) its receiver. The weak signal drops below the repeater's squelch threshold and is lost.
- The repeater's hang time keeps it on the air for a second or two before dropping the transmit carrier.
- Since the repeater is no longer transmitting, it's no longer de-sensing its receiver. Suddenly, it can hear the distant station again.
- Return to step 2. Repeat until the distant signal ends.
This behavior isn't unique to the RATS equipment. This can be heard under the right conditions on many repeater systems. It's not considered harmful to our equipment. The rate of the cycling is related to the repeater's hang time setting, which is usually around 700 milliseconds.
Can I have a tour of the RATS repeater site?
Unfortunately, no. Our repeater equipment is located in an important transmitter building with numerous other two-way radio, TV, and FM broadcast tenants, and space is very tight. Access to the RATS repeater site is limited to the club's Technical Committee Chairman, the club's President, and members of the Technical Committee under the direct, continuous supervision of either the Tech Committee Chair or the President. We used to be able to bring in the occasional visitor, but due to safety and security concerns this is no longer possible -- it's simply too easy to damage another tenant's stuff. Photos of the RATS repeater equipment are available in the club's asset inventory, accessible to club members.
I heard something about a RATS 900 MHz repeater? P25 digital?
In 2014 RATS Life Member Fred Towers WB4KXS donated the use of a 900 MHz P25-capable digital repeater, and RATS hosted this repeater for several years. It has been removed from service at our repeater site and no longer operates under the W4RAT call sign.
I heard the 146.88 repeater supports DMR. Is that true?
Not at this time. There was a brief test of a dual-mode, non-networked DMR repeater on 146.88 in mid-2020. This test was performed as part of the "noise issue" troubleshooting, in an effort to rule out any internal issues with our old MTR2000 repeaters. Secondarily, we were able to determine that digital transmissions do successfully overcome moderate to severe RF noise.
The current 146.88 repeater is a Yaesu DR-2X which supports analog and C4FM digital input. It is not currently configured to transmit digitally, nor is the repeater linked to any other systems such as WIRES-X.
How much does it cost to operate the club's repeaters?
Recurring expenses include our lease for the tower space, insurance, Internet service, and maintenance on minor consumable parts such as batteries, surge protectors, etc. As of January 2024, these items total approximately $2400/year. This cost does not include major maintenance such as antenna replacements, repeater repairs and upgrades, and feedline replacements. A tower climb for basic antenna work can cost thousands of dollars. If you are a regular user of any of our repeater systems, please consider showing your support with a club membership or donation.