Richmond Amateur Telecommunications Society

RATS operates a Digital Mobile Radio (DMR/MotoTRBO™) repeater as part of the DMRVA system which covers most of Virginia.  This repeater went into service on May 30, 2014 with the generous assistance of Jay Lovelady KD4BPZ and Dave Meier N4MW.  This Motorola XPR8300 was originally placed in service on a backup UHF antenna at around 460 feet.  In December 2019, it became the primary RATS UHF asset and was relocated to an upgraded antenna at 680 feet.  

Before going on the air, repeater users should be familiar with the particulars of DMR operation, as well the RATS Repeater Rules & Policies, basic repeater etiquette, and some general talkgroup etiquette from our friends at DMRVA.  You must also transmit a valid DMR radio ID.  If you need help becoming familiar with DMR or have questions about operating procedures, please contact the RATS Technical Committee.  We will be happy to help in any way we can.  If you make regular use of the system, please consider club membership or a donation to show your support.

Planning to use a DMR hotspot?  Read this first.

Questions about the DMRVA network, including requests relating to nets or special events on a DMRVA member repeater, should be directed to DMRVA.

All DMRVA repeaters are Color Code 1.  C-Bridge talk groups are configured by the repeater owner and can be designated as either dynamic (PTT-activated) or static (always on).  A list of current DMRVA talk groups is available here

Static Talk Groups

Our two static talk groups are Richmond Metro and Virginia Statewide.  These two talk groups are always active.

Dynamic Talk Groups

All other talk groups are dynamic:  they're only active when needed.  Most of the time you will not hear any traffic on these talk groups.  While the repeater will allow more than one simultaneous dynamic talk group to be active, this will produce unpredictable and usually undesirable behavior.  Here are some best practices for using dynamic talk groups:

  1. Best practice:  Have a channel configured in your radio to perform a "monitor all" or "scan" function on all talk groups to ensure nobody else is currently using a dynamic talk group.  You'll need to set this up in advance using your radio's CPS.  Listen for a reasonable amount of time (10-15 seconds).

  2. Select the desired talk group, briefly press the PTT key.  Yes, kerchunk the repeater.  (We know, you've been trained for years that this is bad, but it's better than barging in on top of someone's QSO with your call sign.  Here's the official word from DMRVA.)  This kerchunk will activate the talk group.  Because talk groups are shared with other repeaters on the network, you will again need to wait several moments to begin hearing any distant traffic that may already be taking place on that talk group.

  3. Hearing no traffic on that talk group, make your call.  It's a good idea to say which talk group you're calling on because the receiving station may have their radio in a scan mode.  "AB1CDE, this is K4ABC on Virginia Southwest"

  4. When you are finished with your QSO, transmit your call sign to the "Clear Time slot" talk group.  This will deactivate the dynamic talk group and free the repeater for another user.

Dynamic talk groups are on a timeout and will deactivate if there is no local traffic (that is, no transmissions coming in to our repeater) for 15 minutes (5 minutes on TAC A and TAC B).  You will need to transmit to the talk group to reactivate it after timeout.  If you have a special need for extended access to a dynamic talk group, consider the use of a DMR hotspot device instead of the repeater.

Richmond Metro (formerly "Local") Talk Group

Our Richmond Metro talk group (27500) is shared with repeaters in Petersburg, Beaverdam, South Hill, Powhatan, and Lexington.  This is an always-on talk group for all six repeaters, creating a 24/7 linked system covering a good chunk of central and southern Virginia.  It is also carried on the Richmond Brandmeister DMR repeater as talk group 31511.

Selecting a Talk Group

When selecting a talk group for a QSO, use the smallest talk group which will do the job.  The larger the talk group, the busier it tends to be.  Most communication (including extended QSO's) within the local area can take place on the Richmond Metro talk group.  Outside that area, you'll need to consider your talk group options.

For initial calls and short QSO's within Virginia but outside the Richmond Metro cluster (Richmond, Petersburg, Beaverdam, South Hill, Powhatan, Lexington):

  • Try one of the Virginia Regionals:  Virginia Southwest, Shenandoah Valley, Tidewater, or Peninsula.  These are typically static talk groups in their respective regional areas.
  • Another option within Virginia is Virginia Statewide which is typically a static talk group for repeaters in Virginia.

Elsewhere in the United States:

  • Try one of the US Regionals:  Mid-Atlantic or US Southeast.
  • PRN includes many repeaters (67 as of April 2020) in the southeast US, mainly North and South Carolina, with a few in Virginia and Texas.
  • Try the DCI Bridge -- it includes repeaters from DMRVA, NCPRN, AWSVirginia, DMR-MARC, and many other networks

Some options for extended conversations:

  • For QSO's within the DMRVA network or to AWSVirginia repeaters, use TAC A.  This is AWSVirginia "TAC A/CHAT 1"
  • For QSO's within the DMRVA network or to NCPRN repeaters, use TAC B.  This is NCPRN "Chat 2"

The other general purpose nationwide options are TAC 310, TAC 318, and TAC 319, which are shared with repeaters from many different networks around the country.  You can learn more about the history and usage of TAC channels here.

Receiving a Call on a Dynamic Talk Group

If you are expecting a call from someone on a different repeater (including another DMRVA repeater) using a dynamic talk group, you will need to already have the talk group active in order to hear their incoming call.  Follow the procedure described previously for activating a dynamic talk group.  Of course, if you're the one initiating the call, the distant party will need to have done the same, otherwise the talk group will not be active on their end.

About the Repeater

Above:  Map showing projected coverage of the W4RAT 443.5875 MHz repeater, generated using Radio Mobile Online by Roger Coudé VE2DBE
Coverage for other DMRVA repeaters can be found here.

The repeater output (after the duplexer) is about 20 watts.  The antenna, a Commander Technologies 455-5N, is fed by about 750 feet of 1-1/4 inch hardline which is shared with the VHF analog repeater.  A UPS provides short-term backup power for the DMR repeater and Internet connectivity, and the entire RATS repeater system is serviced by a large diesel generator maintained by our host TV station.

Below are pictures of the rack containing the DMR repeater.

Front view of the DMR repeater

Above:  Front view of the DMR repeater


Rear view of the DMR repeater

Above:  Rear view of the DMR repeater

Richmond Amateur Telecommunications Society, Inc. (RATS) is a 501(c)3 non-profit organization. PO Box 70613, Henrico VA, 23255

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