September 2024 RATS Repeater Updates

What do I need to do to prepare?

FM users of the 146.88 repeater will need to make the following adjustments:

• Ensure a receive PL tone of 74.4 is enabled to prevent reception of C4FM digital noise
  
  
• Either engage your radio's Busy Channel Lockout (BCLO) feature OR be sure to STOP and LOOK at your radio's RX signal indication to check for the presence of digital traffic before attempting to transmit with FM.
  
  
• These are the same requirements and procedures that currently exist on the 442.55 repeater.

WIRES-X users of the 442.55 repeater will need to make the following adjustments:

• Prepare to begin using the 146.88 repeater for WIRES-X and C4FM traffic on or around September 21.
  

Why is this happening?

Quick summary:

• High noise levels in the vicinity of our repeater site often make FM communication difficult on the 146.88 repeater.
  
  
• Prior testing shows that the 88 repeater still performs well when C4FM input is used.
  
  
• The 442.55 is one of only two 440 FM repeaters still serving most of the Richmond area, and it's frequently unavailable for FM use due to the presence of digital traffic.
  
  
• There are numerous 2-meter repeaters in our area which offer dedicated FM service and large coverage areas, including a new system on 145.11 in Hanover County.
  
  
• Given these considerations, it makes sense to move C4FM to 146.88 and free up 442.55 for FM users.
  
  
• Additional actions will likely be needed in the future, such as a relocation of the 146.88 repeater, or a move from VHF to UHF.
  

The longer story:

As many have noticed, the receive performance on the 146.88 repeater began to deteriorate around 2018.  From 2018 to 2021 the club engaged numerous contacts who have the skills and equipment to diagnose the source of the high noise levels in the 88's receiver.  In December 2019 the club spent around $8K sending a crew up the tower to make inspections, do minor repairs, install a new high-gain UHF antenna at 680 feet, and perform other work to clean up the 88 and improve overall system performance for all users.  In subsequent years, the repeater rack and RF connections at the ground level were torn apart and rebuilt, and the repeater radios were replaced.

Literally every component involved in the operation of the repeater -- everything between the electrical outlet and the top of the tower -- has been tested multiple times without finding any issues.  Several major components were replaced despite not finding any problems -- including the repeater radios themselves, the cavity duplexer, VHF/UHF diplexers at top and bottom of the tower, power supply, and more.  A local Motorola dealer was also paid to inspect our previous repeaters (Motorola MTR2000's) and perform other checks of the system, again, without finding any trouble.

The RATS repeaters live in a part of town that has an extremely high and somewhat variable amount of noise caused by numerous high power transmitters and other commercial and industrial enterprises in the busy Chesterfield Town Center area.  Our signal mixes with this other stuff and leads to de-sense of the repeater's receiver.

This de-sense was alleviated by a reduction in the 146.88 repeater's transmit power in January 2024.  The decrease from 50 to 20 watts provided immediate relief and briefly restored the reliability of the repeater.  Unfortunately, after several months, additional deterioration of receive performance has been noted.

The 146.88 repeater struggles with high noise levels on VHF FM but still shows reasonably good performance with C4FM digital signals.  Meanwhile, the 442.55 has been working beautifully for local FM traffic but this repeater stays busy for extended periods with distant digital traffic which renders the FM service inaccessible, often from non-members idling on busy national and global WIRES-X rooms.  The primary objective of this move is to free up the 442.55 repeater for local FM traffic by shifting WIRES-X activity over to the 146.88 repeater, which is usually still able to handle C4FM without much difficulty.

Implementation of C4FM mixed-mode operation on the 146.88 repeater was approved by our regional repeater coordinator on September 6, 2024.

Is this a permanent change?

We will make the change and then monitor for feedback specifically from C4FM/WIRES-X users over the following 30 days.  If a large number of those users experience a significant deterioration in performance with the change to VHF, we'll reverse the change and restore the prior configuration while the membership comes up with our next action.

What about the weekly RATS net?  SKYWARN?

The weekly RATS net will QSY to 442.55 on or before 9/25/2024.  Wakefield SKYWARN has also been asked to relocate to that repeater.

What do you mean by "Networked digital traffic has precedence" on the reworked 146.88 repeater?

Our WIRES-X system idles on the statewide Virginia Room when not linked anywhere else.  This means the WIRES-X system is nearly always linked somewhere.  And since WIRES-X carries only digital traffic, distant users on other WIRES-X repeaters can not hear our local analog traffic.  They have no idea if a local FM QSO, net, or other activity is in progress on our repeater or any other dual-mode system on the network.  Digital QSOs may begin at any moment.  On any dual-mode repeater with linked digital service, analog users must yield to digital activity.

Just as you would not deliberately transmit over analog transmissions, you should not interfere with C4FM digital traffic or attempt to transmit on top of it.  Likewise, local C4FM users should yield to local analog activity before initiating a call or connection on the 88's WIRES-X system, as they (should) do today on the 442.55 repeater.

I'm concerned that I won't be able to use C4FM on the VHF repeater given its performance.

That's a valid concern.  We'll be listening closely for complaints about the 146.88's C4FM performance in the 30 days following the changes.  We expect that there will be some users who could reach the 442.55 repeater before but can not access 146.88, even with C4FM.  This is due to slight differences in repeater coverage area caused by the characteristics of UHF vs. VHF signal propagation, terrain and foliage attenuation, as well as the effects of "tower shadow".  (Our VHF antenna is on one side of the tower, and the UHF is at the same height on the opposite side.  Users on the side of the antenna which is obstructed by the tower may experience diminished performance due to signal attenuation.  For most of our local users, the coverage of the 442.55 and 146.88 are historically pretty similar.)

C4FM users that have difficulty after the change to 146.88 are asked to promptly notify techcomm@rats.net.  If a significant volume of complaints are received from C4FM users during the 30-day evaluation window, we will absolutely roll this back and come up with a Plan B.  More on those possibilities, below.  When contacting us, please include the date and time of the issue and the particulars of your station (antenna type and height above ground, location, direction of travel, transmit power).

Is this a long-term fix for the VHF noise issues?

Absolutely not.  This change provides immediate relief for FM users by restoring a reliable full-time 440 repeater -- one of very few in our area (there are more VHF repeaters in our area than UHF, and most of the UHF systems are digital).  It may extend the usable life of the 146.88 frequency pair in our current repeater location by months or years, but this does not stop the VHF noise level from continuing to rise.  It is expected that eventually C4FM traffic will also become unusable on the 146.88 repeater, which would prompt us to evaluate moving the repeater to another location, or a shift from VHF to UHF service at the same site.

Are there any known issues with the 442.55 repeater?

So far, the 442.55 is still nice and clean on analog.  It has been running in a dual-mode analog+C4FM configuration for most of the last three years, usually set to 20 watts transmit power.  With careful observation of audio quality we do notice some very infrequent crackle in received signals when the repeater is transmitting at 50 watts which are not present at 20 watts and under.  It's more like a few little pops an hour vs. the continuous noise on the 88, and most users won't even notice these.  They've been there for years.

We also know the 442.55 repeater will briefly "go deaf" to nearby signals during intense severe weather events, while continuing to work fine for stations a bit further out.  For example, severe thunderstorms that produce very heavy rain may cause even high-power mobile and base station users in Midlothian and Richmond to be unable to reach the repeater, while it still works just dandy for someone out in Mechanicsville or Petersburg.  This isn't an equipment problem -- it's just some sort of propagation anomaly we see from time to time.  This condition usually clears up once storms depart the immediate vicinity of the repeater.

Do the 146.88 and 442.55 repeaters use different equipment?  Will performance change with this swap?

RATS owns three Yaesu DR-2X repeaters, each capable of VHF, UHF, or cross-band analog, C4FM digital, or mixed-mode operation, as either a standalone repeater or part of the WIRES-X network.  One unit is in service as the 146.88 repeater, one is the 442.55 repeater, and the third is a spare unit currently used as a C4FM monitor receiver for our Internet audio stream and voice recorder.  All three have the same features, capabilities, and performance.  RATS only owns one WIRES-X gateway, which will move from 442.55 to 146.88 during this change.

What happens if the 146.88 repeater's performance continues to deteriorate after the change?  or...

What if this change doesn't work out for C4FM users and we have to go back to the old setup?

Additional deterioration is expected as time passes and more noise-makers go on the air near our repeater.  While the Technical Committee and RATS Board are managing the current systems, the future of the 146.88 repeater in terms of any potential relocation or other actions will be left to the preferences of the RATS membership at whatever time those decisions need to be made.

The club seems to have at least four options:

• Move to a new UHF frequency pair at the same site.  We have a spare antenna already on the tower, and we own most of what we would need to convert from VHF operation to UHF, giving us a less noisy receiver without a complete relocation or rebuild.  This would move us off the 146.88 frequency pair but would allow us to maintain two simultaneous 440 talk paths with one repeater operating in full-time analog and the other either in mixed-mode or full-time C4FM-only operation.  Considering the size of the RATS membership and our budget for repeater projects, this might be the most likely scenario.  RATS would operate a total of 3 UHF repeaters.  The cost to implement this is estimated under $2000, primarily related to the cost of a new UHF cavity duplexer, Polyphaser, and some feedline jumpers.
  
  
• Move the 146.88 to a new location.  This will incur build-out costs and probably a monthly or annual lease payment for the additional space.  The current lease for the 146.88, 442.55, and 443.5875 repeaters is a sweetheart deal that's near the maximum price point the club can afford, and it'll be extremely difficult to find a satisfactory location at a price that fits within our budget without significant fundraising efforts, a big increase in membership headcount, and/or an increase in dues.  But if you have a solid lead on a good repeater site that might be within the club's financial reach, please send that information to techcomm@rats.net.  The initial build cost for a repeater relocation could vary from a few hundred dollars for a rooftop site, to well over $20K for a tower site similar to what we have now.
  
  
• Enable cross-band operation on the 146.88 repeater using our spare UHF antenna.  Users would be able to reach the 88 by transmitting on either a to-be-determined UHF frequency or the traditional 146.28 input.  The repeater would continue to transmit on 146.88 only.  Not many radios are capable of operating in this type of band-split configuration (transmit UHF, receive VHF) so only a limited number of users would benefit from this.  The cost to implement this feature is under $200.  (This is experimental.  Additional RF filtering may be required which could increase the cost.)
  
  
• Retire the 146.88 when it becomes unusable, with no replacement.  Obviously, nobody is a fan of losing a repeater or our long-held 146.88 frequency pair.  But we've known since 2019 that this is a possibility since the concept of an eventual retirement of VHF analog services was first introduced by the Technical Committee.  Better options are within our reach and this is the least likely outcome.
  

I have feelings about this.  Who can I talk to?

If you are a previous 442.55 C4FM user experiencing difficulty after the move to 146.88, contact techcomm@rats.net.

All other feedback may be directed to board@rats.net.