Author Archives: bryan

Tampa GMRS interference


Recently our users have experienced severe interference on the 462.5750 repeater input (467.5750). Initially it was though this was FRS 8 or 9 users on splinter channels. FRS 8 and 9 are 467.5625 and 467.5875 respectively and is a 12.5 KHz wide Narrow Band User. A FRS user on either of these channels would have a 1.35 KHz overlap with the repeaters pass band on its input, and potentially 2.45 KHz with a worst case permitted 2.5 PPM drift.

Remotely, we were able to put the repeater into Carrier Squelch mode (“CSQ”), and listen. It was immediately clear these were not off frequency signals of FRS users, but rather on frequency commercial operators.  Commercial operation under part 90 is not permitted on this frequency, and stranger still, there appeared to be multiple operators using this as both and input and an output for their repeaters.

Research was done, and it was found these frequencies were used for ship board repeaters and the port of Tampa.  As this is under 1 mile from the repeater site, these ships running a 5w hand held or 25w repeater on the input cause severe interference to GMRS repeater receiver.  Research showed these users are legal and permitted by the FCC for ship board use.  The shipboard channels are 10 MHz split 457.5250/456.5250, 457.5500/457.550, and 457.5750/467.5750; these last two overlap with GMRS and are only available to non-US users. US flagged vessels are under the FCC authority and 47 CFR 80.373(g)1 specifies 4 channels 457.525/467.750, 457.550/467.775, 457.575/467.800, and 457.600/467.825 with the lower being the repeater output. Note these are 10.225 MHz split and this appears intentional to keep users off GMRS repeater inputs.


There is not much GMRS users can do to have these users shut down in the port, as these users come and go as fast as they can offload their cargo at the port. Perhaps asking the port authority to have ships curtail their use, however most are unaware of the channels they are on.

FSG soultion

Our repeater is not on a duplexer, but rather a split TX/RX antenna system.  The transmit antenna uses a RF combiner consisting of tuned circuits to combine multiple transmitters onto a single antenna. The receiver antenna has dual 4 MHz wide filters on centered 458 and 468 MHz feeding a low noise, high gain pre-amplifier and then receiver multi-coupler. This provides some frequency flexibility as the transmitter frequency cannot easily be moved, but the receiver frequency may be moved.

Our tech committee has enabled scanning mode on the receiver.  It will listed on 467.5750 141.3 Hz and 467.7250 D546, and scan between these frequencies.  This does introduce a slight delay when using the repeater, but most users should have a half second delay upon key-up before starting to speak as this is good radio practice.  Note the P25 NAC is still 0x575 on both.

What many users do is program “Tampa 575 FSG” and “Tampa 575 FSG'” in their radio, with the prime channel being the alternate input. Some purpose built GMRS radios may not support this or likely support it but must be programed via a computer to do it.


ITUR M.11743 Technical characteristics of equipment used for onboard vessel communications in the bands between 450 and 470 MHz

47 CFR § 80.373 – Private communications frequencies.

47 CFR § 2.106 – Table of Frequency Allocations :

US287 In the maritime mobile service, the frequencies 457.525 MHz, 457.550 MHz, 457.575 MHz, 467.525 MHz, 467.550 MHz and 467.575 MHz may be used by on-board communication stations. Where needed, equipment designed for 12.5 kHz channel spacing using also the additional frequencies 457.5375 MHz, 457.5625 MHz, 467.5375 MHz and 467.5625 MHz may be introduced for on-board communications. The use of these frequencies in territorial waters may be subject to the national regulations of the administration concerned. The characteristics of the equipment used shall conform to those specified in Recommendation ITU-R M.1174-2.

Tampa GMRS repeater

We’ve repurposed an older commercial repeater into a GMRS repeater on 462.575 at our Tampa Site.  This is proving to have great coverage in the Tampa Bay area and already has had a bit of activity.

Output: 462.5750 MHz CTCSS/PL 141.3
Input: 467.5750 MHz CTCSS/PL: 141.3
Alt Input: 467.7250 MHz DCS: 546: Use this!
P25 NAC 575 Tx and Rx

This repeater support P25 phase one as well, which is unique in the Tampa Bay region.  We encourage everyone to use PL on their receiver and listen before transmit.  If your radio supports it, please program the alternative input of 467.7250 MHz and D546. There is intermittent interference from ships in the port of Tampa 1/2 mile away.  This will not key the repeater, but it’s plenty to prevent the receiver from hearing other users.

The coverage below shows the 39 dBu signal level for 50% of the time at 50% of locations 6′ off the ground.  This is roughly the expected mobile range of the system for a good voice quality.  Into a typical 1/4 wave receiver antenna, you should expect a -95 dBm signal in the blue areas.

Tampa 575 GMRS Repeater

Tampa 575 GMRS Repeater coverage area

Downtown Tampa Webcam

FSG has added a webcam feed on our YouTube page.  This provides views from our downtown Tampa location at the 500 foot level. This cam is a PTZ and will generally be pointed south, or moving around to a number of locations, or under manual control.

This is a 4k video webcam and we are dedicating about 20 mbit/s of bandwidth to it via HamWan. As far as we can tell, it’s the only 4k webcam in Tampa online. The stream is beta now, it may be up or down. Please inquire on the mailing list or slack if you have any questions or ideas regarding it.

St Pete UHF Analog and P25 frequency change

Due to some severe ongoing malicious interference on 444.375, we moved the St Pete Repeater to 444.325 for testing. The P25 NAC is still 293, PL is still 146.2 Hz.

Please test it out and let us know how it’s working. This move may be permanent after testing.

St Petersburg Repeaters are ONLINE!

Florida Simulcast Group is pleased to announce three new repeaters on the air in downtown St. Petersburg.  Our repeaters are located at the 400′ (121m) level, and should service most of southern Pinellas county for portable users.  These are linked full-time to our repeaters in Tampa and other systems depending on the mode.

Based on early testing we are seeing solid coverage of downtown and the beaches.

The frequencies are:
443.7625 NXDN (RAN1)
444.3750 Analog and P25 (146.2 PL/293 NAC) and Allstar Node 44233
444.9625 DMR (CC1)
All the above have a +5 MHz offset.

For more programming info on the digital modes visit

Having three repeaters work well on a single antenna was no easy task.  FSG had to employ extensive filtering, branching and combining to enable all repeaters to operate without causing self interference.  A gallery of our testing and combining may be found online here, and a reddit thread describing the build is here

A short video tour is available on YouTube.

All repeaters make use of HamWAN for linking to other sites and beyond.

These are open for all amateurs to use and testing is encouraged.

HamWAN St Petersburg is Live!

With help from our technical committee members (Matt KA9RIX, Ryan KJ4SHL, & Bryan W9CR) the St Pete Site is online.  We worked from 8am to 6:30pm on the 29th of December to mount the radios on the roof, run and terminate cable, ground all cables, move the 7′ rack up a flight of stairs and install the router.

This new site is 400′ high in the center of Downtown St Petersburg and will ensure solid coverage of the city and beaches to our standard 30dbi client radios.


All in all it went very well, and the major parts were in place by lunch time, with the 7′ rack being the fun part.  We had to remount the 3.4 GHz link to Tampa, but fund it was aligned very well on the Tampa end with a -65 dBm signal and 130 mbit/s solid signal over 16 miles away.  We still need to tweak the alignment at Tampa, but it’s working well for general use now.  3.4 GHz is a great band for linking on as there is practically no noise across Tampa Bay.

After the router (Juniper EX4200) was installed ISIS would not come up between the Tampa and St Pete Sites so we decided to pack it in for the day.  We did have remote access from Tampa to the St Pete router and I was able to track the problem do to a WDS mode setting in the UBNT M3 radio link.  With a software upgrade the ISIS protocol packets now passed across the backhaul link and routing was able to come up later Thursday evening.

We did some testing on Friday of coverage around St Pete and found from downtown with a 60 dBm signal 45 Mbit/s was achieved to a client radio.  From Gandy Blvd and 4th Street North a solid -75 dBm signal was achieved at ground level with out a clear Line of Sight (LOS).  At the Bay Pines VA hospital a -80 dBm signal was had.

30 dBi client at KA9RIX

We installed a test client at Matt’s QTH at 25′ and found a non-line of sight -75 dBm signal.  We suspect going up another 10′ will greatly improve this signal.  This is over 10 miles away and we’re achieving a signal able to do 15 Mbit/s.




Brent, W8XG did some testing from the roof of his condo building in Sarasota over 30 miles away and was able to link u

p at -87 dBm and get an IP address.  He didn’t have much ability to test but was able to browse a couple internet sites.  This was really unexpected and quite amazing!

We have a plot of expected coverage from the St Pete site with the 30 dBi client radio at 30′.  The inner contour is for -75 dBm, and the outer is for -85.

This next map shows the combined coverage from the other Tampa site.  This is predicting a 75dbi signal in the yellow at 30′ for 70% of the time.

You can download a google earth overlay of this.

Testing HamWAN from PIE

We did some testing with a new client radio today, the Mikrotik DynaDish 5 from the St Petersburg Clearwater airport.  At 8′ off the ground we had a -69dBm signal from the antennas  22 km (13.75 Mi) away in Tampa.  A speed test showed a 22 Mbit/s throughput.

Once installed higher on the roof the signal should improve to -62 to -65 dBm and provide a great link into the HamWAN.



St Pete HamWAN update

We’re making progress on bringing HamWAN to St Pete.

FSG has secured a site downtown and we have a full 3 sector setup and backhaul ready to go up.

The sectors are ready to go, and we expect to have 220, 440 and 900 MHz repeaters up at this site over the coming months too.   We expect this to fill in all over St Pete and southern Pinellas County.

Our deployment of HamWAN, a multi-megabit internet connected network over Ham frequencies, is now live in Tampa.

With a proper CPE setup you can expect to get 10-20 MBit/s TCP throughput to your network.  We support both IPv4 and IPv6 address space.  Anyone who’s licensed (Tech or higher) can get on 5.9 GHz with equipment for under $200-250 dollars.  This is perfect for linking repeaters and other critical points to the internet for redundant radio linking and high speed redundant IP data.  Leave your TNC at home and experience what packet radio should have been.

Below is a coverage map showing a 30 ft client radio elevation (and clear line of sight) to our site in Tampa.  This is an estimate for minimum signal (-75 dBm), as such if you’re marginal it may not work as well, even though the radios will work down to -90 dBm.

-75 dBm or better 30' client

-75 dBm or better 30′ client

Attached is a coverage map you can overlay into Google earth and explore.

To get online please subscribe to our FSG mailing list and we can get you authorized and your client radio configured for our access points.  We have a few test radios available if you want to test a site out before committing to it.