Author Archives: bryan

Tampa GMRS Update

Our Tampa GMRS Repeater on 462.575 has been updated with a separate voting receiver on the 467.725 D546 / NAC575 channel. This will run in parallel with the existing 467.575 receiver. Previously the single receiver in the repeater would scan, but this is not as quick as having two receivers. It was also possible that strong on channel interference would cause it to dwell on non-active channels. This would mean the first second of a transmission would be clipped.

We’ve fixed this by adding an additional Astro-Tac receiver which will vote for the strongest signal and use it. As part of this receiver pre-amp was reconfigured and we should expect 6 dB more gain in the receiver path. This should greatly enhance the performance of handhelds using this site.

We encourage all people to use the alternate input if your radio support it.

St Pete NXDN and P25/Analog Online

The NXDN and Analog/P25 repeaters in St Pete are back online.

Both have been repaired and in the case of the NXDN, power has been increased from 17 watts to 36 watts to the antenna. St Pete is a unique site with three repeaters on the same antenna, meaning there is a combiner and duplexer with receiver filter. The down side is losing 4.5 dB on the NXDN frequency and 3.9 dB on the 444.375 P25/Analog repeater frequency.

HamWAN remote

FSG has been promoting HamWAN and it’s use for connecting parts of Tampa bay over our amateur microwave frequencies. In keeping with this, there’s been a need to connect mutiple remote sites, where there is internet, but outside the coverage area of HamWAN wireless. The soultion to this is a VPN and we’ve come up with a “turnkey” soultion supporting the following:

  • Cheap (100-200 of equipment)
  • IPv4 and IPv6 routed subnet
  • Transparent routing over the underlay network (people shouldn’t be able to tell it’s a VPN)
  • Traverse NAT, even NAT 4444
  • Mutiple switch ports with Power Over Ethernet (PoE) as an option
  • Integrate to the existing HamWAN network, and optionally provide redundancy to wireless
  • Scale to gig+ speed
  • Allow others who have their own IP space to announce it via HamWAN Tampa

Details can be found here https://wiki.w9cr.net/index.php/HamWAN_Remote_Site and if you want to get involved, hit us up on #hamwan on slack or on the mailing list

Orlando Hamcation 2022

FSG members will be attending Hamcation 2022 this Friday, Saturday and Sunday, Feb 11-13 at the Central Florida Fairgounds. We’ll be setup outside and have a tent area. We invite everyone to stop by and check it out.

We’ll generally be monitoring 443.525 FM 146.2 PL tone, but have setup a special Slack channel #hamcation-2022. If you don’t have slack, please install the app and sign up using this link.

Hamcation Info

https://www.hamcation.com/
Location, Date & Time
Central Florida Fairgrounds and Expo Park
4603 West Colonial Drive
Orlando, Florida 32808

February 11, 2022 | 9AM to 5PM
February 12, 2022 | 9AM to 5PM
February 13, 2022 | 9AM to 2PM

462.575 GMRS Update

Due to almost constant interference on the 467.525 input, we’ve set the repeater to 467.725 DPL 546 input only for the time being.

Due to a great gnashing of teeth over this, we’re rolling this change back. Scanning receiver is re-enabled and we’ll be looking at other options on how to deal with the ships on 467.575.

WD4SCD 147.030 Repeater Remote Receiver

FSG believes in cooperation and assisting other amateurs where we can. In 2019 Richard Pomeroy in cooperation with Pinellas County ACS approached FSG about locating a remote receiver at our St Petersburg location for the WD4SCD 147.030 MHz repeater. After some thought FSG agreed to provide the antenna, radios, interface hardware, computer and Internet link required for this cause. Our first iteration (an AllStar RTCM) didn’t work for WD4SCD, and we ended up with a dedicated windows server running echo-link.

It’s online most of the time, but we do not actively manage it; the WD4SCD repeater admins take care of connecting/disconnecting it. This can be accessed on a 147.030/147.630 with a 100.0 Hz PL tone. Extra Low power on most HT’s from St Pete will be full quieting into this site. As this site is at 380′, it’s one of the highest amateur repeaters in Pinellas County. This is yet another valuable service running over the Tampa Bay HamWAN.

This has been in operation since August 2019, or just about two years at the time of this writing.

Site Hardware

The hardware FSG has dedicated to this is simple, only a Motorola CDM radio, commercial gain 148-158 MHz antenna, 1/2″ heliax, a signal link interface and a server PC running Windows.

First Iteration March 2019
  • VHF Antenna
  • WD4SCD Receiver Install at FSG
  • St Pete Ham Rack
  • Receiver In Testing

FSG Board Nominations Open

As it’s that time of year again, we have elections open for the board.

If you’re a member of FSG you may run for any of the positions open:

President
Vice-President
Secretary
Treasurer
Regular Board Member

If you want to nominate anyone please do so via email to the secretary of FSG
jesse@flscg.org

Our members meeting is tentatively scheduled for the 18th of September, but
COVID-19 may change that. As the bylaws require nominations to close out 30 days
prior to the members meeting, this means all nominations must be received by
the 19th of August.

Tampa GMRS interference

Problem

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.

Solutions

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.

References

ITU–R M.1174–3 – Technical characteristics of equipment used for on–board 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.