MarkInTampa

The GP-9 2m/70cm antenna sucks at GMRS, at least in my case. If you have a SWR meter or VNA test it out yourself, your results may vary....

You are about dead on on power loss. 59% according the the calculator, but with the gain of the antenna you have an effective radiated power of almost 200 watts. Keep in mind the tool I used (https://kv5r.com/ham-radio/coax-loss-calculator/) uses dBd for antenna gain, dBd = dBi - 2.15

I put a loop at the antenna because the Comet instructions tell you to do so. I figured if it is in the instructions, there is a reason why.

I did a tone scan and got a tone a few months ago when it was transmitting DMR and tried. Either analog is disabled or it's using a non-standard input. I did think about running a simplex repeater to mess with them but not worth the effort.

Here is one of them https://flscg.org/2021/03/tampa-gmrs-repeater/

It's close to impossible to hijack a encrypted DMR repeater that doesn't do analog.

Not in this case. The NXDN repeater went online six months ago, the P25 repeater has been online for a few years. I'm not complaining, both are really strong repeaters (the most dominant in the area) and most traffic is analog. If there is a bit of digital traffic a few times a month for a minute or two, it's a small annoyance for how good the repeaters are. The encrypted DMR repeater on .700 popped up a year or two ago. It was traced to a security company running illegally and has been reported to the FCC many times but it's still there.

Tampa has two digital/analog repeaters on GMRS, one running P25 and the other NXDN. The connection info is published on their websites and are public. Neither one of them get very much digital traffic, I would guess 95% is analog. There is also someone running encrypted DMR on 700 still, from what I was told it is a business running GPS tracking on fleet vehicle's. It drove the Tampa 700 repeater a year or so ago to .600 and they forced the existing .600 repeater in Clearwater to .550 knowingly but didn't care.

The largest public repeater in my neck of the woods doesn't show up on the map anymore. From what I was told is if the repeater owner/operator doesn't check in with myGMRS within 12 months the repeater is removed from the map. It's still listed (with the map) if you go the the list view and click on it. The owner just got tired of repeater requests so he publicly listed the tones, called it open and disabled access requests and hasn't updated the status in over a year.

It died down but never went away in my neighborhood. One is still linked but doesn't have nearly the traffic it once had but still a lot of out of state traffic.

I've had pretty good luck with the Argent. I originally bought it so I could hook it up to the base station and test HT's and antenna's out in the wild without needing somebody on the other side and it did a excellent job of that. Since it does CW-ID, I loaned it out to a repeater operator to send out the CW-ID through a HT to the repeater until he got a new controller. Also use it on occasion to repeat voice back to the repeater for radio checks if somebody wants to hear what they sound like through the repeater. But most of the time it sits in a box unused, but a nice tool to have when you need it.

The GP-9NC (GMRS/MURS) is rated 153-157MHz and 460-470MHz. The straight GP-9 and GP-9N (ham version) is rated 144-148 and 440-450MHz.

I have both of these antennas. 30ft mast, 50ft LMR400. In my case, the GP9 worked better on VHF and the GP6 better on UHF. Don't know if it is the location of the antenna, the oak tree 20ft away or what but I had a better experience with the GP6 over the 9. I dropped my mast to 15ft and the GP6 made it just fine though the Cat3/4/5 hurricane that hit me last week in Tampa. Don't have to worry about the oak tree....it didn't. Power is still down, no air conditioning sucks.

Me back in the day with a Siltronix 1011D that popped up on my sisters FB page yesterday...

I've broken the ring many times. From a hour or two when installing new switches to a week or so at a time when one of my guys drove a underground fiber warning post right through the fiber before it was fixed. Every switch that part of the network has passive fiber coupling, if the switch or power goes down the fiber is coupled together to keep the fiber live bypassing the switch. Also all are on large UPS's, IP accessible power strips, etc. Every pullbox for the fiber has at least 50ft spare cable looped in it. The strange thing is the way different districts test things. The UPS's all have ethernet ports and are connected to the network. One district will test remotely once a month and send somebody out it it fails and another district actually have crews that go to the site to test the UPS and visually verify batteries are not bulging, connectors are good, etc on a monthly basis.

The fiber network runs in a redundant ring and is divided by 7 districts that run and maintain their own fiber within their district. Some of the districts even have redundant operation centers. For example district 1's primary operations center is in Ft Meyers and the backup is in Bartow 90 miles away. With additions of cameras, traffic detectors, EDMS (electronic digital message signs - and each one of those have a camera focused on them to confirm operation) and the like over the last 10 years that are all IP based and consume a ton of bandwidth fiber is the way to go.

Two different groups run them so I couldn't tell you for sure. The SARNET system runs across the FDOT's (Florida Dept of Transportation) microwave network and towers. I've been to a few of the tower locations - it was kind of strange. The microwave network runs T3/DS3 (54mbs) protocol as a backbone, then divided into T1/DS1 (1.5mbs) lines and then further divided into 56/64k lines. There was even a old analog rotary dial telephone connected using a ancient PBX adapter that still worked at each location. It was like looking at a telco room from the 1960's. DOT is really well connected in Florida using both microwave and fiber they own. Almost everything that ran on the microwave is now running on fiber. Up until 5 years ago almost all the interstate was covered with fiber and have PTZ cameras installed every 2 miles and MVDS (Microwave Vehicle Detection System) every mile with the exception of 130 mile or so stretch of I-10 between Jacksonville and Tallahassee and that's what I helped put in, now it's close to 100%. Now almost everything that was running microwave has been switched to fiber and the microwave network is basically abandoned except for the SARS repeater system. I talked to one of the FDOT IT directors awhile back and they wanted to scrap the microwave network that they don't use and didn't want to have to pay to maintain the towers and system anymore but it wasn't in the cards yet. I'm not sure how long SARNET will stay up or if DOT will allow them to run across the fiber - time will tell. BTW - you can listen to SARNET through Broadcastify: https://m.broadcastify.com/listen/feed/35392

It's covered even better by SARNET (https://sarnetfl.org/)

GMRS Live to shut down on Monday, Sept 30. Statement is on his webpage... https://www.gmrslive.com/

The reason I think it was a simple timer (at least in the case of the radios) is that it makes the most sense. If you are going to detonate all at one time, how else are you going to do it? DTMF maybe, but at what frequency (or frequencies)? Individual or in group addressable, again what frequency and why if you are going to blow 'em all up at the same time would it matter? A simple timer in a battery pack would be undetectable to the radio, it's programming, it's operation, ID or frequency. Once the secret of exploding radios came out (with a boom - sorry, had to say it) I think it was a one and done thing, the enemy knows what to look for now.

I may be proven wrong (it wouldn't be the first time) but I don't think the radios (or pagers the day before) were doctored at all, the batteries were. If your intelligence department finds orders for pagers, batteries or radios being shipped to a known enemies address that acts as a liaison for those in the field, can pose as the vendor or intercept the order and you sent them a battery that had a simple timer and a small explosive charge to go off at a predetermined time. You wouldn't even need the radio or pager turned on, wouldn't have to hack the radio or anything and a heck of a lot simpler to pull off.

The Comet GP-9 2m/70cm antenna sucks for GMRS. I don't know how the GP-9NC (the GMRS version) does on 70cm. The GP-6NC (GMRS/MURS) version works great on 2m/70cm/GMRS though... GP-9 UHF SWR seep followed by GP-6NC UHF and VHF sweeps, same coax (50ft LMR-400) and pole (up 35ft)...

Just make sure you are at least 3.5ft away from the antenna...

If I had to guess there is a really strong repeater around 40 miles away already on 725 with excellent coverage up 400ft that can be accessed from the 575 repeater location with a good radio. Far enough away that occasional local traffic on a different tone on the input of 725 won't really effect it but close enough that you wouldn't want them on the same output. Both are by far the strongest repeaters in the area.

There is ship traffic that causes occasional interference on the Tampa 575 repeater. It has a alternate input of 467.725 as well as the primary input of 467.575. The primary input (467.575) is part of the ITU standard for UHF vessel communications and the repeater overlooks the port of Tampa. The ship traffic doesn't key the repeater but does mix in with normal GMRS traffic so they shut down the primary input if it becomes a problem. FYI - ITU UHF standards for vessel communication coexists with two GMRS repeater inputs, 467.550 and 467.575 as well as GMRS channel 8 (467.5625)