Lscott

I’m not familiar with that one. It sounds like it looked similar to an old CB radio. At least the radio didn’t die on you when you needed it the most. I guess that’s one main point about the experience.

What was the marine radio you had on the boat? And what was the antenna setup like?

Wow!! You sure were lucky to get back!! I can't image if some foul weather blew in while you were out there what the end result would have been.

Yup. Considering the crazy weather in the southeast right now for some it's more than a "theoretical exorcise" at the moment.

Even that experience would be welcomed. I'll bet there is a carry over between different services that would be a lesson for all to learn from.

I see posts where people buy a radio(s) to use in an "emergency". How many people have REALLY used their radio in an emergency, not some simulated drill? What was the experience like? Were the preparations made before hand sufficient? What would you have done differently after the experience and lessons learned? I think the above are the only real relevant questions. Simply buying a radio and keeping it in the draw with some battery packs until the SHTF doesn't really cut it I suspect. I'll take real experience over some hypothetical situation or simulated condition.

All of the radios I have I try to get the service manuals for them along with the operators manuals. Being an engineer I look through the schematics at times to see what makes a specific radio "tick" so to speak. What I've found is just about, if not all, the commercial LMR radios I have use some kind of turntable front end filtering. Those filters are typically before the first IF stage and acts as a pre-filter to improve the image response and the possible desense of the IF amplifier chain after the filters. One of two techniques I've seen used are varactor diodes or variable inductance chokes. Both are "biased" by an output from the micro running the radio. As the frequency is changed the front end filter is electrically tuned to match the programed RX frequency. The reason why CCR's are so cheap as you pointed out the front end filtering is minimal. This isn't just a problem with CCR's however. Many Ham HT's, from name brand manufactures, suffer from the same problem. As Hams we like the idea of a wide RX range for scanning etc. however that comes at a price, a wide open front end. To add in the fancy tuneable front end filters adds cost and complexity to the radio. To show you what is in some of the CCR's I found a schematic, reportedly, for the commonly mentioned UV-5R. I'm going to guess that derivatives of this radio the schematic won't look too much different. After all what did you expect to see in a radio that sells for about the same price as a kid's FRS bubble pack toy radio? Oh, the harmonics on TX suck too. If you'll notice some of the harmonic tests were done at a load impedance of 25 ohms, not the expected nominal 50 ohms. At 25 ohms that would correspond to an SWR of 2:1 so the party doing the testing wanted to see if the harmonic content was SWR dependent. SCHEMATIC Baofeng UV-5R.pdf UV-5R VHF Harmonics Test.pdf

These GMRS forums is NOT the place to discuss your politics. If you want to do that take it elsewhere.

The best I’ve heard was the machine maintenance staff at a close by business to where I work. They got FRS radios to use. One day the supervisor called one of the staff. They didn’t answer right away. Supervisor called several more times. Finally the staff member answered. Supervisor asked why he didn’t respond right away. Staff member replied with an obvious “attitude” that he was busy. Supervisor then proceeded to rip the staff member a new one, used the “F” word frequently explaining why that shouldn’t happen again. The staff person simply replied “Yes Boss!!” and that ended that communication.

CCR’s have their place. But I wouldn’t recommend one if you’re depending on it to save your life. Articles I’ve read the people in the photos likely got the radios more for appearances. It’s part of the “costume” to impress people along with the military type fatigues. Any of them that truly thought they were reliable never tested a sample, bounce one off the cement a few times and get it soaked with rain water, see if it still works. I dropped my BTECH tri-band HT on the floor from a high top table at Twin Peaks just once. The speaker got buggered up. Those cheap radios are fragile.

Might have it all wrong. Maybe they got the CCR's because the FBI undercover agents wouldn't take them seriously, leave them alone, and just follow the guys around using Motorola radios. The FBI would figure those guys are the smart ones.

One shows up at an event like 1/6 and then bets their safety on a $30 Chinese radio? Yeah they should be prosecuted, for stupidly.

Just for the record this is the FCC rule part covering public safety frequencies. https://www.law.cornell.edu/cfr/text/47/90.20

So a fiber link would be more reliable than a cable link? I would agree if we're talking about a cheap DSL connection to the local telco. Just for information purposes what is the typical link speed you think, or based on experience, makes a high quality link for VOIP traffic between linked repeaters?

Well what about all the old boat anchor equipment out there using analog VFO's? Those radios can very easily run outside of the official band limits. As a Ham it's YOUR responsibility to ensure station operation occurs within the service's band limits. In fact crystal calibrators were popular projects at the time to check RX and TX dial calibration. Some radios had them built in. Hams have gotten spoiled by the firmware in modern radios that prevent out of band operation. So would the section referenced in a prior post now make owning one of those old radios illegal?

Wouldn't that also be true with other digital voice modes using Internet linked repeaters? That would be independent of whose equipment was used at the end points for the RF part.

The few I got were between $50 and $100 each.

http://www.w3pga.org/Antenna Books/Reflections III.pdf

I’m going to look into that a bit more. It would be nice to have some cheap hardware that does digital modes that would be costly buying commercial radios to do. Might be more fun than screwing around with a hot spot.

It's a cheap way to experiment. If the radio gets bricked with funky firmware won't cry much. Better than bricking a $500 radio.

https://www.law.cornell.edu/cfr/text/47/90.407 https://www.law.cornell.edu/cfr/text/47/97.403 https://www.law.cornell.edu/cfr/text/47/97.405

That would be a very interesting test. I would like to see just how much adjacent channel rejection the radios really have. The transmit bandwidth can be controlled through careful pulse shaping while in digital mode. That's why you see mention of such things as GMSK modulation for some digital modes. https://en.wikipedia.org/wiki/Gaussian_filter https://www.electronics-notes.com/articles/radio/modulation/what-is-gmsk-gaussian-minimum-shift-keying.php https://urgentcomm.com/2001/04/01/does-the-digital-radio-standard-come-up-short/

My question about using two adjacent 6.25KHz channels, or even 12.5KHz channels, is how steep are the filter skirts in the radio's IF section. They typically use cheap ceramic resonator type filters. If they're not extremely steep the attenuation of the adjacent channels will be noticeably degraded because the IF filter pass response would still be fairly high as it overlaps the adjacent channel's bandwidth boundary. For example you might see a selectivity specification of negative 60db at 30KHz using a 16KHz wide signal, 5KHz deviation with 3KHz audio. That would imply the filter skirt's roll offs are 14KHz total for both sides. Reducing the signal bandwidth to 11KHz, 2.5KHz deviation with 3KHz audio, and adding in the same filter skirt bandwidth, roll off is the same but pass band is narrower, results in a possible performance of negative 60 db at 25KHz. The total bandwidth is less but it's not as narrow as you would first assume. For mobile/base radios there is enough room to put in better analog filters with steeper roll offs. However in portable radios' HT's, PCB area is limited. Perhaps replacing the analog filters with a high order DSP based one at a lower IF frequency might work. You can design a DSP filter in hardware using an FPGA which would give better performance than a DSP type micro could provide. Any claims that going to a bandwidth of half of the former value the number of channels can be doubled I'm very skeptical about it without some major improvement in the filter technology IMHO.

I think the FCC, and other agencies in other countries, will move most users to 6.25KHz, most likely digital, when the technology is easy and cheap enough. There was a post somewhere I read where the FCC considers 12.5KHz as an intermediate step before moving to the narrower 6.25KHz bandwidth. If you don't have a radio that can do 6.25KHz now I would start looking for one. That's why you see mention of the TDMA method used for DMR as being 6.25KHz "equivalent" bandwidth even though the channel bandwidth is 12.5KHz. NXDN uses FDMA and can do 12.5KHz and 6.25KHz bandwidth, both in digital mode, depending on the VOCODER data rate used so it's already when the ultra narrow bandwidth is mandated by the FCC. https://en.wikipedia.org/wiki/NXDN