gman1971

Yep, I can certainly vouch for that. Since putting a super high gain antenna high up, the analyzer was reading a massive noise threshold.... needed 2 cans (cavities) to bring it down to an "acceptable" level. I think the radio range these days, aside from more TX power, is also limited by receiver being overloaded by RF noise; b/c after finding out the noise threshold at my location I was blown away how high it was... so if you don't have a radio that has a tight front end you won't receive signals from very far... Don't sell yourself short, Marc, you are being helpful to others, and nobody knows everything.... point is that sometimes little tidbits like that are the eureka moment that makes it, even for knowledgeable ppl. G.

Absolutely! One can never be too careful

WRAF, I don't think I ever stated, nor implied, that anyone was/should be using the SLR8000 for GMRS. I just pointed the figures to show it on a chart. Whether it is or not part 95 accepted it is hard to argue that the figures on that thing are just amazing, plus it has additional blocking of 110 or 120 dB, so its probably loaded up with filters of all kinds... hence why that is the kind of receiver front end performance one should strive to get, compared to the bottom of the barrel GD77... which is fine for certain things. Yes, thats it right there WRAF: "A lot of the nicer handheld radios have tracking filters on the frontend that gives them stronger desense protection, and you won't find that feature at the CCR price point." I understand that for very advanced guys/gals, like you, the statements I've made are like 1st grade math, but for some of us who trained in other fields, this is the kind of stuff that marketing preys upon to sell CCRs. It would've saved a lot of hassles, time, and ultimately money, should I've have known about what I posted in here. Is it simplified? Yes, but so are Newton's classical mechanics vs the more complete Maxwell's equations... yet we still use Newton's for pretty much anything were v << c... In the end its someone else's money, they can spend it however they like it. I only wrote this in an effort to help others, who may, or hopefully not, be as clueless as I was when I started buying radio gear. G.

WRAF, yes the GD77 is probably one of the worst CCRs out there. While Anytone 878 radios fare much better, these still desense easier than the EVX radios I have. LScott, The chart was calculated using the specifications printed on the radio service manuals. For the GD77, the selectivity figures were calculated using a VNA using a similar procedure to the one outlined here. The sensitivity of the GD77 is claimed by the manufacturer to be -122.dBm The point of this chart was to show at a quick glance why these radios are inferior to things like the SLR8000 repeater from Motorola... I understand desense is a fairly more complex issue, but the chart is easy to read for most people. If you can determine the noise level in you area, that is half of the battle right there. G.

I just made this new thread, trying to explain the whole CCR situation from a receiver standpoint, and why those things aren't that great. https://forums.mygmrs.com/topic/1661-the-definitive-ccr-thread-why-you-wont-really-save-anything/ G.

I'll start the Cheap China Radio (CCR) thread by showing this picture. That shows the sensitivity of the receiver combined with the channel rejection filtering in dB, which means, any signal value that is above the dBm curve plot will desense the receiver. You can pretty much extrapolate this curve from the last point where it is computed if no advanced filtering is used, like the SLR8000 repeater, with over 120 dB blocking for off frequency stuff, etc.. but unless you have one of those, most mobile radios don't have that kind of additional filtering. So if you live in an are with a noise floor of -50 dBm like I do, pretty much most CCRs will fall apart and desense so bad you won't hear squat. OTOH, radios like the XPR7550e, with super tight front ends, will effortlessly reach over miles when the CCR is deaf as a rock. This also shows why more sensitivity is not better, in fact, more sensitivity with a poor front end filtering means it will desense even faster. IMO, the graph above should be pretty much definitive as to why the pricing is directly proportional to the selectivity + sensitivity on those devices: with the Motorola SLR800 repeater leading the pack at well over 2 grand, the Vertex EVX-5300, new, was around 600 bucks, the TM-V71a, is around 350 bucks new, and well, the GD77 CCR can be purchased new for 65 dollars on eBay. And here is a very simple procedure to gauge a CCRs performance and if its even worth the expenditure. 1) First off, If no channel selectivity figures are offered, then move on. "These are not the droids you're looking for." 2) Now get the receiver sensitivity figure, usually measured in uV, but with this nice chart you can convert it to dBm at 50 Ohm, link here: http://www.repeater-builder.com/tech-info/measuring-sensitivity/dbm2uv.pdf 3) Knowing that any signal above the receiver sensitivity threshold (at any frequency) will desense the receiver you add the selectivity in dB at 25 kHz to the receiver sensitivity in dBm, pay attention to signage, the sensitivity is negative dBm. 4) Repeat the same for 12.5 kHz. Now, some brands show even narrower kHz dB figures offered. You can add it and find out, but that is usually not as important as the real selectivity for further away signals. 5) As a general rule, any signal received within the receiver frequency range (and in the CCRs even further than that) that is stronger than the 25 kHz selectivity value calculated will desense the receiver. Have at it, and please, correct me if I made any mistakes. G.

I have a similar radio to that one, reception is lacking, and desenses fairly easily. If you can't replace the antenna then I would just get a Baofeng BF-888S for 9 dollars from Amazon. G

AT the risking of possibly starting a fire, I would say that I don't consider Ham Gear mission critical either. Most of the ham stuff I've tried is flimsy, and has RF front ends that are wide as barn doors too. For example, when using my TM-V71a with a triple 5/8 over 5/8, its hammered by intermod pretty hard, mostly due to a NOAA station (and other high powered junk) blasting 2 miles from home from a 1400 foot tower..., and while the CCRs don't hear squat, the TM-V71 hears much better, but still severely desensed and the intermod hurts it really bad. I can hear the NOAA breaking on the GMRS frequencies if I don't run any filtering... In contrast, I don't have that issue with the EVX-5300 radios, even without any filtering added; sure, the EVX-5300 is only an 8 channel mobile with just a single digit numeric LED, and it won't even go below 450 Mhz, but its perfect for GMRS and also allows the option to use DMR. Yes, exactly, a couple of CCR GD77s gave me a taste of DMR, and since then I upgraded all my GMRS FM only gear to high end DMR capable gear, but I still run it on FM. But let me tell you, once you move into high end DMR radios like the EVX-5300, you realize how bad these CCRs really are, even the Anytones (Alinco DJ-MD5) still don't hold a candle to the EVX radios from Vertex Standard (Motorola now) We shall see how it all shakes down. Whatever the future awaits, I am ready to embrace digital the moment the regulations allow for digital voice modes on GMRS. G.

I am not saying don't buy CCR, just know what you're getting. That's all, so you don't put too much faith on those inexpensive radios. GMRS won't do it b/c it is only FCC, but in theory, if another country who follows the FCC ruling has a GMRS repeater linked you could talk all over the world too... I know, not RF direct call, but still cool nonetheless.

I thought max legal was 50W? could it be, perhaps, a super high gain antenna? I mean, with 50W and a 9+ dB antenna on a mountain top you'll get pretty darn far... G.

I don't know about the Luiton, etc... But like I stated in some other post I made, gauging your radio performance based on its ability to hit repeaters is doomed to succeed (its a useless test to gauge performance). Those BTech stuff RF performance in simplex, when there is no repeater around that is using $2000 radio gear to do the heavy lifting, in simplex, they'll simply fall flat in their face. Especially so in a congested RF area, these are just worthless pieces of junk for anything mission critical. For the money you're better off picking up a used commercial UHF portable, that will have a proper dual conversion superhet receiver with a front end that isn't wide as a barn door, nor will desense with the 89.7 latest 80s tunes radio station. I am glad it works, but won't be surprised if it doesn't when you need it the most. It has happened to me... and since that day, no CCRs for me. I'd take an Icom, or a Kenwood (like my TH-F6a) any day of the week over anything CCR, especially if it is for anything that is mission critical. Myself, for GMRS I own several used/new Vertex Standard EVX radios. I do use the cheapies for intercom at home, where the range I need is just 20 yards, which those afford fine, but when I walk out the door for anything that requires a radio that won't desense into oblivion? Vertex Standard all the way. The noise at my location, measured with a VNA, is in the -50 dB threshold range in the GMRS range, I live 2 miles from a 1400 foot antenna tower, that makes nearly all the CCRs useless beyond 1/4 of a mile in simplex. G.

If that is the case, I am sorry. In regards to the Godwin's law, nah, I am cool. I just like my radios too much sometimes... G.

TYT radios, IMO, are some of the worst at desensing in crowded RF enviroments, so they are making it easier to look elsewhere. The Vertex VX-5500 is a phenomal radio, can be found dirt cheap on eBay, and it has a super selective (and sensitive) receiver that will draw rings around anything TYT will make for the next two decades... G.

LMAO, I build electric vehicles, so I don't like either one of the above (carburetor nor fuel injection)... but who cares... Why would the FCC force to go digital? I meant to also allow the digital stuff, honestly I don't care either way. Its not for me to decide, nor impose rules. It is just my opinion, and..., well, everyone has one. Cheers. G.

I would avoid that thing. For ~200 dollars you can find a great deal on an XPR4550 Motorola Mobile that will draw rings around that. G.

Fighting against change is the surest way to failure. One thing is to state that digital is currently not legal, and leave it at that. I understand that, its the law, and we have to respect the law. But the "resist change to the last breath" attitude, especially when defending a technology that is pretty much obsolete in terms of features and quality of transmissions, I simply don't understand your radical posture against change for the better on GMRS. Also, the excuses and lame reasoning you've given, aside from the legality matters, which can be addressed (laws can be changed), I see no reason why digital couldn't be allowed, and offer a lot of functionality that FM analog can't offer. You sound like the guys who fought fuel injection b/c carburetors were simpler to tune... And if you have interference from digital systems, then perhaps you need to use more filtering and better radios... since I am using TX/RX cavities the intermod/interference problems I had are all gone. Even if only GMRS was remain fully analog, the rest of the spectrum is ALL going digital, there will be interference no matter how hard you try to prevent the inevitable. G.

LMAO... hahaha....

LMAO.. hahaha... pesky and expensive... indeed... I would also think allowing mixed mode with FM would be great too. I believe Motorola repeaters can do both. Oh man, I am already thinking about opening the flood gates and replace all the GMRS BF-888s house intercom with DMR... that is just going to be sooo cool... basically like those crappy old wireless phones with a station and a few extra handset, but this time on steroids!!! Dreaming is always for free tho.... haha G.

Wow, considering how bad I hate RF INTERMODULATION, I really like you intermod!! haha....

Intermod, now you're talking!!! Almost like a mini GSM GMRS tower. And now for the "dreaming is for free part" <deep breath> "....if I was made out of gold, man, I would be on TETRA faster than I can blink..." <end dream mode> G.

Is this FB6 designation true? can this be verified? Thank you.

Unfortunately for the old stuff, Vocoder tech does indeed make a huge difference.... enough difference to make DMR sound better at even (arguably) half the bitrate. So it is not about the theoretical max bitrate being transmitted, its about how much those bits are actually encoding useful information, and a better compression algorithm will provide, like MP3, better audio quality at lower bitrates. I like to compare Vocoders to the Fraunhoffer MPEG Layer-3 audio (MP3) which can store audio at 1/10 the bitrate of an uncompressed PCM 16-bit WAV file and deliver near identical quality to that. Sure, an MP3 is still not as good as a 16-bit PCM uncompressed, which in theory is not as good as a true analog LP vinyl 33 RPM, but it takes 1/10th (at 128 kbps rate) the space of a PCM to send nearly identical information to the analog LP signal, and because the brain knows how to put it back together (ECC is in your brain, filling all the missing FFT analysis gaps, etc) you get a pretty much near perfect song. The MP3 codec was far superior to pretty much all of the pre-MP3 era audio codecs that preceded it. and the bitrates needed for an Mp3 to sound great were almost unheard of at the time (1:10 compression ratio in the early 90s was huge, when most consumer hard drives were still measured in megabytes) The same principle pretty much applies to newer Vocoders. Hence why I say, P25 Phase I its obsolete. Much like DMR will be made obsolete once a new Vocoder tech, or something new comes along and renders it obsolete (like Tier I DMR). GSM is obsolete not because of the more sophisticated radio modulations, but because the increased processing power than didn't exist at the sizes of today three decades ago to make such advanced modulations feasible. Newer modulations ranging from OFDM, WCDMA, LTE, QAM.... cell phones can do gigabits per second on just RF... compared to a 9600 baud FM radio the difference is measured in orders of magnitude, that is just ridiculous. So, to sum this long winded paragraph. Its about useful information density, not the bitrate, more bits doesn't mean a better useful information density. Newer Vocoders offer that, older vocoders don't. As for Dual Capacity Diret Mode, or DCDM, it requires no infrastructure to work at all. Please understand DMR terminology (not just read it from Wikipedia) before emitting such statements, DCDM is a simplex Tier II DMR feature and pretty much any DMR Tier II compatible radio I've tried can do it. Even my 44 dollar CCR Baofeng BF-1801 DMR (a low grade GD77 clone) radios can do DCDM, and have two conversations on a simplex frequency. Can't do that with P25 Phase I, nor analog. Again, DCDM is simplex ONLY. Then you can also go with a Tier I DMR on simplex if you want to run legacy stuff, operating the thing on full single carrier, which is obsolete too b/c you pretty much throw away all the benefits that a Tier II TDMA system has to offer. In a Tier II DMR environment you're not limited to having to use a repeater, you can choose what kind of infrastructure use: you can go with a simplex double slot approach, simplex DCDM, or even simplex Tier I continuous single carrier. And then if you need it, you can chose the repeater double slot option too. You have infrastructure options, which you simply don't have on legacy obsolete stuff. Sure, for ham, P25 Phasie I is certainly fine, to talk about that SWR increase of the newest patch cable on the shack, that doesn't matter, but for a commercial customer, having these options, it makes the difference. (also for a family too) ETSI TS 102 361-x (DMR) was designed pretty much from the ground up to replace FM analog. Timing slots are for the radios talking at any given moment, there is no need to create an universal timing for the entire country. At any given site, its either the radios themselves (double slot simplex, or dcdm simplex) or a repeater infrastructure that takes care of the timing, and when interconnecting different sites, either using IP Site connect, or any kind of MMDVM, b/c these convert CAI to IP, those packets get sent over the wire to be rebroadcast somewhere else, so how its timed or modulated back to CAI at destination is up to whatever is being done there. Hence why MMDVM can do all this multi mode "ham stuff", you get the IP packet, retrieve the digital voice information and pack it up as P25, NXDN, Fusion... etc. Also, timing on a DCDM simplex setup (b/c there is no DCDM on repeaters since repeaters operate on 2 timeslots), DMR Tier II radios on DCDM simplex will select a timing leader automatically, and I can see that they will chatter once in a while for a fraction of a second to figure out the timing between all of them, so when you press the PTT, all the radios are already synced up and communication happens. In regard to DMR radio mixed mode, my Alinco DJ-MD5 does DCDM simplex with mixed mode analog+digital on the same channel, and will transmit back on whatever modulation the last received transmission was on just fine: It can listen and demodulate correctly DMR or analog depending on the signal that is being received. There is no "interoperability" with FM problem there, but at the same time I have all the DMR Tier II options that a legacy system like P25 Phase I simply lacks. I still don't understand why range, or operating near threshold is relevant to this discussion? Nobody has argued that having better audio to threshold is bad. DMR has that too.... but FM wideband will still reach further. In addition, RF range can be extended using the right infrastructure, better radios, or both. As for hearing kids on GMRS: here is what happens. First off, I don't hear them breaking the squelch, ever, I never said that. when I hear them is when key my BF-888S running @ 1 watt power, which opens the squelch on all the radios used in the intercom, but if at the same time I am keying my intercom, a 5W portable starts talking, I can hear both radios on the channel. That is the issue I've experienced, which has nothing to do with signaling. Now, when testing DMR all we noticed was a slightly lower audio quality. G.

Holy pendantic bold caps reply man. Would you please read carefully what I said before jumping the gun? On my earlier post I stated very clearly that A) I don't care if people hear my stuff (as in, I have no expectation for privacy). B ) I also stated NOT use encryption, b/c, once again, its illegal. But thanks for reiterating what I've stated already in an all bold caps statement. Oh, and I have a cellphone if I want privacy. (more like 10 of them, but whatever) The GMRS regulations in effect are the ones post-2017, I use whatever regulations are currently in effect, b/c you know, that is what the FCC laws currently say. If you want to use old laws that have been superseded, that is your call, not mine. Who said P25 was encryption?... not me, so, where did you get that from? I am fully aware that P25 is just another digital format based on the AMBE2 vocoder, etc. Now, here is what I did said, and I will repeat it: P25 phase I is obsolete. And FM does offer DTMF signaling, sure, its not embedded, but you can achieve the SAME type of signaling for opening different radios, etc, on analog FM. I've done it in the past, is not as clean as DMR, but it can be done. What? ham MMDVM is not equally compatible, dude, Multi Mode Digital Voice Modems are just devices that "translate" CAI to IP packets, not a ham digital format. And why are we bringing here the fact it operates better at threshold? why is that relevant? It is pretty much a fact that FM wideband can reach further than anything digital at the moment. Sure, its arguably not going to be crystal clear, but you can copy stuff that the best digital radios simply won't decode... and then, there is always the cellphone. As for P25 better quality than DMR, yeah, that is like your opinion, man, and everyone has one. That's not factual, b/c now here is my opinion, I think P25 sounds worse than Motorola XPR or Vertex EVX high end DMR radios. So, who is right? who cares. Now, here are the facts, on DMR you CAN have: -Single Frequency repeaters. -Single Frequency, two concurrent conversations. I think there is some confusion here: There is Tier I DMR which is basically no timeslots, no pulsing, and effectively a single 12.5 kHz digital carrier, the same as P25 Phase I. And then there is Tier II Dual Capacity Direct Mode, which allows for two concurrent calls on a simplex channel, and that is AFAIK, part of the DMR ETSI standard. Then there is Tier II Repeater Operation, which uses two timeslots on receive and two timeslots on transmit. So on any given repeater you can have 2 concurrent conversations using a repeater pair of frequencies, and I believe that with the advanced Moto repeaters you can do pseudo trunking using the timeslots so you can have more than just 2 voice channels. When you say that one timeslot is wasted, Its not wasted, the other timeslot is just available for a 2nd conversation to take place. But hey, wait a minute... you can't have two conversations on the same channel on P25 Phase I. G.

Wow WRAF213, amazing info, thank you!

Well, my understanding is that GMRS was devised for family use, so why would anyone who is licensed want an unlicensed person, with an easy to acquire bubble pack radio, hear all their family traffic and cause interference, be it intentional or non-intentional. Now, I am fully aware that I can't prevent my radio signals from being listened by others (nor I have a need to prevent that), but say, if I switched tomorrow my entire GMRS setup to digital DMR, added RAS to a short range intercom repeater to limit who can talk through the repeater (not even going with AES encryption), etc, then all the neighbor kids who bought these 5W FRS radios after seeing the "cool" antennas going up on the roof of my house, these kids will no longer hear us talking on my house intercom, nor we'll hear them yap when we talk through the intercom and they also happen to be talking on their 5W portable as well. Ham radio, amongst other reasons it was meant for tinkering and EMCOM, and you need a license to use it. The problem is, you see, that most 5 year olds can't get a ticket, most significant others (male and female alike) might not be interested enough to bother taking the exam, etc, so now, if you have a large family, say, 4 or 5 kids and wife, even if it was a family of little Mozarts who all were able to get their tech license by age of 4, the moment those 4-5 year old kids start swamping the ham channels with kid's talk about their latest GiJoe toy, or the Barbie that is pink, etc, the typical grumpo self-righteous ham operator will railroad the channel and assert grumpo dominance by stating "hey kids, you've hogged this frequency for your personal stuff, you need to move elsewhere.... this channel might be needed in an emergency situation." Even if all the 4 year olds were ham licensed. The moment anyone railroads on a private radio conversation for no reason, even if its a bunch of 4 years old, unless its an emergency, that anyone is the one causing harmful interference to those licensed operators, who where talking Barbies or pink unicorns on a ham frequency. While the regulations are what they are now, it doesn't mean we can consider and discuss a future. Life is not set in stone, things evolve. May I ask why P25 Phase I over analog FM? So they can run encryption? Which, BTW, its illegal to encrypt stuff in GMRS. P25 Phase I is the same thing as FM, it has nothing that can't be offered in FM analog with a DTMF setup. Now, once you enter TDMA territory, the fact that you can have two conversations on a single frequency, and single frequency REAL TIME repeaters, which will make any radio a hotspot, etc, then P25 Phase I is, simply put, obsolete, b/c it doesn't offer anything that FM can't offer already, and then, like DMR, its not interoperable with FM either. So, IMO, if you are going to get digital, there has to be a reason, beyond having the little encryption checkbox, to make the swap. That reason, for me, the reason why I would go digital DMR is b/c I could implement single frequency repeaters (as in , receive in TimeSlot 1 and immediatly retransmit on TimeSlot 2, single frequency, no delays, NOT a simplex repeater) and then have two conversations going on at the same time on a single frequency, all that without having to buy any additional infrastructure. Can't touch that with FM nor P25 Phase I. G.