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#1 STTScott

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Posted 18 November 2020 - 01:31 AM

I received my BTech BF-F8HP, along with a Nagoya UT-72 external NMO-mount antenna. Inwas slightly bummed to scan a range of frequncies to hear ... crickets, even with thesquelch set at 2. To be more precise, I'm roughly 1,000 feet above the lowlands here. Our island is 13 miles long and 4 miles wide.

I work in the lowlands on the other side of the mountain, so I took my radio with me and got the same crickets even on my local repreater. A burst of static here and there, but that's it.

So ... I'm sure my radio works. I'm just figuring either I need a 50w mobile unit with a power supply to use also as a base station, or I'm the only guy on this island with a GMRS radio.

Or am I missing something?

Scott
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#2 Lscott

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Posted 18 November 2020 - 01:48 AM

FCC database search for the Virgin Islands shows only 15 active licensed GMRS users. I didn’t drill down to see who was located where however. If they are spread out over multiple islands your chance of contacting one on the air likely isn’t very high. The chance of contacting someone using a cheap FRS radio, simplex only since they don’t have repeater functions, might be higher. I would also suggest you look at getting at least your Ham Tech class license. That will increase the opportunity of contacting somebody during an emergency. About a third of the group of GMRS users on my local repeater are also licensed Hams.

#3 Lscott

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Posted 18 November 2020 - 01:57 AM

Don’t forget with the change in the rules both GMRS and FRS now share the same frequencies. One of the major differences between them is FRS can’t use repeaters, thus my comment about using simplex, and FRS is narrow band. I have two sets of memories programmed in my radios, one for the wider bandwidth for GMRS, the other for narrow band for FRS.

#4 gman1971

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Posted 18 November 2020 - 02:07 AM

Also, the higher gain you hook up to those Baofengs the less you'll actually hear... as they desense really bad...  a -20 dBm Effective Sensitivity Loss is typical on those things with a 1/4 wave antenna.

 

They might be hearing you, but you can't hear them...

 

G.



#5 GuySagi

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Posted 18 November 2020 - 08:13 AM

I'm really confused on your comment gman1971. Sorry. The higher gain antenna you use with the radio the worse your receive? I apologize if I'm missing something in my pre-caffeinated state. Maybe it's specific to that radio or handhelds in general. 



#6 RDH

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Posted 18 November 2020 - 09:33 AM

I received my BTech BF-F8HP, along with a Nagoya UT-72 external NMO-mount antenna. Inwas slightly bummed to scan a range of frequncies to hear ... crickets, even with thesquelch set at 2. To be more precise, I'm roughly 1,000 feet above the lowlands here. Our island is 13 miles long and 4 miles wide.

I work in the lowlands on the other side of the mountain, so I took my radio with me and got the same crickets even on my local repreater. A burst of static here and there, but that's it.

So ... I'm sure my radio works. I'm just figuring either I need a 50w mobile unit with a power supply to use also as a base station, or I'm the only guy on this island with a GMRS radio.

Or am I missing something?

Scott
WRJX210

Since there are so few actual gmrs licenses where you live try using the database to contact them and see if they would be interested in a weekly net on one of the repeaters. If you get just 2 or 3 guys using the repeater and sending traffic that will usually generate more interest in those listening to either hop in or maybe those hearing you on frs will get their license and join in. That is how I end up getting a repeater capable radio. Our family had a license since 2017 but I only ever used FRS handhelds, this summer there was alot of traffic on the local repeaters due to people being locked down due to Covid so I went and ordered a btech 50x1 to be able to join in the conversation.

#7 RDH

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Posted 18 November 2020 - 09:35 AM

Another thing you can do is key up the repeater and state your call sign, state that you are new to GMRS, and ask if anyone can hear you and that you are interested in casual conversation

#8 Jones

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Posted 18 November 2020 - 10:10 AM

I'm really confused on your comment gman1971. Sorry. The higher gain antenna you use with the radio the worse your receive? I apologize if I'm missing something in my pre-caffeinated state. Maybe it's specific to that radio or handhelds in general. 

gman's comment only applies if you are in a high-RF environment. Say you lived next to a tower that had a lot of other communications gear loaded up on it, particularly operating in the 450-470 MHz UHF band, such as a lot of police, fire, ambulance, taxi cabs, business band radios, etc... - When one of those repeaters is transmitting, say for instance at 462.950 (a medical paging channel) your radio tuned to 462.600 (GMRS 17) would be overloaded by the nearby strong signal, so it wouldn't hear anything on your desired frequency. Putting a high-gain antenna on a radio with this easy overload-state only makes it overload worse. This is VERY common in CCRs, which typically have no front-end filtering of any kind, and thus no selectivity.

 

It doesn't have to be just a repeater interfering with a CCR either.  My Baofeng's get overloaded when the police are using the radios in their cars 2 blocks away. Also, if you have a local TV station on UHF channels 14-21, you can just about forget using a Baofeng radio within 5-10 miles of its tower.


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#9 STTScott

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Posted 18 November 2020 - 10:44 AM

I'm currently studying for a Tech license, since there is a Ham club on the island that I've been in contact with about joining and participating., and they do nets. I just figured that in the meantime GMRS would be a good stopgap. I certainly don't regret getting my radio and license, but it would be a lot more interesting if there was more activity on the band, abd we do have a repeater here. Still, I keep it on scan just in case.

FCC database search for the Virgin Islands shows only 15 active licensed GMRS users. I didn’t drill down to see who was located where however. If they are spread out over multiple islands your chance of contacting one on the air likely isn’t very high. The chance of contacting someone using a cheap FRS radio, simplex only since they don’t have repeater functions, might be higher. I would also suggest you look at getting at least your Ham Tech class license. That will increase the opportunity of contacting somebody during an emergency. About a third of the group of GMRS users on my local repeater are also licensed Hams.



#10 GuySagi

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Posted 18 November 2020 - 01:57 PM

gman's comment only applies if you are in a high-RF environment. Say you lived next to a tower that had a lot of other communications gear loaded up on it, particularly operating in the 450-470 MHz UHF band, such as a lot of police, fire, ambulance, taxi cabs, business band radios, etc... - When one of those repeaters is transmitting, say for instance at 462.950 (a medical paging channel) your radio tuned to 462.600 (GMRS 17) would be overloaded by the nearby strong signal, so it wouldn't hear anything on your desired frequency. Putting a high-gain antenna on a radio with this easy overload-state only makes it overload worse. This is VERY common in CCRs, which typically have no front-end filtering of any kind, and thus no selectivity.

 

It doesn't have to be just a repeater interfering with a CCR either.  My Baofeng's get overloaded when the police are using the radios in their cars 2 blocks away. Also, if you have a local TV station on UHF channels 14-21, you can just about forget using a Baofeng radio within 5-10 miles of its tower.

Thanks for the information and now it makes sense. I apologize for a asking, but sure to appreciate you taking the time to explain. 


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#11 Lscott

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Posted 18 November 2020 - 02:19 PM

I certainly don't regret getting my radio and license,

One can never have enough radios. 8-) GMRS is a good way for people to test the water and see if they like radio communications without having to do any testing. Good luck getting your Tech Class license. Later you can upgrade to General Class which gives you access to all of the HF bands for world wide communications, very handy if the worse happens and local public communications resources are completely wiped out.

 

Some commercial band radios are FCC certified for Part 95, and the programming software will allow Ham 70cm frequency entries even if they are outside of the "official"  range for the radio, the software throws up a warning message, but allows the entry. I've used two so far, both Kenwood radios, TK-370G-1 and the TK-3170. I can get them down to around 440MHz or so which covers the simplex and repeater sections of the Ham 70cm band. Now I only need one radio for both services and its legal since I'm licensed for both.

 

There is one other radio service on VHF that could prove useful too. That's MURS and no license is required. You can find some MURS certified radios out there.

 

https://en.wikipedia...e_Radio_Service

 

https://www.intercom...echnology-guide


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#12 AdmiralCochrane

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Posted 18 November 2020 - 05:40 PM

I don't think having both licenses technically allows you to use a ham radio on GMRS even if the radio is fully within FCC parameters for GMRS.  The regulation says you are only allowed to transmit using part approved radios in the band. 

 

Its probably the most frequent subject on any GMRS forum



#13 Lscott

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Posted 19 November 2020 - 02:26 AM

I don't think having both licenses technically allows you to use a ham radio on GMRS even if the radio is fully within FCC parameters for GMRS.  The regulation says you are only allowed to transmit using part approved radios in the band. 

 

Its probably the most frequent subject on any GMRS forum

If you're referring to me the radios I'm using are Part 95 certified, no modifications, and will accept entry of frequencies in the Ham 70cm band too, the programming software complains with a warning pop-up window but will accept the entry. That's why I use them.

 

TK-370G-1

 

https://fccid.io/ALH29473110

 

TK-3170

 

https://fccid.io/ALH34713110

 

The FCC grants show Part 95A, among several others, since at the time that was the section for GMRS. When the rules were updated it changed to Part 95E, but that will not invalidate the original grant. You will also notice the grant is for both wide and narrow band too. It seems a lot of the older Kenwood commercial band radios have Part 95 certification.

 

For Amateur Radio the only thing the FCC certifies the radios for is Part 15, making sure the radios can't receive cellular phone frequencies.



#14 gman1971

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Posted 19 November 2020 - 05:33 AM

To elaborate:

 

These CCR have no filters that prevent every other frequency from getting into the receiver, even when the CCRs are tuned to a frequency, all others still get through... so what happens is when the desired signal gets inside the receiver, it gets mixed with a dozen or so kW (kilowatts) level strong signals coming from commercial antennas, broadcast, etc, etc. So your little 5W signal is mixed with a bunch of those kilowatt monsters, and radio goes into clipping, or in layman terms: your radio receiver is overwhelmed, so it lowers the sensitivity in hopes to try to make something out of the signals, so it doesn't clip.... and you lose sensitivity. How much? A LOT. 10-20 dBm average.

 

Now, when you add more gain to the antenna all you're doing is basically making the problem worse, b/c the CCR radio has no front end filtering, and you're "amplifying" all these kW (kilowatt) super strong signals even more... result is that you end up with an even more scrambled mess, thus receiver will desense even more, thus range will be even lower. This is the reason why I now recommend people buying an XPR6550 as their first GMRS radio. And please, save the legal Part 90 excuse to have an excuse to buy crap radios... there hasn't ever been a single part 90 problem or case in GMRS from the FCC.

 

In regard to the "its only valid for close to RF towers" fallacy: Sorry, that is not true. Police might be putting out 100W 150W, that isn't much, but the six megasupeduper 200 kW ( YES, 200,000 watts) TV stations that are coming from that angry 1000 footer antenna located like 20 miles away from your house are also being picked up by the CCR receiver, and those kW signals have a stronger dBm presence than your 50W GMRS mobile placed 2 miles away. They get mixed in, and your 50W mobile is drowned by the angry antenna towers spewing CBS, FOX, MSBNC... whatever...

 

So, to sum it up: Those radios are just inferior, plain and simple, I hope my explanation was clear. And since most people live in cities, or where some sort civilization exists, the fallacy falls apart really quick. I hear people having 2 mile range out of 50W mobiles... so you wonder, and then you find out what kind of mobiles... not Motorola XPR4550 or XPR5550e etc... you find out they are running some lousy overpriced CCR... they think they need more power... 20dBm of additional power to make up for the loss of sensitivity would be the equivalent of running a 5000 watt mobile... I think its pretty clear why receivers are the most important part of the radio.

 

How do I know? Well, I've measured many CCR radios with ISOTEE time and time again, in many places, and in different situations, etc, and the average Effective Sensitivity loss is in the order of 10-20 dBm compared to an XPR6550, and 20-30 dBm compared to an XPR7550e... so, there is your answer: a 30 dBm is the difference between 50W reaching barely 2 miles, and 50W reaching 10+ miles.

 

In the end its your money, and your time, so waste them accordingly. I wasted too much of mine, sadly, before I realized I wasted my money and most importantly, my time.

 

G.



#15 AdmiralCochrane

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Posted 19 November 2020 - 05:58 PM

Excellent explantion of why a higher end radio will recieve a good signal 20 miles away when a CCR only gets it 16 miles away.  Too bad everyone inside the 15 mile circle will never know the difference.


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#16 Ian

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Posted 03 December 2020 - 07:06 AM

Sometimes you don't __need__ to know the difference.  I occasionally find it useful to hand someone a really stupid radio, and say something like "If you can't hear me on 20, try channel 28" 

 

Perhaps hand them a radio with only three channels programmed -- half a watt, five watts, repeater input.  As far as a non-radio-person knows, they're just turning up the power…

 

I've been half-seriously accused of "walmart ops" a few times, and such strategies (as well as handing people single-channel radios) definitely make it easier on nontechnical people.

 

Sometimes, a little communication is good enough.



#17 gman1971

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Posted 03 December 2020 - 08:41 AM

Well, if someone has taken the time to pay for their GMRS license, and taken the time to post here, asking questions, then it would seem logical to me they might want to know the difference.

 

Ignorance makes anybody an easy target for misleading claims, misleading advertising and anything in between, and more.

 

I don't know how many broadcast towers/stations are in the location where the OP lives, but I am certain the answer is > 0, and all it takes is a one of those RF firebreathing angry 1000 foot towers to screw up the front end (or lack thereof) on nearly all CCRs... How do I know? B/c I've owned several CCR mobiles that couldn't hear their own way out of a paper bag... no matter what.

 

It wasn't until I started purchasing 2nd hand Vertex Standard LMR gear that I realized that those CCR radios needed several hundreds dollars worth of preselector/cavities to make them come even close to what a lowly Vertex Standard EVX-5300 mobile could do with nothing but the radio mated to the antenna... 

 

While I think CCRs walkies have their use, going CCR on a mobile is, IMO, a waste of money. Why? b/c If you don't see a range in the 10+ mile range, with a couple of 25W mobiles, one at base, and another with an NMO 1/4 wave antenna on a car then chances are the receivers are garbage. Been there, done that.

 

Again, you can all gang up on me, saying how horrible, cocky, hurtful, etc etc, gMan1971 Motosnob comments are, how he is not very PC, how he is hurting my feelings about my expensive CCR mobile, etc, etc... In the end, all my business/personal family radio range problems ended once I started listening, and doing things the same way professionals build their commercial/LEO grade communication networks, and that meant using the same equipment they use, and saying bye bye to ALL CCRs... and surprise surprise, my radio range started to increase, and is now measured in tens of miles, rather than tenths of a mile. If transmitting with 25W doesn't reach, 50W is not going to make the slightest difference. A 3dB increase is nothing when rolling terrain can attenuate the signal by -10 to -20 dB...  then you add that -20dBm attenuation due to receiver desense, and you have a -40dBm signal drop, which means, you hear zip. The TX guy cranks power to 50W thinking it has to reach now... but all you're doing is reducing the -40 dBm attenuation to a -37dBm.. still 37 dB short of hearing zip. 

 

G.

 

 

Sometimes you don't __need__ to know the difference.  I occasionally find it useful to hand someone a really stupid radio, and say something like "If you can't hear me on 20, try channel 28" 

 

Perhaps hand them a radio with only three channels programmed -- half a watt, five watts, repeater input.  As far as a non-radio-person knows, they're just turning up the power…

 

I've been half-seriously accused of "walmart ops" a few times, and such strategies (as well as handing people single-channel radios) definitely make it easier on nontechnical people.

 

Sometimes, a little communication is good enough.



#18 AdmiralCochrane

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Posted 03 December 2020 - 05:04 PM

gman, can you explain this to me?  

This morning I had the opportunity to park adjacent to the local RF firebreathing angry 1000 foot towers, actually 2 of them adjacent to each other. One hosts multiple local PD transmitters, business transmitters and I know not what else. the other has the local UHF TV on top. Close enough that my vehicle's AM radio desensed.  Obvious signal suppression.  Both my CCR and my Icom 880H functioned with the same reception clarity.  What did I do wrong in this experiment?



#19 gman1971

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Posted 03 December 2020 - 08:55 PM

I cannot without being there to asses and perform an ISO-tee.

 

What I can tell you, tho, is that if those two RF firebreathing angry towers you mention in your post are nearby where you live, the desense (if any) will be the same up to about 10-20 miles away, maybe even more. The Candelabra tower <2 miles from base here has multiple kW broadcasts, range is 100+ miles...  that is a lot of dBm coming out of those towers.

 

With that said, since you were at the bottom, or near the bottom of these towers, you'll get the highest null since most of the radiated energy is projected towards the horizon, not downwards; hence why repeaters use vertical separation when using a TX and RX antenna pairs.

 

Desense is only part of the problem, then there is intermodulation. Most CCRs which claim to have superhets have no tuned front ends ($$$$). B/c how a superhet works is by converting signals into IF frequencies, when the incoming RF that gets through into the IF stages is a multiple of the IF stage frequency, then it gets mixed with the desired signal (intermodulation), and while the receiver might've not desensed significantly, you still get a garbled signal, or nothing at all.

 

During tests performed on EVX-5300 mobile setups I realized that the measured signal strength was about the same with and without a RFS preselector (whcih adds a 1.5 dB insertion loss), but without the preselector the EVX-5300 mobiles were getting a garbled, almost unintelligible audio in NFM, even though the signal was there and about the same RSSI. Adding a preselector increased effective sensitivity by just 2 dBm, which isn't much, but the signal was now crystal clear as opposed to before which was all garbled, even with the 1.5 dB Insertion Loss from the preselector. Again, superhets work by using intermediate frequencies to reject unwanted stuff, problem is that without a tuned front end it won't reject the incoming frequencies that are multiples of the IF stage frequencies. IIRC the EVX-5300 has a 5 varactor tuned front end, and the superhet was getting hammered by RF towers in the Madison WI area... it needed me adding a -60dB preselector filter to properly receive signals that otherwise couldn't before, not due to sensitivity, but due to selectivity. A radio without a tuned front end is going to require a lot more than just a simple preselector to work... which explains why the 5550e demolishes every other radio I own in range tests... b/c its selectivity is off the charts compared to anything else I own, along with its effective sensitivity.

 

My findings can be summarized in one sentence: Range increased when selectivity improved. The more selectivity the radio being tested had, the more range I had, as measured... which seems to match my astrophotography parallel experience, the narrower the band of the filters I used, the better I could pick up stuff like the horsehead nebula, etc, in heavily light polluted skies.

 

Selectivity == $$$$

 

G.

 

gman, can you explain this to me?  

This morning I had the opportunity to park adjacent to the local RF firebreathing angry 1000 foot towers, actually 2 of them adjacent to each other. One hosts multiple local PD transmitters, business transmitters and I know not what else. the other has the local UHF TV on top. Close enough that my vehicle's AM radio desensed.  Obvious signal suppression.  Both my CCR and my Icom 880H functioned with the same reception clarity.  What did I do wrong in this experiment?



#20 AdmiralCochrane

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Posted 03 December 2020 - 09:00 PM

I was approximately 1km from the base.  I did notice greater desense of the AM signal about twice as far away, but nothing 3 times as far or farther. 

 

My real question isn't about the scientific measurement, but about the practical application.  Theory is great, but when it lacks in the real world, its use diminishes. 






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