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Emergency comms: HAM or GMRS?


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Guest Roverbill
17 hours ago, kb2ztx said:

 

13 hours ago, MichaelLAX said:

If I understand your point correctly, you are assuming that a FRS Radio has the same receiving sensitivity as a 50 watt GMRS radio and that is not the case.

I am assuming that a Search and Rescue Volunteer, equipped with only a FRS Radio, has a better chance of hearing a distress message that is being transmitted with 50 watts from a GMRS Radio than one transmitted with only two (2) watts from another FRS Radio.

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4 hours ago, Guest Roverbill said:

I am assuming that a Search and Rescue Volunteer, equipped with only a FRS Radio, has a better chance of hearing a distress message that is being transmitted with 50 watts from a GMRS Radio than one transmitted with only two (2) watts from another FRS Radio.

I am still confused by your original point, even as you clarify it, but my confusion is moot because Wyoming picked Channel 3 and not Channel 21:

17 hours ago, Guest Roverbill said:

Not necessarily. Any user of a current model FRS Radio can now transmit at full power (two watts) on Channels 15-22 without need for a license, while a licensed GMRS user can transmit at up to 50 watts on the same frequencies. In a “Call for Help” situation what matters most is that Search and Rescue (SAR) can HEAR the call. For that purpose SAR Responders only need a FRS Radio that can receive on Channels 15-22, with no GMRS License needed.

It seems to me that SARs can hear ALL calls better on a 50 watt GMRS Radio than on a FRS Radio.

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Guest Roverbill
5 hours ago, MichaelLAX said:

I am still confused by your original point, even as you clarify it, but my confusion is moot because Wyoming picked Channel 3 and not Channel 21:

 

It seems to me that SARs can hear ALL calls better on a 50 watt GMRS Radio than on a FRS Radio.

My original intent was to commend the State of Wyoming for organizing emergency communications in the combined FRS/GMRS Band, while only regretting that the channel (frequency) they chose did not allow use of full transmitter power by GMRS users.

As to the second statement, are you saying that SAR can better hear calls made FROM a 50 watt GMRS Radio (which I agree with), or are you saying that the higher powered radio itself has better receiver performance than the lower powered radio?

 

 

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45 minutes ago, Guest Roverbill said:

As to the second statement, are you saying that SAR can better hear calls made FROM a 50 watt GMRS Radio (which I agree with), or are you saying that the higher powered radio itself has better receiver performance than the lower powered radio?

While I cannot speak to EVERY transceiver made for GMRS, any manufacturing company worth its salt and that expects to sell radios against its competitors, will design transceivers which have higher power transmitters with receivers that have more sensitivity and selectivity (than the receivers on their lower power GRMS/FRS HTs for example)

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2 hours ago, MichaelLAX said:

While I cannot speak to EVERY transceiver made for GMRS, any manufacturing company worth its salt and that expects to sell radios against its competitors, will design transceivers which have higher power transmitters with receivers that have more sensitivity and selectivity (than the receivers on their lower power GRMS/FRS HTs for example)

Anecdotal, I know, but I found my midland HTs (gxt1050) go deaf almost as easy as baofengs, while the basic yaesu ham ht (ft4x) works quite a bit better, much closer to the vertex stuff.

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I find zero correlation between measured sensitivity of any of my radios and their output power capability. All radios (HT, mobile and base alike) have basic sensitivity within a few dBm of one another. I have not measured any of the radios with non-removable antenna.

The degree to which radios are desensed by other RF signals in the area is a separate topic. I would expect the higher-end radios with good front-end filtering to appear substantially more sensitive and usable in noisy environments.


Michael
WRHS965
KE8PLM

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50 minutes ago, mbrun said:

I find zero correlation between measured sensitivity of any of my radios and their output power capability.

 

50 minutes ago, mbrun said:

I would expect the higher-end radios with good front-end filtering to appear substantially more sensitive and usable in noisy environments.

Unless you do not own any "higher-end radios," I find these two statements to be completely contradictory.

Can you clarify and/or be specific?

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Unless you do not own any "higher-end radios," I find these two statements to be completely contradictory.
Can you clarify and/or be specific?

The basic sensitivity of all radios I own open squelch between -124dBm and -119dBm and provide full quieting around 12dBm higher. These are numbers as measured in a closed circuit connected directly to test equipment.

All radios are affected by the presence of off-channel signals. The the better the front end filtering the less the radio is affected. The effective sensitivity therefore is the net usable sensitivity of the radio within a given RF environment. Measured effective sensitivity will almost always be worse than basic sensitivity except when the radio is used in a low noise environment.

For example. If I measure the basic sensitivity of a radio in a closed circuit it might be -122dBm. If I perform an effective sensitivity of the same radio operating in my shack it might drop to -100dBm. If I then hook that same radio up to the outdoor antenna 40’ in the air, the effective value might change to -110dBm. If I then perform the same tests using a higher end radio under the exact same conditions the basic sensitivity might be exactly the same, but the effective sensitivity number might be -109dBm and -118dBm respectively. So, despite equal base sensitivity, the radios with better front-end filtering will effectively receive better in noisy environments, but will not receive any better in low-noise environments.

As a point of reference, a year ago a generous friend of this forum loaned me (7) commercial radios so i could conduct field experiments against less costly products in my low-noise environment. Results were enlightening. Findings were reported on this forum.


Michael
WRHS965
KE8PLM
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1 hour ago, wayoverthere said:

Start here for the context. Findings are linked later in the thread.

https://forums.mygmrs.com/topic/2421-side-by-side-range-comparison-wouxun-kg-805g-vs-part-90/

These results are about what I'd expect. That's not an especially hostile/dense RF environment. Given that only about a half-mile of reliable coverage was achieved, I believe there was an LoS issue, probably caused by terrain. There's no cheating the laws of physics - barring a serious sensitivity issue with the Chinese radio, it will perform about the same as the Motorola in a low-noise-floor environment. Put it in an environment with a high noise floor and it will struggle.

 

Another interesting point - 0.5 square miles of full quieting coverage was achieved compared to 1.13 square miles of copyable but noisy coverage. A digital mode such as DMR, P25, or NXDN would 'clean up' the audio in that 0.4-0.6 mile band, more than doubling the area in which noiseless communications are possible. Beyond that, it will also be spotty - P25 doesn't defy the laws of physics either. Just something to consider, as digital modes are normal and accepted in the amateur service. (I also know of a couple digital repeaters in GMRS, operating under FCC experimental authorizations).

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1 hour ago, DeoVindice said:

T There's no cheating the laws of physics - barring a serious sensitivity issue with the Chinese radio, it will perform about the same as the Motorola in a low-noise-floor environment. Put it in an environment with a high noise floor and it will struggle.

Yeah, some members are strong Motorola devotees for exactly that reason...they hold up well in high rf environments. what's the term @gman1971 uses....fire breathing RF monsters?

Edited by wayoverthere
typos, edit not working on mobile.
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16 hours ago, Guest Roverbill said:

As to the second statement, are you saying that SAR can better hear calls made FROM a 50 watt GMRS Radio (which I agree with), or are you saying that the higher powered radio itself has better receiver performance than the lower powered radio [FRS Radio]?

 

 

On 2/15/2021 at 7:13 AM, mbrun said:
On 2/15/2021 at 6:01 AM, Lscott said:

 

e1822156d7c3ad2d9bb611126ac17995.jpg

 

 

This is where you send me to read a comparison of receivers on a FRS HT vs a receiver on a 50 Watt transceiver?!?

Good luck with suggesting to your SARs to use FRS HTs when they could also have 50 watt mobile rigs in their recovery vehicles on the theory that both receivers are just as good!

With all due respect, I will withdraw from this debate.

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Start here for the context. Findings are linked later in the thread.
https://forums.mygmrs.com/topic/2421-side-by-side-range-comparison-wouxun-kg-805g-vs-part-90/

Thanks for tracking down and posting the requested link. I did not get around to it this morning but observed you had already done so.

While the linked report out did focus on HT testing, mobile/base units have been measured during my play since then.

Of the sensitivity numbers I mentioned earlier, the radio with the least basic sensitivity is a 50w mobile.

Thanks again.


Michael
WRHS965
KE8PLM
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Guest Roverbill

“Good luck with suggesting to your SARs to use FRS HTs when they could also have 50 watt mobile rigs in their recovery vehicles on the theory that both receivers are just as good!”

 

Although the author of the above quote has respectfully withdrawn from this ‘debate’, I wish to offer the following comment:

Without regard to receiver sensitivity, having a 50 watt GMRS TRANSMITTER in a SAR (Search and Rescue) vehicle does seems like a good idea IF the “Control Operator” has the necessary GMRS License.

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21 hours ago, MichaelLAX said:

This is where you send me to read a comparison of receivers on a FRS HT vs a receiver on a 50 Watt transceiver?!?

Good luck with suggesting to your SARs to use FRS HTs when they could also have 50 watt mobile rigs in their recovery vehicles on the theory that both receivers are just as good!

With all due respect, I will withdraw from this debate.

From the quoted message it would seem like those radios are mine. They’re not. 

These are below. And this isn’t everything either. I have some base and mobile radios not in the photo. There are a few more HT’s I keep sitting around the home office too.

The HT’s are mostly Kenwood, a few different Chinese and a few Motorola’s.

Since a mention was made about digital I have radios for D-Star, DMR, P25 and NXDN so far. No System Fusion yet.

What I can say about radios is you get what you pay for, and in the cheaper models maybe not even that. If you’re going to bet your safety or life on a radio don’t go cheap. 

image.jpeg

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On 10/22/2021 at 11:14 PM, wayoverthere said:

Yeah, some members are strong Motorola devotees for exactly that reason...they hold up well in high rf environments. what's the term @gman1971 uses....fire breathing RF monsters?

Indeed...

Also Vertex Standard radios do well, especially for the price point at which you can find them used on eBay, et. all. 

Those giant angry RF firebreathing towers get in the way of long range comms...

However, what I've found out as of lately, while doing site studies, etc,  is that traffic lights are even worse offenders than  angry firebreathing towers... b/c those traffic lights spew so much RFI, especially in the VHF-hi band that the noise floor around many intersection creeps all the way up to -90 dBm... so, good luck listening to anything, and the CCRs range will probably be measured in inches, rather than tenths of a mile... to date, the XPR 5550e was the only radio that I've tested that can actually recover DMR signals from base in those troublesome intersections, even 10 miles out...  

G.

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I agree, don't cheap out on your equipment if you think your life might depend on it.

Seen this far too often... for example, you see some folks carrying super expensive rifles with even more expensive optic(s), just to then see a Baofeng UV-5R as their "tactical" radio...  wait if you need to cross a river, or you get in the mud... etc...  

G.

 

 

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Wow. Did this thread get colorful fast. I spent ten years with search and rescue, carrying a one-watt Motorola VHF brick so I think my assumption the SAR folks in Wyoming will come at this pretty practically is a good one. Send hasty teams with HTs to high peaks, usually predesignated as communications points discovered/used during practices in the area (it's a practice to mark those spots on the map whenever you find a really good one). They stay put, lighting fires as a "trap team" to attract the lost person or p/u a signal of any sort (not just radio). Somewhere relatively close is a mobile unit with higher powered radio and solid communications back to town (our porcupine on four wheels was Rescue 3). If a team on a peak picks up a signal, it radios the truck, it's relayed back to town if a helivac is needed and all is good. If a team on the move finds something they can radio a nearby peak that's manned. And there are lots of people caring enough to volunteer who cannot handle the cliffs/long hikes, but jump at the chance to babysit those peaks and trucks during operations. In fact, our in-town radio guy was handicapped, and his calm, soothing and never-flustered voice on the radio probably saved more lives than us grunts in the field ever did. I apologize for the long response. I think Wyoming's approach could be better, but a solid foundation to build on....sucks adding even a few ounces to a searcher's backpack, though. 

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Well, 1 watt on VHF will reach a LOT further than 2 watt on UHF, under nearly all conditions, and especially so if you append the keyword Motorola to it. 1 watt VHF is equivalent, roughly, to ~10W UHF, or around 10 dB difference in free space loss at equal distance. VHF also hugs the terrain much better too... again, VHF-hi beats the pants off UHF for long range comms.

My XPR7550e radios, on VHF, on just 1W can reach well over 2 miles under most conditions, and in open terrain, atop a modest sized hill we've managed 20 miles on 1 W VHF, with the 6.5 inch duck... again, even my XPR7550e in UHF flavor can't compete with the VHF variants at the long range game.  VHF != UHF, an those 10 dB of additional loss per equal distance is a significant difference between the two bands that cannot be easily overcome with rubber duck antennas.

Now, if you involve repeaters and other infrastructure, then that will be certainly a huge crutch for crap CCR radios (be it FRS, or penta-band CCR garbage) 

Motorola, ICOM, Kenwood, Vertex, et. all, commercial or LEO grade radios, even on 1W, are not the same thing as a FRS HT... not even close.

G.

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Guest Roverbill
8 hours ago, gman1971 said:

LOL... an FRS HT for SAR is like using a 10/22 LR with subsonic ammo to take out an M1A2 MBT tank...

G.

In the case of low-priced FRS Radios, the Wyoming “307 Channel” strikes me as an attempt to leverage existing resources to give Search and Rescue Volunteers a chance to contact persons in distress.

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4 hours ago, gman1971 said:

My XPR7550e radios, on VHF, on just 1W can reach well over 2 miles under most conditions, and in open terrain, atop a modest sized hill we've managed 20 miles on 1 W VHF, with the 6.5 inch duck... again, even my XPR7550e in UHF flavor can't compete with the VHF variants at the long range game.  VHF != UHF, an those 10 dB of additional loss per equal distance is a significant difference between the two bands that cannot be easily overcome with rubber duck antennas.

Wow, that is interesting. Inside of multi-floor building, would you recommend UHF in that instance?

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