Emergency comms: HAM or GMRS?

[GuySagi]

13 hours ago, gman1971 said:

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.

Sure no argument on VHF beating the pants off UHF in most outdoor cases, or the poor performance of cheap radios. I can beat you on 1 watt VHF distance, though. 155.16 mhz, on a cliff at night (elevation maybe 7,000 feet), I had no problem sending vitals to the helicopter PJ as he and the pilot waited for authorization to take off (they were at about 2,800 feet). Distance 30 miles, Motorola brick in my hand and I have no clue what the Air Force had in that old UH1 Huey at the time, but it was obviously amazing. Straight line of sight, unimpeded, but crystal clear enough I that I breathed a sigh of relief when I could hear the blades whir to life. I was young and dumb enough to take that kind of performance for granted, sigh. 

[gman1971]

Well, like I said, VHF reaches very far... at 20 miles, or 30 miles, etc, that is already pretty decent range... for 1 w.

Antennas on helicopters vary, it could've been a good old inverted Vee dipole on the tail (like the OH-6 had) etc... 

[gman1971]

On 10/25/2021 at 9:33 PM, Lscott said:

if VHF != UHF {
    UHF *= 10db_gain;

}
             

This will not compile, you are missing the declaration of VHF, UHF and 10db_gain.... along with brackets around the (VHF != UHF) if statement...

G.

[gman1971]

Depends on several factors to chose VHF over UHF (or the other way around). The biggest drawback of VHF as of lately is the ever increasing noise floor due to Cheap China LED bulbs... which pollute the heck out of the VHF band... also most electronics found inside buildings (in particular LED fixtures and wired Ethernet) will put out a lot of VHF noise, thus reducing your range indoors... so its a tradeoff, you need to determine the noise floor of the site, and determine with an RSSI meter which radio works best. The lower the noise threshold the better.

G.

[Lscott]

14 hours ago, gman1971 said:

This will not compile, you are missing the declaration of VHF, UHF and 10db_gain.... along with brackets around the (VHF != UHF) if statement...

G.

oops.

float VHF, UHF, 10db_gain;

if (VHF != UHF) {
    UHF *= 10db_gain;

}

[IanM]

On 10/28/2021 at 3:52 PM, gman1971 said:

Depends on several factors to chose VHF over UHF (or the other way around). The biggest drawback of VHF as of lately is the ever increasing noise floor due to Cheap China LED bulbs... which pollute the heck out of the VHF band... also most electronics found inside buildings (in particular LED fixtures and wired Ethernet) will put out a lot of VHF noise, thus reducing your range indoors... so its a tradeoff, you need to determine the noise floor of the site, and determine with an RSSI meter which radio works best. The lower the noise threshold the better.

G.

Interesting observation, and might explain my experiences. I'm maybe a mile and a half from a local 2m repeater up on a hill I regularly use, and the voice modulation comes in strong and clear, there's a very high noise floor of static and buzz. UHF, both 70cm and GMRS come in just fine, very quiet. I'm in a midrise in the middle of Seattle. There's for sure a lot of noise pollution in every band (don't even get me started about WiFi interference in a 150 unit building!), but that might be why VHF is particularly problematic. 

To the earlier topic about power vs sensitivity/selectivity; my observations jive with @mbrun as well as to there being little correlation; I was up on the roof doing a side-by-side with the 905G, UV8H and a commercial-grade Motorola  this evening, playing musical antennas (a test for another thread) and testing with someone on a distant repeater, both 70cm and GMRS. The 8W, SoC UV8H was the loser on all counts, and the 4W Motorola ( @gman1971—an XPR6550, also with the stock, albeit UHF antenna) came out way ahead on reception. Again, we're talking very fringe situations on a site 30+ miles away. 

That all said—I have no idea how Wyoming's SAR operates, but good on them for advertising this frequency. Looks like it's not actively monitored. @GuySagi, thanks for sharing your SAR experience as well, and I wonder what equipment they specifically will implement; around here, both SAR volunteers and the Sheriff's Office are on VHF, so at the very least its another radio to pack.

Remember, we're not talking about intra-agency communications. We're talking about them being able to monitor a frequency in the off chance someone's got a radio on them, which is such a huge advantage. No, cheap bubble-packs are not the optimum means of communications backwoods, but it's still another tool, period—I can't think of anyone else I know outside my family and regular hiking friends that carry a radio of any kind, let alone the kind of gear we use here. If someone is going to have anything at all outside a cellphone, It'll likely be a Talkabout or a Midland or some such, capped at 5W, so the channel itself is sort of a moot point as long as it's memorable. That might be a problem for those with a 50W mobile with power output locked on certain channels, but I also think most of us here might be savvy enough to figure a way around that.

For myself, if I'm in the woods (as I somewhat often am) and an emergency arises outside a cell site, heck, I'll try anything—146.52, GMRS 1 or 20, any repeater on either service. Tremendously valuable just to have that with me anyway.

[gman1971]

18 hours ago, Lscott said:

oops.

float VHF, UHF, 10db_gain;

if (VHF != UHF) {
    UHF *= 10db_gain;

}

Well, thats better, but you will get some warnings about uninitialized variables ... LOL

G.

[gman1971]

2 hours ago, IanM said:

Interesting observation, and might explain my experiences. I'm maybe a mile and a half from a local 2m repeater up on a hill I regularly use, and the voice modulation comes in strong and clear, there's a very high noise floor of static and buzz. UHF, both 70cm and GMRS come in just fine, very quiet. I'm in a midrise in the middle of Seattle. There's for sure a lot of noise pollution in every band (don't even get me started about WiFi interference in a 150 unit building!), but that might be why VHF is particularly problematic. 

To the earlier topic about power vs sensitivity/selectivity; my observations jive with @mbrun as well as to there being little correlation; I was up on the roof doing a side-by-side with the 905G, UV8H and a commercial-grade Motorola  this evening, playing musical antennas (a test for another thread) and testing with someone on a distant repeater, both 70cm and GMRS. The 8W, SoC UV8H was the loser on all counts, and the 4W Motorola ( @gman1971—an XPR6550, also with the stock, albeit UHF antenna) came out way ahead on reception. Again, we're talking very fringe situations on a site 30+ miles away. 

That all said—I have no idea how Wyoming's SAR operates, but good on them for advertising this frequency. Looks like it's not actively monitored. @GuySagi, thanks for sharing your SAR experience as well, and I wonder what equipment they specifically will implement; around here, both SAR volunteers and the Sheriff's Office are on VHF, so at the very least its another radio to pack.

Remember, we're not talking about intra-agency communications. We're talking about them being able to monitor a frequency in the off chance someone's got a radio on them, which is such a huge advantage. No, cheap bubble-packs are not the optimum means of communications backwoods, but it's still another tool, period—I can't think of anyone else I know outside my family and regular hiking friends that carry a radio of any kind, let alone the kind of gear we use here. If someone is going to have anything at all outside a cellphone, It'll likely be a Talkabout or a Midland or some such, capped at 5W, so the channel itself is sort of a moot point as long as it's memorable. That might be a problem for those with a 50W mobile with power output locked on certain channels, but I also think most of us here might be savvy enough to figure a way around that.

For myself, if I'm in the woods (as I somewhat often am) and an emergency arises outside a cell site, heck, I'll try anything—146.52, GMRS 1 or 20, any repeater on either service. Tremendously valuable just to have that with me anyway.

 

Absolutely, carrying a properly setup radio on you is having another means of communication at your disposal, more so if you've also taken the time, and gone through the effort, to setup a solid infrastructure around it to meet your needs.

Unfortunately, tho, for most people it will be just dead weight, given than most people won't even bother learning how to use the radio, let alone build any infrastructure to use it even remotely effective.

Emergencies are all about fringe situations, as in: if something can go wrong, it will, and the worst possible moment...  and when something goes wrong, you really want on you a radio that has the capability to save your life... (not that it will) but also keep in mind that a radio is only as useful/important/capable as the person listening on the other side is... so you really want to make sure beforehand that your radio is capable of reaching the people that can, and will do something about the situation.

G.

[MichaelLAX]

You never know what information can result in a rescue.

Local Ham, Benjamin Kuo, AI6YR:

Missing Hiker Found After Man Using Computer at Home Pinpoints His Location

 

[Lscott]

15 hours ago, gman1971 said:

Well, thats better, but you will get some warnings about uninitialized variables ... LOL

G.

I believe they would be initialized to zero by default. One could also set the compiler warnings to ignore it too depending on whose you use.

[gman1971]

On 10/30/2021 at 7:03 PM, Lscott said:

I believe they would be initialized to zero by default. One could also set the compiler warnings to ignore it too depending on whose you use.

Only when optimizations are disabled, once you do /03, etc the memory is not guaranteed to be zero.  lol

[Lscott]

1 hour ago, gman1971 said:

Only when optimizations are disabled, once you do /03, etc the memory is not guaranteed to be zero.  lol

You're likely right about that. I haven't written much code in a while. I do mostly power electronics design. From time to time I do get involved with some embedded microcontroller stuff.