Map: Is this area too steep for GMRS?

[snowfiend]

Here is a topo of an area we frequently camp and explore, coordinates 40.36163,-121.33817 (don't steal my spot! ). The camp is down in a valley with two ridges, once you get past either ridge (marked in blue or red) my 5W Midland GXT1050VP4 radio on high won't reach back to the other one in camp 1.5 miles away (yellow X to camp marker as an example).

Using Midland MicroMobile units as examples, if we put a 40W MXT400 in the camp trailer and 15W MXT275 in a vehicle would that be enough power to communicate over the ridge? If not, what about MXT400'S all around? Or is this too steep and forested for effective GMRS usage?

 

[Airmapper]

Power doesn't really mean crap, GMRS is line of sight, meaning if there is no clear path the signal can't make it. Power helps when you have a path but maybe it's obscured by trees or light stuff. Land mass, i.e. rock, is a hard stop to the signal.

Only way power might help there is if it reflects off something, and I don't see much there for it to bounce off of. That frequency range only really reflects off buildings and such.

What would help is altitude on an antenna, but camp is down in a hole. Whoever calls camp has to be higher than camp on the same side of the ridge, or higher than that ridge if beyond.

 

[dreadlocks]

yep you cant transit through earth at these frequencies, line of sight is required as GMRS dont skip off the atmosphere like you can w/CB.

You'd have to put a repeater on the peak between the two camps.

 

[snowfiend]

Thanks, that's kinda what I thought but needed to ask before spending money and not getting the result I wanted. I don't see us getting a repeater or going HAM, so I guess it's either CB or just get high as possible to communicate.

 

[Billoftt]

You would be hard-pressed to get a CB to reach that too in many cases.
Here is a neat little calculator to determine best-case-scenario for line of sight and radio horizon.
https://www.everythingrf.com/rf-calculators/line-of-sight-calculator

 

[dreadlocks]

yeah CB has the capability to bounce off atmosphere, but that dont mean you can rely on it... for example atmospheric conditions are far more favorable for HF use after the sun sets.. CB would also be a crap shoot getting around terrain as environmental conditions change.. for example they might hear you but you cant hear them.. Working HF w/a Ham License at least gives you many more band/frequency and radio options, and there could be VHF and UHF repeaters nearby that give you direct LOS communications.. honestly if maintaining coms between these two camps is a high priority, getting a few people licensed up on HAM would be the most likely to succeed.

Check out: https://mygmrs.com/ and see if there's a public GMRS repeater nearby you can use.. chances are slim but you might be lucky.
Otherwise check out https://repeaterbook.com/ and see if there are any VHF/UHF Ham repeaters within range of your sites.

 

[DaveInDenver]

Topology and line of sight make all the difference, especially with UHF.

 

[DaveInDenver]

CB isn't HF, it's low band VHF for propagation. You can sometimes find it experiences tropospheric ducting but it's not skip in the same sense as HF.

 

[Ray_G]

The electronic LOS reality has been well covered here, but I'd note that if you really, really need comms between the two I'd think about each site having a Garmin inreach or other suitable SATCOM device. HF shots are certainly feasible, but in practice....well, I'd just go with a GMRS repeater but absent that...SATCOM.
r-
Ray

 

[dreadlocks]

CB isn't HF, it's low band VHF for propagation. You can sometimes find it experiences tropospheric ducting but it's not skip in the same sense as HF.

11m is low band VHF? hrmm I mean its close but I thought VHF started at 30Mhz and 11m is lower than that.. abiet slightly so it propagates more like VHF than say 30m

Citizens band radio - Wikipedia

en.wikipedia.org

 

[BigDaveZJ]

Topology and line of sight make all the difference, especially with UHF.

View attachment 524290

Is that map showing LOS from the purple marker?? If so, how/where did you do that?

 

[DaveInDenver]

Is that map showing LOS from the purple marker?? If so, how/where did you do that?

It is a hasty RF coverage map. I used the GPS coordinates in the post and assumed 5 watt TX with 2.13 dBi antenna gain on both TX & RX. I assumed 0.5uV receive minimum sensitivity I think. Height of 2m over ground on both antennas.

There's several software packages and sites to do them. FCC requires it for most tower installations and its commonly done for repeater sites.

 

[DaveInDenver]

11m is low band VHF? hrmm I mean its close but I thought VHF started at 30Mhz and 11m is lower than that.. abiet slightly so it propagates more like VHF than say 30m

Citizens band radio - Wikipedia

en.wikipedia.org

It's generally true to call VHF 30 to 300 MHz. But EM fields don't always follow our arbitrary definitions. CB was put where it was because at the time it was "very high" relatively. Also at the time 150 MHz was "ultra high", thus why they called the PL259 a "UHF" connector, the limit of its usefulness.

Point being practically low band radios are typically 29 to about 88 MHz, which bumps up to the top of CB. This spectrum tends to propagate LOS and not skip, so is treated in practice like VHF (2m for example). The FCC did not want a CB device that would interfere over DX and this part if the spectrum achieved it. It's why commercial TV and FM radio got put there too. Commercial AM is LF/HF, for example, and after dark will propagate long distances via sky or ground wave.

So the 12, 11 & 10 meter bands sit below the "VHF" threshold on a chart but don't act quite like HF really. It's why we hams geek out during solar cycles where 6 and 10 meter openings pop up. The ionosphere favors DX where it normally won't.

 

[dreadlocks]

ah thanks for the explanation, I'm just a tech so I dont work HF and have not been too terribly interested in it other than mebe HF APRS for middle of nowheres.. CB was my first radio and sometimes at night I could talk to people in towns a couple hundred miles away but it was never anything reliable.. I havent used it since I was a teenager though.. my TS2000 will do HF (about all its good for anymore since its deaf on VHF) but I keep that around more for TEOTWAWKI type stuff.. My house already has enough antennas on it as it is without a real tower, I figured the retired me will have the time and desire to work HF, especially if I'm on an island in the south pacific or just some random continent..

 

[DaveInDenver]

That TS2000 shouldn't be all that bad, it's rated 0.25 μV 12dB SINAD on 144-148 FM. When the ARRL tested the TS2000 they found it to be 0.182 μV at 146.0 MHz using the pre-amp and normal bandwidth and 0.2 μV using wide bandwidth, so Kenwood's being conservative in their specs.

A TM-V71 is 0.16 μV, the FT-857 is 0.2 μV on 2m FM and an FT-8800 is 0.2 μV. On UHF FM the TS2000 is 0.18 μV.

That's roughly a 2 dB difference from those mobiles and we're talking a sensitivity down at approximately -119 dBm. I have a pretty bulletproof Vertex VXD-7200 (guts of which are a Motorola XPR4550) DMR mobile and it's only rated 0.22 μV at 12dB SINAD, so within 1 dB of the TS2000. A measurement or rounding error almost.

Did you get the TS2000 new? If not maybe it's been hit with static or just needs an alignment. Without the pre-amp they measured sensitivity over 1 μV, which would be -107 dBm. Perhaps that's all it is?