How many MURZ farz in the woods?

[GreggInFL]

Is MURS a good alternative to simplex GMRS in a setting that is flat and chock full of vegetation?  Looking to put together something for emergency comms and would love to avoid a repeater.  Farthest distance is ~2.7 miles and elevation delta is roughly 50'.

I know, I could try it, just wondered if anyone has experience with MURS in this setting.

TIA.

[WRWE456]

Very likely will work. I have done that far at least in mostly wooded conditions using the Wouxun KG-805M radios (which put out the full 2 watts on MURS and are very good radios IMO). Have reached five miles base to mobile and base to HT from hilltop base with rooftop antenna. That is the furthest I have tried so far, that reminds me I need to go out and test at further distance.

As you said the only way to know is to test it yourself.

[OffRoaderX]

Theoretically, on paper, MURS is a better choice due to the lower frequencies - HOWEVER, in my head-2-head testing, it was not much/if any better than GMRS. I assumed because of the additional power on GMRS.

HOWEVER - i have not done much testing in THICK forest or anywhere chock-full of vegetation, because we don't have that were I live so i defer to anyone with better/more data.

[marcspaz]

So... couple of possible answers.  I have done head-to-head-to-head testing for a customer, through 10 miles of heavy woods, with GMRS, MURS and CB.  I will make this as concise as possible.

 

With everything being equal, the lower in frequency you go, the less foliage and trees absorb RF... therefore the less the impact on range. That said, due to rules of the services, that doesn't mean anything as far as practical application.

Again, no Line of site restriction, heavy woods, abiding to the FCC rules.  From and to the exact same locations, on the same day, within an hour time frame.

With a mobile CB, legal limit on AM, the max usable power of 4w (3 measured) and a 1/4 wave antenna, range was about 2.5 miles.

With mobile MURS, max usable power of 2w (1.8 measured) and a 6dB gain antenna, max range was 1 mile.

With GMRS. max usable power of 50w (48.5 measured) and a 6dB antenna, we were able to talk the full 10 miles with about a 50:50 SNR.

[LeoG]

That's a really good answer.  Wish you had tried the GMRS on 5 watts to see how an HT might have worked.

[marcspaz]

16 minutes ago, LeoG said:

That's a really good answer.  Wish you had tried the GMRS on 5 watts to see how an HT might have worked.

 

I thought about doing it for my own interest, but I didn't think of it until after the project was done.

 

The customer was looking for a cheap alternative to commercial radios, to communicate between two campus' with base stations. Handhelds were also in the site survey and setup, but they only needed coverage for about a mile in each direction, per campus and only to the base station. I missed an opportunity for sure... but was focused on the job and requirements.

[LeoG]

You did what you were asked.  It would have been nice to see CB vs GMRS because both of them are about the same wattage and vastly different frequencies and tech, AM vs FM

[WRYZ926]

I would like to see a CB radio tested on FM since that would be a closer comparison to MURS and GMRS.  GMRS and MURS are FM frequencies.

And yes I have been looking into getting a CB radio with AM, FM, and SSB capabilities.

 

[marcspaz]

4 hours ago, LeoG said:

You did what you were asked.  It would have been nice to see CB vs GMRS because both of them are about the same wattage and vastly different frequencies and tech, AM vs FM

 

10 minutes ago, WRYZ926 said:

I would like to see a CB radio tested on FM since that would be a closer comparison to MURS and GMRS.  GMRS and MURS are FM frequencies.

And yes I have been looking into getting a CB radio with AM, FM, and SSB capabilities.

 

 

 

I still have most of the gear and plenty of woods. I may repeat the test with "like-model" comparisons. I have to see how the calendar shakes out and if I can find a volunteer with a proper CB install.

[WRUI365]

Don't even get into the QRP side of HF, depending on atmospheric conditions, you could reach out quite a distance.

[GreggInFL]

23 hours ago, marcspaz said:

So... couple of possible answers.  I have done head-to-head-to-head testing for a customer, through 10 miles of heavy woods, with GMRS, MURS and CB.  I will make this as concise as possible.

 

With everything being equal, the lower in frequency you go, the less foliage and trees absorb RF... therefore the less the impact on range. That said, due to rules of the services, that doesn't mean anything as far as practical application.

Again, no Line of site restriction, heavy woods, abiding to the FCC rules.  From and to the exact same locations, on the same day, within an hour time frame.

With a mobile CB, legal limit on AM, the max usable power of 4w (3 measured) and a 1/4 wave antenna, range was about 2.5 miles.

With mobile MURS, max usable power of 2w (1.8 measured) and a 6dB gain antenna, max range was 1 mile.

With GMRS. max usable power of 50w (48.5 measured) and a 6dB antenna, we were able to talk the full 10 miles with about a 50:50 SNR.

Nice work!  Thanks for that.

I should have mentioned that our interest is in HTs as a backup to cell phones here in Hurricane Central.  I knew that the lower frequencies of MURS would be a helpful characteristic, but the lower power would be a negative vis-a-vis GMRS.  That's probably the trade off Randy experienced.  Ideally we would just hand out HTs in the community and leave it at that.  We've tested GMRS HTs successfully at a distance of ~2 miles, but that was purposefully between the two tallest points on site, which isn't going to cut it.  Looks like MURS HTs won't work either.

A portable repeater put up after the event may be the way to go.  We had sustained winds of 120 during Charlie in 2004; add in the gusts and the seldom-mentioned fact that hurricanes spin off tornados and anything resembling an amateur installation is just going to get blown over like everything else.

For reference I've attached a photo of the view from my front door.  The problem is obvious.  Sigh.

[WRYZ926]

Nice view from your front door @GreggInFL But yes you are correct, all that will affect both VHF and UHF unless you can get an antenna above all the trees.

[WRYZ926]

There are instructions online for making 2m and 70cm roll up J Pole antennas using faraday clothe. It would not be that hard to modify a 2m faraday cloth j pole for MURS or modify a 70cm faraday cloth j pole for GMRS. You would need some way to get the antenna up high along with some coax cable to connect it to your HT. There is usually a solution or two for every problem.

https://www.youtube.com/watch?v=X7K6DNLD9Wo&t=3s

[Borage257]

N9taxlabs makes a dual band GMRS Murs roll up jpole. Quite easy to pull it up in to a tree with a throw weight and some line.

 

I recommend get the 16’ cable and BNC connector options. BNC mod what ever HT you plan on using with the Jpole.
 

12lb test fishing line or higher will make getting the antenna into a tree easier. Tie the fishing line to your throw weight (or water bottle) heave it over a branch, cut it off the bottle and tie it to your paracord and pull it back over the branch with the antenna.

 

https://n9taxlabs.com/shop/ols/products/dual-band-murs-gmrs-slim-jim-with-10-or-16-foot-cable

[Borage257]

Another option would be to make a moxon antenna or yagi centered on 152.15 MHz or so

[WRYZ926]

16 hours ago, Borage257 said:

N9taxlabs makes a dual band GMRS Murs roll up jpole. Quite easy to pull it up in to a tree with a throw weight and some line.

Those type of roll up j pole antennas definitely work. The faraday clothe j pole antennas will roll up into a smaller package and are pretty easy to make. The guy that made the video I posted earlier also sells them built for 2m and 70cm. You could definitely make your own and tune it for what ever band you want.

https://vfcomms.com/product-category/antenna/

I have to agree that BNC connectors will be better than using the SMA connectors.

There are quite a few YouTube videos of guys using those faraday cloth j poles and they are generally using them at 20-30 feet high in trees. And there are many ways to get your string up to pull the antenna into the air.

Either type of roll up j pole will serve well in an emergency situation to get your antenna as high as you can to get more farz out of a HT.

[WSAA635]

So how would MURS do at 5 watts to put it on equal footing with GMRS/CB? 

[dosw]

It would do fine at 5w, just like a 2m ham does at 5w. There's plenty of dialogue online about 2m ham at 5w.

 

But it's an unlicensed set of channels intended for short range use. Increasing power would potentially interfere with adjacent frequencies in the MURS neighborhood. 

 

There's not enough difference in propagation between VHF and UHF for the FCC to carve out a new set of frequencies to do pretty much exactly what is being done with GMRS, and charge for a $35 license, when we already have GMRS. The VHF spectrum is crowded, so it's an uphill battle to make it happen in a GMRS similar fashion. Amateurs get to leverage the difference in propagation because they jumped through the test hoops and paid their fees.

 

I don't think MURS will or can go to higher power as an unlicensed service because of the impact to paid license neighboring frequencies. And there's just no room for repeaters with only five channels at funky offsets from each other with some allowing wideband and some allowing only narrowband.

[SteveShannon]

4 hours ago, WSAA635 said:

So how would MURS do at 5 watts to put it on equal footing with GMRS/CB? 

Because RF is emitted in all directions equally from an isentropic antenna, one way to compare the range of different power outputs is to think in terms of the volume of a sphere:

Two watts fills the volume of a sphere of a radius of 0.78159 (the units in this case end up being the cube root of watts.)

Five watts fills the volume of sphere of 1.06078.

So, all other things equal, the range of a 5 watt radio compared to a 2 watt radio, to produce the same RF strength, will be approximately 36% further.

Increasing it to 10 watts (five times the power of the two watt radio) results in 70% greater range.

Increasing power to 20 watts gets you a little more than twice the range of the 2 watt radio (2.14 times to be exact).

Finally, increasing it to 50 watts gets you less than three times the range of the 2 watt radio. (a factor of 2.917).

Hopefully this illustrates how little/much RF power actually matters. 

[marcspaz]

38 minutes ago, SteveShannon said:

Because RF is emitted in all directions equally from an isentropic antenna, one way to compare the range of different power outputs is to think in terms of the volume of a sphere:

Two watts fills the volume of a sphere of a radius of 0.78159 (the units in this case end up being the cube root of watts.)

Five watts fills the volume of sphere of 1.06078.

So, all other things equal, the range of a 5 watt radio compared to a 2 watt radio, to produce the same RF strength, will be approximately 36% further.

Increasing it to 10 watts (five times the power of the two watt radio) results in 70% greater range.

Increasing power to 20 watts gets you a little more than twice the range of the 2 watt radio (2.14 times to be exact).

Finally, increasing it to 50 watts gets you less than three times the range of the 2 watt radio. (a factor of 2.917).

Hopefully this illustrates how little/much RF power actually matters. 

 

The information above is technically accurate, but should we caveat that for the woods?  Since the forest isn't consistent in density, levels of foliage change, the amount of water in the trees vary, etc.  actual results may vary.

[WRYZ926]

While VHF does do better than UHF in forested areas, both will be affected. I know all of the Eastern red cedar trees really mess with the 70cm and GMRS bands. There are plenty of spots where red cedar trees were allowed to grow up in the fence lines at the edges of most rural roads. 

I'm still curious how a CB transmitting on FM compares to MURS. I might ask around to see if anyone has HT's for MURS and FM capable CB.

[dosw]

2 minutes ago, WRYZ926 said:

While VHF does do better than UHF in forested areas, both will be affected. I know all of the Eastern red cedar trees really mess with the 70cm and GMRS bands. There are plenty of spots where red cedar trees were allowed to grow up in the fence lines at the edges of most rural roads. 

I'm still curious how a CB transmitting on FM compares to MURS. I might ask around to see if anyone has HT's for MURS and FM capable CB.

There's a wealth of information available on 10m propagation, and on 2m propagation, since they are both amateur, ham bands. Probably a lot more you can read up on than if you search for CB vs MURS propagation. I'd start there. CB is 11 meter, ham has 10 meter. They're close enough to be very similar. And with ham 10m, you'll find a lot of information about SSB, FM, and AM: SSB is usually at 28.3MHz to 29.3MHz. AM is usually 29MHz to 29.2MHz. And FM is usually at 29.6MHz, all within the 10m band. And in 2m, you can find allocations for SSB and FM, including weak-signal work. Each of those categories is a world of pet projects for some people (this time I'm using "some people" in a good way, I hope).

Consider MURS approximately equivalent in propagation characteristics to FM simplex over 2m. And consider CB approximately equivalent to AM and SSB in the 10m band.

[WRYZ926]

Just now, dosw said:

There's a wealth of information available on 10m propagation, and on 2m propagation, since they are both amateur, ham bands. Probably a lot more you can read up on than if you search for CB vs MURS propagation. I'd start there. CB is 11 meter, ham has 10 meter. They're close enough to be very similar

I am well aware of that. I don't have any HT's that work on 10m though. My Wouxun quad band is 1.25m, 2m, 70cm, and 6m. A hand held CB radio capable of FM and a hand held MURS radio would be best for real world comparisons. Especially since neither requires a license.

[dosw]

20 minutes ago, WRYZ926 said:

I am well aware of that. I don't have any HT's that work on 10m though. My Wouxun quad band is 1.25m, 2m, 70cm, and 6m. A hand held CB radio capable of FM and a hand held MURS radio would be best for real world comparisons. Especially since neither requires a license.

I'm not saying your use case isn't legitimate. I'm aying there's a lot that can be learned by investigating what others have already learned as they work the 10m, 2m and 70cm bands. I think that you're asserting that you need to know for your specific situation which will work better; CB, MURS, GMRS, at an equivalent power. For that, sure. You're going to have to set a GMRS radio to 2w, and set a MURS radio to high power of 2w, set a CB to 2w if possible, and do your comparisons. But in a broader sense you're asking questions that may be answered by looking at the body of knowledge developed over decades of amateur experimentation with 10m and 2m and 70cm.

 

So I'm not suggesting "Go get your amateur license and be a ham."  ...you may already be there, but that's not relevant. I'm just suggesting that the findings of others in those bands would apply to answering your question in general ways, though probably not specific to your neck of the woods.

[WRYZ926]

Yes I have my General amateur radio license. And I was just curious about testing the different license free bands with a hand held. I really have no need to test other than curiosity. 

And I already know that FRS/GMRS and 70cm is affected the most by foliage, especially cedar and pine tree. I hit dead zones all of the time even with our repeater antennas at 900 feet above ground on 70cm and GMRS running a 50 watt mobile with a good antenna in my vehicle. This same spots have no issues with 2m.

My inverted v 10m dipole is also resonant on the CB band. And there is definitely a difference between what I hear on each band when listening with my 20 watt Xiegu G90. I here way more traffic on 10m and I live 15 miles from a major interstate and 3 blocks from a major state highway.

I mentioned testing with a CB capable of FM since @marcspaz did his tests for a customer but was using a CB on AM. Again this is all out of curiosity on my part.