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.