2.4 vs 5ghz

15 posts / 0 new

Sun, 11/05/2017 - 19:37

KE0EYT

2.4 vs 5ghz

Hey All, As I'm starting to build up my equipment, I wanted to ask this question...

There's not much out there in Minnesota for existing networks, so I'm not worried about that. I forsee most of my setups being in rural areas, linking a search and rescue mission base with other parts of an airfield, or maybe if I get really lucky someday, a node in an aircraft which is already acting as a radio traffic repeater.

Why would I want to go with 5ghz over 2.4? I'm not too concerned with interferance, as most of our operations are well outside city limits.

I understand the networking aspects of this, need a little help with the RF. :-)

Thanks!

Sun, 11/05/2017 - 20:13

K7DXS

1. 5GHz has more space. 2.4

1. 5GHz has more space. 2.4 is capped at 20MHz bandwidth. Not sure about 5GHz but I would assume at least 40. I'm trying to get people in Southern AZ to start buying 5GHz equipment.
2. You can find a bunch of UBNT M5 equipment cheap on eBay because it's all being replaced by 802.11ac equipment.

Sun, 11/05/2017 - 20:22

(Reply to #2) #3

KE0EYT

What is the difference in

What is the difference in effective range?

Sun, 11/05/2017 - 20:48

n4tna

If I'm not mistaken 5GHz will

If I'm not mistaken 5GHz will have a 6db weaker signal at longer distances vs 2.4GHz. The thing that makes 5GHz more appealing to me is that it has a smaller fresnel zone than 2.4GHz. Which means that it's easier to get a clear line of sight at longer distances with 5GHz. Any obstruction ie trees, hills, or buildings that are in the fresnel zone will degrade the signal. There is a great online tool from Ubiquiti that allows you to plot perspective node locations on Google Maps and try different frequency equipment to see what kind of obstructions and signal quality you will theoretically get. airlink.ubnt.com

Hope this helps
Chris N4TNA

Sun, 11/05/2017 - 20:50

(Reply to #4) #5

KE0EYT

I'm aware of the frensel zone

I'm aware of the frensel zone differences, and it's definitley a consideration in the final output. I'm more curious about effective range differences if I commit to 5ghz over 2.4.

Sun, 11/05/2017 - 21:04

n4tna

Generally the lower the

Generally the lower the frequency the better the propagation so 2.4GHz will give you better range. I guess it really depends on how and where you will be deploying them. I typically use 2.4GHz for short distances and do backhaul with 5GHz. Where I live there is lots of hills in the way so for me to get a 5 mile point to point using 2.4GHz both devices would need to be on a 100ft tower. Whereas I can get a reliable 5 mile link with 5GHz using a 16ft push up painters pole.

Chris N4TNA

Sun, 11/05/2017 - 21:15

(Reply to #6) #7

KE0EYT

Help me reconcile your

Help me reconcile your situation. I understand that the lower the frequency, the better the propagation, but how is it that you do better with 5ghz than 2,4 in your situation?

Sun, 11/05/2017 - 21:38

n4tna

Because of the fresnel zone.

Because of the fresnel zone. On 2.4GHz the fresnel zone at 5 miles has a radius of roughly 52 feet. On 5Ghz the fresnel zone at 5 miles is around 36 feet. Given the hilly terrain where I am located along with trees and buildings 5Ghz gets me a better quality signal at lower heights than with 2.4GHz.

Chris N4TNA

Sun, 11/05/2017 - 21:55

n4tna

There were also other

There were also other variables in my testing that had an effect on my results. The 5Gz radios I have are the NanoStation M5's which are MIMO devices and have a higher gain antenna. The 2.4GHz radios I was using was Rocket M2's with only a 3db antenna on it. So my testing wasn't exactly an apples to apples comparison. With the Nanostations they have a vertical and a horizontal antennas and have a much higher gain than the single diversity antennas I was using with the rocket m2's.

Chris N4TNA

Sun, 11/05/2017 - 22:57

#10

W6RUF

You will use both

I'm running two M5 Nanobridge radios as a backbone link, one to our Mount OSo site at 34 miles and my second is to Mount Bullion at 36 miles. Good throughput and reliable connections even when the fog settles in. I am in a relatively flat farm valley surrounded by 3000 ft mountains ridges to the East and West. Both radios up around 20 feet, light vegetation nearby. I would go 5.8 Ghz. At each node end you will use low power 2.4 Ghz radios to allow your laptops, cells, and tablets to connect to the backbone anyway. You will end up using both.

Mon, 11/06/2017 - 08:55

#11

K6AH

2.4 and 5.8 link distances nearly identical

While it is true 2.4 GHz has a 6dB advantage over 5.8 GHz, for a given dish size the opposite is true. If you compare the UBNT Rocket Dish models you'll see the 5 GHz version is spec'd at 30dBi while the 2.4 GHz version is only 24dBi. In practical use, this offsets the 2.4GHz propagation advantage.

Andre, K6AH

Mon, 11/06/2017 - 09:50

(Reply to #11) #12

KE0EYT

Awesome, thanks Andre.

Awesome, thanks Andre.

So, is there any reason in your opinon why I would want to consider 2.4 over 5.8?

Tue, 11/07/2017 - 00:27

(Reply to #12) #13

K6AH

Nope

If hams in the area haven't already bought a bunch of 2GHz nodes, then I can't think of a reason to not go 5GHz.

Tue, 11/07/2017 - 01:03

(Reply to #13) #14

KL5T

How about 3.4?

Not seeing any mention of the possibility of using 3.4. More channels, exclusive use of the band, lower noise floor, but a bit more expensive. It's what we've generally opted for here in Anchorage. Works great.

73,

Kent, KL5T

Tue, 11/07/2017 - 10:37

(Reply to #14) #15

KE0EYT

Good point, unfortunately, I

Good point, unfortunately, I need to operate under part 15 some of the time due to regulations with my SAR org.

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