Microwave Systems and Remotes Links

[Project25_MASTR]

These days, you're more likely to find 45 MBPS DS3 speed radios on those channels.

That only goes to remind me of how fast microwave radio has advanced in the last decade. When I went to work for big oil in 2015 we were working on removing the TDD based equipment in favor of equipment that was native IP based. I remember one of my friends (who owned a WISP) called me saying, "I just upgraded my PTP800 from 10M to 45M and it's blazing." He asked me what I was doing and I was like, "I just installed a new Aviat link up in Colorado. 45 miles, 200 Mbps FDX." Few years later he asked me if my longest unlicensed link was still the 75 Mbps, 20 mile Ubiquiti (Rocket M5) link I installed for him and I said no...now a 36 mile, 150 Mbps Mimosa (B5c) link I put in for a friend to tie in a remote Capacity Plus/Connect Plus site to the rest of his system. Today we talk about his 400 Mbps unlicensed backhauls and I tell him about my gigabit short range backhauls in 60 GHz and we talk about Aviat's 10 gigabit backhaul.

While this has all be going on, I've worked on converting some Astro 25 systems from TDD circuit switched to IP based systems and that has been quite an interesting feat. The old circuit based stuff used to be limited by the number of time slots available and while the total data overhead has gone up (9600 bps for an active call versus 12 kbps to 14 kbps for an active call)...those DS1's can push nearly 5 times as much traffic as IP compared to what they could as TDD switched.

 

[mikewazowski]

When I started, we had all sorts of 4 DS1 radios installed and the backhauls were typically 3DS3.

Now everything has either gone fiber and at a minimum on microwave, 200mbps.

 

[mmckenna]

When I started, we had all sorts of 4 DS1 radios installed and the backhauls were typically 3DS3.

Now everything has either gone fiber and at a minimum on microwave, 200mbps.

I used to have an 18GHz link that a couple of E-1's over a few miles. Each E-1 gave me 30 DS0's a sync channel and a data channel. That was a solid link. One day we were down at the far end and noticed the feed horn had been snapped off (no idea how, found it laying under the antenna) with just the open wave guide pointed at the other end. System stayed up just fine.
Eventually replaced with 2 T-1's, and then eventually fiber.

 

[ab3a]

If you don't mind the increased likelihood of a path fade, there are 11 GHz radios that run 150 MBPS with some impressively large I/Q constellations. But I really liked the 6 GHz stuff because it rarely ever faded. The only time we ever got in to trouble with it was on clear calm fall nights when radiation fog would form over most of one particular path. The hot/cold, humid/dry air masses, if they got close to the altitude of the dish, could refract a beam right in to the ground or in to space. I have watched a path with a fade margin of nearly 40 dB completely squelch out. Thankfully, this one path where that sort of thing could happen was on a ring and in about 50 milliseconds the ring would switch (This was in the days when FDM was the only way to get any decent capacity).

So at most, a perceptive person might notice a click and a slight change of background hiss on a quiet VF channel, but that was it.

 

[mikewazowski]

All our 6GHz stuff was space diversity.

 

[merlin]

Nothing new about microwave links, just that they are getting into numbers and more in the public spotlight.
Late 50s, these links were mostly telephone networks with those huge horn reflectors on mountain tops.
TV stations later cut the landline and use studio/transmitter links. Microwave links used for wide distribution of cable TV.
Your typical satellite receiver picks up microwave links fro satellites.
Enter modern technology and having WiFi and internet delivered by microwave links.
Public safety is shifting to a cellular sort of network, mostly on 700 and 800 Mhz, not quite microwave but works a bit the same.
Are they monitor-able ?? to a degree, yes, but you need the proper equipment for it.
High end scanners, and some SDR radios can pick up a lot of this stuff.
I had no cable where I lived, but lived right in the path of a cable AML link on 12 Ghz. using the block down converter and a satellite dish, I then had cable TV like the cable coming into your home.
Remote link is a bit ambiguous, a link to a remote site or mountain top. A link from top to top.
I get my internet via a 5.6 Ghz link from a mountain top to my home.
In the end. this is all radio and with the right equipment one can pick up what comes to your home, even from space.