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Author Topic: ALL Simplex users, Echolink, IRLP node operators, etc., PLEASE READ  (Read 1889 times)

Posts: 534

« on: December 20, 2016, 08:48:46 AM »

I want to make a plea for everyone to please be aware of the satellite sub-bands on the VHF-UHF sub-bands, but especially on 2m. There is a continuing problem with both amateur and non-amateur stations transmitting on the frequencies that are used to uplink to amateur satellites, especially in North America. These folks are completely unaware that their transmissions are being relayed all across the continent and having the unintended consequence of causing debilitating QRM.

For example...

In the case of the SO-50 satellite, stations are transmitting on or near 145.850 Mhz, but doing it without the required PL tone and often with way more power than what many satellite ops are using (sometimes 5 watts or less). The result is, satellite stations are being covered over by these stations, causing QRM. But we cannot identify the stations because only short snips of audio can be heard in the squelch tail of the satellite, since the proper PL is not present to make their signals audible. It is presumed that there is some sort of remote base or internet connected station in the southeastern US on this frequency as it is heard with regularity when the satellite is over this area and often during the same time periods as if a weekly net were being conducted. (Saturday mornings, if memory serves.)

In the case of FO-29, which is an SSB/CW satellite, FM carriers can be heard that seriously degrade the signals of all stations on the transponder. (Transponders are wide band and the power is shared; loud stations will use up a lot of the power and cut back the signals of other weaker stations.) Attempts to copy these stations are not easy and seldom is a callsign heard. It is unknown whether they are unlicensed stations that bought a couple of ham radios and dialed up what they thought were 'unused' frequencies or two licensed hams thinking the same. (Just the other day I heard two guys with rural US accents ending a conversation discussing that he better go as the dog had started barking.) In one incident, callsigns were heard, but they were from all over North America and some in parts of the country not in range of the satellite at the time. Turns out it was a ham station rebroadcasting a local UHF repeater onto two meters over his home dual band radio in cross repeat mode and the UHF repeater was hooked up to some type of internet linking. It took some serious sleuthing, cooperation of the repeater trustee and a lot of luck to figure all this out... it was not simple by any stretch of the imagination.

I realize that many may be unaware of amateur satellites and be thinking, 'Well, I was on there first and the FCC says... so, they need to move somewhere else.' But what they may not understand is that ham radio satellite frequencies are specified both within the FCC rules and by international agreement, and are assigned prior to launch and CANNOT be changed once in orbit. (Incidentally, some of the satellites currently in use were launched before internet linking existed! FO-29 is over 20 years old.) This situation would be no different than if someone starting having a simplex conversation (or set up a remote linked station) on the input frequency of a terrestrial repeater. The common expectation is for the frequency agile simplex station to move, not the coordinated repeater, right? The difference here is, it is much easier for the typical repeater owner to figure out and contact the person transmitting on the repeater input... with the interference to satellites, not so much.

So PLEASE... help spread the word. The two primary satellite sub bands 145.80-146.00 MHz and 435.00-438.00 MHz may very well be in use, despite never hearing any signals there. And while setting up a small station there may seem harmless, please remember that even at very low power a receiver overhead in the sky may hear you better than someone a half mile down the road! Great interference can be caused, not just to other hams, but many of these satellites are conducting educational and scientific experiments and are transmitting telemetry to the ground. This is one of the ways that the ham satellite groups gotten access to launch opportunities is by a cooperative effort with educational institutions... the experiments benefit education and science and when they are done (or even at the same time) we get to play radio over them. (Simply put, they get a platform and we get a ride. Win-win!) So again, lots more folks are affected than just a couple of hams across town.

Bottom line... even though it sounds clear, yes, the frequency may be in use.

Thank you for any efforts to get the word out in the VHF/UHF and internet linking communities!

Posts: 280

« Reply #1 on: December 21, 2016, 02:37:51 PM »

would have thought this was common knowledge but guess not. I personally don't use sats but know of 0 remotes on the 145.8 to 146.00 spec on 2m

I do know a repeater on 145.77 which shouldn't be there since 145.50 to 146.00


Posts: 75

« Reply #2 on: December 21, 2016, 03:56:51 PM »

I wonder if somebody is operating a 145.250 repeater with a +600 input.
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