From: invalid@see-sig.invalid   
      
   On 5/28/2023 6:28 PM, Bill Horne wrote:   
   > On Sat, May 27, 2023 at 09:17:25PM -0000, Garrett Wollman wrote:   
   >> ...   
   >> You might be surprised how many radio stations, after conditioned   
   >> analog lines and ISDN ceased to be available for new installs from   
   >> ILECs, came to depend on the Internet for their studio-transmitter   
   >> links, especially now when it's audio-over-IP all the way from the   
   >> mixing console to the transmitter.   
   >   
   > At the time I retired, Verizon had substituted specialized T-Carrier   
   > channel units for the conditioned lines: the T-Carrier links didn't   
   > require any equalization, and since most local pairs aren't loaded,   
   > there was usually no need to equalize the local pairs beyond seting   
   > some computer-generated options in the channel units.   
   >   
   > As for ISDN, I'm surprised that it would ever be used for "STL"   
   > circuits in the first place: ISDN was a dialup service, and even if   
   > the radio station owner was willing to bear the expense of the   
   > Nailed-up "data" connections, they would be risking disconnects caused   
   > by all of the usual problems that can interrupt both digital and   
   > analog connections: T-Carrier failure, etc.   
   >   
   > Were you thinking of IDSL connections?   
      
   Radio stations used ISDN for events, like school sports and   
   appeareances at shopping malls. STLs were either microwave or fixed   
   circuits.   
      
   Nowadays stations do use the Internet for STLs, though it may be   
   accompanied by a microwave channel. One major-market FM station I have   
   worked with is a good example. They have an analog (900 MHz) STL from   
   a high rooftop near the studio to the main transmitter tower on a big   
   hill some miles away. But that's now just a backup. GatesAir has a   
   clever new system where stations can fill in coverage gaps within   
   their licensed contours via booster transmitters. A booster is an   
   additional lower-power transmitter on the same frequency (vs. a   
   translator, which needs its own channel). Obviously a booster can't   
   listen to the main transmitter and retransmit it (on frequency) the   
   way a translator can, but it can use its own STL. The trick is that   
   the STLs to both the main transmitter and boosters are digital and   
   they all have GPS sync. So they all buffer the broadcast for enough   
   milliseconds to make sure that they're all in perfect alignment with   
   GPS timing. The booster antennas are directional, pointing away from   
   the main transmitter, so the signals from both transmitters arrive in   
   sync and don't interfere. For the main STL, it's unlicensed 5 GHz   
   microwave. That can go quite a few miles between decent size dishes,   
   and it's cheap; the dishes not only give gain but help null out all   
   the Wi-Fi noise below the path. The boosters use cable modems for   
   their STLs. If something fails, it falls back to the analog STL on   
   just the main transmitter.   
      
   >> Many radio transmitter sites have just a commodity Internet   
   >> connection that feeds their remote control and the transmitter: no   
   >> Internet = station off the air.  More profitable stations,   
   >> especially those that haven't moved around a lot, may have an   
   >> analog microwave path for backup, or even an optical wide-area   
   >> network, but this costs a lot more money and is hard for many   
   >> engineering managers to justify to barely-profitable companies   
   >> constantly seeking to cut costs.   
   >   
   > It's been a while since my "First Phone" was renewed as a "General   
   > Radiotelephone" license, but what I recall from my days as a radio   
   > tech was that even clear-channel stations avoided mircowave like the   
   > plague. The siting effort was incrediby expensive, with   
   > complementary towers at each end of the path, with the risks of any   
   > off-kilter microwave oven killing the link, and with a never-ending   
   > need to pay someone to predict what buidings would be built in the   
   > middle of the Fresnel Zone.   
      
   Not true. Aural analog STLs are on 900 MHz, which doesn't get rain fade,   
   and have been there pretty much forever. Microwave in general, though,   
   is pretty easy to make reliable, based on current digital technology,   
   and the radios have gotten quite cheap. Buildings do get put up in the   
   path if you're in an urban core, but you can usually get time to work   
   around them (engineer a new path) before they're done. TV STLs are   
   usually microwave on 7 or 13 GHz. Back in the olden days, stations had   
   to buy their STLs from Ma Bell, who used microwave.   
      
   > Of course, we all know the on-again, off-again love triangle that has   
   > fiber-optic cable, Ditch Witch machines, and competent fiber splice   
   > technicians at the vertices. I've never met a chief Engineer who   
   > trusted fiber any more than microwave - but it's been a while, so   
   > perhaps the reliability has improved.   
      
   Backhoe fade continues to be a problem. You can't foolproof things --   
   we keep getting greater fools.   
      
   --   
   Fred R. Goldstein      k1io    fred "at" interisle.net   
     Interisle Consulting Group   
     +1 617 795 2701   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)