Towers & Such 2019

This topic contains 124 replies, has 19 voices, and was last updated by  Jeffrey Kopp 16 minutes ago.

Viewing 15 posts - 61 through 75 (of 125 total)
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  • #41769

    LinleyG
    Participant

    In a DOH moment, I forgot the other, and so very obvious spectral difference between ATSC1 and ATSC3 transmissions.

    Like ATSC1, ATSC3 is sent in “frames” or groups of data. In ATSC1, the frame length is a fixed 24.3 mS and you have to be decoding the signal to observe it. In ATSC3 the length of the frame is variable and is always preceded by a discovery or Bootstrap transmission that narrows the transmission bandwidth to 4.5 MHz for 500 uS (centered in the channel). At the station’s discretion, the length of the ATSC3 frame can be as short as 50 mS or as long as 5 Seconds with the typical said to be 250 mS.

    The photos so kindly moved to this site by Andy Brown show a typical off air spectrum of the two signals (ATSC3 is the lower photo). I can’t identify a dip in the spectrum at 250 kHz from the lower channel edge mentioned by Jr Tech so I can’t comment. The photos were taken after a bunch of antenna rotation to make the signals flat as possible but some residual bumps remain. Ideally both signals would be flat across the middle of the channel.

    If one is using a manually tuned receiver to measure the signals, I would expect an ATSC1 signal to have a CW signal at 309.44 above the channel edge that will make a nice coherent tone when the BFO is turned on. Everywhere else will be loud white noise.

    The ATSC3 signal, on the other hand will have a distinct buzzing sound when you are tuned within half a MHz or so of the upper or lower channel edges due to the signal suddenly narrowing to a 4.5 Mhz transmission bandwidth during the Bootstrap cycle leaving dead air where there was a data signal a moment before.

    I haven’t tried this, but the ATSC3 signal is also likely to have a number of semi-coherent “tweets” as you tune across it with a communications receiver in say a ~2.5 kHz bandwidth with the BFO on. The ATSC3 signal has a fairly large number of pilot signals that are, in theory, scrambled in phase. However, their sequence of phase shifts is slow enough that they stand out as being, larger than the adjacent data carriers and thus are “not noise like” on a spectrum analyzer. I was able to identity the transmission mode of the WatchTV ATSC3 transmitter when it was on by noting the number and frequency of the pilots.

    In addition, there are always pilots at the extreme upper and lower edges of the ATSC3 channel. ATSC3’s documentation indicates their phase is scrambled but those of WatchTV transmitter were CW. We will learn more when ATSC3 arrives in Portland.

    #41775

    jr_tech
    Participant

    “ We will learn more when ATSC3 arrives in Portland.”

    And hopefully, the more distant stations such as Seattle, Eugene will be detectable here, but perhaps as easily as the distant ATSC1 stations.

    #41781

    LinleyG
    Participant

    KKEI-CD RF36 Vir38 has returned to high power operation again yesterday. The other WatchTV stations on RF15, RF16 and RF35 in the Portland market remain silent.

    WatchTV’s applications for K28FP-D, Astoria; K14SC-D, Ashland; K25GA-D Redmond/Prineville; and K28GG-D, Medford to convert to ATSC3 were granted on Friday May 31.

    #41833

    LinleyG
    Participant

    Except for putting it on the record I would omit mentioning that after two days at full power KKEI again was back to low power when I checked on the evening of June 4. It has remained at low power the six days since then. It was my intent to reduce the number of postings by noting it had be low but had returned to full power when it came back. Good idea but a total of seven down days (so far) makes one wonder when it will return.

    #41892

    LinleyG
    Participant

    Today, June 22, is the day all phase 3 repack DTV stations are to be on their new frequencies. This morning KNMT Vir.24 has moved from RF45 to RF32 as expected. A rescan will be necessary if you are a KNMT fan.

    KATU Vir.2, RF43 was also expected to move from RF43 to RF24 today, but is still on RF43 this morning. KATU received a hurry-up STA yesterday to delay its move until phase 6. While phase 6’s completion date is October 18th KATU has been told to shut down its transmissions on RF43 by August 2nd.

    The station pleaded that while it had all the material on hand to install its new antenna, there were delays in obtaining the necessary permits to do the tower work. The STA documentation says that antenna work is scheduled to start on July 8th and is thought to require 60 days for completion. That doesn’t seem to jibe with the FCC’s orders to vacate RF43 so that is something to watch for.

    Sinclair Broadcasting filed for and got that STA in a day or two; Liberal amounts of “grease” must have been applied to get it that fast. Amazing.

    KKEI-CD remains at very, very low power.

    #41894

    Jeffrey Kopp
    Participant

    “We are tentatively aiming for a September 6th transition date.”

    http://www.katuengineering.com/hesk/knowledgebase.php?article=49

    In Milwaukie, I can get 2 on the living room TV with a Terk amplified antenna but not in my bedroom with plain rabbit ears.

    #41917

    LinleyG
    Participant

    This is the third night that KKEI (Vir38, RF36) has been back to full power again. It appears that it may stay awhile to it’s worth mentioning.

    #41951

    russell-curry
    Participant

    Does anyone know what’s going on with KWBY? When they first went off, I thought they might be about to implement their CP, but by now it’s obvious there must be something else going on.

    #41953

    semoochie
    Participant

    You could still be on the right track. These things take awhile.

    #41981

    chessyduck
    Participant

    While plowing through the FCC databases for FM and TV stations I noticed several Northwest stations retained artifically lower-than-expected ERPs. The common thread was that these stations had transmitter sites on BLM or National Forest lands. By any chance is the some RF exposure rule floating out there forcing lower power limits on the federally-leased transmitter sites? I guess bears and hikers do not want to be cooked while enjoying the outdoors….

    #41986

    LinleyG
    Participant

    Could you give the call letters of a few examples? Need data to prime the pump.

    #41991

    chessyduck
    Participant

    My bad…

    Below are some concrete examples. Using the FCC FM 50-50 contour protection page: http://www.fcc.gov/media/radio/fmpower

    * KVBL 103.1 Union, Oregon [C2] 950 watts 768 M HAAT (permitted would be 1.2 kw)

    * KJIV 96.5 Madras, Oregon [C2] 1 kw 671.4 M HAAT
    (permitted would be 1.7 kw)

    * KYSF 97.5 Bonanza, Oregon [C2] 550 watts 670 M HAAT
    (permitted would be 1.7 kw)

    * KHKF 92.9 Island City, Oregon [C2] 900 watts 772 M HAAT
    (permitted would be 1.2 kw)

    * KDOA 101.5 The Dalles, Oregon [C3] 175 watts 564 M HAAT
    (permitted would be 630 watts)

    These are all high-altitude locations. Now, maybe some of these are simply that the broadcasters don’t want to waste energy broadcasting to sagebrush…

    Also noted was a Central Oregonian article (12.17.2018 – Pamplin Media) featuring KJIV-Jive Radio’s Jeff Cotton noting “…The low-power station currently emits 1,000 watts, the maximum allowed by the federal land management on the butte” . ( The “butte” being Grizzly Mountain.

    So, is this a local BLM thing because of federal land mobile radio or a deeper RF-exposure concern?

    #41993

    chessyduck
    Participant

    Follow-up research shows each BLM-controlled mountaintop has its own Communications Site Management Plan built upon a standard template. The overall uses of the site (LMR-Broadcast-Govt) and the intra-site antenna placement drive the upper limit for any given emitter… If you want to a good example check out the Soda Mountain Site Comm Management Plan… for that peak down by Ashland, home to JPR and at least one Medford TV station (KOBI?)

    #41998

    Andy Brown
    Participant

    FYI, it’s getting more and more difficult (you may read that as “impossible”) to propose a) a new broadcast site on BLM land and b) adding new service at an existing site. It usually requires a ton of money for lawyers to grease the skids at the site in question and even then, it’s a long shot. I don’t know if commercial two way radio/microwave relay are fairing any better. State or Federal communications gear usually is all you see being added these days. The last one I did on BLM land up on Mt. Hood was for Metro East and never got built. I assigned it to Brightwood, the only possible COL within the 60 dBu contour and although they are not incorporated, they do have a school. Anyway, because the policy changed to basically a moratorium on new service, it never got built (they did kind of drag their feet because of access problems in the snow). It was for 91.1. As a result of that, XRAY was able to use that freq. on Rocky Butte to get the old Reed College property back on the air.

    Also, in general, not only the BLM can down-power the ERP of proposed service when the site is on their land, the FAA also does this. Back in 1989 when I applied to do 105.9 on Livingston Mt. in Clark County, the then C2 assignment in combo with the HAAT which I had to calculate by drawing radials on actual maps and plotting points and doing seven tons of calculations would have allowed about 7 kW. The FAA reviewed the proposal (since I was proposing a new stick) and knocked it down to about to around 3 kw claiming they didn’t want as much field intensity on the runways anywhere near their VOR frequency. They don’t even use that technology anymore, but the FAA can still be a pain in the butt. The consultant told me not to worry since back then if you got the CP, you could apply for the power increase to max facilities and that process didn’t require FAA notification since the upgrade application would indicate an existing tower. I’m not sure if they’ve closed that loophole.

    Lesson: do not propose a new tower anywhere if you can avoid it but if you must, make sure it is less than twenty feet higher than the ground or the top of the existing structure you are locating on. That way you can avoid even notifying the FAA (technically, you have to fill out an FCC test page which tells you whether you have to file the current FAA form for new tower proposals) but if you keep it under 20′ you’ll get an instant waiver and the FAA won’t hassle you unless you are on the edge of an airport runway (where most likely you could fail the FCC flight path test).

    The proliferation of rooftop LPFMs and translators only works because the ERP is so low. You couldn’t, for example, propose an ERP of 3 or more kW on a twenty foot stick on a building because the radiation danger zone would penetrate the upper floors of the building. With only LPFM power of 0.10 kw max the radiation danger zone (depending on what antenna you choose) is less than the 20′ you have to work with. You can make a 0.250 kW translator work by using antenna gain (implement a two bay antenna) so that the actual TPO and antenna input power is still fairly low, using the two bay to get the gain and 250 w ERP.

    #42088

    Jeffrey Kopp
    Participant

    KATU upgrade status: “7/18/2019 UPDATE: Both the transmitter and antenna crews have arrived and installation has begun. As with most large projects, there are some unique challenges which preclude setting a finishing date, but the work proceeds apace.”

    http://www.katuengineering.com/hesk/knowledgebase.php?article=49

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