I have a DirecTV Commercial Public Viewing system that is getting blasted by some kind of microwave interference. It is in a ten story Washington, DC hotel, about a mile to the north/north-northeast of National Airport and ten blocks west of the White House. I installed a SWM-5 dish there and connected two H-25s to it about two months ago.
They have reported intermittently having the signals degraded to unwatchable on ESPN and ESPN2. Lodgenet provides the free to guest channels there from 1.2 meter, Alaska/Hawaii dishes using Pro:Idiom QAM, and they are experiencing the same HD reception symptoms on their ESPN, ESPN2 and HBO-E channels in the guestrooms. Those are the only DirecTV based HD channels in their system. We, of course, cannot access HBO in the lounge.
I moved the dish 30 feet but am experiencing the same problem there. It is intermittent, but chronic when occurring.
For testing, purposes, I swap the SWM-5 LNB for a SLM-5, which lets me see nearly one fourth of the transponders at one time on my Blonder Tongue, BTSA-5 spectrum analyzer. Over a testing interval of about five to ten minutes, I occasionally saw what looked like a powerful radar sweep when the spec analyzer is calling for 22 KHz, 13 volts, which should include Ku 110 (Sat C) and 119 (Sat odds and, if my memory of this system serves me correctly, the 103 slot odds. Would someone confirm for me the Ka satellite and polarity that is selected by 22KHz/13 volts?
Each time I saw the severe radar sweep going through the 22KHz/13 volt spectrum, I would toggle the voltage and tone selectors but did not see that interference on any of the other three sets of waveform displays. My spec analyzer was set to show 950-2,200 MHz on the screen and I didn't bother to drop the frequency range to try to see the Ka low (250-750 MHz).
I saw this exact same symptom over a decade ago on a DirecTV Ku dish about three blocks away on another ten story hotel owned by the same hotelier. It was first reported to me in late July or early August of 2001, and continued to about late 2001 or early 2002. Back then, it appeared on the 101 (Sat A) degree evens, and it wiped out the HBO standard definition programming, which was on either transponder 30 or 32 at the time. Visually, it was obliterating the whole 950-1,450 MHz Ku spectrum then, too, but as I recall, all the other important programming was being carried on odd numbered transponders and they were not affected, and disruptions of other even transponder programming were not reported to me, even though they were surely occurring.
Unfortunately, it was not possible for me to simultaneously view the channels on a TV screen and view my spectrum analyzer to observe the disruption, and it isn't even possible for me to definitively say that none of the other three combined bands were similarly disrupted because I just can't make the instant comparisons that I'd like to. The interference subsided and when it didn't return during about the next five minutes, I discontinued this testing.
Can anyone tell me the polarities of the transponders carrying those three channels? I got this transponder information from forum member gtc's "Transponder Maps:..." sticky thread in the DirecTV Tips and Resources sub-forum ( TPN_MAP_Domestic_13921_121121.xlsx ), but I can't determine the Ka band transponder polarities from it:
ESPN 99C TID 136 VPID 1010 ESPN2 99C TID 136 VPID 1050 HBO 99C TID 130 VPID 1020
According to Lyngsat, ESPN2HD is on 103C, whereas the Transponder Maps ESPN2 table entry says it is on 99C. The Transponder Maps thread incorporates the term "New Data 11/21/2012 " in its title, whereas the ESPN2 entry in the Lyngsat table was updated by c hoffman on 120119, which I think means 01/19/12 to us American civilians.
For what it is worth, the last time I visually checked Lodgenet's three channels in a guest room, their ESPN and HBO were horrendous but their ESPN2 was perfect, which is more consistent with ESPN2 being on a different satellite. Does the H25 menu enable me to select a single transponder test of the channel that the receiver was tuned to before entering signal test? I remember some earlier receivers that sometimes included that test feature, but I also remember that during their lifetime, DirecTV had "updated" receiver software and taken that feature out.
I had tried to mitigate the problem back in 2001 first by moving the dish, which was on a non-pen mount, around the rooftop mechanical room, using it as a shield, but it made no difference, leading me to conclude that this interference was coming from aerial-based or look-down radar. Then, in desperation, I set up a dish in the parking lot and dropped a 150 foot coax down to it. Down there, the intensity of the interference was less severe, but still created unacceptable degradation.
I made a couple of informal requests for assistance to the FCC but they never replied, and then, nearly six months later, the problem went away on its own.
And for those who have not yet considered this, it began a month or so before the 9-11 attacks, leading me to suspect that it may have been part of an intensified effort to detect an airborne threat.
Anyway, last night, I lagged a j-tube mast to the inner wall of the cinder block structure surrounding the rooftop cooling tower, so I will try using a dish there that is physically shielded by cinder block from all sides and wait and see what is subsequently reported to me. The interference had subsided by the time I got that mast installed, so I wouldn't have been able to definitively pronounce on the efficacy of that shielding even if I had connected it to their satellite SWM downlead.
I haven't spent much time studying the operation of the H25, but I see that the HD channels are accessed using the same channel numbers that are used for those same channels in standard definition systems, meaning that ESPNHD, for example, is on 206, as is ESPNSD in standard definition receiver channel tables. That differs from how the channels were numbered back when I was installing H10s and H20s, when the HD versions of channels were numbered in the 70s and 80s and the STD versions were simultaneously accessible. Since it is possible that the standard definition Ku transponders are not being disrupted by this interference, it there any way for the users of this system to still access them? For now, it would be preferential for this customer to "downres" his viewing to standard resolution if the problem recurs during an important sporting event.
If I am not able to remedy this problem, I will have to consider switching this customer to DISH Network if I can establish that DISH Network HDTV signals are reliable there.
Here's an interesting thought. Since I only observed interference when I has selected 22 KHz but this customer is not using the 110 and 119 degree signals, I could cover over the 110 and 119 degree waveguide openings with tin foil and maybe that will help, and if it does, then I would replace the SWM-5 LNB with a SWM-3.
Edited by AntAltMike, 19 March 2014 - 11:34 AM.