Mohu Sky 60 on the easternmost apex of our roof
This is our new Mohu Sky 60 antenna, suitable for indoor or outdoor use. Its design is based on a mudflap antenna developed for covert military communications by Mohu’s parent company, GreenWave Scientific.
Mounting it in the attic is difficult in our house due to our vaulted ceilings. It’s hard to reach a good place in the attic to hang the antenna, then to get the cable down to the TV. You also lose some of the signal every wall it passes through.
I wanted the maximum signal strength, so an outside mount as high as I could get seemed best.
I didn’t feel that the risk/reward ratio favored my scaling the steep roof to install it, so I hired help. Even the installer had qualms about clambering up there.
The Sky 60 comes with a filtered amplifier (powered by either USB or wall wart), mounting bracket, a short mast, and a 30′ RG59 cable.
RG59 is the lighter, more flexible kind. RG6 is the thick, heavy-duty one that the cable company uses. The installer was very down on RG59, even wondering if it is still made. Yes, it is. And it does quite well for indoor use and short runs. But I agreed with him that RG6 was the best choice for an outdoor installation.
(Click to enlarge)
I was able to save him time, and therefore me money by reusing the existing cable to our den, which I had traced to the cable box a week before. (After I did that, I hooked up the Sky 60 outdoors and hung it on a couple of nails at my highest reach for a few days to try it out, with good results.)
Once he got the mast in place, I did a Will Rogers and hurled a coil of the RG59 cable up there like a lasso. To my utter astonishment, I scored a ringer on the first try.
He lightly attached the antenna to the mast, and I connected up the cable temporarily so I could go indoors and check signal strength on all the stations with various antenna orientations.
To finish up, he tightened down the screws on the antenna, attached RG6 cable, and used a tall ladder to fasten it down the side of the house. He then grounded the antenna properly.
Indoors, I had already connected the TiVo tuner to the existing cable wall outlet. The Sky 60’s USB power cord connects to one of the TiVo’s two USB ports. (I use the other one to power a little LED clock, needed to show us the time with the cable box gone.)
The Sky 60 seems well-suited for a rural setting, where there is a lot of distance (as many as 60 miles), and a clear path to a distant antenna farm.
However, its compact, ultra-wideband design makes it an excellent choice for suburban areas like ours (81st & Memorial).
I want my RSUTV!
A majority of Tulsa-area antennas are located in Coweta and Oneta, 12-15 miles east-southeast of us. That’s close, but our street slopes down and away from them. That’s why I wanted to go as high as I could get.
But there are also tall trees in our immediate neighborhood between us and those antennas.
As I learned previously (High winds can affect TV reception), the higher frequency stations are more often affected by trees and the movement caused by wind. Those shorter wavelengths are close enough to the size of tree trunks and branches that the signals are more easily blocked or diffracted.
Tulsa-area TV transmitter locations from our house. See http://transition.fcc.gov/mb/engineering/dtvmaps
The standard advice is to point your antenna right at the antenna farm and hope for the best. That was the advice of the installer as well. We tried it and it worked.
But I also wanted to pick up KRSU-35 (RSUTV) in Claremore, to our northeast. It wasn’t happening with that orientation.
So I had him fudge the direction to slightly north of east, toward a low-tree corridor through our neighborhood. I still got high signal strength from almost all the other stations, but also a consistent signal and picture from Claremore.
The Sky 60 is billed as multidirectional, and it is, but its orientation made a critical difference in receiving the Claremore station, which is almost 30 miles from us.
We have been very satisfied with our reception of all the area stations, but one…
The Riddle of COZI
KWHB-47/COZI-47.2 (Independent, real channel 47), one of the higher frequency channels, occasionally freezes and not infrequently suffers brief, blocky blotches of pixelation on the screen. But KOTV-6 (CBS, real channel 45), close to COZI’s frequency, is rarely affected. Both of their antennas are in Oneta.
The signal strength we get for COZI is about what we now get from RSUTV, both on the low side of the acceptable range. KOTV and all the other channels in the Tulsa area (excluding KDOR, way up north in Bartlesville) show high signal strength as measured on the TiVo’s tuner.
(Click to enlarge)
The chart at right is custom for our street address and free from TV Fool.
It shows that KOTV’s “Noise Margin” (a rough estimate of signal strength, based on the topography of the area) is 65.3 dB, whereas COZI’s is 51.9. It’s lower, but not that much lower (KRSU is 26.4).
It also shows that the COZI and KOTV antennas must be either side by side or on the same mast!
The full wavelengths of the KOTV and COZI signals are between 17.5″-18″ so they would seem to be equally vulnerable to tree interference, and should behave very similarly.
By contrast, I have a flat amplified antenna taped to an east-facing inside wall in the theater room. I found one and only one spot on the wall where it works. (I could find no spot near the den TV where a flat antenna worked acceptably. That’s why the Sky 60.)
The flat antenna in the theater room does a better job with COZI than the outdoor antenna in the den, but worse with RSUTV to the northeast. That makes some sense, because the flat is aimed straight east, slightly more toward COZI and slightly away from RSUTV compared with the Sky 60.
But COZI’s signal strength on the theater room set, like KOTV’s, measures near the maximum, and pixelation occurs far less frequently, though high winds can still affect COZI’s picture in there.
Why does that antenna/TV tuner show maximums for both KOTV and COZI, but the Sky 60/TiVo combo reads a maximum for KOTV, yet much lower for COZI?
It’s a bit of a puzzle:
- Are we getting a freak “bank shot” of COZI’s signal in the theater room, or finding a gap in the tree cover?
- Is the compromise angle of the Sky 60 critical for COZI, but not for any of the other stations at precisely the same location?
- Is even minimal tree movement periodically pushing COZI over the “digital cliff” despite my seeing steady signal readings?
- Maybe the KOTV antenna is higher on the mast as well as having more power?
Since a small shift of the Sky 60’s angle was decisive in getting a consistent picture from RSUTV, might that same shift might have been decisive in losing a consistent lock on the lowest-powered
(though not by much) signal at nearby Oneta?
Maybe not; new info: I did some digging at FCCinfo.com for KWHB (COZI) and KOTV data.
Key facts: both stations are indeed on the same tower and KOTV is 113 meters higher than KWHB. That’s 124 yards, more than a football field.
But here’s the eye-popper: KOTV broadcasts at 840.1 kW ERP (effective radiated power). KWHB at 50 kW ERP. Huge difference! No wonder KWHB has a harder time blasting through the tree clutter.
Re the misleading (at least to me) “Noise Margin” figures quoted above, TV Fool’s TV Signal Analysis FAQ states: “Please understand that this is a simulation and can only be treated as a rough approximation. Reception at your location is affected by many factors such as multipath, antenna gain, receiver sensitivity, buildings, and trees – which are not taken into account. Your mileage may vary.” Did it ever!
The mystery now is how I am getting a strong signal in the theater room, but only when the antenna is at a particular spot at the center and top of the wall.
It appears to me that the offset position of the theater room vis-à-vis the den gives it barely enough clearance from the trees to avoid impairment of COZI’s signal, at least at that one little spot. I wish I had “radiovision” so I could see the radio shadows and reflections in there.
We haven’t yet experienced the blooming of trees in the spring with the Sky 60 on the roof, so we’ll soon see how or if that affects our reception.
Luckily, COZI is more my channel than Gaye’s (it has “Run For Your Life“, which I record with my WMC/Pi setup in the theater room), so this isn’t a big crisis. And it is watchable a lot of the time.
As I had previously found (Placing an indoor TV antenna), you need to experiment with inside antennas for best performance. The same is true for outdoor or roof mounts. It’s difficult to predict where the best spot is going to be, and it is often surprising.
Experiment at leisure with different antenna orientations and positions on an inside or outside wall, or in the attic, and find out what works best at your house. Then you’ll be better prepared if you choose to do an outside mount.
When the stations you want are not all clumped together, tweaks and trade-offs may be necessary.
I had hoped that maximum antenna height would completely eliminate reception problems.
It almost did, but I had to tweak the direction to pick up a distant desired station (RSUTV) while keeping the others.
Sometimes-impaired reception of COZI may be the trade-off, but given its low power and our tree-laden, partially-obscured location relative to its antenna, COZI would likely be problematic for any antenna in the location I selected, regardless of its orientation. (I seem to have barely caught a gap in the trees with the theater room antenna’s precise positioning.)
I learned that two stations (RSUTV and COZI) received at roughly the same signal strength, albeit on the lower side of the acceptable range, can differ greatly in quality. One can come in consistently, and the other can be subject to frequent interference if it is on a high frequency and nearby trees are in the path.
Signal strength as measured on your TV doesn’t always tell the whole reception story.
(This guy had better luck placing his Mohu antennas in and near the basement window to pick up reflected signals! He also found a way to combine two antennas.)
The Mohu Sky 60 is doing a bang-up job for us. It’s solidly constructed and was light and easy to move around in the experimentation phase. I like the unique appearance of the antenna up there; Gaye thought it looked like an alien artifact (which is to say she likes it a lot).
With the TiVo Roamio OTA DVR/tuner and the Mohu Sky 60, plus Netflix and Amazon Prime, our TV cable cord is well cut.
According to my calculations, we will save about $1750/year! And we didn’t even have any premium channels like HBO, etc.
(Full disclosure: Mohu sent me the antenna for free to review.)