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I bought two antennas for over-the-air TV reception. They are the "Mohu Sky 60" and the "Channelmaster CM2020." I was wondering which is likely to get the strongest signal before amplification when the transmitters are about 35 miles away. I have the Mohu mounted at the peak of my roof, but some channels are still dropping out or pixelating severely - even with amplification. I have excellent signal strength but very poor signal quality. I'm wondering whether I will get a better signal if I mount the ChannelMaster in its place. ChannelMaster CM2020 antenna Mohu Sky 60 I searched StackExchange sites and it looks like this is the most appropriate community where I could ask this question.

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  • \$\begingroup\$ which one is which? \$\endgroup\$ – The Photon May 12 '20 at 20:04
  • \$\begingroup\$ The ChannelMaster is the long one. The Mohu is the "X"-shaped one. \$\endgroup\$ – Stephen Daddona May 12 '20 at 20:06
  • \$\begingroup\$ How do you know you have excellent signal strength? \$\endgroup\$ – SteveSh May 12 '20 at 22:30
  • \$\begingroup\$ @SteveSh I have a ChannelMaster DTV tuner tells me the signal strength and quality, among other things. \$\endgroup\$ – Stephen Daddona May 13 '20 at 1:52
  • \$\begingroup\$ You folks gave me some really great answers! I wanted to "accept" both Dave Tweed's and Aaron's answers but it would only let me choose one answer to accept. Thank you so much! \$\endgroup\$ – Stephen Daddona May 13 '20 at 1:57
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If you have good signal strength, but poor signal quality, that means you're getting a lot of interference. In that case, the Channel Master, with its greater directivity, will help attenuate any off-axis interferers.

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It depends on where the stations are located. The Channel Master has a lot more gain, and so will be much more directional. ie. You will have to point the antenna more directly at the station.

Examine these two gain patterns plotted on the same graph. The dipole in green has more gain than the Isotropic antenna in blue. But at 90°, the Isotropic would be the better choice.
enter image description here

The same applies to the two antennas you have shown.

Update To address the comments:

An isotropic antenna is a theoretical antenna that radiates equally in all directions. ie. sphere.

A dipole is just two wires, one driven and one ground. Like this image from ARRL. And for reference back to the plot, the wires would be along the Y or vertical axis (from the markings -90 to 90).

enter image description here

Update 2 From Channelmaster, here is the pattern for the CM2020 enter image description here

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  • \$\begingroup\$ All the stations I care about are between 201 degrees and 203 degrees from my location. The Mohu is currently pointed in that direction, but is omnidirectional anyway, to my best understanding. I'll switch it out with the Channel Master, per @Dave Tweed's recommendation. \$\endgroup\$ – Stephen Daddona May 12 '20 at 22:54
  • \$\begingroup\$ I will have to look up Isotropic and Dipole. These terms are over my head. :) Thank you so much for the great answer. Engineers are way smarter than I am. \$\endgroup\$ – Stephen Daddona May 12 '20 at 22:57
  • \$\begingroup\$ @StephenDaddona, unless the Mohu is a vertically-mounted dipole and that plastic cover is just for show, it's directional. It's just nowhere near as directional as the ChannelMaster. \$\endgroup\$ – Mark May 13 '20 at 22:45
  • \$\begingroup\$ Based on its shape, I'd say the Mohu is a variation of the DIY type: youtube.com/watch?v=TRKRRJuoFNQ \$\endgroup\$ – Aaron May 14 '20 at 0:12
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Does the moHu have a built in amplifier? If so, that would skew the results.

If not, you would be better with the Channelmaster CM2020. Mount it outside, on a short mast. That should be sufficient for a 35 mile range to the transmitters.

I have something similar, only I need a pre-amp as I am close to 60 miles away from the stations. Here's a picture:

enter image description here

EDIT 1

If you go to https://www.fcc.gov/media/engineering/dtvmaps and put in your address, it will tell what directions your stations are located relative to your house. If you click on the individual stations, it will give you an estimate of the signal strength. Note that the signal strength is in dBm, and is negative. That means a lower number (less negative) means a higher strength. This site will also give you a rough idea of the kind of antenna you need. If you're only 35 miles from the stations, the CM2020 seems to be overkill to me.

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  • \$\begingroup\$ I don't think the Mohu has a built-in amplifier, but I have an amplifier on the coax cable behind the TV. I think the amplifier should have been placed at the antenna end of the cable, though. I think I will hook up the Channel Master. \$\endgroup\$ – Stephen Daddona May 13 '20 at 2:12
  • \$\begingroup\$ @StephenDaddona I'm afraid that the amplifier placed like that is useless at best, possibly actively harmful. In addition to the useful signal from the antenna, it also amplifies all the noise that gets into the cable on the way down (and if that noise is strong or the amplifier isn't very good, it can saturate the amplifier and drown out the signal even more). Your TV has a variable gain amplifier on its input anyway. How does your reception change if you remove the amplifier or move it closer to the antenna? \$\endgroup\$ – TooTea May 13 '20 at 8:44
  • \$\begingroup\$ You shouldn't need an amplifier at all with the CM2020. But if you need one, it needs to go as close to the antenna as possible, as TooTea said. There are some discussion on this in the Home Improvement forum. There is an outside chance you "poor reception" is because you're overloading the front end of your TV sets. \$\endgroup\$ – SteveSh May 13 '20 at 10:40
  • \$\begingroup\$ Figures I had it backwards. :) Back when I first installed the entertainment system, I think the amplifiers helped a little. When I put the Channel Master antenna up, I will pull the amplifiers out of the system. \$\endgroup\$ – Stephen Daddona May 13 '20 at 22:15
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Excellent Signal Strength but poor signal quality

Sounds unlikely that this can be remedied with a better antenna. "High power but low quality" means that a signal that isn't your TV signal interferes and contributes power.

Unless, and that's the most likely explanation here, this quality/power measurement comes from consumer electronics device and doesn't actually mean much.

But let's assume these measurements are accurate and meaningful:

The TV bands belong to the TV stations, only. So:

  1. Any interferer that you can observe with your TV receiver is unlawful. Since fines are quite heavy, unlikely someone has a strong transmitter "for fun".
  2. Since your antenna currently is probably not pointed at anything but the direction of the TV transmitter, it is likely that the interference doesn't actually happen on any straight line from your antenna to the TV transmitter – there's typically mostly air and a few birds there, and neither is likely to be a strong emitter of electromagnetic waves in TV spectrum!

So, the most likely explanation (again, assuming that not just the power report of your TV is being bogus) is that there's some source of noise / interference in your installation. Make sure all your TV cabling has good connectors, is properly connected, not corroded. Make sure the power report goes to zero when you unplug your antenna cable.

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  • \$\begingroup\$ Probably my cables. There are tons of them in my attic and probably cheap connectors. Eight of them are for closed-circuit TV to cameras all around the house and they have power cords running along with the coaxial cables. Not powered now, though, because the cameras all died. \$\endgroup\$ – Stephen Daddona May 12 '20 at 23:00

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