|Originally posted by Ursa
BobChase - any chance of your posting a synopsis of your testing with various consumer models? If you want to hook up some gear to an attic mount, I'll offer up my installation.
I have some VERY preliminary data. What I have been struggling with is putting words around the pictures. If you will excuse the expression - "dumbing down the engineering". I have also been in discussions with some of by peers around the country talking about measuring multipath. Signal strength is only half of the equation. (Maybe only a third.)
No big surprises in the winners so far. The 4221 and the 4228, both inside and outside.
Big surprise in the looser category is the 4248. I don't know how many times I have recommended that antenna. Plus I have owned it twice (at two different homes).
The only all-band antenna I have tested so far is the HD7210P. It's middle of the road for UHF signal strength, better than the Square-Shooter, not as good as a 4221. And, of course, it gets both ch-9 & ch-5 quite well.
Here is the data. Zero dB is 1, - 10 dB is 1/10 , -15 dB is 3/100, -20 dB is 1/100, -25 dB is 3/1000. A dB is a logarithm referenced to some value (power, voltage, or in this case, a reference antenna). So the chart is antenna gain referenced to a Scala 1469B log-periodic antenna's gain. The Scala is a $600 "broadcast quality" low-power transmit antenna. It has a gain of 8 dB over a dipole (+8dBd), which is x6.3 gain. It's gain is also dead flat from ch14 to ch 69 so there is noe of that "averaged gain" small print to worry about.
I really didn't believe the data at first, so I did some checking around. Some 60's data on inside UHF reception at 3500 sites said that this data is right in the ballpark. Which is scary because you are loosing from 99% to 99.9% of the signal with an attic antenna.
But is also explains why the CM7777 works so well! I couldn't figure out how an overloaded amplifier could ever work for DTV. It turns out that there is a 20 to 25 dB attenuator in front of the antenna that keeps the 24 dB gain amplifier from overloading!
Call me at the station and lets take a peak in your attic. I'll bring my antennas and we will play mix & match.
2004-12-11 testing attic antenna performance v03.pdf 129.5986328125k . file