Zenith DTT900 vs. Zenith DTT901

The Zenith DTT901 has the added feature of analog passthru, so naturally it should be a little less sensitive than a Zenith DTT900 because an electronic switch will introduce maybe a dB of loss.  I traded my hostage for a May build Zenith DTT901.  I decided to test it against my March build LG tuner Zenith DTT900.  The Rabbit Ears feed a balun, and coax connects it to a two way splitter. One output of the splitter goes to the 900, the other output to the 901.  Each Zenith fed its TV through coax.  I powered up, selected a weak channel, and compared the two horizontal signal bars.  I was amazed at how they seemed syncronized, as if both TV’s were being fed the same source.  The Signal Strength beep rate for the 901 is slower than the 900.  What counted is which produced pixel pus first as the signal got weaker.  The difference was slight, but definitely the 901 was better. 

 This caused me to realize that there are two problems to consider:  The ability to pick up a weak signal, and the ability to exorcise multipath hauntings.  The 901’s could have a better tuner, or it could be a better demodulator.  I tried a more directional antenna in hopes of eliminating the chance of haunting, but that antenna didn’t have a sharp enough pattern to draw a valid conclusion.  It could also be just the individual variation and luck that in the particular units used, the 901 was better.  Different channels produced the same result. 

 Experiments not only lampoon theory with facts, they reveal the unexpected.  In this case, it was the sound.  I would adjust the Rabbitt Ears for a weaker signal, and then readjust for best signal.  Both Zeniths would lose lock or picture when the signal went weak.  When the signal returned, the picture returned and everything was normal, almost.  Sometimes, the sound changed.  A definite delay was introduced in the sound from the 901 compared to the 900.  It was longer than reverb, and sounded like the 901 was echoing the 900.  If I changed channels and then changed back, the sounds from the TV’s were once again synchronized.  I tried this on different channels, and got the same result.  The delay is way too small to lipsync the picture with the original sound or the echo as correct, so I don’t know which Zenith was doing the timeshift. 

Operationally, this quirk is meaningless, and without this test, there’s no way to know the timeshift happened.  My conclusion is that if better reception is needed, I should upgrade from the Rabbitt Ears.  The difference in sensitivity between the Zeniths is too small to worry about.