I am amazed at the time and energy that the members of this blog have spent on such a trivial matter! Hey, with the government discount of $40, this a/d converter box only costs $20 plus tax - it's not like you were spending thousands of dollars on a new car that you were planning to drive for five years. Get a life! There are so many factors in signal strength that it's not worth quibbling about - the converter box, the antenna, the position/height of the antenna. the distance to the transmitter, the terrain (ghosts, etc.), ad infinitum.
I purchased a DTX9950 (at Radio Shack) and using common sense, attached it to my TV, replacing the use of the Cox Cable with OTA via the DTX9950. I used a Phillips MANT410 amplified indoor rabbit ears/UHF loop set-top antenna. I have a line of sight access to Mt. Wilson on which are located 90+ per cent of the Los Angeles/Orange County TV station transmitters, approximately 40+ miles away. The antenna was sitting a TV set height above ground.
I made all the connections necessary, turned the converter on, and went thru the scanning process, where it picked up every digital signal channel/sub-channel among the LA/Orange County stations (total approx 40), missing those stations located in neighboring San Bernandino and Ventura Counties. I feel positive that if I had a roof-top rotatable antenna, I would have gotten more, perhaps even as far away as San Diego.
I then ripped thru all of channels/sub-channels - no video or audio problems were encountered. I then pushed the A/D button, and punched in the actual VHF/UHF broadcast stations in order to observe the analog signal reception. Due to the limitations of the VHF portion of the indoor antenna, the analog signals from the lower freqs were not good, however the UHF stations came in fine. That was my experience with the pass-thru - I have no complaints.
For $20, this unit is a real bargain. It does its job well.
Now for those of you who are knowledge-challenged about digital TV, let me throw in a few facts:
(1) In some cities, TV stations that are currently broadcasting their analog signals on UHF channels have in many cases been assigned VHF frequencies to use for their simulcasted digital signals. (Fresno, CA for example - all analog stations there are UHF, so for those who are contributing their experience to this blog, please identify your geography.) Receiving digital signals at lower VHF signals involves other factors than UHF signals. So, my experiences with an indoor antenna receiving UHF signals would not be relevant for a Fresno resident - they're trying to capture VHF signals!
(2) Come Feb 2009, MOST US TV stations will abandon their temporarily assigned alternate frequencies and start broadcasting a digital signal on their currently assigned analog frequency. However, those stations currently assigned to channels 52-69, will be assigned new transmission frequencies as this portion of the broadcast spectrum will be abandoned by the FCC to other than TV usage. Any station currently using these frequencies for TV will move, whether they are broadcasting a digital or analog signal on that freq. They may or may publish their move, since with the NTSC tuners, the viewer really isn't aware that their TV is tuned to channel 31 when the screen says 5, for example. The point is, just because my DTX9950 works today very well with a small indoor UHF loop doesn't mean anything regarding this configuration after Feb 2009. Here in the LA area, the "big"/network stations are all VHF, and use 2,4,5,7,9,11,13, all of which are not received well with my "rabbit ears" - I will have go shift to a better VHF antenna, probably an attic-mount or roof-top.
(3) Low-power stations (there are 3 in LA) are NOT required to cease their analog broadcast in Feb 2009, so the analog-pass-thru feature is valuable here for those who desire to watch them.
(4) The analog-pass-thru feature will also be VERY important for the millions of US TV viewers who live in San Diego, Detroit, Buffalo, El Paso, and other US cities located along borders with Mexico and Canada. Those two countries have completely different plans regarding the shift to digital TV signals. Canada has a date, I believe two years after the US, and in Mexico, the shift to digital is on a station-by-station basis. Some stations, for example, in Tijuana (just across from San Diego) already are simulcasting and will follow their US counterparts. Actually at least one of the "network" channels serving San Diego is physically located south of the border ( a Mexican licensee) and will definitely be shifting in Feb 2009.
Bottom line, for the price of 4 super lattees at your local Starbucks, this box does the job very well. And your experience with it today may change dramatically come Feb 2009, so be prepared.