Four ATSC receiving devices compared

[Robert Grant]

Here is a comparison of four digital TV (ATSC) receiving devices.
The RCA DTC100 is a receiver for analog TV as well as digital (it was also a satellite receiver for DirecTV service, but is no longer used for that purpose). This big heavy unit features two antenna inputs (either of which work for analog or digital), a built-in RF modulator, two sets of composite video/audio L/audio R outputs, and a VGA output for HD video. The DTC100 also allows you to "turn off" virtual channel recognition, allowing tuning by actual channel only.
The sleeker RCA ATSC-11 is better known to DXers. It has composite, S-video and component video outputs, as well as DVI output (an adapter can be used for VGA monitors), but lacks an RF modulator.
The Sylvania 6427GFF is a whole TV set with a flat-face 27" CRT. It lacks any video output, but has a coaxial digital audio output (which I've never tried). The 6427GFF needs a remote to switch between analog and digital modes. Even though the HDTV video is converted to 480i (the only format the deflection circuitry can support), picture quality is superb provided one is not too close to the CRT. The difference in horizontal sharpness between HD programs and SD programs is obvious (which is surprising, considering the CRT's aperture grille only has about 450 phosphor triplets).
The Philco TB100HH9 is a new coupon-eligible converter box (CECB), and, like all CECBs, outputs only in 480i. It is far smaller than the other three. Believed to be similar to the Magnavox CECB, there are differences. The Philco lacks the mechanical on/off switch found on the Magnavox (it is totally dependant on the remote, having no switches nor knobs at all!) and offers an RF pass-through mode. The built-in RF modulator is a not very good (audio buzz is a problem when white appears in the video), but sound and picture are fine with the composite/audio L/audio R outputs.

Sensitivity comparisons were made with a Channel Master CM3020 all-channel antenna with about 60' of RG-6 feeding a variable attenuator, which fed a splitter, feeding two hopefully identical 6' cables (same brand, next to each other on the rack at the store when purchased) to both receivers.
Lowband sensitivity was on the only local lowband DTV station - WLMB 5 (40) at 24 miles. Even with the attenuator, the antenna had to be aimed off-mark to make their signal weak enough for the test. The UHF stations were WKBD (50) on 14, WDIV (4) on 45, and WJBK (2) on 58. All are licensed to Detroit and transmit from Southfield at 50-52 miles distant. The area I am in does not have any VHF-high DTV stations at present.
This test was not perfect- there may have been cases where the tuners interacted with each other through the splitter, or where one tuner may have had a better impedance match than the other. At channel 58, the ATSC-11 seemed slightly more sensitive than the DTC100, and the Sylvania slightly more sensitive than the ATSC-11, but somehow the Sylvania comes out as only being about equal to the DTC100.
The multipath test used the same setup, but without the attenuator. The Detroit stations were not strong enough for the multipath test (they can only be seen with the antenna aimed at them - multipath-free signals are the result). Much closer Toledo stations at 9-14 miles distant were used. WTVG-DT 19 (13), the closest, actually has the most multipath problems (perhaps because it is the furthest West, and the buildings of downtown Toledo reflect them more efficiently). Reception was observed with side-by-side receivers as the antenna was rotated in all directions. Where "dropouts" were observed, the antenna was slowly turned through that angle, so a fair comparison could be made among receivers with different "response times".
The sensitivity tests show that none of the receivers differ greatly, with the exception that the RCA DTC100 is less sensitive on lowband VHF channel 5. The RCA ATSC-11 may actually be the best for weak-signal tropo, as it has a lower "squelch threshhold" than the others (i.e., it will gladly display pixellated gibberish from a too-weak signal) and is good at quickly producing a PSIP display.
What really stands out is the performance of the Philco STB in multipath conditions. The tests merely proved what was obvious just minutes after I unpacked it. You almost can't make it fail with multipath! It works indoors in "wrong-side" rooms and in the basement where all the others are useless. One could expect the same from the Magnavox STBs from Wal-Mart and rumour has it that the Insignia and Zenith boxes are even better. Just when I though that only the coupon-eligible boxes would have this performance advantage, I had a chance to observe a newer ILO integrated tuner set, and it was getting good reception in the "wrong-side" room of a brick building as well. This is good for DXing, but is a HUGE difference for regular viewers, and is cause for optimism for the future of TV without wires.


EQUAL= (self-explanatory), 1= very slight advantage, 5= overwhelming ("night-and-day") advantage.

RCA DTC100 vs. RCA ATSC-11
SENSITIVITY MULTIPATH
5 ATSC-11 2 17 ATSC-11 1
14 ATSC-11 2 19 ATSC-11 2
45 ATSC-11 1 29 ATSC-11 1
58 ATSC-11 1 49 EQUAL

RCA DTC100 vs. SYLVANIA 6427GFF
SENSITIVITY MULTIPATH
5 SYLVANIA 4 17 EQUAL
14 SYLVANIA 2 19 SYLVANIA 2
45 SYLVANIA 1 29 SYLVANIA 1
58 EQUAL 49 EQUAL

RCA DTC100 vs. PHILCO TB100HH9
SENSITIVITY MULTIPATH
5 PHILCO 4 17 PHILCO 5
14 PHILCO 1 19 PHILCO 5
45 PHILCO 2 29 PHILCO 4
58 PHILCO 2 49 PHILCO 4

RCA ATSC-11 vs. SYLVANIA 6247GFF
SENSITIVITY MULTIPATH
5 SYLVANIA 2 17 ATSC-11 2
14 ATSC-11 1 19 ATSC-11 1
45 SYLVANIA 2 29 EQUAL
58 SYLVANIA 1 49 ATSC-11 1

RCA ATSC-11 vs. PHILCO TB100HH9
SENSITIVITY MULTIPATH
5 PHILCO 4 17 PHILCO 5
14 PHILCO 2 19 PHILCO 5
45 PHILCO 2 29 PHILCO 4
58 PHILCO 2 49 PHILCO 3

SYLVANIA 6427GFF vs. PHILCO TB100HH9
SENSITIVITY MULTIPATH
5 PHILCO 1 17 PHILCO 5
14 PHILCO 2 19 PHILCO 5
45 PHILCO 1 29 PHILCO 5
58 PHILCO 3 49 PHILCO 3

[robandjeanne]

Hi and thanks for posting your test. I'm not sure I digested all the information. I guess you had a step attenuator and checked the sensitivity as well as the threshold on the various receiver pairs? I also gather that numbers from 1 to 5 refer to the quality advantage of one vrs the other (not to y specific attenuator setting)? I'm not sure if the threshold or multipath capability that you mentioned is apparent from the numbers?

I just purchased two Insignia NS-DXA1 units from Best Buy and they seem very good. However, the Philco TB100HH9 and yet to be introduced Echostar TR-40 have a big advantage in that they can feed the antenna through to the set. This is described in the coupon program as passing through an analog signal to the TV set. I gather this must be similar to the way a VCR passes the antenna through (with very little insertion loss) when not on. So complicated setups where you may want to feed the signal through would require the Philco or Echostar (actually I don't think this pass through will be nearly as valuable after the switch to digital next February, but it still seems like a nice feature).

From your test it looks like the Philco did very well in multipath and sensitivity. Do any of the big local stores sell the Philco?

Thanks,

Rob

[Robert Grant]

The "left column" of each comparison addresses the sensitivity, the RF channel of the test station is followed by the brand (if other than RCA) or model (if RCA) of the DTV receiver which appeared to have an advantage over the other, followed by a number which hopes to give an idea of just how much more sensitive the named product was over it's competitor (named at the top of the paragraph), examples: "PHILCO 1" means that on this particular channel, was only trivially more sensitive than the other receiver, "SYLVANIA 4" indicates the Sylvania IDTV is significantly more sensitive to the other receiver.

The "right column" of each comparison addresses the ability of the receiver to properly receive a signal that is affected by multipath (e.g., reflections of "ghosts"), the RF channel of the test station is followed by the brand (if other than RCA) or model (if RCA) of the DTV receiver which appeared to have an advantage over the other, followed by a number which hopes to give an idea of just how much more resistant to loss of reception due to multipath the named product was over it's competitor (named at the top of the paragraph), examples: "ATSC11 1" means that on this particular channel, the RCA ATSC11 HD receiver was only trivially less liable to lose reception due to multipath than the other receiver, "PHILCO 5" indicates the Philco STB is overwhelmingly more able to receive a signal affected by multipath on this particular station than the other receiver. (In the case of the Philco, it usually took the kind of severe multipath that would case an analog signal to be incapable of being horizontally synched to case reception failure, a fine null zone only a few degrees wide, as I have said before, a quantum leap).

My attenuator does not have gradations, and, the other sources of signal strength differences that may have occurred (different RF input impedances, tuner interaction) make such precision moot in this case.


Rob

[Robert Grant]

Oh, I forgot.

The first impression I'm getting is that the Philco is going to independent and regional chain stores, and not to "big box" retailers like WMT, CC and BB.
In Southeast MI, ABC Warehouse (regional electronics/appliances chain) and Meijer (regional chain of hypermarkets, not unlike WMT supercenters) are carrying the Philco (and only the Philco).
I strongly suspect you'll get the same performance from the Magnavox product sold at WMT.

Rob

[Robert Grant]

Another two comparisons to make, since I acquired the Zenith DTT900 recently.

Zenith DTT900 vs. Sylvania 6427GFF

Sensitivity Multipath
5 SEE BELOW 17 Zenith 5
14 Zenith 2 19 Zenith 5
45 Zenith 2 29 Zenith 5
58 Zenith 2 49 Zenith 3

Zenith DTT900 vs. Philco TB100HH9

Sensitivity Multipath
5 SEE BELOW 17 Equal *
14 Zenith 1 19 Philco 1
45 Philco 1 29 Equal *
58 Equal 49 Equal

(*) In the cases of 17 (WTOL-DT) and 29 (WGTE-DT),
turning the antenna failed to cause any loss of signal in any
direction on either STB (!)

One STRANGE observation - where as the Zenith was much more sensitive on channel 5 that the Sylvania IDIV, and slightly more sensitive on 5 than the Philco STB, these advantages apply for DXing only. At this time, Neither the Philco STB nor the Zenith STB are useful for actually watching a program on WLMB-DT. There is a problem on both of these boxes when tuned to WLMB-DT. At irregular intervals, with no apparent trigger and unknown cause, reception of WLMB-DT will inexplicably "drop out" on both of these STBs. When the boxes are running together through the splitter, the losses always occur simultaneously, but the Philco recovers more quickly than the Zenith. When either is running with the Sylvania TV, the reception on the Sylvania TV is unaffected. Reception of WLMB-DT on the Sylvania TV (twinned of alone) is reliable, (barring the presence of lightning in the immediate neighborhood).

Now, this could be a problem with the digital encoding at WLMB-DT. Perhaps something in their bitstream is non-standard, such that older receivers are unaffected, but newer receivers (e.g., the Zenith and the Philco) are made to fail.

If anyone who has one of these STBs lives in the service area of a lowband DTV, please check this out.

The only annoying thing about the Zenith is that one has to set the display mode (i.e., letterbox/squeezed/full screen) individually for each channel the Zenith receives. If you want the picture normal shape and fulling the screen (I personally could not imaging leaving it an another mode), you have to save the "cropped" display mode for each channel.

One neat feature of the Zenith is called "EZ Add" - a channel search for new channels that does NOT clear out the channels already scanned.

73, Rob, N8NU

UPDATE: I can only presume that WLMB had a problem in the way it encoded their digital signal. Sometime (likely early in 2009), WLMB fixed the problem, and is reliably received by all DTV devices I have access to.