AD Shootout: 91XG vs. C4 vs. DB4e

[re_nelson]

Here are some numbers to crunch involving three AntennasDirect UHF antennas, including the new DB4e. Each was hoisted atop a 16-foot AGL stepladder (with the help of a neighbor and his wife) and then adjusted for the best readings on channel 31, roughly the middle of the band. No modifications were made to any of the antennas. The "as shipped" baluns were used with a 20-foot length of RG-6 quad shield from the antenna to the measuring device.

With the caveat that these are point-in-time measurements made on a late Saturday afternoon (November 19, 2011), I'll leave it to you experts to analyze. These values are all from a Sencore SLM-1456 at the location shown below in the TV Fool report:

http://www.tvfool.com/?option=com_wr...ec1262feab52a5

91XG

+----+-----+-----+------+----+
! CH.!LEVEL! MER ! BER  !DIG.!
!    !POWER! CCN !      !QLTY!
!    !dBmV ! dB  !      !    !
+----+-----+-----+------+----+
! 14 !- 5.3! 30.6!2x10-9!PASS!
! 18 !-17.6! 30.3! <10-9!PASS!
! 19 !- 1.7!>36.0! <10-9!PASS!
! 20 !-24.3!>36.0! <10-9!PASS!
! 21 !-15.0!>36.0! <10-9!PASS!
! 23 !- 1.3!>36.0! <10-9!PASS!
! 25 !-27.6!>36.0! <10-9!PASS!
! 27 !-26.8! 34.2! <10-9!PASS!
! 28 !-22.9! 32.6! <10-9!PASS!
! 29 !- 1.2!>36.0! <10-9!PASS!
! 30 !  2.9!>36.0! <10-9!PASS!
! 31 !-20.7!>36.0!1x10-7!PASS!
! 32 !- 3.8!>36.0! <10-9!PASS!
! 34 !-22.0!>36.0! <10-9!PASS!
! 35 !-10.5!>36.0! <10-9!PASS!
! 36 !- 7.0!>36.0! <10-9!PASS!
! 39 !-  .0! 33.1! <10-9!PASS!
! 40 !   .1! 35.9! <10-9!PASS!
! 41 !-  .5!>36.0! <10-9!PASS!
! 42 !- 8.0!>36.0! <10-9!PASS!
! 43 !-11.3! 35.4! <10-9!PASS!
! 44 !-11.2! 35.0! <10-9!PASS!
! 45 !- 6.4!>36.0! <10-9!PASS!
! 46 !-10.3!>36.0! <10-9!PASS!
! 48 !- 5.4! 35.4! <10-9!PASS!
! 50 !-21.5! 34.1! <10-9!PASS!
! 51 !-26.7! 33.7! <10-9!PASS!
+----+-----+-----+------+----+

Clearstream 4 (C4)

+----+-----+-----+------+----+
! CH.!LEVEL! MER ! BER  !DIG.!
!    !POWER! CCN !      !QLTY!
!    !dBmV ! dB  !      !    !
+----+-----+-----+------+----+
! 14 !- 3.7! 30.7!6x10-8!PASS!
! 18 !-21.1! 29.8! <10-9!PASS!
! 19 !- 2.0!>36.0! <10-9!PASS!
! 20 !-21.7!>36.0! <10-9!PASS!
! 21 !-18.6! 35.3! <10-9!PASS!
! 23 !-  .4!>36.0! <10-9!PASS!
! 25 !-26.2!>36.0! <10-9!PASS!
! 27 !-25.0! 34.2! <10-9!PASS!
! 28 !-23.1! 32.8!5x10-8!PASS!
! 29 !- 2.3!>36.0! <10-9!PASS!
! 30 !  2.9!>36.0! <10-9!PASS!
! 31 !-23.2!>36.0!1x10-7!PASS!
! 32 !- 6.0!>36.0! <10-9!PASS!
! 34 !-23.8!>36.0! <10-9!PASS!
! 35 !-13.5!>36.0! <10-9!PASS!
! 36 !- 8.3!>36.0! <10-9!PASS!
! 39 !- 1.6! 33.4! <10-9!PASS!
! 40 !-  .2!>36.0! <10-9!PASS!
! 41 !- 1.1!>36.0! <10-9!PASS!
! 42 !- 9.3!>36.0! <10-9!PASS!
! 43 !-11.5! 35.5! <10-9!PASS!
! 44 !-18.8! 34.4! <10-9!PASS!
! 45 !- 8.7!>36.0! <10-9!PASS!
! 46 !-13.1! 35.6! <10-9!PASS!
! 48 !- 8.6! 35.0! <10-9!PASS!
! 50 !-23.7! 33.5! <10-9!PASS!
! 51 !-31.6! 32.1! <10-9!PASS!
+----+-----+-----+------+----+

DB4e

+----+-----+-----+------+----+
! CH.!LEVEL! MER ! BER  !DIG.!
!    !POWER! CCN !      !QLTY!
!    !dBmV ! dB  !      !    !
+----+-----+-----+------+----+
! 14 !- 3.1! 30.7!3x10-9!PASS!
! 18 !-20.2! 29.8! <10-9!PASS!
! 19 !- 2.8!>36.0! <10-9!PASS!
! 20 !-22.6!>36.0! <10-9!PASS!
! 21 !-18.7! 35.8! <10-9!PASS!
! 23 !   .5!>36.0! <10-9!PASS!
! 25 !-25.6!>36.0! <10-9!PASS!
! 27 !-24.3! 34.8! <10-9!PASS!
! 28 !-22.4! 33.2! <10-9!PASS!
! 29 !- 3.0!>36.0! <10-9!PASS!
! 30 !  3.4!>36.0! <10-9!PASS!
! 31 !-21.8!>36.0!1x10-7!PASS!
! 32 !- 4.0!>36.0! <10-9!PASS!
! 34 !-22.0!>36.0! <10-9!PASS!
! 35 !-12.8!>36.0! <10-9!PASS!
! 36 !- 6.5!>36.0! <10-9!PASS!
! 39 !  2.0! 33.8! <10-9!PASS!
! 40 !  3.4!>36.0! <10-9!PASS!
! 41 !  2.0!>36.0! <10-9!PASS!
! 42 !-10.1!>36.0! <10-9!PASS!
! 43 !-14.4! 35.4! <10-9!PASS!
! 44 !-17.5! 34.6! <10-9!PASS!
! 45 !- 9.9! 35.3! <10-9!PASS!
! 46 !-13.9! 34.3! <10-9!PASS!
! 48 !- 9.8! 33.8! <10-9!PASS!
! 50 !-20.4! 32.7! <10-9!PASS!
! 51 !-27.7! 31.1! <10-9!PASS!
+----+-----+-----+------+----+

[300ohm]

So the DB4e was the best of all three on channel 27 ?

[re_nelson]

So the DB4e was the best of all three on channel 27?

The numbers in the POWER column indicate that. In fact, the DB4e bested the others on channels 39-41. Why was channel 27 of particular interest?

[tvlurker]

re_nelson, thanks for the shoot-out. I'm interested in high gain for channels 18 and 23.

I'd like to caution others that these results are most useful for channels that are within a degree or two of channel 31's position at 192 degrees magnetic, since the reception was peaked for reception on channel 31.

For example, on channel 18, reception seems to be worse on the DB4e than the other two antennas, while on 14 and 23 the DBe looks better.

On closer inspection, one can see that channel 18 is at 179 degress, while 14 is at 190 and 23 is at 192 degrees. Since the higher the gain, the lower the beamwidth, ome would expect that the gain at 11 degrees off the main lobe for a higher gain antenna would be worse than 11 degrees off for a lower gain antenna. Had the antenna been peaked for channel 18, it's possible (but not necessary) that the DB4e would have won out.

[300ohm]

Why was channel 27 of particular interest?

Its one of your weaker LOS stations.

Can you post some measurements of the DB4e ?

[re_nelson]

Can you post some measurements of the DB4e?

I'll defer on that and pass the torch to someone with the tools and skills to perform such measurements. I've seen that others here in DHC land have acquired a DB4e and may be better equipped to do that.

[lithOTA]

Great work, R.E. When you plug these results into an Excel spreadsheet and generate a line chart, some things become clear:
1. The 91XG is just about unbeatable above RF 43.
2. The C4 is probably better than a lot of people give it credit for.
3. The DB4e matches the performance of the other 2 (for the most part). The fact that it does this with a much wider horizontal beam pattern is the real news. While this may not be good for those with multipath issues, it could be great for me, as I'm trying to find a way to combine signals from 4 different directions. If the DB4e is able to grab all of my desired UHFs from a fixed mount, it would save me a whole lot of fooling around with multiple antennas and feeds.
I plan on getting one for Christmas. I can photograph it and use GIS software to generate measurements, which should work better than hand-measuring.

[re_nelson]

The C4 is probably better than a lot of people give it credit for.

I very much agree (with the understanding that I don't have much in the way of signal challenges here in the broad flat plains and in the land of tall towers and high powers).

When push comes to shove and I'm not experimenting with different antenna configurations, I always go back to the old standby of the C4 paired with the C5. That's easily the smallest footprint and it means I can spread all of the other accumulated cruft in my attic around without bumping into some huge hunk of metal.

[lithOTA]

Yes, for it's size, the C4 does very well, but I've found it to be quite a sail when up on the outdoor mast. It also has a lot of mass concentrated in a small area, so when I have had it up outside I would get a lot of sway. The 91XG doesn't have this problem, despite the fact that it just looks like it has more windage.
RE, how is that DB4e doing with all of your Dallas transmitters? Does it give you the full boat?

[be236]

How can I know if I have multipath issue with a channel?

For example, my RF 22 (using M4 bay antenna with reflector)... on some days my Sony will shw it with a solid 43% signal (still no picture lock), while other days it jumps from 0% to 43%, back and forth.

I know tropo conditions could do this, but I figured it should just jump back and forth or stay steady at 43%... help?

[300ohm]

How can I know if I have multipath issue with a channel?

One way to know is that if you had ghosts on that channel in analog before the digital changeover, you have a very good chance of having multipath. Multipath is basically the digital version of ghosts.

[be236]

Yeah, I dont have any analog channels in my area anymore...

Any other way to know multipath with digital channel? I had heard that jumping signal bars would indicate this...?

[holl_ands]

Yes, jumping signal bars or percentages would usually indicate strong multipath.

An "Eyeball" test can also be useful. If it's indoors or attic, nearby metal objects such
as heating ducts and strut nailing plates could be a problem. Tall buildings, bridges,
water tanks and terrain are likely reflectors for multipath. Airplanes can cause
very rapid multipath signal fluctuations. Ground Reflection and Diffraction across
a ridge of hills are other frequently occurring sources of multipath:
http://www.hdtvprimer.com/ANTENNAS/siting.html

The first line of defense against multipath is LOCATION, LOCATION, LOCATION.

And the inherent ability of the adaptive equalizer to coherently sum multipath
components, unless they exceed the capabilities of the equalizer...newer is better:
http://www.digitalhome.ca/forum/show....php?p=1355458

[be236]

What's funny is that these channels, (say RF 17 and 20)... on a "good" day (possibly Tropo), they have great solid stable signal and SNR (say 65% and SNR 20)... then on "bad" days they signal goes down to say a stable 40% signal, SNR 0 (obvious no picture lock) ... then on worse days, they will jump from 0% to 50% signal...

This is with an M4 outdoors about 15 feet AGL pointed to trees about 300+ feet away and of course hills after that (these channels are 2EDGE and 107 miles away).

I tested a LPDA (similar to Yagi) VU 160 RS against my M4 and when I swapped them out at the same location, the M4 would pick up those channels, while the VU 160 did not... so I was guessing that a bay-type antenna is better for my situation, which contradicts conventional wisdom that a Yagi is better for me? Those channels are on the same mountain (Mt Seymour 107 miles away) and I thought Yagi would have been better? hmm..

[holl_ands]

ATSC Diversity Combining Receiver System:

What might be better protection against multipath is a multiple antenna receiving
system, although the implementation losses in conventional RF Combiners might
be more than the combining gain. BUT THERE IS A BETTER WAY.....

Since it's a bit off-topic here....I posted an ATSC Diversity Receiver Update in the
"Smart Antenna, Adaptive Arrays, et. al. Thread":
http://www.digitalhome.ca/forum/show....php?p=1358142