4 bay bowtie antennas Low UHF and VHF-HI capability?

DB4e and DB8e use PCB (Printed Circuit Board) Baluns, which are VERY lossy in Hi-VHF Band, which is something NOT modeled by 4nec2:
http://www.hdtvprimer.com/antennas/temporarypage.html

mclapp M4 Super-4-Bay (9.5x9.0) is an easy DIY (from scratch or a kit) with exceptional UHF performance with better than 9 dBi in FORWARD direction on Hi-VHF and SWR between 4 and 14:
http://imageevent.com/holl_ands/multibay/4bayrefl

You can buy an inexpensive 5, 6 or 10-Element Hi-VHF Yagi or Log-Yagi Antenna....or using dimensions below, build a simple DIY Hi-VHF Antenna that can be combined with a UHF antenna using VHF/UHF Combiner (aka UVSJ) including Circular Loop with Loop Reflector (or Screen Reflector like A-D C2), 2-Bay Bowtie with Reflector Rods, Hi-VHF Bi-Quads with Reflector Rods, Hi-VHF Yagi's and others:
http://imageevent.com/holl_ands/loops/looprefl
http://imageevent.com/holl_ands/loops/hivhfhourglassloop
http://imageevent.com/holl_ands/multibay/hivhf2bayreflrods
http://imageevent.com/holl_ands/biquads
http://imageevent.com/holl_ands/yagis

Although it MIGHT be true (MUST model to determine the answer), I wouldn't like to generalize as to whether a contiguous full-width Reflector is NECESSARY to provide more or less "usable" Hi-VHF Band performance. A good counter-example would be two side-by-side CM4221HD 4-Bays using an RF Combiner:
http://imageevent.com/holl_ands/multibay/8bayrefl/horizstackcm4221hd
Note that although it uses two separate Reflector Rod structures, it is a FAIR-to-GOOD, but imperfect Hi-VHF Band antenna, with moderate Gain Loss in the Forward Raw Gain response, oftentimes with more Gain to the REAR....and Excessive SWR on some channels.

The 8-Bay CM4228HD, with contiguous, full-width Reflector Rods, isn't all that much better, with a Forward Raw Gain null on a different frequency, but at least it has more Gain FORWARD than Reverse....but Excessive SWR on some channels.

And the RF Combiner Mod version of the CM4228HD (and older CM4228) provided higher, more consistent Hi-VHF Raw Gain, except on Ch7, although with Excessive SWR (so the Horizontal Harness was NOT helping Hi-VHF performance as I has ASS-U-MEd):
http://imageevent.com/holl_ands/multibay/8bayrefl/cm4228hdmod
http://imageevent.com/holl_ands/multibay/8bayrefl/cm4228asbuiltrcm

Note that nearly ALL of the 8-Bay antennas designed for UHF provide imperfect performance in the Hi-VHF Band, despite their contiguous, full-width Reflectors. And note that M4 4-Bay with Double-Angle Reflector is equal or better than nearly all 4-Bay and 8-Bay antennas in both UHF and Hi-VHF Bands:
http://imageevent.com/holl_ands/multibay/4bayrefl

Each antenna is, of course, different so we shouldn't draw broad generalizations.
So FWIW, here are the 4nec2 simulation results for the Antennacraft U-8000 8-Bay Bowtie:
http://imageevent.com/holl_ands/multibay/8bayrefl/acu8000refl
Hi-VHF Raw Gain is minimal in the FORWARD direction but is very usable in the REVERSE.

If the 1/4-in Gap between Reflector Elements was eliminated, the Hi-VHF Raw Gain is directed in the FORWARD direction, but has significant Gain Loss on Ch 10, with Excessive SWR on Lower Channels. So the Hi-VHF performance was far from ideal. This mod also significantly reduced the UHF F/B & F/R Ratios, but UHF Raw Gain remained within +/- 1 dB:
http://imageevent.com/holl_ands/multibay/8bayrefl/acu8000fullwidthrefl

So whether Full-Width or Split Reflector we see the same sort of Hi-VHF problems in most 8-Bay Antennas.

just to add my 0.02cad:

i am using a db4 (the 'old' model) in my attic and am getting vhf in addition to uhf.
in fact, i am even getting channel 6 (global in ottawa) without any problems!

of course, it might have to do with the fact that vhf signals are quite strong in the area, making it possible for me and others to get vhf-low with what is supposed to be "just" an uhf antenna.

if you only want to get local signals, a db4e (or an 'old' db4) is perfectly adequate in most circumstances.

if you do not benefit from strong vhf signals in your area, maybe an accessory like the "ClearStream 2 VHF Reflector Assembly" that you could add to your db4e (you should find it on the antenna direct website and elsewhere) could do the trick for you?

cheers.

Thank you for the advice.
Now, I get all the '10' Montreal local TV stations including TVA and CTV which are on ch10 and ch12 (VHF-Hi) at 100% by using a simple DIY antenna "2 bay bowtie" placed indoor near the window.
In July, when I move, I can use an outdoor antenna (the mast is already placed). Here is my tvfool report for my new location:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=1dda6ed6ba096f
To summarize, my problem won't be the local TV stations as I can receive them with a small DIY indoor antenna, but the problem is the U.S TV stations and specially ABC on ch-13 and fox on ch-43 (weak signals).
Yes, that would be a great option of using the db4e for UHF which has almost 11dbd gain average on UHF and combine it with another Hi-VHF antenna.
Another option would be to simply use a compact combo UHF-VHF yagi or panel antenna.
My original question was regarding the db4e antenna gain on VHF-hi and its capability since the antenna direct website shows only its uhf performance.
Now I understand that this antenna is designed only for uhf and strong vhf signals and not for weak vhf signals.
I discovered also that the CM-4221HD has a gain of 3.5dbi==>1.35dbd on ch-13.

According to my understanding and my calculation.
For the ABC ch-13: the NM(db)=0.9db.
Let's say that the cable, connectors.... loss would be -2db.
I would use a pre-amp with less than 0.5db noise and 10db of gain
So in that case the gain of my antenna should be > 0.5-0.9 lets say 0.
Which mean that the gain of my antenna should be superior to 0dbd ==> 2.15 dbi.

I didn't considered the cable loss as my pre-amp gain is 10db, I only considered the pre-amp noise in my calculation.

Can any one tel me if that correct? or tell me what would be the minimum gain that I would need on VHF and UHF according to my tvfool report.
Any suggestions would be appreciated!!!

Cheers,

We rarely suggest using any of our UHF designs for VHF reception since that is not what they are designed and characterized for. What VHF reception takes place is out of design band and is generally assumed to be coincidental to the intent of the design.

For most n-Bay antennas, one will usually find that VHF reception peaks and nulls are quite irregular and change tremendously with azimuth. Generally, they tend to receive VHF better off the back than the front, but it really depends on the specific design on the particular antenna under discussion.

Unless VHF channels are close by and strong, we assume it is better to recommend an antenna or accessory that has known VHF performance unless someone wants to give a UHF design antenna a try by itself first. They tend to work okay for "close in" situations or if at certain azimuths relative to the primary aiming direction.

Hi all,
Here is my new tvfool report with the exact elevation :
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=1dda856879a397
I did a calculation based on the chart sent by Holl_ands :
I considered the coax loss (1.68), balun loos(1.5), pre-amp gain (10) and noise (0.5), the tuner noise (16db instead of 6 figured on the chart since my tv lock up when its SNR level indicate a value of 16db) and ended with -9.68dB let's say -10db.
PS: I experienced the the SNR threshold level (the minimum SNR to have a picture) for my tv tuner since I can't find it in the specs.

tvlurker: If I understand, the ch12 which has a strong signal will be noisy for the ch13!!!!So, Should I focus on UHF band only? and what would be my chance of getting the channel 43?
Holl_ands: how can I calculate the received signal level if I don't know the gain of my antenna?

Let's consider an antenna with a gain of 10 db ==> SNF=10-10=0db.
If I consider channel 43 with a power level of -87dbm==> my received signal level would be the same -87dbm. What this number can tell me? I don't know what is the minimum level of signal required by my TV.
PS: My TV is an LCD 46'' Samsung.
Thank you for your help and suggestions.

Cheers

Assuming 10 dBd (12 dBi) Gain for a 4-Bay Antenna will give you a reasonable "ballpark" number. DB-4E is close to that number on low-mid frequencies and is a couple dB better on high frequencies. It's also in the ballpark of CM4221HD, although high performance M4 and Kosmic-Quad 4-Bays are considerably better:
http://www.antennasdirect.com/cmss_files/attachmentlibrary/Technical Data PDF's/DB4E-TDS.pdf
http://imageevent.com/holl_ands/multibay/4bayrefl

As I remarked in the earlier cited post, the System NF Chart assumes an exceptional ATSC Tuner Noise Figure = 6dB. For presumed ATSC minimum SNR=15.2 dB (if no multipath) and Thermal Noise Floor = 106.2 dBm, this corresponds to Sensitivity = -85 dBm.

In 2008, a batch of Low-Rez CECB Converter Boxes were tested, finding a MEDIAN Sensitivity between -85 dBm and -86.6 dBm (variation was about +/-2 dB). These are the ONLY ATSC Tuners that had to pass an actual Sensitivity Specification Test derived from ATSC A/74 "Guidelines", which manufacturers complained was very difficult to meet, esp. when later required to also provide an Analog Pass-Thru feature. New (e.g. 2008 and later) HDTV's are "probably" also providing NF's in 5-8 dB ballpark, which varies across the TV Bands....and there is NO REASON to expect new Tuners to be significantly better than 2008-era CECB's.
http://www.nabfastroad.org/NABSTVDigitalConverterBoxEvaluation/DigitalConverter.asp

" The median on-channel RF sensitivity values, when considering each CECB unit across all the tested RF channels (low-VHF, high-VHF, and UHF) varied from -85.0 dBm (unit #1) to -86.8 dBm (unit #6), thus providing reasonable margin beyond the NTIA spec of
-83.0 dBm. Even analysis across all CECB units on the same channel showed that there is very little difference among RF channel frequencies across the three television bands: -85.2 dBm (CH 2) to -86.7 dBm (CH 6). Importantly, no sensitivity problems
existed in the low-VHF band where previous FCC lab testing showed problems on some of the early DTV receivers."

Older (2005-2006) HDTV's and HD-STB were found to have considerably higher Noise Figures:
http://transition.fcc.gov/oet/info/documents/reports/TR-05-1017-ATSC-reception-testing.pdf

"Median across all receivers (dB) 8.8 dB (Ch2), 7.6 dB (Ch10), 6.9 dB (Ch30)
Deviations of receivers from median
--Best performing receiver (dB) -2.5 dB, -1.3, dB, -1.3 dB
--Worst performing receiver (dB) 12.2 dB, 4.5 dB, 2.6 dB"

Note that NM "should" be positive by 10-20 dB to ensure year-round performance in the presence of
multipath, co-channel & adjacent interference, man-made interference (esp Lo-VHF), etc.
This is frequently called the "Fade Margin" in communication systems....

You also might need to guesstimate additional losses due to trees, surrounding buildings
blocking the signal (good luck!!!!), clutter loss if the signal grazes the rooftops and indoor loss
if located indoors (est 13 dB +/- 7 dB)....or more if Low-E glass & aluminized moisture barrier.
Yes, some people get intermittent reception with slightly negative NM...but troposcatter
propagation (esp across water) can't be relied on.

Also bear in mind that TVFool is based on the NTIA's Longley-Rice STATISTICAL Propagation Prediction model which calculates the NM that would apply for 50% of people in the presumed "Location" for 90% of the Time....hence the need to include 10-20 dB "Fade Margin" for 1-Edge and 2-Edge paths and perhaps 5 dB for LOS paths:
http://www.digitalhome.ca/forum/showthread.php?p=1480896