[opendtv] My Return to OTA

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 10 Jul 2008 11:29:29 -0400

Interesting approach, to create a much smaller antenna than you'd normally get 
with VHF/UHF models.

"I combined an Antennas Direct Model DB4 two-bay UHF bow-tie antenna having 14 
dBd gain with an AntennaCraft Model Y5-7-13 VHF high band antenna having 7 dBd 
gain. I then used a 3 dB combiner to feed a 16 dB gain Channel Master Model 
Titan 2 mast-mounted preamplifier."

And you don't need a diplexer.



My Return to OTA
A broadcast engineer goes 'back to the future'

by Dane Ericksen, 7.09.2008

Editor's Note: Dane Ericksen, a senior engineer with Hammett & Edison in the 
San Francisco area and longtime SBE National Director, relates his experiences 
in setting up a terrestrial DTV system in his Sonoma County home.


After almost 20 years of cable TV, I decided that it was finally time to return 
to over the air.

Since my house is more than 60 km north of the Sutro Tower in San Francisco, 
and almost 70 km from San Bruno Mountain, another multi-DTV station 
transmitting site, this meant installing a rooftop antenna (Fig. 1). That, in 
turn, meant adding a support mast, bringing in a down lead cable, and routing 
the cable through existing walls so the feed could be accessed by my living 
room TV. Not impossible tasks, but not trivial tasks, either.

My house is a single-story residence in Sonoma County, just outside the Sonoma 
city limits. As shown by the satellite photo in Fig. 2, it's a nice quiet 
neighborhood with a fair number of trees. I was a little apprehensive that 
after taking all the antenna-installation steps I might not have useable DTV 
reception. This is because as shown by Supplemental Figure S1 my house lacks 
line-of sight to Sutro Tower and to the San Bruno Mountain antenna farm just 
south of San Francisco (for interested readers, all of the supplemental figures 
are available for viewing on the H&E Web site, www.h-e.com). However, the 
Terrain Integrated Rough Earth Model (TIREM) predicted service from both San 
Bruno Mountain (Fig. 3) and from the Sutro Tower (Fig. S2). So, I decided to 
make the hardware investment that would allow for OTA.


My first discovery was that no manufacturer makes a VHF high-band/UHF-only 
rooftop antenna; since there are no VHF low-band DTV assignments in the San 
Francisco Bay Area, I didn't want to deal with the greater element and boom 
lengths of a conventional VHF-UHF rooftop antenna.

So as shown by Fig. 4, I combined an Antennas Direct Model DB4 two-bay UHF 
bow-tie antenna having 14 dBd gain with an AntennaCraft Model Y5-7-13 VHF high 
band antenna having 7 dBd gain. I then used a 3 dB combiner to feed a 16 dB 
gain Channel Master Model Titan 2 mast-mounted preamplifier. Since I wanted the 
ability to experiment with DTV reception from several sites, I also installed 
an AntennaCraft Model TDP-2 rotator.

As shown by Fig. S3, an existing gable above my garage made a convenient 
mounting for an 8-foot mast, which gets the antennas just above a beautiful 
cherry tree that occupies my front yard. Plus, from the street, you have to 
look hard to even spot the antennas (Fig. S4). The coax and rotor control 
cables were brought into my attic using a RadioShack wall feed-through tube, 
part number 15-1200A.

There is pass-DC 3 dB splitter in my attic, with one leg going to my living 
room, where a power supply inserts its DC voltage up to the coax to power the 
preamplifier. The other leg goes to a guest bedroom. As shown by Fig. S5, an 
F-fitting antenna discharge unit (ground block) was installed at my roof gable, 
and a ground wire was connected to an existing utilities ground wire next to 
the side of my house. While lightning is rare in Sonoma, prudence and Section 
810 of the National Electrical Code require that a rooftop antenna be grounded. 
Since I had one mast mounting bracket left over, I used that as a pipe clamp. I 
was going to trim off the unneeded legs, but decided that the clamp looked sort 
of neat as installed, and so left the legs on.


I purchased a Samsung Model DBTH260F 8-VSB tuner, which has a fifth-generation 
chip set (Fig. S6). Programming the tuner was straightforward, and the initial 
channel search returned 16 DTV signals with 46 program streams-impressive. The 
Sutro Tower UHF DTV stations showed 8 out of 10 bars in the signal strength 
display mode. The KNTV D12 signal from San Bruno Mountain was weaker, at only 3 
bars, but that has proven sufficient to give only rare (and momentary) freeze 

As shown by Fig. 5, taken using a Rhode & Schwarz Model FSL6 spectrum analyzer, 
the receive carrier levels for the UHF signals are around Ð60 to Ð70 dBm. As 
shown by Fig. S7, D12 from San Bruno Mountain was significantly weaker, at Ð98 
dBm. Note the DTV pilot feed through from KCBA-DT, D13, Salinas, transmitting 
from Fremont Peak, 193 km to the south, and feed-through of the KOVR-TV, N13, 
Stockton, visual carrier. KOVR-TV transmits from a 610-meter tower near Walnut 
Grove, 86 km east of Sonoma.

Fig. S8 shows two mountain ridges between my house and the Walnut Grove 
antennas, so it's surprising that any N13 signal is seen. Plus, the Figure S7 
spectrograph was taken with my rooftop receiving antennas aimed south, not east.

As an unexpected bonus, I found that not only could I also receive the Monument 
Peak/Mt. Allison DTV stations, but that the long over-the-bay paths shown in 
Fig. S9 didn't seem to bother my reception. And, the antenna orientation for 
all four sites was the same from my location. The only disappointment was no 
signal from KFTY-DT at Mt. St. Helena, 42 km to the north. That path has only 
one relatively minor blockage, so knife-edge refraction should provide plenty 
of signal. But, nothing. A check of the CDBS shows an out-of-core D54 license 
for 30 kW ERP and an in-core FCD32 CP for 19.9 kW ERP. Given this relatively 
modest D54 ERP, and the presence of a co-channel NTSC station, KTEH, at 
Monument Peak, I suspect that no KFTY reception will be possible until that 
station shifts from D54 to FCD32.


I ordered a Sansonic Model FT-300A coupon eligible converter box (CECB) and a 
RCA Model DTA800B CECB. The Sansonic CECB worked great, and has the same 
excellent sensitivity as my Samsung tuner. Like the Samsung, setup of the 
Sansonic CECB was easy (Fig. S10).

The RCA CECB (Fig. S11) was a disappointment; it had markedly less sensitivity, 
and had difficulty holding lock on the weaker KNTV D12 signal. Indeed, the RCA 
CECB was right in the nether region between a perfect DTV signal and no DTV 
signal. The RCA CECB remote control was also much worse, requiring a kluge 
approach of entering your TV receiver's remote control code for audio control.

Because of its excellent performance, the Sansonic CECB is now doing service in 
my guest bedroom, where a second antenna outlet was installed. The RCA CECB 
should be suitable for use at my daughter's San Francisco apartment; even using 
an indoor, back-of-set low-gain antenna should provide sufficient signal for 
this sensitivity-challenged CECB.


So, to paraphrase the famous MasterCard commercial: UHF antenna, $59.99; VHF 
high band antenna, $19.99; pre-amplifier, $56.99; antenna rotor, $64.99; mast 
and mounting hardware, $60; coax and rotor cables, $30; handyman charge to 
install antennas, $200 (I am recovering from a motorcycle accident broken leg, 
so ladder climbing is a no-no for now); Sonoma Phone Man charge to route cables 
through existing walls and add coax outlets, $234; Samsung HDTV tuner, $179.99; 
Sansonic CECB, $19.99 (after coupon); RCA CECB, $19.99 (after coupon); total, 
$946. The ability to not worry about my local cable company telling me that it 
will be turning off the analog signals on my cable service and that I will have 
to start renting digital cable set-top boxes: Priceless.

Mr. Ericksen is a senior engineer with Hammett & Edison, Inc. Consulting 
Engineers, near San Francisco. He is a registered professional engineer (P.E.), 
and holds SBE CSRTE, 8-VSB and CBNT certifications. Mr. Ericksen is Chairman of 
the ATSC TSG S3 Specialist Group on Digital ENG and serves on the SBE 
Certification Committee. He is in his sixth term as a SBE National Director and 
is currently the SBE Chapter 40, San Francisco, Secretary.
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