Design and Installation of Outdoor TV Antenna

Tom Schmidt

http://www.tschmidt.com

Post Transition Update 7/31/2009

Summary

Digital television (DTV) transition scheduled for June 12, 2009 (postponed from February 17) motivated us to review existing outdoor antenna system and undertake upgrade during fall of 2008. We live in a rural area able to receive Boston and NH stations. Boston stations are 42 miles away; nearest NH station is only 13 miles distant. This paper documents steps we took to evaluate requirements and install new outdoor TV and FM antenna.

Over the air (OTA) TV reception has fallen out of favor over the years with rise of Cable and Satellite providers. About 15% of American households rely exclusively on OTA TV. A significant number of Cable and Satellite subscribers use OTA for one or more TVs. Transition to DTV may impact choice of using OTA reception. OTA quality is often better then Cable or Satellite because program is not recompressed (transcoded) to fit available channel capacity. Being free, except for cost of antenna, OTA may be preferable to monthly fee for cost conscious customers. On the down side some viewers will have fewer stations available due to digital transmission characteristics. With analog transmission picture degrades gradually becoming snowy as signal decreases. Digital is perfect until signal reaches critical threshold, the cliff effect. At that point receiver is no longer able to recover picture and sound. In many cases antenna used for analog reception will work fine for digital. In others optimum-viewing experience requires a better antenna.

Now that full power analog is shutdown and stations relocated to final channel allocation both station owners and OTA viewers are fine-tuning their systems. It will probably be another year before we can definitively determine how well DTV is working for OTA viewers.

Background

We live in southern NH. This gives us access to both NH and Boston stations. Being 42 miles from Boston in hilly forested New England requires a high gain outdoor antenna. Current system is 20 years old. Thought it was a good time to see if anything could be done to improve reception.

Existing system consists of separate VHF and UHF antennas mounted on gable side of house with mast-mounted preamp. Rotor positions antenna between NH and Boston stations. A separate omnidirectional antenna is used for FM.

Design goal:

• Receive more stations
• Minimize or eliminate need for rotor
• Integrate FM distribution so all TV outlets have FM capability
• Bring grounding up to date

There is no such thing as a digital TV antenna. Antenna does not care if it is receiving an analog or digital program. That being said digital reception is more demanding then analog. Analog reception slowly degrades as noise increases showing up as snow. DTV is subject to cliff effect. Reception remains perfect until signal falls below a critical value. When that occurs receiver is no longer able to recover video and audio. Longley-Rice propagation modeling is used to predict coverage area. During planning phase FCC and stations engineered transmitter and antenna to meet coverage requirements. Modeling criteria has been criticized for producing overly optimistic results. There is widespread concern digital TV (DTV) broadcast coverage area will smaller then expected. In addition cliff effect makes determination of identical coverage area problematic.

Digital TV, like analog, is affected by multipath. Ideally signal arriving at antenna traveled a single path. In real world TV signals bounce off buildings, airplanes, mountains etc. Reflected signals are delayed in time relative to main signal. With analog NTSC TV multipath results in ghosting. Digital ATSC tuners used to be very susceptible to multipath. Newer designs do a much better job rejecting multipath but if extreme will still corrupt signal.

Antenna design must have enough gain to receive weak distant signals while not causing overload due to nearby transmitters. Cost and convenience must be factored in. Using a rotator to move antenna makes viewing difficult in multi TV homes. Antenna height is normally dictated by structure used to mount antenna. It is possible to mount antenna on tower to gain more elevation but that is usually not feasible due to cost and esthetic considerations.

Interested readers are encouraged to visit Ken Nist’s HDTV primer site, particularly the antenna section. Much of the information in this paper was derived from Ken’s site.

TV Broadcast History

Historically television has been transmitted as an analog signal. Color and stereo audio enhancements were done in the analog domain. For last several years US TV stations have been authorized by FCC to simulcast programs in both digital and analog format. Digital transmission offers a number of advantages but as with any change of this magnitude there are bound to be teething problems.

Digital TV (DTV) refers to way program is transmitted. Just because a program is digital does not mean it is high definition television (HDTV). HDTV picture quality is much better then Standard Definition television (SDTV). HDTV is more like watching a movie. Digital is more efficient then analog making it possible for station to deliver not only better image quality but also multiple programs, called sub channels, within existing 6 MHz RF TV channel. Station has the option of transmitting combination of HD and SD programs.

On June 12 full power US TV stations stopped broadcasting in analog, except in some cases a month of analog “nightlight” service. Some stations moved from temporary UHF channel assignment to VHF. This makes antenna design challenging as need to take into account pre-transition and post-transition channel allocation.

Finding Local Stations

First step is to find local stations and determine how situation changes June 12. The most popular RF modeling site is AntennaWeb run by the Consumer Electronics Association. Antenna Web is very conservative so it excludes some stations receivable with good antenna. In our case Antenna Web only shows 4 stations when in fact we reliably receive 14. FCC recently created a web site to view predicted signal. We mainly use TV Fool by Andy Lee. Both TV Fool and FCC sites provide detailed report.

Pre Transition DTV Channel Assignment
RF Chan	Virtual Chan	Call Sign	TV Fool dBm	Old Antenna
2-13	VHF
14-17
18	62	WMFP	-83.9	Mid
19	2	WGBH	-83.0	Mid
20	5	WCVB	-83.2	Mid
21
22
23	66	WUTF	-85.9	No
24	41	WVTA	-102.9	No
25	31	WNNE	-107.4	No
26-28
29	27	WUNI	-86.5	No
30	4	WBZ	-84.2	Mid
31	25	WFXT	-98.4	No
32	68	WBPX	-98.6	No
33	21	WPXG	-64.6	Mid
34	60	WNEU	-40.1	Mid
35	50	WZMY	-81.3	No
36
37	Reserved non-TV
38	13	WGME	-106.5	No
39	38	WSBK	-93.9	No
40
41	56	WLVI	-90.6	No
42	7	WHDH	-88.3	Mid
43	44	WGBX	-89.0	No
44	6	WCSH	-100.7	No
45
46	8	WMTW	-99.9	No
47	48	WYDN	-102.8	No
48-56
57	11	WENH	-66.4	Mid
58
59	9	WMUR	-29.0	Strong
60-69
Converter Box: Insignia NS-DXA1-APT (Yellow) Stations of interest (Green) Viewable stations

Prior to March 12 stations simulcast in analog and digital format. FCC authorized use of temporary second RF channel for DTV. After transition some stations will move to different channel assignment. This is important for planning purposes. In our area three stations, two in NH and one in Boston move from UHF to VHF. VHF frequencies are split into two blocks channels 2-6 and 7-13. VHF low is not ideal for DTV due to man-made noise and propagation characteristics. In most markets there will be no digital VHF low stations. This provides an opportunity to use a VHF high antenna. VHF high antenna is optimized for channels 7-13. For a given gain eliminating VHF low results in a smaller antenna. Even though not optimized for FM (located between channels 6-7) and VHF low if signal is strong enough VHF high antenna may still provide adequate signal. This is convenient if need to receive some analog VHF low stations prior to transition.

Once transition is complete Channels 52-69 will no longer be used for TV. They have been auctioned off for other purposes. Antennas optimized for reduced UHF allocation may provide better performance because they do not have to cover as wide a range. So far antenna manufactures have not marketed post transition optimized antennas.

Fringe viewers like us typically have access to multiple stations serving different markets. Because they are distant need a high gain directional antenna to receive station. Down side of directional antenna is pointing accuracy. If antenna is not pointed directly at transmitter signal level is significantly reduced.

Antenna rotators have been used for years to change antenna direction as needed to pick up wildly dispersed stations. Rotors are the bane of multi TV households and digital video recorders (DVR). Changing antenna direction determines which stations are viewable. Rotors present problems for DVR use because DVR is not able to change antenna direction.

In designing antenna system need to carefully consider which stations are of interest to minimize need to constantly change rotor position. An option is to use multiple antennas orientated in different directions and combine them. In our case decided to use separate VHF high and UHF antenna and offset VHF high antenna by –105 degrees relative to UHF antenna. When UHF antenna is pointing at Boston VHF antenna is aligned with Channel 11 WENH. NH. It is slightly misaligned for Channel 9 WMUR NH but transmitter is so close antenna still delivers adequate signal.

With this arrangement able to simultaneously receive all post-transition stations of interest except: WHDH Channel 7 Boston and WZMY Channel 50 in Derry NH. That means unless someone wants to watch either of these channels there is no need to move antenna.

Channel Assignment as of June 12 2009
RF Chan	Virt Chan	Callsign	Network	TV Fool dBm	Dist	Az True
2-6
7	7	WHDH	NBC (MA)	-79.2	41.7	147
8	8	WMTW	ABC (ME)	-94.5	85.1	33
9	9	WMUR	ABC (NH)	-36.1	12.5	19
10
11	11	WENH	PBS (NH)	-63.5	34.4	43
12
13	13	WYCN	IND LP (NH) – Analog	-86.5	11.1	108
Ý VHF (offset –105 degrees) UHF ß
14-17
18	62	WMFP	RTV (MA)	-84.5	41.7	147
19	2	WGBH	PBS (MA)	-82.9	41.2	148
20	5	WCVB	ABC (MA)	-83.0	41.2	148
21-23
24	41	WVTA	PBS (VT)	-102.9	58.6	318
25	31	WNNE	NBC (VT)	-107.4	58.6	318
26
27	66	WUTF	TEL (MA) (Spanish)	-76.1	31.1	163
28	28	W28CM	IND LP (NH) analog	-85.1	12.4	120
29	27	WUNI	UNI (MA) (Spanish)	-84.9	33.1	184
30	4	WBZ	CBS (MA)	-83.5	41.2	148
31	25	WFXT	FOX (MA)	-99.2	42.1	147
32	68	WBPX	ION (MA)	-99.1	41.7	147
33	21	WPXG	ION (NH) (WBPX sat)	-64.6	31.3	35
34	60	WNEU	TEL (NH) (Spanish)	-40.1	12.6	19
35	50	WZMY	MyTV (NH)	-81.3	15.1	111
36
37	Reserved non-TV
38	13	WGME	CBS (ME)	-106.5	97.5	38
39	38	WSBK	IND (MA)	-93.7	41.2	148
40
41	56	WLVI	CW (MA)	-90.6	42.1	147
42
43	44	WGBX	PBS (MA)	-88.8	41.2	148
44	6	WCSH	NBC (ME)	-100.7	87.2	34
45-46
47	48	WYDN	Daystar (MA) Religious	-99.8	41.7	147
48-51
52-69	Reserved new service
(Yellow) Stations of interest Post transition rotator selection: A) Most stations B) Channel 7 C) Channel 50 http://fjallfoss.fcc.gov/edocs_public/attachmatch/FCC-07-138A2.pdf http://www.tvfool.com/

Now that we have a performance baseline for current antenna, post transition channel assignment and estimated signal levels are able to evaluate upgrade requirement. Modeling receive signal strength is part science part black magic. We receive some stations predicted to be significantly weaker then some we cannot receive. With current system able to receive all stations stronger then –84.4 dBm and not able to receive any weaker then –88.3 dBm.

Post transition weakest channel of interest is –99.2 dBm. That means new system needs a 14.8 dB improvement. That is probably unrealistic. Current system consists of separate VHF and UHF antennas and high quality mast mounted preamp. The unknown factor is how much old system has deteriorated in 20 years.

For readers without an engineering background dB (decibel) is a convenient method to specify signal level. It is logarithmic rather then linear. Given huge differences in level it keeps numbers manageable and easy to add/subtract. For example a signal 3 dB larger is twice the power, 3 dB smaller half power, 10 dB ten times, 20 dB one hundred times and so on. Strongest signal we are interested in is about – 35 dBm the weakest –95. 60 dB difference means there is a factor of one million between strongest and weakest signal.

Selecting Equipment

UHF Antenna

There is general agreement Channel Master 4228 antenna is the best UHF fringe antenna on the market. As mentioned on Ken’s site even though billed as UHF only it can be used on VHF high. Channel Master recently announced new version, 4228HD, which is lighter and specified for VHF high (channels 7-13) in addition to UHF. Unfortunately it appears to be less sensitive on UHF then old version. Luckily we are using the old version.

Antennas increase gain by being more directional. Directional antennas are large and need to be accurately positioned. An advantage of directionality is that it reduces problems with multipath.

VHF Antenna

After transition there will be no VHF low stations in our area. We chose Winegard YA-1713 VHF high antenna. VHF high antenna is lighter/smaller as well as providing greater gain then antenna designed to receive entire VHF band.

Using separate VHF and UHF antennas allows VHF antenna to be offset by –105 degrees relative to UHF. When UHF antenna is pointing at Boston stations VHF is aligned with weaker NH station, WENH. This minimizes need to use rotor to position antenna.

VHF/UHF Preamp

The other critical piece of equipment is pre-amp. Once antenna has captured signal do not want it degraded traveling over coax to get to TV. Purpose of preamp is to compensate for losses between antenna and TV. Amplifier cannot create a signal it can only increase what is captured by antenna. Preamp should have enough gain so signal is as strong at TV as antenna.

The other important benefit of using a preamp in weak signal area is improved receiver noise figure. Signal captured by antenna is tiny. It must be amplified before receiver is able to process it. In real world nothing is perfect. In addition to boosting signal amplifiers add noise. The more noise added by amplifier the larger received signal must be to overcome it.

TV designers are not overly concerned with noise figure (NF). Most customers receive programs via Cable or Satellite presenting strong signal to TV tuner. Most of the rest are in fringe areas relying on OTA antenna and mast-mounted preamp. In that case it is preamp noise figure that is important not that of the TV. Noise figure isn’t normally even listed as part of TV specifications. In testing DTV receivers FCC found typical UHF NF to be around 7 dB. A good mast mounted preamp will have a much lower NF. Channel Master 7777 preamp has a UHF NF of 2 dB. That means when using a preamp received signal can be 5 dB weaker then if TV is directly connected to antenna. That is a lot of bang for the buck.

To be able to ignore receiver noise figure preamp must have enough gain to overcome distribution losses and receiver noise figure.

Rotator

TV stations are at different compass headings forcing us to use a rotator. TV rotators do not monitor antenna position directly. They use synchronous AC motor in control head and another to turn antenna. Being synchronous both motors move through the same number of degrees assuming there is no slippage. This works well enough but errors build up over time necessitating resynchronizing control head and antenna.

Higher end TV rotators dispense with motor in control unit. A microcontroller tracks antenna heading, controls antenna motor and processes IR remote control commands. Microcontroller counts power line transitions to maintain synchronization with rotor motor. It is much easier to jog rotor a few degrees with microcontroller based unit then electrometrical unit. Our intention was to minimize how often rotor is used. Wanted to control rotor from control head and NOT be forced to use IR remote control. We choose NTE U-106 rotor. Controller has several alphabetic keys used to select antenna position and clockwise and counter clockwise buttons for fine-tuning. Azimuth display is only two digits. The least significant digit is not displayed. Getting antenna perfectly aligned with true North is difficult so lack of least significant digit is not a major issue. Monitoring TV signal strength indicator while using manual buttons to jog antenna clockwise or counterclockwise fine tunes direction. I assume controller tracks heading with greater precision then displayed.

Another nice feature is when turned off controller remembers current position. This eliminates need to resynchronize controller after power failure or when turning controller back on.

FM Antenna

Did not do a rigorous analysis of FM reception. FM stations we are interested in come in fine using automobile whip antenna. FM stations, as with TV, are in various locations. Luckily good FM reception does not require nearly as much signal as TV.

Chose Channel Master HD-6010 onmidirectional FM antenna. Basically it is just two dipoles stacked on top of one another offset by 90 degrees. Gain for this antenna is 3 dB less then using a single dipole since energy picked up by one dipole is radiated out the other. The advantage is onmidirectional coverage so antenna picks up stations equally well in all directions (This is not precisely true but works well enough).

FM Amp

For FM distribution purchased discontinued Winegard DS-205 VHF amp. Amp is mounted indoors not on mast. VHF signals are less affected by coax loss and stations tend to be stronger. VHF amps frequently have FM traps to attenuate nearby FM stations. This amplifier is no exception. However rather then simply flipping a switch had to remove several components and install a jumper. If you are not comfortable soldering through-hole components may want to select different amp.

Combining TV and FM

Old system distributed FM over separate coax. This led to problems because when we built house did not provide FM drops at each TV outlet. Design goal of new system was to use single coax to distribute TV and FM to each outlet.

When combining signals from multiple antennas need to be careful not to degrade noise margin. I could have used a two-port splitter to combine FM and TV signals. The splitter would incur 3 dB loss but that is not a major issue as amp has adequate gain. Splitters/combiners are not frequency sensitive, they cheerfully combine all signals, including noise and multipath. Winegard has a clever device called a FM combiner (CS-8800) to addresses this problem. Combiner has two inputs one for TV one for FM. TV input filter attenuates range of frequencies used by FM, 88-108 MHZ. FM input has a bandpass filter that only passes FM frequencies. Using this device allows TV and FM to use the same coax while not degrading either.

UHF Signal Budget

UHF Signal Budget
Thermal noise floor 6 MHz TV channel	-106.2 dBm
Minimum ATSC SNR	15.2 dB
Antenna preamp noise figure	2.0 dB
	-------------
Absolute minimum Rx signal level	-89.0 dBm
Antenna Gain (UHF – Chan 31)	16.0 dBi
	-------------
Absolute minimum antenna signal level	-105.0 dBm
Atmospherics impairment fudge factor	10.0 dB
	------------
Desired field strength at antenna	-95.0 dBm
http://www.hdtvprimer.com/ISSUES/erecting_antenna.html http://www.tvfool.com/

Thermal noise floor for 6 MHz TV channel is –106.2 dBm. ATSC specification requires a 15.2 dB signal to noise ratio. Receiver must be able to decode signal if it is at least 15.2 dB above background noise. As mentioned preamp has 2 dB NF. 7228 antenna has 16 dBi (isotropic) gain on worst-case channel of interest. Isotropic is a theoretical antenna that receives equally well in all directions. Antennas obtain gain by being directional. Combining these factors yield absolute minimum signal level at antenna of –105.0 dBm.

DTV transmission suffers from cliff effect. As long as signal is even slightly above minimum threshold image is prefect. If signal drops even a little receiver is unable to process signal, program pixelates or freezes. To minimum signal level we added a 10 dB atmospherics impairments fudge factor. This compensates for signal fade due to changing atmospheric conditions. Factoring in atmospherics yields desired field strength of at least –95 dBm at antenna.

On paper antenna system is not adequate to receive several weakest channels. In addition even with roof-mounted antenna it is lower then nearby trees. Trees do not have much effect on VHF but almost totally block UHF. That is our situation. Trees block line of site to UHF TV stations. Need to accept we will not be able to receive weaker stations 24/7/365. Some will exhibit high occurrence of dropouts making them unwatchable. The good news is in winter when trees lose their leaves reception will improve.

Having expended this effort capturing faint TV signal want to make sure it is not degraded between antenna and TV. For this we need to examine loss budget between antenna and TV. Preamp gain should be about 10 dB greater then loss between antenna and TV. TV receiver NF is about 7 dB want to make sure weakest signal at antenna arrives at TV well above TV’s internal NF. On the other hand need to be careful amplifier does not have too much gain. Excessive gain will cause strong stations to overload TV front end.

Distribution Loss Budget

Signal Distribution Loss Budget
Antenna mast coax 10’	0.5 dB
Surge Suppressor	0.2 dB
Roof ridge coax 30’	1.6 dB
FM/TV combiner	0.4 dB
8-way splitter	11.0 dB
TV drop coax ~ 40’	2.2 dB
FM/TV splitter (@TV)	0.4 dB
	----------
UHF loss (VHF & FM 14.0 dB loss)	16.3 dB

RG-6 coax has about 5.5 dB loss per 100 feet at 700 MHz (channel 51). First length of coax connects preamp output to grounding block surge protector. Second Coax section runs from gable-mounted antenna to attic wiring closet. FM/TV combiner injects separately captured FM signal so it can be distributed over the same coax used for TV. Home has 6 TV outlets necessitating use of 8-way splitter. Lastly need to account for coax from wiring closet to TV and if FM radio is used at that location another .4 dB loss from FM/TV splitter. Cable from TV outlet to TV is typically RG-59 rather then RG-6. It has higher loss the RG-6 but being only a few feet long is not a significant contributor to loss budget.

Total distribution loss is 16 dB (14 dB VHF and FM due to lower frequency). Channel Master Preamp has 26 dB UHF gain and 23 VHF resulting in signal at TV about 10 dB higher then at antenna.

Gain is a double edge sword. One does not want an amplifier with too much gain. Doing so may overload TV receiver front end on strong signals. As long as gain exceeds distribution loss plus receiver NF there is no benefit of additional gain.

In designing antenna system one must take into account possible overload from nearby TV, FM and public service transmitters. Often overload is due to nearby FM or public service transmitter not another TV station. TV Fool has a companion FM Fool site. This allows modeling FM stations in addition to TV. If all TV/FM stations are below about –10 dBm overload should not be a problem. In general signal overload will not be a problem unless one is nearer then about 10 miles from FM transmitter. Public service transmitters are difficult to predict since they are mobile and do not maintain a schedule. If overload is a problem either orientate antenna to minimize strength of offending channel or use attenuator to reduce interference level.

Installation

In general higher the better for antenna, toyed with mounting VHF above UHF antenna to reduce wind loading. In the end opted to mount UHF antenna on top to maximize signal. VHF antenna is mounted three feet below and offset by –105 degrees. Rotor is two feet below VHF antenna. Used thrust bearing to reduce rotor loading and increase stability.

Bottom of rotor is two feet above roof peak. FM antenna is centered between roof peak and bottom of rotor. This provides 3 feet of separation between antennas. The greater the separation the less antennas interact with one another. Heavy-duty wall mount secures antennas to gable.

New antenna is about three feet taller then old one. Being gable mounted it is not practical to guy antenna. To reduce possibility ice or wind will take it down used heavy gauge 1.5” diameter mast rather then more common 1.25.” Most mast sections are 5-foot. It is possible to order 10-foot heavy duty 16-guage mast. Instead opted to use 1-1/4 EMT (electrical metallic tubing) commonly known as conduit. 1-1/4” trade size conduit has OD of 1.510” and .065” wall thickness resulting in very strong mast. Each mast section ended up being about 8-feet long. In December 2008 Southern NH experienced a severe ice storm. Many trees were knocked down. We were without power for a week. Antenna came through with flying colors.

Antennas are directional in both azimuth and elevation. Rotor takes care of pointing antenna in correct direction. Given how marginal estimated signal is wanted to do everything possible to maximize signal capture. If signal arrives more then a few degrees above or below antenna horizontal centerline signal strength is reduced. This is not significant for FM or VHF but is for UHF.

We live in wooded area. Even though antenna is roof mounted it is well below top of tree line. Line of sight to UHF stations is blocked by tree line 200’ away and about 70’ high, 40’ higher then antenna. Trees block almost all UHF signal. To antenna looks like signal originates at treetop level. Tilting antenna up 10 degrees points it at skyline maximizing signal pickup.

Since I chose electrical conduit for mast thought it would be easy to contact local electrical contractor and have conduit bent 10 degrees. Turned out no one was interested in doing a one off bend or they did not have proper equipment. Contacted local muffler shop but they did not want to do it. Concerned their equipment would crush conduit.

Fell back to plan B. Purchased four “L” shaped reinforcing brackets and made a hollow box 3.75” on each side. Used it to offset lower antenna mount. Hole spacing on bracket is close to antenna u-bolt pattern minimizing amount of filing and drilling. Because UHF antenna is no longer parallel to mast was careful not to deform horizontal mounting brackets. U-bolts were a too short due to large mast and tilt offset. Replaced them with 1/4 –20 bolts. Bracket tilts antenna up about 8 degrees from horizontal. Was not able to conduct test with antenna mounted normally and tilted so do not know if tilting antenna is effective at increasing signal.

Channel Master pre amp has two switch selectable options, 1) combined or separate VHF/UHF input and 2) FM trap on/off. Switch access requires removing amp from housing. We use separate VHF and UHF antennas so set input for separate and switched FM trap on since we are using a dedicated FM antenna.

Coax from VHF/UHF preamp needs a loop between upper and lower mast so upper mast is able to rotate. To minimize stress on coax sleeved upper and lower section where it is ty wrapped to mast with short length of small diameter automotive hose. This insures coax experiences a gentle bend radius.

Fabricated antenna and wired it up. Temporally mounted it on deck by drilling 1.5” holes in couple of scrap 2x4s and screwing them into railing for testing.

Removed old antenna and installed new heavy duty wall brackets. Brackets were drilled for ¼” fasteners and came with lag screws for building attachment. Did not think that was adequate. Drilled out holes and used 5/16” toggle bolts. Attached lower portion of mast to bracket and set it so when upper mast section was attached bottom of rotor housing temporally rested on upper wall bracket.

Complete assembly is pretty heavy and unwieldy. I was not about to walk up ladder with entire antenna. Removed VHF antenna, FM antenna, and lower mast section. Upper mast section now consists of UHF antenna, preamp, 8’ of mast, rotor and wiring. My son went up on the roof and I carried antenna up ladder. Attached rotor and thrust bearing to lower mast section. Use short section of 2x4 to raise assembly high enough so we could attach VHF antenna. I was careful to mark correct antenna position on ground. Then we used longer piece of 2x4 to set antenna at correct height. Attached FM antenna and weather station to lower mast. Bolted everything tight and congratulated ourselves for job well done and not falling off roof.

It is important to keep water out of coax connectors. At antennas and grounding block used Coax-Seal to wrap connectors. Stuff is pretty tenacious so install it only after system has been fully tested.

Used a small plastic utility box as a junction box mounted under the eaves. Cable for rotor is spliced in J-box, as is wiring for weather station.

Both coaxes terminate at wiring closet in attic. That houses VHF/UHF pre amp power supply, FM distribution amp, FM combiner and 8-way splitter.

Lightning Protection

TV antenna is likely highest object near your home. As such makes unintentional lightning rod. Lightning packs a tremendous amount of energy. Lightning protection is designed to provide low impedance path to Earth and bond all metallic conductors together to minimize potential differences during lightning events.

Back years ago when I installed original antenna common practice used 8-gauge solid Aluminum wire to bond antenna mast to building ground system, typically nearby copper cold water pipe. Grounding/bonding requirements have tightened over the years. National Electrical Code (NEC) Article 810 requires antenna be bonded to building ground system and have it own ground rod. Bonding conductor needs to be 6-gauge copper or larger. Typical ground electrodes sold for TV antenna use are only 5 feet long. Longer is better, so purchased standard 8-foot ground rod used to protect building electrical service entrance. Antenna mast is connected to ground rod and ground rod bonded to building ground system. Used PVC conduit and conduit body, below siding until it enters the ground, to protect ground cable.

Two coaxes enter building, one for TV, one for FM. Dual F connector grounding block grounds both coax shields. Two gas tube surge suppressors limit voltage between center conductor and shield in event of lightning event. Rotor cable and old aluminum ground wire enter building at the same location. Reconnected old ground wire to mast even though grounding job has been assumed by improved grounding system.

Good grounding/bonding is not just for lightning protection. Air movement over antenna builds up static charge, just like a Van de Graaff generator. Proper grounding provides a path to drain off this charge rather then having it discharge though expensive electronics. Proper grounding also potentially improves reception by minimizing current flow through coax shield.

Moment of Truth (October 2008)

RF Chan	Virt Chan	Call Sign	TV Fool dBm	Old Antenna	New Antenna
2-13	VHF
14-17
18	62	WMFP	-83.9	Mid	Strong
19	2	WGBH	-83.0	Mid	Hi Mid
20	5	WCVB	-83.2	Mid	Hi Mid
21
22
23	66	WUTF	-85.9	No	Mid
24	41	WVTA	-102.9	No	No
25	31	WNNE	-107.4	No	No
26-28
29	27	WUNI	-86.5	No	Mid
30	4	WBZ	-84.2	Mid	Strong
31	25	WFXT	-98.4	No	Mid
32	68	WBPX	-98.6	No	Mid
33	21	WPXG	-64.6	Mid	Strong
34	60	WNEU	-40.1	Mid	Hi Mid
35	50	WZMY	-81.3	No	No
36
37	Reserved non TV
38	13	WGME	-106.5	No	No
39	38	WSBK	-93.9	No	Mid
40
41	56	WLVI	-90.6	No	Lo Mid
42	7	WHDH	-88.3	Mid	Hi Mid
43	44	WGBX	-89.0	No	Lo Mid
44	6	WCSH	-100.7	No	No
45
46	8	WMTW	-99.9	No	No
47	48	WYDN	-102.8	No	No
48-56
57	11	WENH	-66.4	Mid	Mid
58
59	9	WMUR	-29.0	Strong	Strong
60-69
Converter Box: Insignia NS-DXA1-APT (Yellow) Stations of interest (Green) Viewable stations

We use Insignia (Best Buy private label of Zenith DTT-901) converter box. Converter box has a bar graph indicating signal strength. For comparison purposes recorded signal levels with old antenna before it was removed. With new antenna analog channels look better and converter box picks up more digital stations. Existing stations experience fewer dropouts.

With previous antenna was not able to receive any stations weaker then –88.3, with new antenna lower limit is down to –98.6. Stations weaker than –90 dBm, even though designated in green, suffer from dropouts. Post-digital transition signal level for some stations will increase and there will be less cochannel interference. It is possible FCC may allow stations to modify antenna design or increase transmit power.

Modeling for Channel 50 shows relatively strong signal. Not clear why signal is inadequate. TV Fool elevation plot indicates large hill between station and us. Contacted engineer at WMZY and was assured they were transmitting at full rated power.

Bottom line short of building an 80 foot tower to get above tree level and/or spending several hundred dollars for an even lower noise figure preamp this is about as good as it gets.

Post Transition Experience

As part of postponed analog shutdown some stations ran nightlight service for 30 days after June 12^th. Rather then shut off analog cold turkey they ran DTV public service announcements for a month. As of mid July nightlight service was discontinued. The only analog stations still transmitting are low power and translators used to fill coverage voids of full power stations.

As to be expected in aftermath of anything as significant as transition from analog to digital TV there is a lot of post transition tweaking. In our area the most significant change is WHDH’s decision to remain on UHF, which is good news for us. VHF DTV coverage turned out to be much smaller then expected resulting in numerous viewer complaints. VHF DTV coverage seems to be a common problem as documented by Rabbit Ears.

Default TV fool signal strength modeling is based on FCC license and construction permit data. Optionally site allows modeling based on application requests, not yet approved by FCC. Stations go through multiple steps to build or modify broadcast facilities. They submit an application that is reviewed by FCC. If FCC accepts application station granted a construction permit. Once construction is complete and verified station license is updated. Being able to see predicted signal strength based on application request provides heads up on future changes. Caution is advised about using application data as it may be withdrawn or modified by FCC or station.

“Technical Data and Screencaps” link at Rabbit Ears is a convenient way to check station FCC filing status. For our purposes the important FCC record types are:

DT – Prefix indicates full service digital

DT-LIC - Full service digital operating license

DT-CP or DT-CP-MOD - Full service digital construction permit

DT-APP – request to modify full service digital transmitter

DS – Prefix indicates special digital temporary authorization during simulcast period

DX – Prefix indicates auxiliary backup digital transmitter

There is another signal modeling limitation to be aware of. Once FCC grants a construction permit model uses that information to predict receive signal level, there is no way to precisely verify when station actually finishes construction phase. For stations with construction permits actual signal level may be significantly different then predicted.

As chart shows many stations in our area are making transmitter and antenna modifications. In addition to approved construction permits: WPXG, WLVI, WBPX, and WYDN have applications pending to increase coverage area. WHDH is requesting permission to stay on UHF rather then return to VHF. If you are having difficulty receiving a station check Rabbit Ears or FCC database. May find reassuring information that station is working to modify DTV coverage area.

Stations ranked by TV Fool (current) signal strength

Callsign	RF Chan	Virt Chan	Current Pwr dBm	Future Pwr dBm	FCC Status (as of 7/31/2009)
WMUR	9	9	-36.1	-36.1	DT-CP
WNEU	34	60	-40.1	-40.1	DT-LIC
WENH	11	11	-63.5	-63.5	DT-CP-MOD
WPXG	33	21	-64.6	-61.8	DT-APP
WUTF	27	66	-76.1	-76.1	DT-CP-MOD
WZMY	35	50	-81.3	-81.3	DT-LIC
WGBH	19	2	-82.9	-82.9	DT-LIC
WCVB	20	5	-83.0	-83.0	DT-LIC
WBZ	30	4	-83.5	-83.5	DT-CP
WMFP	18	62	-84.5	-84.5	DT-LIC
WUNI	29	27	-84.9	-84.9	DT-CP
WGBX	43	44	-88.8	-88.8	DT-LIC
WHDH	42	7	-88.8	-88.8	DS-APP (stay on UHF)
WLVI	41	56	-90.6	-89.6	DT-APP
WSBK	39	38	-93.7	-93.7	DT-LIC
WMTW	8	8	-94.5	-94.5	DT-CP
WBPX	32	68	-99.1	-84.6	DT-APP
WFXT	31	25	-99.2	-99.2	DT-CP-MOD
WYDN	47	48	-99.8	-89.8	DT-APP
Green – good signal Yellow – occasional no signal Red – frequent no signal Plain – don’t care stations (WNEU, WPXG, WUTF, WUNI good signal – WMTW occasional no signal - WZMY and WYDN never received.)

Once things settle down plan on experimenting with antenna height. Fringe areas tend to have hot spots and cold spots where signal strength varies dramatically. Will also check if tilting antenna up helps or hurts reception. Hopefully will be able to improve reception a little.

Overall pleased with upgrade result, able to consistently receive 14 of 19 local stations. Based on FCC data WLVI, WBPX and perhaps even WYDN ought to move to green bringing total to 16 of 19. WGBX and WSBK will probably be fine in winter, they were during pre transition, that brings total to 18 of 19 during six months of the year.

WMTW came as a surprised. Had not even considered checking for Maine stations because they are so far away. WMTW happens to be near heading we use for NH VHF stations. Would probably come in almost all the time if antenna were better aligned. It is the only Maine station we receive, not able to pickup any UHF stations that far away. We already receive two other ABC affiliates so there is not a lot of practical value other then weather subchannel, mainly just fun being able to receive station so far away.

Not able to receive either Vermont stations. Both were very snowy in analog.

Not able to receive any low power analog stations. This is where terrain poses a serious challenge. Low power stations typically use fairly low antenna so terrain obstructions are serious impediment to reception.

WGBX was a big disappointment, as we watch a lot of PBS. Reception is worse then stations modeled with lower signal strength. I contacted station and was advised they are transmitting at full rated power and using licensed antenna. So far they have no plan to change.

WZMY is still a no show. Emailed station and was informed they are transmitting at full licensed power.

The good news is with WHDH on UHF and WZMY a no show rotor is no longer needed. Use is limited to fine-tuning antenna direction.

Bill of Materials

Total parts cost was about $500. We replaced everything except cabling within home.

Qty	Description	Mfg	Pt #	Price
1	UHF antenna	Channel Master	4228	$50
1	VHF high antenna	Winegard	YA-1713	$40
1	FM antenna	Winegard	HD-6010	$30
1	VHF/UHF preamp	Channel Master	7777	$50
1	Rotor	NTE	U-106	$70
1	Thrust bearing	NTE	TB-105	$22
A/R	Rotor cable
A/R	RG 6 coax
2	1½” 16 gauge mast		1 ¼” EMT	$31
1	HD wall mount 12”	Channel Master	9034	$20
5	4” 5/16” toggle bolts			$5
4	3-1/2” L brackets			$3
1	Dual ground block	Holland	GRB-2DHR	$1
2	Surge suppressor		4251 TV	$8
1	Junction box (rotor)		15523 BX	$2
A/R	#6 stranded bare wire			$.44 ft
1	8’ ground rod			$11
1	Lug (ant mast)			$3
1	Clamp (ground rod)			$5
1	Clamp (water pipe)			$5
1	#6 Split bolt			$2
1	FM amp	Winegard	DS-0205	$15
1	FM combiner	Winegard	CA-8800	$16
1	8-Way splitter	Holland	GSV-8	$8
A/R	Black TyWraps
1	Connector seal	Coax-Seal	25-7955P	$9
1 pk	100 RG6 F connectors	Digicon	DS6_100	$32
1 pk	100 Quick-Tye Nail	Vanco	20-06600-100	$14
1 pk	100 Coax clips		SKY32213NW	$2
				-------
				~$500

Suppliers

Electrical Supply of Milford

Marlin P. Jones Associates

Solid Signal

Tech Tool Supply

Warren Electronics Distributing Co.

Tooling

Having expended a lot of effort to extract signal out of the air did not want to lose it due to poor coax connector termination. Coaxial TV distribution use F series connectors. Unlike other types of coaxial connectors there is no center pin. Inner conductor of coax connects directly to female receptacle. Connector outer shell provides threaded fitting and extends shield. Key to good high frequency operation is to minimize signal perturbation introduced by connector.

F connectors fall into two broad categories, crimp and compression. Crimp style connectors slide over shield under outer jacket. A ring is crimped over cable jacket making electrical contact between shield and inner portion of connector. The problem with crimp connectors is crimp has multiple faces while cable is round. This results in unequal contact between connector and shield. Crimpers come in two styles narrow and wide. Typical bargain store crimpers are only about a 1/8 of an inch wide, commercial quality crimper is about ½ inch.

The best F connectors are compression. Compression style connectors have been adopted by the Satellite TV industry, as frequencies they use extend much higher then OTA or Cable. Compression connectors consist of inner and outer concentric sections. Compression tool pushes both sections together with great force resulting in high quality 360-degree contact with shield.

I decided to use compression connectors. Purchased Ripley Universal-FX compression tool ($55) and Cable pro PSA596 coax stripper ($25). Stripper makes precise cuts to remove outer jacket and inner insulation. Another handy tool is Holland CI-1 F-connector wrench ($5). Wrench is convenient for tightening F connectors in tight places.

When purchasing compression tool be sure it is correct model for specific brand of connector you are using.