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by Kent Britain, WA5VJB A Cheap And EZ HDTV …

Here s an inexpensive way of helping along that newDigital TV converter you just got with the governmentHD converter coupon you requested. And the goodnews is that this antenna (Photo A) is not limited to just DTV,but will also work well with the UHF low-power analog andtranslator stations which are not covered by the new laws (see Countdown to Digital Television elsewhere in this issue formore on the topic).Haven t gotten a converter yet? First make sure you pay aquick visit to , fill out the on-line form, andin a few weeks you ll get your coupon for $40 toward the pur-chase of a converter. Not connected to the Internet? Then youcan call 1-888-DTV-2009 (1-888-388-2009) and apply for amail-in form. The HDTV coupons work like credit cards andare tracked by address, so you can apply for your parents, grand-parents, great aunt, etc. Just use their address to help them getready for the switch over. As I mentioned last time, when choosing your converter youreally want a model that has an antenna bypass switch.

MHz for TV Channel 58, the reflector is too long, and too far back, so I’ve added the second reflector element, which is tuned to the higher end of the band.

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Transcription of by Kent Britain, WA5VJB A Cheap And EZ HDTV …

1 Here s an inexpensive way of helping along that newDigital TV converter you just got with the governmentHD converter coupon you requested. And the goodnews is that this antenna (Photo A) is not limited to just DTV,but will also work well with the UHF low-power analog andtranslator stations which are not covered by the new laws (see Countdown to Digital Television elsewhere in this issue formore on the topic).Haven t gotten a converter yet? First make sure you pay aquick visit to , fill out the on-line form, andin a few weeks you ll get your coupon for $40 toward the pur-chase of a converter. Not connected to the Internet? Then youcan call 1-888-DTV-2009 (1-888-388-2009) and apply for amail-in form. The HDTV coupons work like credit cards andare tracked by address, so you can apply for your parents, grand-parents, great aunt, etc. Just use their address to help them getready for the switch over. As I mentioned last time, when choosing your converter youreally want a model that has an antenna bypass switch.

2 Thecheapest converters usually don t. And that automatic antennaswitch is worth a few extra bucks. As with your VCR, when youturn off the VCR, it connects the cable or TV antenna back tothe TV set. Many of the low-cost HDTV converters saved a fewpennies by leaving off the antenna switch, but remember, notall the analog stations are going off the air. Stations running 10kW ERP or less are not required to go off the air. And, whilethe government plans to auction off TV Channels 53 to 68, notall of those channels will be going off the air. Many of the low-power and translator TV stations get to stay on until the newowner actually starts to use the frequency. And that may be alongtime in some parts of the antennas are limited in how wide a frequency rangethey will cover, so I m pulling several tricks on this one. At thelow end of the band, we have the driven element and the longerreflector. Down at 470 MHz for TV Channel 14, this is basi-cally a two-element Yagi.

3 The directors are pretty short at TVChannel 14 and are helping a little bit, but not much. Up at 700 THE ANTENNA ROOMby kent britain , WA5 VJBA Cheap And EZ HDTV Antenna ProjectPhoto A. Easy-to-build HDTV 2008 / POP COMM / 23 MHz for TV Channel 58, the reflector istoo long, and too far back, so I ve addedthe second reflector element, which istuned to the higher end of the three directors are now doing theirjob and really helping the gain of the means the antenna has more gain atthe UHF channels in the 50s than it doesin the teens, but this works out just you go up in frequency the signal hasmore path loss and the walls of the househave more loss. And even the coax itselfhas more loss as you go up in frequencyso the extra gain is put to a good 1is the pattern of this Yagi at 476 MHz for the low end of the band, andFigure 2is the pattern at 700 MHz. ConstructionFigure 3shows the lengths and spac-ings for the elements.

4 The elements canbe made from almost any rod materialabout 1/8 inch in diameter. You can use#10 to #12 copper wire, aluminum groundrod wire, tubing from a hobby store, or,my favorite, bronze welding rod as ele-ment material. Desperate? Clothes hang-er wire can even be used, but find somerod or wire made out of brass or copperfor the driven element (it s kind of hardto solder coax to iron wire).With an antenna this broad, elementdiameter is not as critical as it would befor single-frequency Yagis. For the boomI used 1/2-inch wide wood. Wood dowelalso works. I know several of you will alsoask about PVC pipe. Personally, I don tlike it, and it will look pretty ugly on theTV set, but, yeah, it works. Just paint itblack or something!Again, I want to stress that the drivenelement needs to be made from copper orbrass so you can solder the coax more eas-ily. The element spacing is designed toallow the driven element to directly drive72 Ohm coax (Photo B).

5 Now you canuse that old RG-59 or RG-6 jumper withonly one good end. Dimensions for thedriven element are given in Figure 4. UseFor one version I made a smallpedestal to get it up off the shelf a bit sincePhoto B. Close up of the coax 1. EZ HDTV pattern on UHF TV Channel 2. EZ HDTV pattern on UHF TV Channel / POP COMM / September 2008 Scan Our Web Sitemetal a few inches from the elements can detune the another version I made the boom several inches longer anddrilled holes for a U-bolt so I could attach it to a mast. But Imust confess that mine is really in the attic sitting on a card-board box. The box got the antenna a foot higher and awayfrom some electrical wires. Again, remember to point the endwith the shorter elements toward the TV 5is a spectrum analyzer plot of one of the proto-type s coverage of the UHF TV band in the Dallas, Texas, shows us virtually channeled out. At last count only twochannels do not have a signal, so the band is pretty busy.

6 Figure6 is a plot of a local UHF analog TV signal. On the left side isthe Video carrier; the noisy area is the video signal and over onthe right is the Audio carrier. Down and almost in the noise isthe Croma carrier. Kind of weak isn t it? Now you know whythe picture fades back to black and white when the TV signalis weak the TV loses the color 4. Driven element 3. Element lengths and 2008 / POP COMM / 25 CCQQ ss GGeettttiinngg SSttaarrtteedd sseerriieess nnooww aavvaaiillaabbllee oonn DDVVDDss!!Our renowned Getting Started videos have been grouped together on DVDs!Ham Radio Welcome Pak 3 in1-Three programs on one DVD for only$ Radio Horizons-An introduction for the prospective ham to what our hobby is all Started in Ham Radio- How to select equipment, antennas, bands, use repeater stations, grounding, basic Started in VHF- Intro to VHF. Repeater usage, VHF-DXing, satellites and more!VHF Specialty Pak 3 in1 Three programs on one DVD for only $ Started in Amateur Satellites- A newcomer s guidethrough the equipment, techniques and jargon of satellite Started in VHF- Introduction to VHF.

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8 AMERICANAMERICAN EXPRESS EXPRESSF igure 5. Dallas area UHF TV 6. Spectrum analyzer plot of an analog TV / POP COMM / September 2008 Scan Our Web SiteIt's a differentkind of hammagazine. Fun to read, interesting from cover tocover, written so you can understandit. That's CQ. Read and enjoyed bythousands of people each month in116 countries around the 's more than just a 's an also sponsors these world-famousaward programs and contests: TheCQ World-Wide DX Phone andCW Contests, the CQ WAZ Award, theCQ World-Wide WPX Phone and CWContests, the CQ World-Wide VHFC ontest, the CQ USA-CA Award, theCQ WPX Award, the CQ World-Wide160 Meter Phone and CW Contests,the CQ World-Wide RTTY Contest, theCQ 5 Band WAZ Award, the CQ DXAward, CQ iDX Award, CQ DX FieldAward, CQ DX Marathon and thehighly acclaimed CQ DX Hall of the the fun. Read TODAY!CQ The Radio Amateur's Journal25 Newbridge RoadHicksville, New York 11801 Please start my CQ subscription with thenext available issue.

9 Enclose payment or charge information withorder. Term and rate (check one):USAVE/XEForeign1 Year Years Years _____Address_____City _____State _____Zip _____( ) Check ( ) M/C ( )VISA ( ) AMEX ( ) DiscoverCard No. _____Expires _____IIII ffff yyyyoooouuuu eeeennnnjjjjooooyyyy AAAA mmmmaaaatttteeeeuuuurrrr ''''llllllll eeeennnnjjjjooooyyyy Please allow 6-8 weeks for delivery of first 516-681-2922 FAX 516-681-2926In Figure 7you see the HDTV signalwhich uses 8 VSB modulation (again, referto the feature for moreinformation and explanations of unfamil-iar terms). In the industry this waveformis affectionately called a Bart s Head since it looks like Bart Simpson s hair. Youcan clearly make out the Pilot carrier. Thisreference carrier for your 8 VSB demodu-lation chip is exactly 309,441 Hz, kHz above the bottom of the chan-nel. This carrier is specified to never havea frequency error exceeding 3 Hz, so theymake great calibration standards for wide-band receivers and even spectrum analyz-ers.

10 Just put your ICOM R-7000 or simi-lar radio in SSB mode and zero beat thecarrier. As an example, TV Channel 14 isassigned 470 to 476 MHz. The Pilot car-rier for HDTV Channel 14 would MHz, and usually with lessthan 1 Hz of are several mathematical waysof measuring NTSC and 8 VSB power, butthe 8 VSB transmitters are running 14 to17 dB less power. That means the digitaltransmitters only need 2 or 4 percent ofthe power to get the same coverage as ananalog signal requires that makes a bigdifference in the station s power bill at theend of the month. I saw one VHF HD8 VSB transmitter covering an entiremajor population center, and it justplugged in the the moment I don t know how thosein charge plan to transition channel num-bers. In this area analog TV Channel 8uses Channel 9 for its digital signal, butTV Channel 2 uses Channel 43 for its dig-ital signal. Over 95 percent of the digitalstations are on UHF, but there is no rhymeor reason to the channel allocated for theanalog s digital signal.


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