A Better TV Reception Predictor

Antennaweb.com revolutionized the concept of predicting TV reception for a new generation of enthusiasts installing over-the-air antennas. It graded reception by color and gave recommendations, if flawed, about what kind of antenna to put up. When they went conservative with the results, those who had put real work into their systems found the predictions only listed a fraction of the stations they could get.

For those who want a little more science, there’s a new kid in town. Try out TVFool.com and for the address you enter, you will get a chart of precisely calculated reception parameters. I especially like the listing of antenna heights needed for line-of-sight (LOS) and -100 dBm thresholds. You also get a marker for all those nasty co-channel allocations we have in SoCal now.

It turns out that for my home just east of La Jolla, predictions come pretty close, though I’m guessing that some transmission antennas outperform predicted levels because of what I see on my flat response receive antenna. For example, I consistently receive KCBS-DT (real channel 60) better than some locals and better than even consistent KTLA-DT 31 on my recently rebuilt Create log-periodic. In reality, there are numerous factors that I haven’t bothered to measure scientifically, but the empirical results match closely enough those of TVFool.

Making Waves: RIP Gateway Electronics

Those of us who love to homebrew and tinker have lost a friend when Gateway Electronics in San Diego closed their doors in late April. The store sold a couple of years ago, but Manny and Fong couldn’t keep the cash flow positive, and a new lessee was to take over.

Here’s why I think Gateway closed:

  • People don’t have the time to tinker;
  • The integration of electronics has become so cheap and large-scale that small-scale projects don’t have much value;
  • Specialized small electronics items can now be found online;
  • The internet has made it possible to repurpose surplus gear through auction and direct sale sites without using retail outlets; and
  • Because of all of the above, retailers additional cash streams through either technical services, web sales, or local sales of higher traffic computer gear.

My favorite Gateway find was when, while looking at their selection of LEDs at the front glass counter shelves I saw in my peripheral vision a small container of tiny mechanical clocks. These are the kind of sealed, elapsed time counters they put on very expensive equipment that allowed you to log and time maintenance. This was in the mid-1990s when KFMB-TV had in service four Philips LDK-6 Plumbicon studio cameras that made great pictures. But their camera head timers had a habit of making a terrible noise when they presumably wore out their internal gears or just lost their lubrication. Philips charged $400 each for the neat-looking devices the size of your thumb. As far as I know, the LDK-6 may have been the only product they made that used this special 400Hz clock, and they had to manage their inventory and pay tax, year after year. Having worked in manufacturing, I understand parts costs. But here they were at Gateway, small, matte black, 400Hz, 100,000 hour elapsed time counters, $5 each. I bought four and we installed at least two of them over time.

I also liked their supplies of cheap LEDs, connectors, stainless hardware, and a great line of prototype circuit boards. They also stocked all kinds of transformers, switches, basic kits, and computer cables. Some items, like used switches and some really old test gear, you might not want to take home for fear of creating more of an expediture of time and energy than a savings that good engineering practices would dictate.

Gateway wasn’t the only surplus electronics supply store in the region, but they were the only one in Kearny Mesa within a short drive from most broadcast outlets. Industrial Liquidators doesn’t really count–they’re useful for some tools and pneumatic supplies, but have very little electronics stock. Murphy’s and California Surplus continue to operate from the same neighborhood of Johnson Avenue in El Cajon, and I’ll be the first to say that they do a good job of keeping their shelves tidy enough to make hardware relatively easy to find. If you ever have to replace or install a new one of those mil-spec MS “Amphenol” connectors, Cal. Surplus has a huge barrel of them that has saved me from the misery of waiting 8-10 weeks for a new one. Willy’s Electronics in National City still stocks some hobbyist electronics supplies, but its all new stuff and you pay full retail price. There’s the monthly Santee Swap Meet, but with the internet and declining electronics hobby, it’s become more of a big garage sale. I visit once a year for a load of tools, hi-fi cables, and fresh avocados.

The king, the acme, nay, the apex of surplus electronics is Apex Electronics in Sun Valley in the heart of the San Fernando Valley in Los Angeles. I happened by there once when, during a visit to my mother-in-law’s, I took a side trip. With an acre or so of indoor shelves that must be 20 feet high and an outdoor lot of surely another couple of acres, this place is big. Good luck in an earthquake, pal. Take the virtual tour on their website. Microwave gear for pennies on the dollar, though that was before the price of copper went through the roof. If they don’t have what you want, then you should reconsider your design.


When Manny and Fong closed the Gateway doors, they handed out little pieces of paper with contact information and a promise of opening a new store. I tried to call and write to ask a few questions, but have yet to receive a reply.

What are your experiences with surplus buying? Are there other Southern California stores you know about? Tell us about it.

Big Catalina Fire Originates at KBRT

(From the CGC Communicator) A fire that started at the KBRT(AM) transmitter plant on Catalina Island near Los Angeles apparently ignited the 4,200- acre wildfire that ravaged the island’s interior and threatened Avalon, the resort’s main town. One home and six industrial buildings were lost but no one was seriously injured. The fire is expected to be fully contained by Tuesday evening.

According to a published report supplemented by information from the island, a tower contractor hired by KBRT had been warned against using a cutting torch because of dry brush fire danger.

While the station’s transmitter engineer, Bill Agresta, was inside the transmitter building and temporarily away from the work site, the contractor used a gasoline-powered circular saw to cut metal, and sparks from the blade apparently ignited the brush.

Bill reportedly said he saw a small blaze when he went outside the transmitter building. Then he ran back inside to call 911.

By the time he went outside again, the fire had moved several hundred feet downhill and engulfed the contractor’s tool truck – the blackened hulk of which remained at the site as of Saturday.

Commercial power and telco lines feeding the “KBRT Ranch” (as the transmitter site is known) were destroyed in the fire. The station resumed operations Sunday using its own power generator and CDs hand-carried to the island for programming. Joel Saxberg is reportedly at the site attempting to set up a Ku-band satellite downlink as an STL, but is said to be having trouble acquiring the satellite. As of 9:30 AM Monday, the station was off the air again, but this time voluntarily until the program feed bugs are resolved.

Meanwhile, Bill Agresta is nursing some fractured ribs suffered when one of the construction workers commandeered his tractor and accidentally ran into him during the fire melee.

May 2007 Meeting – Taste of the NAB

Larry Bloomfield brings his famous Taste of the NAB roadshow to San Diego Tuesday, May 22 at noon at TV Magic. Come see wares from some your favorite vendors and win a door prize.

Exhibitors this year:

  • Omneon media servers
  • Leader Instruments test gear
  • Blackmagic Design edit system media I/O cards
  • ESE timekeeping and interface products
  • AJA video interface and terminal equipment
  • Telecast fiberoptic transmission equipment
  • InPhase Technologies holographic storage
  • Network Electronics fiber, terminal, and compression gear
  • Henry Engineering interface devices
  • Telecast fiber systems
  • Clark wire and cable
  • DSC Labs test charts
  • SMPTE standards publishing
  • Verbatim blank media
  • ADS Tech video capture devices
  • Key Digital computer cables
  • Canon lenses

Plan to eat a free lunch provided by Canon. Lucky engineers will walk away with one of multiple door prizes donated by the roadshow sponsors. Larry’s giving away polo shirts, DVI cables, capture devices, CD media, gift certificates, and standards CDs, and other goods at the show.

Those attending will also be entered into a national drawing for prizes that include a Fluke multimeter, Burst Electronics digital video switcher, Coaxial Dynamics RF wattmeter, a copy of VidCAD software, a Radiosophy HD table radio, and a genuine Chuck Pharis Indian Head TV test pattern.

Members and guests welcome to TV Magic, 8112 Engineer Road, May 22 at noon.

CBS and Clear Channel Partner on Soledad Antenna Project

A new multiplexed FM antenna on KGTV’s Mt. Soledad site is open for business and radiating. John Rigg, San Diego market Director of Engineering for Clear Channel Communications says that his stations KMYI 94.1 MHz, KIOZ 105.3 MHz, and CBS Radio’s KSCF 103.7 MHz have been on the 4-port system since April 5 of this year.

ERI designed and built the system, an SHPX-10AC-HW center-fed 10-bay half-wave spaced array with approximately 5 dB gain. John says “ERI was chosen because their SHPX series antennas present less weight and wind load than comparable antennas from other manufacturers. Their combiner is more modular and easier to install in tighter places, specifically the attic space above the transmitters.”{mosimage}

Clear Channel and CBS have partnered before on a similar project on the site.  KIOZ and KSCF have been combined on an adjacent tower for several years. The main tower owned by McGraw-Hill Broadcasting now hosts the new community antenna. Two site developments motivated the participants to build the antenna: the need for a reduction in RF radiation at ground level due to a new residence to the west of the site, and the steep rise in rent at neighboring towers owned by Midwest Television, KFMB-FM/TV.

They now occupy a position just below the tower top, below the KGTV channel 10 antenna, but sharing the aperture of the KGTV-DT UHF array. John says that they did extensive modeling before construction to assure little interaction between those antennas. In fact, the modeling resulted in the fabrication of antenna mounting brackets out of non-conductive materials.

The quest for the master antenna began after completion of a new home two lots away, adjacent and northwest of the neighboring fire station on Via Casa Alta. Hammett and Edison studied ground level radiation at the home and determined a particular hot spot at a steel column that wasn’t going to go away unless a substantial rearrangement of radiators took place. RFR laws state that any contributor of more than 5% of the maximum permissible exposure (MPE) is equally responsible for mitigating the problem regardless of the contribution percentage. Since KFMB and its tenants KIFM and KYXY were farther away and had just completed their new combining array with low downward radiation values, they were let off the hook. Two other Soledad FM broadcasters using the UCSD-owned tower, KUSS 95.7 MHz, and KLQV 102.9, have had to temporarily decrease power to meet the public RFR guidelines.

In February of 2006, the FM broadcasters on the KGTV and UCSD towers agreed to decrease power temporarily by 25% each. The one exception was Super Class B grandfathered, normally 100 kW, KMYI 94.1 (“Star 94”), which due to a null at the site in question did not have to decrease power at all. KMYI was added to the combiner system to allow the new antenna to be installed on the KGTV main tower removing its weight and wind load contribution to the overall tower loading.

Each of the Clear Channel and CBS stations obtained construction permits in mid-2006. ERI delivered the antenna system in late March this year, and crews were waiting to erect it immediately.

John Rigg reports that their expectations regarding both the increased performance of the antennas and their decreased downward radiation have exceeded expectations. They’ve now got KMYI at 77 kW ERP and he’s happy with the coverage. He says the new antenna is higher and the pattern is cleaner than before, so they need less power now to reach their licensed contours.

For his part, Mike Prasser, San Diego Market Director of Engineering for CBS Radio, appreciates John taking the role as project leader. “He should be commended for how smooth the project went. As for the results of the project, I am extremely pleased.” He’s satisfied that they’ve mitigated the RFR issues and says that he is now working hard to get KSCF broadcasting in HD-radio, which should be up in June.

Society of Broadcast Engineers, San Diego