Many stations and contractor engineers need to provide a public e-mail address on their Web site so users can contact them. However, leaving your full address in print or even using a regular link like "E-mail Me!" but using a "mailto:firstname.lastname@example.org" in the HTML code will inevitably let your address be harvested by a "spam bot." Soon enough, you'll be drowning in spam.
Even getting fancy often doesn't work; making your address read "yourname at yourstation dot com" won't do, as the spam bots are constantly refined to account for such tricks.
When a link is actively clicked on (something spam bots can't do), the browser acts as if a real e-mail address was there; the user's e-mail program of choice will open to compose a message to a real address.
It's a dirt-simple process. Just go to www.jracademy.com/~jtucek/email/index.html and follow the steps. To see this in action, go to Aaron's site's contact page: www.broadcastsignallab.com/contact.php3
Remember, this only works at the critical junction: keeping your address off the spam lists in the first place. If you're already getting a lot of spam, it's too late; this process will do nothing for you. You'll need to get a new address and be more vigilant in protecting it in the future.
Aaron Read is a staff engineer at Broadcast Signal Lab in Medfield, Mass. Reach him at email@example.com
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Walt Jamison is retired after 30 years with Fisher Broadcasting, now Fisher Communications. We met after I gave a talk to the Society of Broadcast Engineers Convention in Seattle a couple of years ago.
Walt wrote with comments about the July 16 Workbench column, the subject of which was transmitter cooling. Although he agrees with what was written about the importance of moving an adequate amount of cool air through a transmitter, Walt is not a fan of thermostat-controlled exhaust fans.
During cool weather, the on-off cycle of the fan causes temperature cycling of the transmitter components. Now that ceramic envelopes have replaced glass for power tubes, Walt expects that the temperature cycling is more serious for solid state transmitters.
Walt's recommendation: a proportional damper combined with a constantly running blower, to maintain a positive pressure across the transmitter and in the building and a constant temperature in the transmitter air space.
In addition, Walt has used high-efficiency bag filters to filter the outside air, greatly reducing the need for regular cleaning of the transmitter air passages. A pre-filter just ahead of the bag filters will keep the bugs and large pollen particles from clogging the bag filters. This arrangement has eliminated the costs of air conditioning in areas where the maximum summer temperature is well below the maximum operating temperature of the equipment. Reach Walt at firstname.lastname@example.org.
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If you've never worked with Continental's J. Fred Riley, you've missed a real treat.
J. Fred has an encyclopedic knowledge of transmitters and their sites. That's why he's such a resource in the company's field service division.
When he saw the ventilation "hood" in the July 16 issue, he was quick to point out that the hood violated one of Riley's Ruthless Rules of Radio Realism: never connect a transmitter exhaust to a duct.
To be fair to the engineer who contributed that picture, the hood doesn't really "connect" to the transmitter; it sits about an inch or so above the top of the transmitter.
(click thumbnail)Fig. 1: J. Fred Riley reminds us to keep our transmitters ventilated. (Used with permission of IDT-Continental Electronics)
J. Fred's point is well taken, however. If anything happens inside that ductwork to block the flow, the transmitter is starved for air. Use a cooking hood to channel the air out and allow the air to spill over in the room should the duct become blocked.
He also points out that because most transmitters (right or wrong) use air pressure sensors instead of air flow sensors, you can have lots of air pressure, and no air flow.
Fig. 1 summarizes J. Fred's point and leads us to a story.
One summer, Cap Cities called J. Fred into a station to consult on why a transmitter constantly was losing parts. When he and the engineer got to the transmitter site and the chief opened the door, the door jumped into the building. You could hear the "swoosh" as the partial vacuum inside the building was relieved.
The building held an FM and TV transmitter, both plumbed through shared ductwork to the outside. The exhaust ductwork was beautiful. There was even an exhaust fan inside the ductwork. But nowhere could J. Fred find an air inlet.
Finally, in the back of the building, there was a half-block missing in the cinder block. Rebar inserts had been added to keep out intruders. A TV transmitter and a full-power FM, and the only inlet air supply was a hole half the size of a concrete block!
Keep J. Fred's cartoon in mind. If you find your transmitter is eating tubes or losing components due to excessive heat, check the ventilation.
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Benjamin Davis writes, "By all broadcast engineering standards, I am a rookie." However, he tends to read a lot, when he can find the time. In his note, Benjamin remarks that he recently found back columns of Workbench on our Web site.
In one of the archived columns, I asked if anyone had any suggestions for inserting ground rods into the ground. Benjamin has done a few grounding jobs; and believe it or not, sinking ground rods can be an easy task.
After you find the spot you would like to place the ground rod, pour a gallon of water in the spot. Let it soak into the ground for about five minutes. Place the end of the rod on the watered spot, and start working the rod up and down into the ground, using your hands in a vertical motion.
A 10-foot ground rod will normally take less than five minutes to go down, not including the pouring of water and waiting for it to soak in. In cases where the earth is densely packed or composed of clay, you may need to remove the rod and add more water.
Benjamin's method is safer than trusting someone with a sledgehammer or having to swing a hammer from a ladder. It's also less expensive than renting a jackhammer.
Davis is an assistant engineer for Regent Communications of Evansville/Owensboro in Indiana.
Submissions for this column are encouraged, and qualify for SBE recertification credit. Fax your submission to (703) 323-8044, or send e-mail to email@example.com