Create an Old-Timey Radio Feel
Alan Peterson, a longtime Radio World colleague who works for the Radio America Network, writes about an antique radio in the Network’s lobby. The beautiful old General Electric floor radio you see in Fig. 1 isn’t functioning but it is the centerpiece of the lobby of the network, based in Arlington, Va.
|Fig. 1: Turn an old-time radio into a holiday jukebox.|
Throughout the year it sits silently, looking majestic and historical, enjoying its retirement. But once a year, during the holidays, it magically comes to life, playing seasonal tunes 24/7 for guests and the front office staff.
Ok, it’s doesn’t run by magic, Alan admits. Turn the cabinet around and you would find a spare office computer inside running Rivendell Radio Automation, packed with 11 hours of Christmas tunes and connected to a KRK Rockit 5 monitor speaker.
With the bass bumped up a bit and placed against a wall to spread the sound, and a yellow bulb behind the dial, the illusion of a comfy old AM parlor radio at Christmastime is complete.
The radio is owned by Fred Gleason, the network’s chief engineer (who is also the lead developer of the open-source Rivendell software). Assistant Chief Alan Peterson breathes the holiday magic into the old chassis every year.
The takeaway? You can create a bit of fun for your staff and visitors over the holidays next year by placing an old receiver or jukebox as a prop in the lobby of your station. An automation computer is unnecessary; this can be done with WinAmp on a junk computer, or by just connecting a portable MP3 player to an amp attached to the cabinet's speakers.
For information on Rivendell Automation, visit www.rivendellaudio.org. And email me your own fun ideas for creative lobby displays, for Christmas or anytime. I’m at firstname.lastname@example.org.
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|Fig. 2: Use this assortment of parts to build an RF MOSFET tester.|
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Frank Hertel of Newman-Kees RF Measurements and Engineering writes in with a quick easy project, one that most every engineer will want to build.
|Fig. 3: Non-Destructive Go/No Go Mosfet Tester.|
(Click to Enlarge)
If you service RF amplifier modules as used in most of today’s solid-state AM and FM transmitters, you will come to know that sometimes a MOSFET doesn’t blow up when it fails. Over time, Frank began to recognize that the “gate” junction of a MOSFET could become “leaky” — still working but with degraded performance. However, a “leaky” gate can be tricky to diagnose.
Some repairs are akin to “throwing the baby out with the bathwater” in that some individuals will simply replace all of the MOSFETs. Good (and expensive) MOSFETs end up being thrown away.
Frank doesn’t like using this “shotgun approach” when doing repairs, given the cost of several hundred dollars each. It’s also a personal thing for him to not waste. Frank’s simple project will give you a method to verify the “usable” performance of the RF MOSFET in question.
You likely have all of the parts somewhere in your shop. If you don’t, a visit to your parts store will produce everything you’ll need for around $10 or so.
|Fig. 4: Brads and buss wire serve as solder points for the components.|
Construction can be simple. Frank used a small block of plywood and some 1-1/2-inch brass brads as the solder points, as shown in Fig. 2. The resistor values are on the schematic in Fig. 3.
Build it any way you desire; layout is not critical. Frank chose to use the old “breadboard” technique, which reminds him of the “good ol’ days” and satisfies his desire to avoid buying an expensive enclosure.
As you use the tester you will become familiar with its use — and how a good vs. questionable/bad MOSFET will react.
Thanks, Frank, for a great little project that will save the station money.
|Fig. 5: As built, with components labeled.|
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Author John Bisset has spent 43 years in the broadcasting industry and is still learning. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award. He works for Elenos USA.
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