Used Ham Equipment

SMS Alerts Boost 'Ham' Radio Contacts:

Radio amateurs now have a helping hand in their quest for contacting rare or distant radio stations. 'DX Station' is an innovative SMS text message service that alerts radio amateurs when the sought-after radio station's signal is spotted on the radio dial.

In this internet age, the radio amateur hobby is still very popular, with millions of licensed 'hams' around the world. Many of them operate on the shortwave bands, where it is possible with relatively simple equipment to contact radio amateurs in distant countries.

The American Radio Relay League (ARRL) offers a range of awards and certificates for amateurs who succeed in contacting other hams in more than 100 countries. Those who achieve contacts with every country are eligible to join the coveted 'Honor Roll' - an achievement which can take decades of hard effort to obtain. Awards are also offered by the Radio Society of Great Britain (RSGB) for contact with ham stations on islands.

To assist in tracking down those elusive radio signals from far-flung corners of the globe, DX Station operates a network of automated radio receivers, which constantly monitor the radio amateur bands for sought-after stations, and then instantly sends a text message alert to those hams who have indicated their interest in contacting that particular 'DX' station.

The use of real-time text messages gives subscribers to DX Station a competitive advantage, since they can hopefully contact the distant radio station before their colleagues join the fray. Since thousands of hams may be seeking contact with a single amateur radio station, the resulting cacophony of calling stations can hopefully be avoided by being 'first to know' that the rare station is on the air.

DX Station cannot guarantee that the radio amateur will be able to contact the distant station - that is down to radio signal propagation and the efficiency of antennas and transceivers of both calling and receiving radio station. But it can certainly put the canny ham ahead of the crowd!

The DX Station text messaging service can be used on more than 800 mobile networks worldwide, and the low monthly subscription fee is easily paid by Paypal or credit card. These fees, which include a quota of text message credits, are used to maintain the network of automated radio receivers that the DX Station service relies upon for it's operation. A reduced fee trial is offered for the first month of subscription. Alert profiles are managed via a user-friendly interface on the service web-site at www.dxstation.

Adjustable voltage and polarity tester - Hack a Day

Instructables user [Rudolf] wrote in to share a handy little tool he created with ham radio operators in mind. Now and again, he found himself connecting to an unknown power supply, and rather than blow out all his expensive radio gear, he decided to put together a simple polarity and voltage tester that can be easily carried out in the field.

The tester features a pair of powerpole connectors, which are used quite often for connecting HAM gear. A PIC12F675 runs the show, acting as an adjustable comparator for detecting voltage levels. By default, his probe glows amber when the supply voltage is below 11.5V, turning green when the supply is between 11.5V and 15V. When the detected voltage is too high, the built-in LED glows a bright red. When the polarity is reversed, the LED flashes red regardless of the supply voltage.

All of these trigger levels can be set in the PIC’s code, which [Rudolf] is kind enough to include on his page, along with schematics for making your own.

Very very nice! Clean interface with the LED and power connectors, and nice design and board. I really wish this wasn’t behind instructibles though – this is a project that I wanted to check out, but due to a promise never to use instructibles, I won’t be able to. One thing I might emphasize for anyone else who wants to use the circuit is to read carefully the section detailing the voltage divider – it determines the range of input voltages that you can hook this detector up to. Thanks for this!

Posted at 1:33 pm on Jun 14th, 2011 by Adrian

Posted at 3:50 pm on Jun 14th, 2011 by Shazzamy

Seriously, I’ve got an autoranging multimeter that’s the size of a thick credit card and it also checks diodes, fuses, and reads resistance…

So, now ypu’re at that swap meet and you find a table with some transformers and power supplies. You quickly determine that the poer supply is borked due to a bad fuse, short the fuse and determine itis a 14.5 volt ac transformer and use it to determine that the transformers are actually 8k:16ohm output transformers. Serious win for the guy with the $9 pocket multimeter.

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