New England Radio Discussion Society News

Discussion of upcoming radio events.

New England Radio Discussion Society News

Postby AI2Q » Mon Feb 17, 2014 5:30 pm

New England Radio Discussion Society News
February 17th, 2Ø14


The New England Radio Discussion Society will meet again on Tuesday, February 18th, 2Ø14, at The New School on Route 1 in Kennebunk, Maine. We'll convene at 7-PM in the roundtable room. Bring something to show-and-tell for Tech Tales.

Feel free to invite fellow ham radio operators, family, and friends.


Kennebunk, Maine -- In this centennial year of the American Radio Relay League, a focus is on the amazing advances in Amateur Radio communications technology over the past century. While technical progress marks ham radio as much as it does in the electronics industry in general, Amateur Radio also maintains a unique spirit of camaraderie and union.

Regardless of the deplorable antics of some contemporary hams (and hopefully temporary ones at that), the ham spirit is as alive and well today as it was in decades past.

This fact was driven home to me recently in an e-mail exchange with GØMGX, Mark Jones of Belper, England. Mark's technical article about an Arduino-based accurate HF wattmeter called the tandem match, appeared in a recent issue of RadCom magazine. RadCom is the monthly journal of the Radio Society of Great Britain (the RSGB is also celebrating its centennial).

Not too long ago, I had read another article about an accurate HF wattmeter, authored by W7IEQ, appearing in the January 2Ø11 issue of our own QST magazine. Bill Kaune described a modern version of the venerable tandem match, first described in QST back in January 1987 by John Grebenkemper, then KA3BLO.

John's sensor and metering, a rather new departure in RF measurement for hams at the time, was rather complex. It used a logarithmic and anti-log signal conditioning circuit comprised of numerous op-amps. It was rather state-of-the-art for the time, but due to its complexity I doubt too many hams adopted or duplicated KA3BLO's project.

Bill's more recent tandem match article described the use of a PIC microcontroller. The PIC ran software that would process the tandem coupler's RF signals, and neatly sidestep the complex op-amp circuitry of the KA3BLO predecessor. It was also based on the nifty little 8-pin AD83Ø7 log amp chip, available from IC maker Analog Devices Corp.

When I read Mark Jones's tandem match article using the Arduino and the AD83Ø7, I was reminded of Tom, NV1T, a New England Radio Discussion Society frequent attendee. Tom hosted a number of NERDS sessions about ham radio applications for the Arduino.

If you're not familiar with the Arduino, it's a so-called "open-source" hardware platform that comes with a free integrated development environment, or IDE. The IDE runs on your PC and let's you cut-and-paste freeware, as well as write your own programs in a high-level language. Ask Tom about it!

As NV1T always pointed out, the neat part of the Arduino IDE is that you can immediately load the code into your little low-cost Arduino board using a USB cable, and then run it right away to see how it plays.

That's in sharp contrast to a PIC microcontroller that requires assembling source code and then "burning" a PIC chip in a separate module; the PIC chip must then be removed from the programming module and installed in the target circuit.

In any case, I ran into problems when constructing and testing my version of the GØMGX tandem match. So, with a bit of hesitancy, I sent an e-mail off to Mark, hoping he might answer a few of my novice questions about his Arduino-based tandem match article.

I was delighted to see an almost immediate response from Mark. Moreover, in the next few weeks we exchanged e-mails more than a dozen times, and Mark always replied immediately and with detailed technical support. He carefully listened to my tales of woe and made suggestions. He supplied me with requisite Excel spreadsheet formulas, and verified files I sent to him. Mark also QSPd power measurement notes between himself and VK2TIL and MØHCN.

Thanks to Mark, I got my version of the Arduino tandem match up and running in my shack.

That ham radio e-mail exchange proved to me, beyond any doubt whatsoever, that the ham spirit of yore is alive and well---and still spans continents!

Vy 73 for now,

== AI2Q, Alex


Participate in the New England Radio Discussion Society! The next roundtable is slated for Tuesday, February 18th, at 7-PM. Membership is free.

CU there!

Posts: 187
Joined: Thu Oct 20, 2011 11:36 am

Return to Events

Who is online

Users browsing this forum: No registered users and 2 guests