Monthly Archives: December 2015

Icom IC-R72: a repair story

Icom-IC-R72-Front-Mehdi-Asgari In this post I’m going to tell you how I repaired my Icom IC-R72 receiver. Although it’s about a specific device, the logic and methodology applies to all radios.

I bought an Icom R72 from a friend for about $200. At first, I just checked 7.0MHZ (40 meter band) and 21.0MHZ (15 meter band) and it was OK. After some time, I tried to listen to some ham radio on 20 meters (14.0MHZ) and it was deaf! I checked everything: antenna connectors, balun…everything.

With some trial and error, I found out that it was deaf from 11-15 MHz. With the help of the members of “Icom R72” Yahoo Group, I found one of the usual suspects: bandpass filters’ switching diodes.

I took a look at the service manual and apparently this radio uses multiple bandpass filters for different frequency ranges.

Schematic-Icom-R72-1

As you see in the above picture (grabbed from service manual), one of the bandpass filters is for 11-15 MHz range–that’s the range where my radio was deaf.

Note that there are multiple ways to test that a radio is deaf at a frequency. One of the simplest ways: connect an antenna or even a long wire to the antenna socket of radio. The noise level should increase; if not, there’s a problem.

Schematic-Icom-R72-2

After testing diodes with a multimeter, I found out that D31 is faulty. Almost all multimeters have a diode-test functionality.

I replaced it. The original diode was 1SS53, but I used a 1N4148 which is very common and found everywhere. Now I have a working radio! 🙂

If you have a radio that’s deaf at a frequency range, there is probably a problem in bandpass filters.

Here are some internal pictures of my Icom IC-R72:

IC-R72-Internal-IF-Stage-Mehdi IC-R72-Board-1 IC-R72-Board-2 Icom-IC-R72-Open

I should thank my friend and electronics mentor, Saeed (EP2LSH) who always helps me in my electronics adventures.

Mehdi Asgari, the author of this post, is a regular contributor to the SWLing Post. Mehdi lives in Tehran and is an active member of the EP2C amateur radio club.

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1989 RCI Christmas Special: a studio recording

December 24: Tune in NDR’s annual Christmas greetings program on shortwave

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Many thanks to SWLing Post reader, Harald Kuhl, who writes:

As in past years, German broadcaster NDR will transmit its domestic Xmas greetings program for sailors, Gruß an Bord (Greetings Aboard), on shortwave, December 24th.

Here are the frequencies from the official NDR press release [reception reports are encouraged]:

From 19.00 until 21.00 UTC (20.00 until 22.00 clock CET) on December 24, 2015:

FREQUENCY DESTINATION
6185 Atlantic – North
11650 Atlantic – South
9830 Atlantic / Indian Ocean (South Africa)
9885 Indian Ocean – West
9810 Indian Ocean – East

From 21.00 to 23.00 UTC (22.00 to 24.00 clock CET) on December 24, 2015:

FREQUENCY DESTINATION
6040 Atlantic – North
9655 Atlantic – South
9830 Atlantic / Indian Ocean (South Africa)
9515 Indian Ocean – West
9765 Indian Ocean – East

Reception reports are welcomed at [email protected].

Here are direct links just in case NRD changes a frequency:

http://www.ndr.de/info/sendungen/So-empfangen-Sie-die-Gruss-an-Bord-Sendungen,grussanbord326.html

http://www.ndr.de/info/sendungen/Gruss-an-Bord,grussanbord306.html

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Fessenden Christmas Eve Commemorative Transmissions

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Embedded image permalink

This was reported in the ARRL Newsletter:

Brian Justin, WA1ZMS, will again put his 600 meter Experimental Station WG2XFQ on the air on for a Christmas Eve commemorative transmission. WG2XFQ will transmit on 486 kHz from Forest, Virginia, to mark the 109th anniversary of Reginald Fessenden’s first audio transmission. Historic accounts say Fessenden played the violin — or a recording — and read a brief Bible verse. It’s been reported that other radio experimenters and shipboard operators who heard Fessenden’s broadcast were astounded.

Justin will conduct a run-up to this year’s event starting at around mid-day Eastern Time on December 23. The “official” Christmas event will begin on December 24 at 0001 UTC (the evening of December 23 in US time zones) and will continue for at least 24 hours. Justin said he plans to repeat the commemorative transmissions on New Year’s Eve and on New Year’s Day.

Fessenden’s transmitter was an ac alternator, modulated by placing carbon microphones in series with the antenna feed line. Justin’s homebuilt station is slightly more modern, based on a 1921 vacuum tube master oscillator power amplifier (MOPA) design. Listener reports are appreciated and may be sent directly to Brian Justin, WA1ZMS, at his QRZ.com address. (Brian Justin, WA1ZMS, built this replica circa-1920 transmitter, capable of CW and Heising modulated AM. Photo by Brian Justin)

While I have not heard Brian’s transmission before, I have actually heard a transmission on the experimental frequencies between 465 – 515 kHz. I never expected to be able to hear anything due to extremely high local noise, but one night the propagation gods smiled upon me and the evening was exceptionally quiet. I listened on my Elad SDR receiver over and over to the Morse Code signal which was extremely weak, but mostly readable. I confirmed with Multipsk software, verifying I was indeed hearing one of the experimental stations out of Connecticut.

For information regarding the 500 KC experimental project you can follow this link.

Why not give a listen? You just might be surprised like I was to hear something on this band, and you could add a little Christmas Eve radio memory to your collection!! 73, Robert

Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.

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WTWW Christmas Shortwave Radio Picture Contest

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Yes, though I'm not entering the contest, I am getting into the spirit of the season!

Though I’m not entering the WTWW contest, I *am* getting into the spirit of things!

(Source: WTWW via David Korchin, K2WNW)

It’s Christmas music on International Shortwave Radio Station WTWW. We want the shortwave radio to take the place of the electric train under the Christmas Tree! We are asking for pictures of your shortwave radios – the most festive picture wins! Include yourself, friends and family, include the Christmas tree, or deck your radio with boughs of Holly and all things Christmas!

Send your pictures to [email protected] for the chance to win the Grand Prize – a TW 2010 Antenna complete with the quadra stand and custom carry bag! During the week we are starting on 5085 kHz at 7pm CST until 11pm CST. On the weekends we are starting at 1pm CST on 9930 kHz until 7pm when we change to 5085 kHz and it will go until late into the night.

Blow the dust off of those classic radios and get them out of the closet or attic and Tune In for Bing Crosby, Montovani, Dean Martin, Burl Ives, Mannheim Steamroller and many more. There is nothing like the sound of Christmas music coming out of the speaker of a classic shortwave radio.

We will even accept creative pictures of not so classic radios and newer radios including SDR’s that look festive and capture the spirit of Christmas. We also love and welcome videos with WTWW playing in the background. If you think your radio can make Santa smile, then send us your picture – you could be our big winner! Other prizes will be announced as we go along.

[email protected]

or

WTWW
P.O. Box 102
Lebanon, TN 37088

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Wired: Inside Bang & Olufsen

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Beolit 39 from 1938, B&O’s first Radio in Bakelite (Source: Wikipedia, image by Theredmonkey)

On the topic of beautiful radio design, I just read this Wired Magazine article which features photographer, Alastair Philip Wiper.

Wiper has been researching the Danish consumer electronics company Bang & Olufsen for his upcoming book, The Art of Impossible: The Bang & Olufsen Story. He was granted unprecedented behind-the-scenes access to B&O, where he learned about the company’s design philosophy, process and history. Here’s a short excerpt from the article:

“In the mid-1950s, design greats like Arne Jacobsen began experimenting with new materials and colors, galvanizing a wave of mid-century modern Danish furniture makers. Everything was sleek, teak, and handsome—it still is—but exhibits showing off the new pieces had a curatorial problem: no one was making modern radio cabinets, forcing curators to display decidedly outdated designs alongside the stylish new furniture. The technology definitely needed a major overhaul.

Bang & Olufsen joined a handful of radio manufacturers in rising to the challenge. The two men spent a few years doing research and working with architects and designers to design devices as beautiful as they were functional—an approach widely taken for granted today but novel at the time[..]”

I encourage you to read the full article at Wired.com and view some of the photographs in their online gallery. If you’re not familiar with B&O design, do a simple image search online.

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Video: How The Teleprinter Works (1940)

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Telegraph

(Source: Stephen, G7VFY, via the Southgate ARC)

Produced by the GPO Film Unit. Models are used to demonstrate the working of a teleprinter. Shown is how the pressing of a key on the keyboard generates a five unit teleprinter code, is then transmitted as a serial code to the teleprinter line and finally is decoded to select the correct character on the type wheel of the printing mechanism of the receiving teleprinter.

https://www.youtube.com/watch?v=HcMHam54EOI

Click here to view on YouTube.

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