Tandberg Huldra 10

Tasos, SV8YM, has written about “The Mysterious Case of the Withering Filters“. This seems to affect not only ham radio transceivers, but FM stereo receivers as well.

Tandberg from the 70’s are collectors items and since I actually worked one summer at Tandberg in the early 70’s they bring back good memories for me. The latest generation of receivers (2nd version of Huldra 10, Huldra 11, and Huldra 12) had ceramic filters for the 10.7 MHz intermediate frequency for FM. It is also known that these filters deteriorate leading to reduced sensitivity over time.

SV8YM has pointed out that ceramic filters deteriorate due to DC on the terminals, especially the output terminal and that this leads to electromigration. In the Huldra 10, both filters have 7.1 V DC on the input. Filter F1 has 0 V DC on the output, while F2 has 2.1 V on the output.

Old filters (left) and new filters

As I got ready to replace mine with new Murata filters (SFELF10M7GA00-B0, 230 kHz bandwidth), I read the same warning in their specifications, which says: “For safety purposes, connect the output of filters to the IF amplifier through a D.C. blocking capacitor. Avoid applying a direct current to the output of ceramic filters.“

I also noticed that the filters had been replaced before. To be sure, I added three coupling capacitors (10 nF – 0.01 uF). This value has a reactance of 1/(2 pi 10.7e6 0.01 e-6) = 1.5 ohms which is negligible compared to the 330 ohm termination impedance. They were surface mount capacitors which is quite some upgrade as they perhaps were not even invented when this receiver was designed. They were fitted under the PCB by cutting the appropriate trace. Whether this has any long-term effect I don’t know, as the Huldra 10 at the age of 40 years is beyond its design life anyway.

My somewhat inaccurate oscilloscope measurements indicated that the passband attenuation in F1 was reduced from 7 to 4 dB and in F2 from 9 to 2 dB, in total maybe as much as 10 dB gain. FM sensitivity seems to have been restored to normal value after this replacement, so it was well worth the effort.

The three new 10 nF coupling capacitors, circled in red

The two filters, circled in red

Sverre Holm, LA3ZA, is a regular contributor to AmateurRadio.com and writes from Norway. Contact him at [email protected].

In this episode, Martin M1MRB is joined by Edmund Spicer M0MNG, Leslie Butterfield G0CIB, Bill Barnes N3JIX and Chris Howard M0TCH to discuss the latest Amateur / Ham Radio news. Colin M6BOY rounds up the news in brief, and this episode’s feature is - Book Review 2018

We would like to thank our monthly and annual subscription donors for keeping the podcast advert free. To donate, please visit - http://www.icqpodcast.com/donate

• Ada Lace Book Features Ham Radio
• Experimental Homebrew Equipment Does Not Require Type Approval
• Radio Hams Assist GirlGuides to go International
• Maplin Collapses as Rescue Talks Fail
• Shoe Tap to Morse Code
• New Swedish Driving Law to Effect Amateur Radio
• Argentinian Balloon Flight Completes 2nd Round World
• MacLoggerDX Version 6.17 Released

Colin Butler, M6BOY, is the host of the ICQ Podcast, a weekly radio show about Amateur Radio. Contact him at [email protected].

Amateur Radio Weekly is curated by Cale Mooth K4HCK. Sign up free to receive ham radio's most relevant news, projects, technology and events by e-mail each week at http://www.hamweekly.com.

It’s the IC-7610 video you’ve been waiting for…

Ray Novak, N9JA joins George, W5JDX and Tommy, N5ZNO of AmateurLogic.TV for an in depth look at the new IC-7610.

Lots of detailed information about this great new transceiver plus comparisons with the IC-7600 and IC-7300.

View on YouTube .

George Thomas, W5JDX, is co-host of AmateurLogic.TV, an original amateur radio video program hosted by George Thomas (W5JDX), Tommy Martin (N5ZNO), Peter Berrett (VK3PB), and Emile Diodene (KE5QKR). Contact him at [email protected].

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Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

I was motivated to write this today after looking at the solar flux number which sat at 67.  I don't know if I've ever seen the flux this low. I think I've seen 68 a lot, but not 67. Truly, things must be really bad.

As it would happen today, with the flux at 67,  I did my 258th SOTA activation on a summit near Santa Fe, NM that has no name, but goes by it's elevation, 8409. There are beautiful views in every direction, from the summit of 8409, and I enjoyed them immensely. With me, on my trek up the mountain, was my KX2, a 21ft. collapsible pole to support a 29 ft. piece of wire through an 81 to 1 transformer. I feed the antenna about a foot above the ground and run the wire up the pole in an inverted L configuration. The pole was propped up among the branches of a pine tree and I tied off the antenna to a close-by pine branch. I had the power set to 5 watts and tuned the wire with the KX2. I  operated CW using the Elecraft plug-in paddle and I logged with a golf pencil on a, write in the rain, index card. The temperature was a crisp 39 degrees, but the sun was shining and not wisp of a breeze. It was a good day to be on the mountain top.

I was on the air from 1642z - 1722z. I operated on 40, 30m, 20m and 17m and completed 40 QSO's in the 40 minutes that I was on the air from 8409. Also, with the flux at 67, I managed to work two EU stations, ON and EA. I heard a 9A calling me but we couldn't complete the contact. So, 40 QSO's, coast to coast in the US and 2 DX QSO's from EU was my catch for the day. Not bad for a short QRP/portable outing. Keep in mind that's with the flux at 67. I'm glad I didn't look at the numbers before I left or I might have been a bit discouraged and perhaps wouldn't have gone out at all. I would have missed the beautiful views, the warming sunshine and a QSO a minute QRP operation. I wouldn't have worked EU with 5 watts and a wire. I would have had to put off my 258th SOTA activation for another day.

The moral of this story is simple, don't look at the numbers. In fact I would recommend that you ignore them. There is plenty of fun to be had keying up your radio even when conditions, or at least the numbers, are this bad.

Keep the Faith. Go call CQ. I was glad I did.
Mike Crownover, AD5A, is a regular contributor to AmateurRadio.com and writes from Texas, USA. Contact him at [email protected].

courtesy: K4VRC Group

An interesting thread has developed recently on the e-ham.net reflector concerning the enjoyment of your radio hobby from a condo / townhouse or similar sites subjected to the typical 'no outside antenna' rules.

Rick, KB2NAT, describes the learning curve in his 'How To Overcome Some Condo Issues' post.

Amateurs contemplating downsizing to a restricted development or those finding themselves in a similar situation to Rick will likely soon be subjected to more noise, less space, more neighbours and an abundance of rules. Hopefully the comments of Rick and others will be helpful if this is your situation.

For many restricted hams, Mag loops appear to be a popular choice and one of the comments points to a good deal of information on building one for yourself. The Villages Amateur Radio Club (K4VRC)  group's 'resources' link will provide some interesting ideas for restricted antenna builders. As well, they have put together an informational presentation, full of great antenna ideas for those contemplating ways to get on the air from antenna-restricted locations.

If you live in the USA, the 'Freedom to Display the American Flag Act of 2005' has been used by many antenna-restricted hams, to legally erect their own 'antenna flagpole'! It may be an easy route for a nice antenna system for you as well.

The 'Novice Rig Roundup' Starts Tomorrow!

Just a reminder that 9 days of CW operating fun begins tomorrow afternoon. After last year's most enjoyable event, the NRR is now one of my 'must do' operating activities. You can read all about it here.

Ron's Logs

courtesy: California State Parks

If you have any interest in tuning around the international shortwave bands or perhaps are wondering what can be heard there, the daily logs of several dedicated listeners can be found in the Groups.io World of Radio as well as in Yahoo's DXLD group. I particularly enjoy the information posted in 'Ron's Logs' and marvel at some of the DX that he hears each morning from his car!




Ron lives in the seaside city of Monterey (CA) and on most mornings he makes the short pre-dawn drive to Asilomar State Beach (CA), a spectacular location on the coast.




After stringing out his 100' wire antenna on the nearby fence posts, Ron proceeds to log and record some truly exotic stuff before heading home.

Early last Fall, before being aware of Ron's daily regime, I had visited his exact location and after watching the big sea lions playing in the surf, had drooled over the location's great DX potential, little knowing that Ron had likely packed his gear up a headed home just a few hours before my arrival! I'm sure you'll be inspired to tune around the SW broadcast bands after checking out theses Group's daily posts.
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].