Tag Archives: QRM

RadioWorld: Steps to Lower Noise Floor and Revitalize AM Radio

(Source: RadioWorld via Richard Langley)

Noise interference is the menace of all wireless broadcast communications services

Background noise interference is degrading the quality of broadcast reception, two-way communications, mobile cellphone services and every other form of wireless communications used today at an alarming rate.

The FCC and the ITU agree that the DC to 60 GHz+ wide-spectrum background noise floor is increasing as more and more unregulated electronic devices are used by more consumers in more ways every day.

While it is true that large numbers of these devices have been in use for some time, the question becomes: What can we do to lower the noise floor now that the floodgates of unregulated devices have been open for so long? Is this an impossible task? I believe the answer is an emphatic “no.”[…]

Continue reading the full article at RadioWorld online.

Disappointment when the power comes back on

Many thanks to SWLing Post contributor, Richard Cuff, for sharing this column from The Athens News. I’m sure many of us relate to Dennis E. Powell (note this is only an excerpt):

If you lose power at just the right time, it can enrichen your life

This is being written last Monday night.

Several hours after the storms of earlier in the day passed, the sun shining, the birds singing, and all apparently right with the world, the electricity went out. Because there is no cellular telephone service in my part of the county, this necessitated a drive much of the way to Athens to register a report with the power company. The power company’s outage report line is the first entry in my cellular phonebook.

[…]The evening was (and as I write this, is) cool, with a bit of wind passing through the open windows, so there was no panic, as there is when the power disappears in the dead of winter or in the 100-degree summer – both of which I have experienced. But there was no fire to build, no need to think of a reason to drive to town for a few hours in some place air-conditioned.

Instead, I remembered that just a few days ago I had pushed the battery-charge button on one of a couple shortwave radios I have around here, this one a decade-old C. Crane CC Radio SW. It has a big speaker and a pleasant sound, though it’s not the sort of radio you get to dig faint signals out of the mud. It is just right for such an evening as this. So I brought it to the living room, extended its built-in antenna, and fired it up.

Shortwave radio is like Forest Gump’s mama’s box of chocolates, and that’s part of its appeal. Poking around the dial I find some Ohio shortwave amateurs putting on a bit of a panel show, passing the mic metaphorically from one to another. Because they are shortwave amateurs, all they talk about was their shortwave equipment.

The power is out all over the neighborhood, so there is not a single static scratch, no 60-Hz whine of interference. And the ionosphere seems stable, no fading in and out of signals.

Heading up the dial, I find a station in accented but easily understood English. I have to listen for a while before I learn that I am listening to Radio Romania International. That broadcast ended, so I retune and find a cranky man and a cranky woman who are discussing how awful things are and how the only thing you can count on is gold.

Moving along, I find an impassioned man with a deep Southern accent. He, too, is discussing how awful things are – and how they soon will be especially awful for those who put their trust in gold or other things of this world.

There is a broadcast from somewhere – from the accents I’d guess the Caribbean or Africa – that features a man and woman talking spiritedly and sweetly about English idioms.

Now I’m listening to the Argentine national shortwave service, which had a talk program in English though they’ve switched to Argentine music.

[…]I do hope the power comes back. Just not tonight. Tomorrow, maybe. Or the next day.

(Note: Just as I set this to email itself eventually to the Athens NEWS, minutes after I was done writing, the power came back on. And it really was a little disappointing.)

Read this full story via The Athens News online…

Advice on cancelling locally generated noise

An SWLing Post reader recently contacted me with the following question:

“What devices work well to cancel out local RFI? I’ve been told that both the Timewave ANC-4 and a number of BHI products are all worth considering.”

Unfortunately (or fortunately, for me) I’ve no experience with outboard DSP or noise cancelling devices because I live in such an RFI-free area.

I know this reader already has a Wellbrook Loop, but he’s looking for a way to even increase noise mitigation further at his home listening post.

Post Readers: Can you help guide him?  Please comment with your experience. Is a product like the Timewave or BHI the next logical step? If not, what is?

Urban DXing: testing the Bonito Boni whip against a 30 metre longwire & the Wellbrook ALA15030

Hi there, if like me, you live in an urban environment, chances are QRM is having a negative impact on the quality of the signals you’re receiving at home. The presence of electrical noise makes antenna choice very important, particuarly if you’re planning to spend more than a few £££s on something more sophisticated than a length of wire. Recently I was considering the the purchase of a second compact antenna, for use at home in my shack and out and about on DXpeditions. I already had the excellent Wellbrook ALA1530 H field antenna, but at more than £250, it’s very costly and thus it seemed rather extravagent to buy a second one, if I could find something with similar performance for less expense. Space is at a premium at home and of course I take much of my equipment out on DXpeditions, so the Bonito Boni whip active antenna appeared to be an ideal choice. A wideband active antenna (from 20 kHz to 300 MHz) operating from 12 to 15V DC, with a very compact form-factor definitely ticked all the boxes. Furthermore, with reasonable second and third order intercept points of +55 and +32.5 dBm respectively, the Boni whip, on paper at least, looked like a pretty good buy at around £100.

 

Now, clearly, an E field antenna such as the Boni whip is not going to match the SNR provided by the H field Wellbrook ALA1530 in a noisy, urban environment. I have uploaded a few reception videos to my YouTube channel to demonstrate this, making a direct comparison of the two. However, what about the performance of the whip versus a simple longwire in an urban environment? Is there a delta in performance? The value proposition of the whip is primarliy in it’s performance, coupled with portability I suppose, but that must be considered a secondary requirement. The whip might be 10 or 15 times more expensive than a reel of cheap equipment wire, but will the reception justify the cost delta?!

Text links follow directly below, with embedded videos thereafter; you will find 3 reception videos comparing the whip and a 30 metre longwire, on shortwave and one each for LW and MW. At the end of each video there’s a section with the Wellbrook loop, just to calibrate where the longwire and whip are in terms of a much more effective H field antenna. The result? Well, there’s not much to separate the longwire and Boni whip, except on LW, where the whip prevails. A friend told me recently, if reception is rubbish at home under a blanket of QRM, don’t blame the antenna, the noise is the real problem. He was right. So, the next tests are to be undertaken out in the field, where the whip has a real chance to shine. I’m rooting for it because to have an antenna that performs as well as, or close to my loop out in the woods, yet can be packed away into a small case would be brilliant. Thanks for reading/watching/listening.



Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

Why good antennas need to be fed with good coax

Dennis Walter, of Bonito Radio in Germany, has just posted an excellent article on his blog regarding the importance of quality coaxial cable to fight local radio interference.

Click here to read his post, “Why even good antennas need good Coax cable.”