Tag Archives: RFI

Indoor shortwave antenna options to pair with a new SDR

Many thanks to SWLing Post contributor, Chris Freitas, who writes:

“I am thinking of the new RSP1A SDR. Would you know of a good indoor antenna that would work well with it?”

Your antenna question is simple, but the answer is complex!

First off, I think the RSP1A is a great choice as it’ll give you proper exposure to the world of SDR (1 kHz to 2 GHz!)  at a modest price.

Unlike a portable radio of course, your SDR must be connected to a PC, laptop, tablet or some sort of mini computer like Raspberry Pi. This limits your ability to easily try different antenna locations within your home compared to, say, a battery-powered portable radio. It might take some dedicated experimentation and patience.

Indoor antennas are so vulnerable to the radio noise within your home.

If you live in an off-grid cabin with no radio interference nearby, even a simple $1 random wire antenna hooked up to RSP1A’s SMA connector would yield results. I occasionally spend my summers in an off-grid cabin and it’s simply amazing what you can do with a modest setup when there are no man-made radio noises around.

Listening to the final broadcast of Radio Netherlands in an off-grid cabin on Prince Edward Island in 2012.

But how many radio enthusiasts live in an off-grid cabin? Answer: very, very few! Most of us only get to experience off-grid life during natural disasters when the electrical grid has been damaged in our neighborhoods.

The reality of indoor antennas

You’ve told me previously that you live in an apartment in an urban setting, hence you probably cope with a lot of RFI.

When an antenna is indoors, it is forced to function within this RFI-dense environment. Your telescoping whip or wire antenna doesn’t discern between radio noise and your target broadcast signal. Thus, noise can overwhelm your receiver, essentially deafening it to all but the strongest shortwave broadcasters.

And simple, inexpensive portable amplified shortwave antennas? I’ve expressed my opinions about them before. They amplify the RFI as effectively as they do broadcasters.

This is why if you had a means to put a small random wire antenna outside–even if it was simply draped outside a window–it would likely perform better than an indoor antenna. I’m guessing this isn’t an option for you, Chris.

Think loops

A broadband loop antenna (image courtesy of wellbrook.uk.com)

Magnetic loop antennas are a popular topic here on the SWLing Post for a reason: they’re one of the best frontline tools for fighting urban noise. (Here’s a great tutorial/presentation [PDF] describing how mag loop antennas work.)

While you can build an amplified mag loop antenna (like our buddy, TomL) it’s not a simple project.  Passive single turn loop antennas, on the other hand, are quite easy to build but are narrow in bandwidth (here’s a very cheap, simple passive loop project). You would likely design a single passive loop to serve you on a specific brodcast band and would have to retune it as you make frequency changes. You could build a passive loop antenna for less than ten dollars if you can find a good variable capacitor. Here’s another tutorial.

Commercially produced amplified wideband magnetic loop antennas are not cheap, but they are effective. If you’re a serious SWL, a good mag loop antenna is worth the investment.

Here are a few of my favorites starting with the most portable:

PK Loops

The PK Loop

The most affordable and portable mag loop antenna I own is the PK Loop.  I have the more compact PK Loop C-LOOP-HDSW6-18 (6 – 8 MHz), but Guy Atkins also touts the slightly larger Ham Loop which he finds tunes beyond the advertised 3.5 – 14.5 MHz range.

PK Loops are not as broad in bandwidth as the other antennas I mention below. You will have to retune the loop with any band changes and sometimes even within a specific meter band.

Click here to check out PK Loop offerings on eBay.

W6LVP Loops

The W6LVP Loop Antenna

To my knowledge, the W6LVP is one of the most affordable larger diameter amplified wideband mag loop antennas. We’ve published positive reviews of this antenna in the past.

W6LVP sells two versions of the antenna–since you’re not operating a transmitter, this $250 model would be all you need. indeed, if I were in your shoes, this would likely be the loop I purchase–very cost effective.

Wellbrook Loops

Wellbrook antennas are the staple magnetic loop antenna for many DXers.

Wellbrook loops are manufactured in the UK and have been on the market for a very long time. Their re-engineered Active Inoor Loop Antenna LA5030 would serve you well. At £240.00 (roughly $330 US) plus shipping, it’s one of the most affordable in the Wellbrook line.

Wellbrook makes a number of loops, but since you have no plans to mount this outside, I believe their indoor model would suffice.

Other loop options

There’s no shortage of magnetic loop antennas on the market, but most are pricer than the models I mention above and I know you have a tight budget. Here’s are some models we’ve mentioned on the SWLing Post in the past:

I have the RF Pro-1B and am very impressed, but it’s overkiil for your application (and twice the price of the W6LVP loop).

Fighting urban noise

Even if you build or purchase a magnetic loop antenna, you still need to eliminate as much RFI as you can on your own.

A couple years ago, our friend London Shortwave wrote a brilliant guest post about fighting urban noise. Read through his piece and try to implement as much of his advice as you can.

I hope this helps, Chris! This post is by no means comprehensive, so I hope others will chime in and comment with their experiences. Good luck fighting urban noise and I hope you enjoy your journey into the world of the SDR!

Can you help Luke identify this radio noise?

Many thanks to SWLing Post contributor, Luke Perry, who writes:

I am experiencing a issue with my shortwave reception at my part-time home. I have been helping out my mother so I have brought over my Sony portable, along with the Sony active antenna. I have a constant ‘clicking’ sound starting at about 5 kHz or thereabouts that make listening unbearable. As the video shows the problem is non-existent below 4 kHz. I tried moving the radio throughout the house thinking it could be something in the room and still get the same interference.

I was hoping that the filter on the active antenna would help but it does little to remedy the problem. I have no issues with MW or FM reception at all.

I have made a short YouTube video to document the problem in the hopes that one of the blog readers can identify it. I looked online at other instances of RFI and I could not find one that is similar. Hope that someone can help me!

Click here to view on YouTube.

After listening to the first few seconds of your recording, I thought it sounded a bit like an electric fence controller. However the interval between pops is nearly random, which suggests a different source. I suppose it’s possible a faulty fence controller could do this. I believe the only way you could defeat this noise (without shutting it down at the source) would be to use a radio with a durable noise blanker. Of course, I know of no portable radios with an NB function (though most SDRs and tabletop receivers include an NB).

Post readers: Can help Luke ID the source of this noise?  Does it sound familiar to you? Please comment!

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?