Tag Archives: DSP birdies

Radiwow R-108: Tracking down mediumwave/AM birdies

As I mentioned in a post yesterday, I’ve been spending time with the Radiwow R-108 in an effort to give it a proper evaluation.

One quirk that has been a little hard to pin down is the occasional DSP birdie on the mediumwave band. [BTW: A “birdie” an unwanted internally-generated noise which, in this case, manifests itself as a variable squeal. Click here to learn more.]

When I first received the R-108, I noticed that each time I turned it on while tuned to the mediumwave (AM broadcast) band, I’d hear a temporary birdie/squeal that would last anywhere from two to seven seconds. After the initial noise, the squeal would go away.

During long (one hour plus) listening sessions, the squeal would sometimes reappear for a few seconds seemingly at random.

Turns out, there’s a pattern that I overlooked.

Yesterday, I turned on the R-108 and a birdie was present on 1600 kHz. Unlike previous listening sessions, the variable squeal was persistent–it didn’t go away after a few seconds. I pulled out my phone and took a quick video (moving quite far away to show that my phone wasn’t the source of noise):

Click here to view on YouTube.

There were two factors I think may have been responsible for the persistent birdie:

  1. The broadcast signal on 1600 kHz was weaker than normal
  2. The R-108 battery was at 50% or less

Perhaps the battery has nothing to do with this, other than it might have had a slight negative impact on the receiver sensitivity?

Still, my observations confirm that when the battery is fully-charged, the birdies are overall less prevalent.

I tuned off of 1600 kHz and the the birdie disappeared. Even on 1590 kHz or 1610 kHz where there were only faint signals, there was no birdie.

I should note here that 1600 kHz is home to my favorite regional AM station, so quite often when I turn on the R-108, it defaults to 1600 kHz (hence the reason the birdie seemed to plague me).

I then tuned down the dial in 10 kHz steps until I noticed another persistent birdie on 1200 kHz:

Click here to view on YouTube.

The birdie on 1200 kHz was fainter than the one on 1600 kHz–perhaps half the intensity.

The pattern seemed way too familiar, so I looked into the SWLing Post archives and discovered that the Sangean ATS-405 also had birdies in the same locations on the MW dial.

Here’s a video of the ATS-405 birdie on 1600 kHz:

Click here to view on YouTube.

Obviously, the ATS-405 and R-108 either share the same DSP chip, or the design/implementation is similar.

I checked the R-108’s entire mediumwave band and discovered one more birdie on 800 kHz, although quite faint:

Click here to view on YouTube.

So far, I haven’t had the time to do a full survey of the shortwave bands to see if the birdie is present on HF as well.

I know that there are a few other R-108 owners out there who took advantage of Radiwow’s special pricing on pre-production models to do initial reviews. Please comment if you have also noticed birdies or any other quirks on your R-108 sample.

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The C. Crane CC Skywave SSB: first production run review

[IMPORTANT UPDATE (October 21, 2018): Please note that C. Crane have addressed issues that I found in the first production run of the CC Skywave SSB. Click here to read the update and click here to read my full review of the CC Skywave SSB.]

Just last month, the little radio that I found most exciting this year hit the market: the C. Crane CC Skywave SSB.

Why the appeal for me?  Frankly, since I do most of my portable radio listening while traveling, and since I typically travel out of one bag, having a compact radio with performance and features is an absolute must in my world.  Up to this point, the original CC Skywave is the radio I often choose when traveling, as it packs so many useful features: AM, FM, Shortwave, AIR band, Weather Radio, and like any good travel radio, clock, alarm, and sleep functions, lacking only SSB mode.  So it goes without saying that I was excited to see its newest edition.

The CC Skywave SSB

What follows is an account of my experience evaluating CC Skywave SSB production units, and a brief summary of their performance.

My hope is that this summary review will help readers with purchase decisions. Note that this is merely preliminary to an extensive, unabridged review that will appear in a future issue of The Spectrum Monitor magazine, then in the SWLing Post the following month.

Pre-production Skywave SSB

As many readers know, I was sent a pre-production model of the Skywave SSB for evaluation this summer.

As I mentioned in my sneak peek and reiterated to a number of inquisitive readers: I never base a product review or comment upon pre-production radios. I don’t comment about the performance of the pre-production model for an obvious reason: pre-production radios are quite simply not the versions that ship to customers upon the product release.

Now that the production model has been in the wild for a few weeks, I feel more at liberty to talk about my experience with the pre-production Skywave SSB.

In short: I have been very pleased, indeed, with the pre-production model’s performance. In terms of features, it is a nice incremental upgrade from the original Skywave. In terms of performance, it’s also tweaked in the right direction. As an early adopter of the original Skywave, I’ve been truly enthusiastic about this evaluation pre-production model.

All the notes I took while evaluating the pre-production Skywave SSB were made for C. Crane so they could hopefully implement any changes or address concerns prior to starting the first production run. But the truth is, I found the pre-production model in my possession to be quite solid, so my suggestions were minor.

Putting my pre-production model aside, I ordered an actual production unit on C. Crane’s website just like everyone else.

C. Crane kindly dispatched my unit as soon as they received the first production batch from the factory so I could get to work on the full review.

Quirks with the first production units

I was eager to get started on the review of the Skywave SSB, so as soon as I received it, I did what I always do: compared it with other radios.

I make my comparisons, by the way,  at least fifty yards from my house to separate the radios from any inadvertent sources of local noise.

Production Radio #1

My first comparison was with the Digitech AR-1780 and the original CC Skywave. I quickly noted that the Skywave SSB was very slightly less sensitive than the other radios. I had tested the pre-production unit enough to know that the Skywave SSB’s performance should at least be on par with the original Skywave.

Upon careful listening, I discovered the production unit had a very faint, internally-generated whine on some of the shortwave bands; when tuned to marginal signals, this whine manifested itself as variable background noise. Between signals it was audible as a faint background whine, hardly noticeable. With that said, the whine was most notable while tuning––since the Skywave SSB mutes between frequency changes, the whine was most conspicuous during audio recovery.

The pre-production unit had no trace of an internally-generated whine. Audio was very clean in comparison.

Here’s a sample of the first production radio being tuned down from 10,000 kHz in 5 kHz tuning steps:

Here’s a sample from the pre-production unit:

Hear the whine in the first sample? Yes, so do I.

I contacted C. Crane promptly, and to their credit, they immediately dispatched another unit from inventory, via UPS Next Day,  along with a return label to send my faulty unit back to their engineering team.

Production Radio #2

The second unit arrived while I was on Thanksgiving vacation, but was sent to me directly at my hotel.  The day I received the replacement Skywave SSB, I put it on the air. The first listening session with it, alone, revealed that this unit did not have the internally-generated whine, however, this unit had issues with sensitivity. All of my comparison receivers were outperforming this Skywave SSB on the shortwave broadcast bands. When I compared it with the pre-production Skywave SSB unit and the first production unit, the second production unit was about four to five S-units less sensitive. Odd.

I sent both production radios back to C. Crane with detailed notes and sample recordings. Their engineering team confirmed my findings and started looking into the variations in QC and double-checking their inventory to make sure none shipped with these problems.

Production Radio #3

A few days later, I was sent a third production unit. After putting it on the air, I immediately noticed the same faint noise characteristics of my first full production unit, which is to say, the notorious whine.

Once again, I contacted C. Crane.  This time, I requested that no less than three radios be sent to me, and they kindly expedite the request.

Production Radios #4, #5, and #6

Yesterday, I tested all three radios. What follows is a quick assessment of those radios:

Performance

In a nutshell, the three production units I tested yesterday performed better than my second and third production radios on all bands. Strictly in terms of sensitivity, these were on par with the pre-production unit.  Very good.

But with that said, even the last three production units I received had internally-generated noises that I couldn’t help but notice. Disappointing.

At this point, I must assume these noises are prevalent throughout the first production run since all but one of the six CC Skywave SSB production units I tested have it. Meanwhile, the only one that didn’t have the noise had serious sensitivity issues.

Noises

Yesterday, I spent two full hours searching for birdies (internally generated noises) and other anomalies on the three CC Skywave SSB production units I received Monday. Each radio’s noise location varied slightly (within 20-40 kHz). The following locations are roughly the average of frequencies:

Birdies

Birdies are a fairly common occurrence among sensitive receivers, and the CC Skywave SSB has about an average number. The birdies I noted are outside the space where I do my broadcast listening:

  • 2,305 kHz
  • 9,220 kHz
  • 11,520 kHz

Background audio whine/tone

All of the production units (save Radio #2) have a very slight audio whine present––either via the internal speaker or headphones––on certain portions of the spectrum.

In my first full production unit, I believe this whine may have slightly affected the unit’s overall sensitivity. On the last three production units, it didn’t seem to have as much of an impact on overall sensitivity.

The whine is still there, however, and occasionally when tuned to a weak signal within one of these zones, other faint sweeping noises could be detected in the background.

Sometimes it’s even more noticeable when the broadcaster is weak and is located within one of the whine zones. Here’s an example of 10 MHz WWV time station comparing the original Skywave with the Skywave SSB. Note that yesterday we had terrible propagation due to a geo storm, so WWV was very weak indeed.

Listen for the sweeping tones:

Here are the frequency ranges where I noted the background whine:

  • 7,830 – 8335 kHz
  • 8,610 – 8,690 kHz (note: very faint)
  • 9,770 – 10,415 kHz
  • 11,585 – 11810 kHz

Another oddity is a noise I found prevalent on CHU Canada’s 7,850 kHz frequency. I’m guessing it may be due to the combination of a DSP birdie on top of a relatively strong broadcaster.

Here’s a video comparing the original Skywave with one of the production models:

I noted no birdies or noises on the mediumwave band. The FM, AIR band, and Weather frequencies perform beautifully.

Summary:  The bad news––and the good

At the moment, it appears the first production run of the CC Skywave SSB has some challenging QC issues. Therefore, unfortunately, I can only recommend it at present if you’re willing to check your unit very carefully for any of the internally-generated noises I noted above.

If, however, you’ve already purchased a Skywave SSB and have noticed the noises, then please contact C. Crane. I’ve been a C. Crane customer for many years and I’m confident they will take care of your issue.

This being said, the truth is, I sympathize with C. Crane. It must be challenging to get things right and truly consistent on the first production run of a radio––especially on a tiny compact radio like the Skywave SSB.  It must be especially hard to keep noises out of the audio chain when so much is crammed into such a tiny package.

I fully suspect these issues will be sorted out in the second production run which, of course, I will test and review.

But the good news, and it’s sincerely good news, is this:  if C. Crane can produce a CC Skywave SSB as good as the pre-production unit, they’ll truly have a winner.  So let’s keep our fingers crossed that C. Crane can do it again…and again.

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DSP noise may come from clock and data line harmonics

ATS-405-9580kHz

In response to our review of the Sangean ATS-405–which noted DSP noises on 800 and 1600 kHz–SWLing Post reader, Steve Yothment, comments:

“Yes, modern radios usually have a micro communicating with the DSP IC through I2C communications.

The inter-IC communications includes a clock and data line. The clock for I2C is typically 400 kHz nowadays. Harmonics from this clock line are probably the source of the interference.

The manufacturer should have designed the product to ensure that this interference does not occur. It may be that they resolved it at one time but with limited manufacturing quality and component substitutions that often occur in mass production, the problem is occurring now even though it may have looked OK earlier in development. At least, that is my experience with such things. (I used to design car radios for the Panasonic Company.)

You can learn more about the I2C bus at https://en.wikipedia.org/wiki/I%C2%B2C.

Many thanks for your comments, Steve! I recall a similar metronomic sound on another DSP-based radio, but can’t remember which model. I need to dig through my reviews as I’m sure I noted this. I believe checking 400, 800 and 1600 kHz will become a standard checklist item when I review DSP-based radios.

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