Tecsun S-8800 – The Birdie Problem

Recently, Tecsun announced and released onto the market the new S-8800 receiver. Thomas Witherspoon has indicated that sensitivity, selectivity and audio fidelity are very good for this new unit.

BUT…..in his post on February 12, 2017, entitled Tecsun S-8800 Update, Thomas discovered that his new S-8800 has a serious fault, one that could potentially drive radio enthusiasts mad! In tuning around the dial, he found the radio has many “birdies”. In the same post, he notes that Bertrand Stehle F6GYY also found birdies on 4 spots in the mediumwave band and 63 frequencies across the entire shortwave spectrum. Not good!

In reading the comments that followed Thomas’ post, I noted that a few writers seemed a little confused about what a birdie is and how it differs from radio frequency interference. Hopefully, the following explanation will shed some light.

The term “birdie” is, I guess, derived from the type of sounds that are emitted from a receiver having this problem. It can take on a variety of forms, like a squealing or whistling sound, or perhaps a warbling sound, or a hash noise, or indeed, even a silent carrier. In a particular radio, a birdie could appear on one or many frequencies across longwave, shortwave, mediumwave or into the VHF spectrum. And it will usually be permanently there on the same frequencies every time.

Occasionally, you will find birdies smack bang on the very frequencies where you might want to do some listening. But, unfortunately you can’t really do anything to get rid of these nuisances because the design faults are in the the receiver itself. You can test to see if what you are listening to is a birdie by simply disconnecting the antenna. If the squealing/whistling/warbling/hash/silent carrier is still there without any antenna, then it’s a birdie – an internally generated carrier by the receiver’s own circuitry.

Click here to continue reading the full story.

Rob Wagner, VK3BVW, is the author of this post and a regular contributor to the SWLing Post. He also blogs at the Mount Evelyn DX Report.

9 thoughts on “Tecsun S-8800 – The Birdie Problem

  1. James Patterson

    I reply to the “Birdie” problem with the Tecsun S 8800 model,Im supprised to read it has it.Readers may remember I posted several comments about the very first PL 660 I bought from a local importer over here in down under NewZealand.I bought it home after picking it up when paying for it.It was the Black one.Well when I switched it on and went through all the functions and bands,I noticed on all SW bands,a high pitched whistle,or gushing sound would start on a frequency I was tunned to.I would hear it starting at a low volume,then getting louder,so loud that it eventurly would drown out what ever I listened to.I noticed it was coming from inside the receiver,not a signal from outside.
    So I changed bands to other SW frequencies and noticed this Birdie or harmonic was acturly climbing through the frequencies.If I tunned higher,I would find it there after passing by the tunned frequency I had.Or lower,catching up to where I was.So I took it back,feeling rather disapointed.I checked another five radios in the presence of the importer,who was shocked at what I found and told me he had never had any returns.So then I asked to check a “Silver” model and to my amazment the one I checked had no birdie whistle or gushing sounds anywhere at all.You can expect a few birdies in every radio,its just the way radios are made,but to have a harmonic that follows you as you go up or down the frquencies and drown out your listening pleasure is not what you would expect in any good receiver.So please do a good check of all SW bands when buying a radio,even SSB was effected ,so beware all SW listeners and try to pick out a good one.Ive owned my PL660 for four years now no problems at all.I fixed a new larger dail knob to it to ease the turning while I tune it,it’s my DX radio,then I put the favourite frequencies into my trusty Sangean ATS 909X memories.

    Reply
    1. Rob Wagner Post author

      Thanks for your comments, James. Generally, I’m not what one would call an “early adopter” of new models, preferring to let others be the guinea pigs while all the bugs are (hopefully) sorted out of the gear. I think this is one case where I’ll be waiting a while!

      Reply
  2. DL4NO

    Birdies have been there since receiver technology advanced beyond audions – 0V1 or 1V1 in ham radio slang.

    Very early on birdies were produced on purpose, using a crystal oscillator on 100 kHz or 1 MHz. You could turn these oscillators on and off with a switch called “calibrator”: Multiples of the crystal frequency appeared over the complete reception range of the set. If the set could receive on 5 or 10 MHz you could tune the calibrator to zero-beat with a time signal transmitter. That is why it was so important to have these time signal transmitters on these frequencies. In WW2 many German sets relied on a 100 kHz calibrator and used VFOs, while US sets most exclusively used crystals, at least for the transmitters. If you ever see a picture of the innards of such a German set you will know why they could do it…

    These days we use digital means to set the frequency which means it is very easy to produce unwanted birdies: The digital electronics uses square-wave signals in the MHz ranges with an amplidude of typically 3 V. Compare that to the µV or nV signals you wish to receive. It is quite an art to identify *all* holes the RF comes out from the digital electronics. I know what I am taking about from my experiences with my SW mobile station.

    Another problem even plagues strictly analog sets: You distribute selectivity and amplification over several frequencies, i.e. the RF frequency you wish to receive and up to three intermediate frequecies (IF). A simple example: You last IF is 455 kHz and the set has a BFO, i.e. an oscillator on 455 kHz. Then it is easy to produce birdies on multiples of the 455 kHz, like 910 kHz or 1365 kHz – both in the medium wave band. It can get even more complicated. For example if you use a first IF of 9 MHz and a second IF of 455 kHz, you need an oscillator at 8545 kHz or 9455 kHz. Designers preferred the 8545 kHz because that avoided a birdie in the 31 m band. If you wonder about the “curious” IF frequencies used in many sets: Much of these choices came from such design decisions.

    Reply
    1. Rob Wagner Post author

      Thanks for your interesting and informative comment, DL4NO. You reminded me of many years ago, long before digital readout, when old valve receivers only offered a vague “bandspread” dial to show frequencies/bands. To work out what frequency I was on, I used an old army surplus piece of equipment called a No. 10 Crystal Calibrator. Next to the receiver, that thing produced specific oscillations on marker frequencies, and you could work out very accurately which frequency you were on – to within 1 kHz! Tedious process involved, but it worked! Another piece of surplus gear was the old BC221 frequency calibrator – similar thing. Thanks and best 73, VK3BVW

      Reply
  3. KenL

    Is the S-8800 going forward, or is Tecsun giving up? I see no sign of it on the Anon-Co site and was wondering the flaws were going to be corrected.

    Reply
    1. Troy Riedel

      KenL,

      I exchanged emails with Anna at Anon-Co about a week ago. She said Tecsun is [still] working on the problem and very soon they hope to have a [modified] version to undergo testing.

      She said there is no timetable for it to be listed on the Anon-Co. site.

      Troy

      Reply
  4. Edward

    Would the technical definition of a birdie be a signal generated internal in the receiver being picked up by the receiver? A BFO signal is not a birdie because it is necessary and desirable for the demodulation of the signal being received, yet the second harmonic of the BFO is a birdie because it is undesirable if near or on the received signal.

    Reply
    1. Rob Wagner Post author

      I would say that’s correct, Edward. My definition of a birdie is that it’s something generated that is NOT supposed to be there and is related to the limitations of the receiver’s circuit design. A BFO is not a birdie because it is designed to produce a generated signal for the purposes of demodulation. Thanks, 73, Rob

      Reply

Leave a Reply

Your email address will not be published. Required fields are marked *