Two strategies to improve Sangean ATS-909X sensitivity

ATS-909XSWLing Post contributor, Moshe, writes:

“I would like to share something I noticed about Sangean sensitivity issue:
As I own the ATS909, I noticed that with fresh set of regular batteries (1.5V) or it’s power transformer, it is very sensitive.
When the voltage of the batteries drops, so does sensitivity! Which means that if one uses rechargeable batteries (1.2V), the radio will be much less sensitive to begin with.”

Many thanks, Moshe! That is a very good reason to keep fresh alkaline batteries for the 909X, or to run it on a quiet power supply. Moshe is correct–fresh rechargeable batteries can’t deliver full voltage.

Several weeks ago, a reader informed me about a modification that increases SW sensitivity by adding a 4:1 impedance transformer.

Click here to download a PDF that documents the 4:1 transformer procedure.

Note that I can’t remember who shared the PDF and am not sure who was so kind to document the procedure with photos. Any additional information would be appreciated.

Have any readers performed the transformer mod on the ‘909X with success?

20 thoughts on “Two strategies to improve Sangean ATS-909X sensitivity

  1. Moshe Ze'ev Zaharia

    Hi Thomas!
    I Have some kind of Block Diagram that shows the reason for this:
    Along the power chain, there is distribution marked as “AM 6V” and “FM 6V”, the 3V regulator is located after this distributor.
    In other words: The front end AND RF preamp is fed (After filtering and Adaptor detection) with battery voltage. So, it needs to be fed with 6V (4 rechargables will give only 4.8V when full!).
    Another thing: If the speaker sounds muffled (more noticable on AM), and distorted, Two capacitors, 470uF and 220uF in the speaker chain needs to be changed.

    Best Regards,
    Moshe.

    Reply
    1. Andrew

      Hi Moshe, which capacitor do you mean?? I have the service manual, can you tell me which capacitor should I change.
      When I bought it, I felt that sound on shortwave it is too less-brightly. I mean, the bandwith is too narrow. Looking at the service manual, I realised that the IF Filters are too narrow. That’s a thing I would need to do.
      Another thing I noticed on SW, it is that AGC is so fast, I don’t like that.
      I would like to know what mods you did.
      Thanks!!
      Andrew

      Reply
      1. Moshe Ze'ev Zaharia

        Hi Andrew!
        I Can’t recall right now the capacitor numbers, but they are located between the two audio amp’s (Two SIP IC’s).
        I Havn’t changed the IF filters since I don’t have the right equipment to recalibrate the radio.
        Try This link: http://www.davidmoisan.org/radio/sangean/909mods.html
        They have the mod for the AGC problem, and more interesting mod’s that will help you.
        For me, replacing the two capacitors made the audio far more better than when it was new.
        Another thing to notice: The black screw that conncts the antenna assembly inside the radio needs cleaning so it will induct better. and most important: follow the white wire from the antenna, it is connected to A terminal that touches AND shorts to the negative speaker terminal, put heat shrink over it and shrink it. this alone will improve reception since the antenna will not shortcircuit to the speaker terminal.
        Having said that, I think that the Sangean needs another reception test, but this time the Sangean needs to be powered properly!

        Reply
        1. Andrew

          Moshe: thks for your answer!
          One question: is your rx an ats909 or ats909x?
          I will try to find the caps. About the link you passed me, thanks! Although it is about 909 model, it will be useful for sure!
          And thanks about the issues of the screw And wire antena. I will check it!
          Andrew

          Reply
          1. Moshe Ze'ev Zaharia

            Hi Andrew!
            My radio is the good old ATS909, not the X model.
            If the radio is laid on the table, when you look at the PCB, the capacitors are located at the bottom right of the PCB.
            You will see the two audio amps (they are NOT parallel to each other), and additional capacitors located between them.
            One thing I can say: after all those mod’s, when I take the radio to work, I Am located inside A control room with PLEANTY of RFI, and still I can receive (ONLY the telescopic antenna is used), RRI, IRIB, CRI, AIR, DW, BBC, VOA.

            Good Luck, and Best Whishes,
            Moshe.

  2. John

    I have done the mod, and while it does work to increase the sensitivity on SW, it comes at the expense of some sensitivity loss on FM. A good way around this is to mount a switch so you can switch the balun in or out of the circuit. I noticed an improvement of about 2 to 4 S units on shortwave. It actually did better than the PL-660 and PL-880.

    A third strategy is to send it in to Radiolabs and have the Clearmod done. I had this procedure done on my ATS-909X in Black, and the increase in sensitivity matched the gain I got in the stock 909X with the balun mod. Also, the wider AM filter made the radio sound better, and I noticed no loss in FM sensitivity.

    73, John

    Reply
  3. Ian from England

    Thanks both Thomas and Moshe. I have rechargeable batteries in my 909X, and although where possible I use mains power, will make sure I put regular 1.5V batteries back in the unit for use away from a power point. Just a quick question – does this point apply to other radios like the PL660 too? I guess it does, purely because of the voltage – it sounds like this is where increased sensitivity outweighs the cost savings of rechargeable batteries!

    Reply
    1. Moshe Ze'ev Zaharia

      Hi Ian!
      I have just looked over at the Tecsun S2000 Block Diagram, if the PL660 is designed the same, you can use rechargeables without any worry.
      The power to all radio circuits is taken After the power regulators, RF front end, And RF preamp are fed with 4V regulated, so the batteries can power the radio without affecting sensitivity.
      The Sangean however, feeds the RF front ends (AM and FM) directly from the 6V line, so any change here will decrese sensitivity. I Am quite sure that the power circuits of the ATS909 and ATS909X are the same.
      From my experience, the difference on Shortwave is between A non detectable station when the batteries reaches less than 50% (according to battery level indicator) and about 70% signal level with full batteries or the power supply.
      This applies to FM as well.
      Best Regards,
      Moshe.

      Reply
      1. Ian from England

        Hi Moshe! Many thanks for your very informative reply. I also own the PL660, and was going to replace the rechargeable batteries with alkaline ones in that radio too. Thanks to your info, I will leave the rechargeables in the 660. Very interesting that this applies to FM as well, as I always prefer using the 909X for FM reception due to it’s superior sensitivity (at least, compared to most other radios I’ve used!). Thanks once again.

        Reply
  4. Patrick

    Hi,

    It would be interesting to record a video showing the reception of a weak SW signal with rechargable batteries and then with 1.5V ones.
    I ran a test with a Sony 7600G : no enhancement !

    Reply
  5. Patrick

    Hello ! I just purchased a (black) 909X and noticed a couple of things :

    – A kind of ‘brown spot’ is visible on the left of the display. (more or less visible according to the orientation of the receiver

    – There’s a kind of ‘internal noise’ on LW, around 145-150 kHz ; I assume it’s an internal noise because it’s audible wherever I am (even on the top of the mountain !) ; this makes reception on 153 kHz almost impossible …

    Is my unit OK or defective ? On the back panel, it’s written 201406, so I guess it’s not an old batch …

    Finally, is the 4:1 balun mod’ easy or does it require specific skill ?

    Thanks a lot

    Reply
  6. Joe

    Does anyone have any experience with, or have any opinions about using Radio Labs in California? The cost of the ATS-909x mod is 70.00.

    http://www.radiolabs.com/products/receivers/ats-909x-mod.php

    http://www.radiolabs.com/products/modifications/modifications.php

    UPDATE: The 909X received a great review from Dave, putting some top contending receivers against each other! RadioLabs 909x Clearmod shines in clarity, filtering and sensitivity! Read about it here Check out Dave’s review on 909x Clearmod!

    The RadioLabs technicians have taken this great radio and made it even better. The ClearMod ATS-909X is a professionally modified version with unbelievable clarity and sensitivity. The upgraded filters that are added directly to the radio’s processor board clean dirty signals up and bring distant stations into the forefront.

    Being as the 909X is already a phenomenal radio, the unit’s sensitivity rivals of many portable radios available on the market, the ClearMod upgrade is a great addition.

    The external of the ATS-909X stays exactly the same, maintaining the sleek modern look and feel of the original radio. This modification is for those who prefer performance over aesthetics, even though the 909X is already a truly 21st century radio with all the functions and quality you would expect from Sangean

    The ATS-909X is a complete worldband radio package, with frequency reception from 153kHz on the long wave band all the way up to 108mHz on the the FM band and complete access to all the short wave, medium wave / AM frequencies (including upper and lower single side band broadcasts) in between via the 5 tuning options (Auto, Direct, Manual, Scan, or Memory). Utilizing the new “Squelch” function to minimize background static noise, distant stations come in clearer than ever. Finding stations in a new area is easier than ever with the Auto Tuning System (ATS) which scans and automatically adds all available FM, LW or MW stations to the 406 preset memory bank.

    Note: RadioLabs offers the 909X clearmod, with smooth detent on the main tuning knob. We charge an additional $10 for this modification. If you would like the Clearmod with tuning knob detent, please specify in customer notes during checkout and we will add this to your radio when we modify it.

    Reply
    1. rod

      Interesting. You start by asking if anybody has any experience with Radio Labs in California, then at the end of the letter you refer to the charges: “We charge an additional $10 for this modification…” If you are responsible for the modifications, why are you asking about others’ experiences with the company? I am confused…

      Reply
  7. Pingback: Dan compares the Sangean ATS-909X with two classic portables | The SWLing Post

  8. D. Raff

    Does someone know if the 909X’s sensitivity directly related to supplying optimal voltage common among other portables? Was this the case with the older ATS-909? Seems like that would be a drawback to want to purchase a 909X.

    Reply
  9. rod

    If I may add my experience with the RF input transformer. I tried both 4:1 and 5:1 versions and find 5:1 to be slightly better. The radio now has excellent sensitivity on SW and comperes favorably to my Tecsun PL-880.

    There is no effect on FM reception because the transformer is on the SW side of the antenna circuit. I definitely think it is worth the effort.

    I hope this helps if anyone is contemplating this upgrade.

    Reply
  10. Tudor Vedeanu

    I just wanted to say that the trick with the batteries improving the sensitivity does not work on my 909X. It may work on the old 909 model, but on the 909X? I don’t think so. The signal strength is the same no matter what I use, fresh alkalines or slightly depleted rechargeables.

    And one more thing about the 909X. I’ve just found a YouTube video showing how to change the FM range to 64-108 MHz (the Russian FM band) without any internal mods. That’s right, no need to open the radio, unsolder diodes, etc. This is absolutely new to me. Here is a link to the video: https://youtu.be/fOntRwy8J7Q

    And even though the guy in the video is using a newer 909X unit with the software version 1.29, the trick worked on my older unit too! I have a 909X made in 2011, version 1.20 which is now able to receive FM stations from our Ukrainian neighbors.

    Reply

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