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Kenwood TS-430S AM broadcast band(US) Receive

Discussion in '"Boat Anchor" & Classic Equipment' started by N4WJL, Jan 14, 2022.

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  1. N4WJL

    N4WJL Ham Member QRZ Page

    My TS-430S will barely receive anything in the AM broadcast band, 5400-1600kHz. Is this common place? I picked this radio up two years ago and have primarily used it on the 40M band and some SWL,with great

    I'm wondering if I have a problem with my 430S or if I'm doing something wrong.

    Thanks,
    LeVan
    N4WJL
     
  2. W9BRD

    W9BRD Ham Member QRZ Page

    Your TS-430S is very likely working as designed.

    Many ham transceivers that include "general coverage" receive capability include hardwired-in front-end signal attenuation when receiving in the mediumwave broadcast band. I just checked the TS-430S schematic available via the Boat Anchor Manual Archive ( http://bama.edebris.com/manuals/ ), and sure enough, there's a pi attenuator built into its "0.5 to 1.6 MHz" front-end filter:

    ts-430s_mwbcb_attenuator.jpg

    The function of the attenuator is to allow reception of strong local mediumwave signals over that wide (3.2 to 1) front-end-filter frequency span while reducing the effects of pairs of strong local signals in that range mixing together in the receiver front-end circuitry to create fake signals at simple sums and differences that also fall within that range. For example, in the Chicago area, such a receiver would tend to create from the 50-kW signals of WBBM-780 and WGN-720 a strong fake signal at 1500 kHz.

    Generally, and assuming equal-strength input signals, adding attenuation to reduce 2nd-order-IMD reduces its products by 2 dB for every 1 dB of attenuation added. So, for example, if that TS-430S attenuator adds 20 dB of attenuation, it's reducing 2nd-order IMD products by 40 dB, give or take.

    Notice that that schematic snippet from the BAMA TS-430S Service Manual indicates where the manual owner apparently snipped the leads of the two shunt (antenna line to common) attenuator resistors to improve the radio's sensitivity in the 0.5- to 1.6-MHz range. There's no harm in doing so; just understand that you may well hear 2nd-order-IMD-created fake signals if you do. But then you're free to have the fun of experimenting with adding an outboard tunable filter -- even just a tunable passive loop antenna would do -- that would let you keep the increased sensitivity while also keeping 2nd-order IMD at bay.

    Best regards,

    Dave
    amateur radio W9BRD
     
    Last edited: Jan 15, 2022
    KS4W and WQ4G like this.
  3. W9WQA

    W9WQA Ham Member QRZ Page

    same on 450d. they shoulda made it switched...
     
  4. N4WJL

    N4WJL Ham Member QRZ Page

    Thanks MUCH for the detailed explanation Dave. I may attempt this mod some day.

    Also, I apologize for the typos in my original post. I searched for a way to edit my post, but I can't find any type of "edit" button.

    Happy New Year. 73's

    LeVan
    N4WJL
     
  5. W9BRD

    W9BRD Ham Member QRZ Page

    No worries -- your question was loud and clear. It's the message that counts.

    Oh -- standard QRZ.com behavior is that you can edit a message for up to 30 minutes after first posting it; then the Edit link is removed.

    Have fun, and Happy New Year!
     
    Last edited: Jan 15, 2022
    N2EY likes this.
  6. KK4NSF

    KK4NSF Ham Member QRZ Page

    that's interesting.... even more so since the TS-440 does not have that problem. All three of mine have excellent distant AM broadcast band performance. I guess they recognised the issue in the TS-430, and fixed it in the TS-440
     
  7. W9BRD

    W9BRD Ham Member QRZ Page

    It wasn't an issue/problem; it was an engineering decision. And a stock TS-440 includes that attenuator as well:

    ts-440s_bcb_filter.jpg

    So maybe someone snipped those 68-ohm resistors in "your" 440s.
     
    W2VW likes this.
  8. KK4NSF

    KK4NSF Ham Member QRZ Page

    I'll have to look and see next time I've got one of them opened up. Whatever the case, all three of mine have very good AM reception. On any given evening, I can pick up 100+ AM broadcast stations..... ranging from West Texas to Memphis to Jacksonville FL. Virtually all of the broadcast slots have an audible station.

    BUT, then again my antennas are optimized for reception with a good pre-amp, and a switchable set of narrow filters. It could be that my antennas system is overcoming an otherwise weak reception. I may have to do some experiments to see if thats the case
     

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