TS-520S DG-5 Display Changes When Transmitting

Discussion in '"Boat Anchor" & Classic Equipment' started by AA5ET, Feb 13, 2020 at 5:41 AM.

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  1. AA5ET

    AA5ET Ham Member QRZ Page

    Here's my situation:

    The TS-520S is new to me, but seems to work fine except for he DG-5 display that it came with. Receiver is great and it tunes fine with full power out - nothing unexpected, although the receiver sometimes has an annoying crackling/sizzling sound - separate problem I'm sure.

    Antenna is a is a ladder line-fed 40 meter inverted V at around 35 ft, about 5 ft of coax between the transmatch and 4:1 balun where it goes into the 450-ohm ladder line outside. DC ground is about 4 ft long, connected to one of those gas discharge tube lightning arrestors between the coax and balun and the electrical service conduit about 1 ft above the ground (buried electrical service). Ladder line is about 38 ft in length. I don't think I'm getting common mode current/RF in the shack. Nothing else is going haywire and no TVI. When installing the antenna I put a 100K resistor across the feed point to bleed off static buildup.

    So, when I transmit (CW) or switch "rec/send" to send (without transmitting) the display shows a frequency about 800Hz lower, then when going back to receive it returns to the original frequency. RIT is OFF. Happens on all bands - same 800 Hz drop. I don't have a mic for this radio yet, so don't know if it happens on SSB. Same when connected to a dummy load.
     
    Last edited: Feb 13, 2020 at 5:46 AM
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Sounds like it just need calibrated.

    Do you have the service manuals ?
     
  3. W5RKL

    W5RKL Ham Member QRZ Page

    AA5ET

    Based on your initial information about the DG-5's frequency display,
    there is no problem with the DG-5 nor the TS-520S and there's no need
    to perform an alignment on either device.

    Download the DG-5 manual here:

    http://www.wb4hfn.com/KENWOOD/Docs/DG5 Operating Manual.pdf

    then go to manual page 7 and read paragraph "3 MODE SWITCH". Note the 2 CW mode frequencies
    displayed, one is 14.100.8 in receive but that changes to 14.100.0 in transmit, an 800Hz
    "OFFSET" frequency. If you switched to 40 meters and tuned to 7.030.0 in receive, switching to
    CW transmit the DG-5 frequency will change to 7.029.2, again the 800Hz CW transmit "OFFSET"
    frequency. The same CW transmit "OFFSET" frequency will be displayed on ALL bands.

    The CW Mode TX OFFSET occurs in the TS-520S 's "CAR UNIT" board by applying a positive DC
    voltage of approximately 9VDC to CAR UNIT CW (T) diode D9. D9 acts as a switch and is turned ON.
    The lead of fixed capacitor C2 is connected to the ground causing a "shift" in the CAR UNIT's output frequency of
    approximately 800Hz. This shift is displayed on the DG-5 as the "OFFSET" in CW transmit. Switching back
    to CW receive, the positive voltage to D9 is removed, D9 turns OFF, and the lead of capacitor C2 is lifted
    off ground, and the CAR UNIT output frequency shifts "UP" by 800Hz.

    The TG-520S's CAR UNIT board provides the "Initial" RF signal to the GENERATOR UNIT board in ALL modes.
    A shift in 800Hz in CW transmit will change the CW transmit frequency by 800Hz and be displayed on the DG-5
    as the OFFSET frequency on ALL bands.

    73
    Mike W5RKL
    https://www.w5rkl.com
    heathkit@groups.io Moderator
    EICOTubeAmpsFanClub@groups.io Moderator
    RMC(SW) USN RET
     
    K7TRF, VA7UO and KA9JLM like this.
  4. W5RKL

    W5RKL Ham Member QRZ Page

    I forgot to comment on the TS-520S RIT control.

    RIT in all 3 TS-520 models is disabled in transmitting in ALL modes by the TS-520S relay RL1-2.
    Therefore, whether RIT is ON or OFF has nothing to do with the CW Transmit OFFSET displayed
    on the DG-5. See the TS-520S schematic to see how RIT is disabled in any transmit mode.

    If you don't have the TS-520S operators manual, which has the full TS-520S schematic and Section 5
    "Circuit Description" section, and complete tuning steps, including setting the final amp
    60ma idling current and other operating steps, you can download it free here:

    https://w5rkl.com/wp-content/uploads/2014/04/TS-520S-Operators-Manual.pdf

    You said the TS-520S was "new to you". That indicates you have never used a TS-520S
    before. Therefore, I recommend you download the operator's manual at the above link
    then spend time reading it so you learn what the controls are for, how to use them, and
    how to properly tune the transmitter. If you do not have a 50 ohm dummy load then I
    recommend you get one. The MFJ-260C 300W dummy load will work, just read the
    carrier level time limits in the manual and the graph on the end of the dummy load.
    If you do not understand what the manual is saying, don't "guess" or "ignore", ask
    for help.

    73
    Mike W5RKL
    https://www.w5rkl.com
    heathkit@groups.io Moderator
    EICOTubeAmpsFanClub@groups.io Moderator
    RMC(SW) USN RET
     
    Last edited: Feb 13, 2020 at 3:41 PM
  5. AA5ET

    AA5ET Ham Member QRZ Page

    Many thanks for sharing your knowledge. I was afraid that the transmitter was going off frequency when transmitting. Glad that it's not an issue and is working as designed. I previously owned a TS-520, years ago, but since it didn't have a digital display there was no indication of a frequency shift - don't see it in modern rigs either, as the frequency display stays the same.

    I do have an operator's manual, and although out of practice I seem to still know how to tune these rigs and get them on the air. Coupled with a manual transmatch and building my own antennas and other devices it's a little bit more than operating an appliance - as is the case with so many modern rigs.

    Again, thanks.

    73, AA5ET
     
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yeah, the Kenwood hybrids show actual frequency in the current mode. IOW, it shows the Rx center frequency while receiving and the actual transmit frequency while transmitting. In SSB mode those frequencies are the same, in CW mode the displayed frequency will shift by the CW offset which is nominally 800 Hz for a properly aligned TS-520, TS-530, TS-820 or TS-830.

    Many newer rigs only display the transmit frequency and don't shift as you shift modes but in reality your rig is shifting the center frequency it is tuned to by the amount of CW offset as you go from Rx to Tx or vice versa. Some rigs only display receive frequency even when you're transmitting so it's useful to know how your main rigs handle frequency display.

    Understanding this is helpful if you ever work a sked or perhaps try to work a DX station based on the frequency reported on the cluster. If for instance someone sets up a schedule to meet you on 7.036 MHz then that's the transmit frequency you both should use. If your rig always displays transmit frequency as many newer rigs do then you just tune to 7.036 MHz.

    But with your Kenwood you want to make sure you'll transmit on 7.036 with the receiver shifted enough to give you the proper CW offset pitch when you are transmitting on that frequency. You can either figure out the offset (e.g. 800 Hz) or you can quickly switch the rig to Tune mode which shifts the display to the eventual transmit frequency, tune it to the pre-determined frequency and then switch back to CW mode to actually operate.

    Similarly if you work a rare DX station and want to upload frequency information to one of the DX clusters make sure you upload the DX station's actual transmit frequency which in the case of your TS-520 with digital display will be shifted 800 Hz from whatever the rig shows while receiving.
     

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