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IC 7300 & Acom 700S

Discussion in 'Amateur Radio Amplifiers' started by KD9VV, Apr 27, 2021.

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  1. KD9VV

    KD9VV Ham Member QRZ Page

    The wording seemed a tad nebulous to me.
    Am I safer at 10ms or 15ms tx delay?
    DElay off on the 7300 is actually ~7ms

    In order to provide time for the relays to switch safely from receive to transmit, the transceiver should provide a dead time i.e. must “notify” the amplifier in due time by grounding the control KEY IN input not later than 10ms before feeding drive power toward the amplifier RF input. Otherwise, the protection system will read “HOT SWITCHING ATTEMPT” and will trip off.
  2. NG1H

    NG1H XML Subscriber QRZ Page

    That wording could stand improvement. They are trying to say the delay needs to be 10ms or higher.

    Personally I would be more inclined to a 100ms delay but that sounds like it is being more than a little overcautious according to what I assume is from the manual above.
    KD9VV likes this.
  3. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    Last edited: Apr 27, 2021
    KD9VV likes this.
  4. KD9VV

    KD9VV Ham Member QRZ Page

    Yes, I'm well aware of the 7300 rf flow after unkey. I dont run cw, mostly ssb, ft8, msk144.
    Sounds like I need at a minimum with the 6300 15ms.
    Although, even I'd digital modes, I am IDing after the 73 in cw...perhaps turn off that feature?
    K1LKP likes this.
  5. K7JQ

    K7JQ Ham Member QRZ Page

    I run a IC-7300 with a Acom 1200S. The Acom manual has the same statement. Val at Acom recommends 15 or 20ms delay as sufficient, with 20ms having less T/R relay clicking. I use 20ms delay setting, semi break-in CW (amp won't do QSK) at high speeds, and VOX on SSB in contests. No problem with hot-switching with this setting.

    However, I did get a hot-switch warning a couple of times from transmitting too fast after switching from Standby to Operate on the front panel. Apparently, the amp needs a slight delay in its CPU logic for the switch to process (you can hear a relay). Once I figured this out, no more warnings.

    Bob K7JQ
    K2TY likes this.
  6. KD9VV

    KD9VV Ham Member QRZ Page

    Thanks Bob.
    That is what I chose, 20ms.
    Amp arrived yesterday; really enjoying it.
  7. EI2IJB

    EI2IJB Ham Member QRZ Page

    Confirm 20ms also on 700s and my 7610
    KD9VV likes this.
  8. KD9VV

    KD9VV Ham Member QRZ Page

    I actually just bumped it to 25ms. Saw one hot switch warning when working ft8.
  9. EI2IJB

    EI2IJB Ham Member QRZ Page

    7300 is known to have big spikes on tx, there is a thead around here somewhere that explains the issue in more details, some build up a delay relay.

    try 25 and see how you get on
  10. KD9VV

    KD9VV Ham Member QRZ Page

    yep...well known issue.
    Some do, some don't..kinda' a crap shoot; only way to know is scoping it.
    Only saw the hot switch warning once; probably the infamous RF spike.

    I believe it is more a problem with near instant on carrier or audio, digital modes, FM/AM etc
    SSB probably not much of a issue with the slow ALC clamp time.

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