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Transmit Delay

K1ESE Member ✭✭✭
edited June 2020 in SmartSDR for Windows
I have a 6500 and a non-QSK amplifier.  I want to setup a delay for T/R switching.

What is the difference between these in Radio Setup -

And this in SSDR -

And which do I use to set a 30ms delay for the relays in the amp?

73 de K1ESE


  • Mike
    Mike Member ✭✭
    edited July 2016
    I'd be interested in the answer to this one. On 6m I have been using the foot switch to keep the ptt from dropping.
  • EA4GLI
    EA4GLI Member ✭✭✭
    edited November 2016
    So this is my take on it and anyone correct me if I am wrong.

    The bottom delay is for CW so ignore that one for the time being,

    The RCA TX1-3 and ACC TX are the RCAs in the back of the radio to engage devices such as amps, transverters, etc... when you PTT de radio.

    This is where you could define a SEQUENCE in the engagement of devices. For example, you might want to engage a relay that shuts off a preamp on a receiving antenna a few ms before it engages the amp. So you might have the PreAmp on AccTX with value 0 and the amp connected on TX1 with a value of 20 (which means 20ms).

    The TX Delay then can have the amount of time between the moment you press PTT on the radio and the moment the Power Amplifier of the Flex sends RF into your amp. You could set this to 30ms.

    In that scenario, once you push PTT in your Flex the PreAmp shuts off right away, the Amp receives the PTT signal 20ms later and 10ms after that the Flex radio send RF.

    TL;DR TX Delay is the one that will define the amount of time between PTT depress and RF being sent out of antenna port.

    You can test this yourself using 1000ms for the TX Delay. That equates to 1 second and you can see that your amp gets the PTT signal right away but there isn't any power until 1 second has passed. When you use 6 ms or even 20ms is not perceptible to the **** eye.
  • Bill W2PKY
    Bill W2PKY Member ✭✭
    edited March 2017
    The delay in the setup panel is the amount of time before the first RF signal is sent out, where the delay in the second panel is the time before the radio returns to receive after sending a character. If you like your relays to stay in the transmit position while sending CW use a high setting on the second panel. The delay in the setup panel is used for all modes.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited June 2020
    The one in the bottom picture is the "return to receive" delay.  i.e. 0 = Full break-in, and delay added makes it what used to be called "semi-break-in" in some rigs.

    The delay setting in the top picture is the delay the rig waits after transmit is engaged before allowing power to be output.  Thus giving time for the amplifier relays to close before transmitting if you have slow relays on your amplifier.

    See this info on page 105 in the current Software Users Guide:


    The FLEX-6000 has hardware interfaces for connecting an external power amplifier.  There are four PTT outputs on the FLEX-6700 and FLEX-6500 and two outputs on the FLEX-6300, each with independently configurable time delays, a transmit hold-off input for amplifiers that have QSK holdoff outputs, and a standard zero to negative four Volt hardware ALC input.  SmartSDR controls the configuration for these interfaces using the TRANSMIT tab in the Radio Setup menu. (Left: FLEX6700/6500 Right: FLEX-6300)  

    (the pictures did not copy from the manual to this post)
    On the FLEX-6700 and FLEX-6500 there are four PTT outputs.  Three are RCA jacks on the rear panel, labeled TX1, TX2, and TX3.  The FLEX-6300 has one RCA jack labeled TX.  On each of the radios there is an output on Pin 11 of the Accessory connector on the rear panel as well.  These outputs are isolated, and each one can have a specific delay.  Some users will want to utilize the delay settings to sequence switch external equipment.

    For external amplifier use, the delay should be set to zero for any output that keys the external amplifier.  This will insure the relay will follow the PTT signal exactly.

    The TX Delay setting can be used if the external amplifier has slow T/R relays and requires a longer time between PTT and RF Emission.  Unless you are noticing problems with the radio emitting RF before the amplifier has switched to transmit position, you should leave the TX Delay set to zero.

    The TX Delay will have a negative impact on QSK operation and other timing specific digital modes.  If the intent is to operate QSK then Delay should be set to zero.

    The Interlocks settings are used for amplifiers that have a hold-off output for QSK CW.  There are two interlock inputs.  One is an RCA jack on the rear panel, and the other is Pin 13 of the Accessory connector on the rear panel. On the FLEX-6300 this is only available on the Accessory connector

    If your amplifier does not have one of these outputs, or you do not use it in your station, leave these settings disabled.  If you need to use the hold-off, select Active High or Active Low to enable the interlock and set the proper polarity of the signal provided by the amplifier.


    Ken - NM9P
  • K1ESE
    K1ESE Member ✭✭✭
    edited June 2020
    Ken -

    If I read through all the information and try to find the simple answer to my question, I think you are saying "set the TX Delay in the yellow circle in my diagram to 30".

    Is that what you are saying?


  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited December 2016
    Salvador's comments are spot-on.

    If you need a time delay for your amplifier's relays to activate before your transmitter sends RF, set a delay in the TX Delay you circled in Yellow.  This will prevent hot-switching your amplifier, which produces all manner of key clicks and also creates transients that can destroy some amps.  The time is dictated by the speed of your amplifier relays.  I have seen people use anywhere from 5-30, depending upon their amp. 

    Unless you are needing to sequence multiple pieces of equipment in a precise order, leave the delays in RCA TX1, RCA TX2, RCA TX3, and ACC TX alone, at 0.  Enable whichever port you are using to send the PTT signal to your amp.

    If your amp is non-QSK, you will also want to set some delay in the CW Delay box you circled in Blue.  (I call that box the "CW Return Delay.") This will keep the amplifier relays in transmit mode in between characters (or between words if the delay is long enough) so the relays don't clickety-clack all the time as you send CW.

    You might want that delay as high as 100-250 or more, which would be a tenth of a second (100 ms) to a quarter of a second (250 ms) Too short and the relays will drive you nuts. (and can wear them out, too.)  Too long and you will miss characters people send you after you stop sending, before your receive antenna is returned by the amplifier relay.   This time is dictated by your personal preference.

    Perhaps some others with more experience with amp relays will chime in....

    Ken - NM9P

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