TS-530S Tuneup & RF in Shack

Discussion in '"Boat Anchor" & Classic Equipment' started by KB1RHB, Dec 10, 2019.

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  1. KB1RHB

    KB1RHB Ham Member QRZ Page

    The receiver has agc, I thought it had to be turned off to work as a sig
    strength meter until duh hit me, thats what it is dummy. It controls
    audio level but its control loop V, s meter reading, is a measure of sig
    strength.

    A lot to learn, but at my age the loss rate >> learn rate....:)


    Regards, Dana.
     
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Just wait... it gets better! >>>>>>>

    It's good to see that radio coming around. They're really great.
     
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yup, it's the AGC loop that drives the S-meter.

    But as posted previously I haven't had great luck with using a second receiver during final tube neutralization as the signal leakage out of the transmitter being tested is usually too strong to see the subtle differences in power leaking through the final tubes as you adjust the neutralization cap. Using a second receiver to measure SSB carrier null does tend to work well but it's quite different in that the carrier null is at a very low level stage with substantial transmit chain amplification so the test receiver method works quite well for that alignment.

    The closer you couple the test receiver to the transmitter's output stage the better it should work but I'm generally unwilling to directly cable a test receiver right to the antenna port of a transmitter even with the SG switch in the OFF position. Some good attenuators between the transmitter and receiver would add some safety margin to that approach but it just feels wrong to cable the two directly together. But using any kind of sniffing loop on the test receiver makes it easy for signal leakage from the relatively high level driver stage to swamp out the test receiver making it hard to see the best signal null during neutralization.

    FWIW, even when I use an RF millivoltmeter to neutralize a Kenwood or similar tube rig I start with a 100:1 voltage divider on my millivoltmeter probe as I start neutralization. Once I'm convinced I won't burn up the probe diodes with excessive signal I'll remove the attenuator for final neutralization adjustment. Call me paranoid but it's something I picked up over the years in commercial labs, always tread lightly and start with attenuation in line when working with sensitive equipment like small signal RF probes or spectrum analyzers.
     

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