Anyone use ALC hook up from Amp to Radio?

Discussion in 'General Technical Questions and Answers' started by W0AKR, Feb 17, 2013.

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  1. W0AKR

    W0AKR Ham Member QRZ Page

    Have heard pros and cons on this issue for some time. Anyone using their ALC from their radio to the amp?
  2. K8JD

    K8JD Ham Member QRZ Page

    It helps if you can possibly over drive the amp with your radio.
    My first amp was homebrew 4x811A tubes and I never built any ALC Feedback into it, the next one was a Henry 2K and I can't recall if I made the connection to my TS520 now.
  3. KO6WB

    KO6WB Premium Subscriber QRZ Page

    I have a TS-590S going into an ALS-600. It needs about 55 watts for full output without over-driving the amplifier. Use of the ALC is added insurance that I won't make a mistake and the rig will not be able to over-drive the amplifier. It also assists in a possible spike that is reported on the TS-590S and other units that also have that possibility.
    Have fun
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    ALC connection, if levels are compatible and all works well, can be very helpful.

    If not, then not.

    Depends on the amp and the transmitter.

    If I use my AL-80B with my Drake TR-7, connecting the ALC not only prevents overdrive, but actually boosts average power, which is very obvious to see on the scope or a wattmeter. It puts the amp inside the control loop of the transceiver, which can be a good thing; however there are many incompatibilities that exist and this isn't always the case.

    With my setup, when I "connect" the ALC loop, literally everyone I work says, "Wow, what an improvement!" and can actually hear me better. But the AL-80B has a very good ALC circuit, not all amps do.
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    It does sound really good.

    I don't use the ALC the three radios I currently use with the SB-220 don't put out enough to overdrive the amplifier and the SB-220's alc isn't adjustable. If I should decide to use the Tempo-One with the amplifier I'll hook up the ALC as that will drive the amplifier hard enough that it will be necessary.
  6. W0AKR

    W0AKR Ham Member QRZ Page

    I run one of my radios, the 1000MK5 with the ACOM amp. Doubtful the ALC will do much but likely, will interconnect as a precautionary note. In years past, I use to always do this but in recent time, I have more or less noted my transmitted ALC range and not relied on the ALC line to the amp. But, probably a good thing to do, either helps but doesn't hurt either if not needed.
  7. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    If it works for you, you'll likely have a better signal with it than without it. However, there can be incompatibilities in levels and time constants that negate that. Takes some experimentation.

    If you have a scope, take a look at your output envelope with and without the ALC connection. If it looks "fuller," with higher average power with the ALC connected, I'd say leave it connected. Mine does.
  8. W0AKR

    W0AKR Ham Member QRZ Page

    Yeah, no scope here Steve, but will see about "on the air" reports.
  9. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Sure, try that.

    Be prepared to switch very quickly, though, as propagation changes everything very quickly.

    I tried the same test (ALC connected, or not) about 500 times and can switch from one to the other in much less than one second, by flipping a switch. That helps reduce the varagries of propagation.
  10. WA7PRC

    WA7PRC Ham Member QRZ Page

    An average-responding meter will indicate more signal if there is any peak limiting (or compression) happening.

    I don't use ALC with my TS850 and unmodified SB220. Instead, I use a box ahead of the mic input that reduces the dynamic range of the audio (a compressor). The signal into the rig's mic input won't go above a certain level. After tuning up and adjusting so my inexpensive and easy to use 100 MHz lab oscilloscope shows maximum output and I'm not flat topping (clipping), I'm done. I often get unsolicited "you sound GREAT" and "you're VERY loud" reports.
  11. KD0CAC

    KD0CAC Ham Member QRZ Page

    I would like more detail if you would ?
    " a box ahead of mic input "
    I have a TS-850Sat ,
    MC-60 mic ,
    Yeasu FL-2100B
    Rigol DS1102E

  12. WA7PRC

    WA7PRC Ham Member QRZ Page

    Your Rigol 100 MHz DSO will work fine as a monitor. A "box ahead of the mic input" refers to an audio processor unit that alters the audio in one or more ways.

    One way to modify the audio is to limit the dynamic (loudness) range of the audio signal that passes through the "box". By doing so, you can increase the average power, which is what our hearing responds to. At the same time, if you also use an oscilloscope, you can set it up so your rig & amplifier never clips or flat-tops. A signal that is clipped also has a higher average power but also has significant harmonic content (the signal is significantly wider). That's not a good thing.

    I use a box that does the above (compressor), and has other useful features. It has a good preamp, an expander, and a three band parametric equalizer. The expander reduces gain when there's less signal. That works as a "soft gate" to smoothly reduce transmission of background noise when I pause. A gate would sharply open/close the signal path. The parametric equalizer has three channels in parallel where each channel's center frequency, bandwidth, and gain/attenuation can be adjusted. When contesting/dxing, it is helpful to roll off the low frequency response and add some emphasis on the higher audio frequencies for better intelligibility. Each section of my box (Symetrix 528E) can be switched in/out as needed.
    Last edited: Feb 19, 2013
  13. K8JD

    K8JD Ham Member QRZ Page

    I used a compressor on the mic input to my first SSB rig, a National NCX3 that had NO ALC circuit at all. It was easy to flat top the pattern on a scope , by just talking too loud. I put together a simple audio compressor with pots so I could control the attack and decay timing for the best sound. At the time I had been working in AM/FM broadcasting for a while and understood the need for compression. It can make you sound louder without the distortion of hard audio limiting and not quite overmodulate.
    The only drawback was the sweep tubes in the NCX3 did not like the increased demand from a higher duty cycle and after several months started failing. I think the plate cap on one finally had melted solder and came loose !.
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