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COR circuit in ARRL 2001 HB

Discussion in 'Homebrew and Kit Projects' started by KB7NRN, Jun 13, 2011.

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  1. KB7NRN

    KB7NRN Ham Member

    Looking for the Carrier Operated Relay circuit in the 2001 Handbook. Need it for an amp project.

    PM me if you have it.

    Thanks,
    John
     
  2. W9GB

    W9GB Ham Member

  3. KB7NRN

    KB7NRN Ham Member

    Who says it has to be solid state?

    I've seen the ARRL COR circuit mentioned and would like to take a look at it
    without having to purchase another Handbook
    You see the SG 2020 doesn't have a keyed output for an outboard amp

    The COR-3 is a bit overkill as well as being designed for repeater use.
     
    Last edited: Jun 14, 2011
  4. W9GB

    W9GB Ham Member

    I have the 2000 and 2004 Handbook editions. Under what chapter?
    I did not see a DIY project in the 2000 Handbook edition.

    Check with your local library, if they don't have a copy -- they can get photocopy of page.

    w9gb
     
  5. K7JEM

    K7JEM Ham Member

    Something like this could work:
     

    Attached Files:

  6. WB2WIK

    WB2WIK Premium Subscriber

    RF keying an amp isn't usually a great idea, especially for CW or SSB work where you might want a variable delay drop-out (depending on operating conditions, keying speed, etc). Using RF keying absolutely guarantees you'll be "hot switching" RF at the transmitter's output, since when you first key the transmitter, the amp won't be keyed yet, and the relay will take some milliseconds to close. When it does, you're "hot keying" the relay (RF is already at the relay contacts as they're closing) and may even trip the SWR protection circuit in the transmitter.

    I'd recommend not doing this.

    Some solutions would include keying the amplifier instead (directly, with a wired connection) and letting a pair of auxiliary contacts in the amp key the rig, which can be done via pin 2 of the 8-pin front panel mike connector; or using a state change point in the SGC2020 to hard-key (direct wired) the amplifier. In many rigs, a state change can be found easily at the front panel where an LED turns on to indicate "XMIT." I think the SGC uses all LCD displays and no LEDs, but even an LCD display likely has an XMIT indicator of some sort, driven by a logical change (pull-up or pull-down) that can be buffered and used to key the amplifier.
     
  7. KB7NRN

    KB7NRN Ham Member

    Steve,
    I agree, direct keying is best but there are alot of HF, VHF and UHF amps that use COR keying with out much problem.
    I would like to use this amp with other radios, it's a shame to modify each radio so it can be used with the amp.

    This amp is not considered QRO, just a single 811A. It will only put out 100-150 watts.

    John
     
  8. WB2WIK

    WB2WIK Premium Subscriber

    John, I don't think there aren't any certificated HF amps that use RF keying, it's technically unlawful under Part 97 provisions. The only HF amps I've ever seen with RF keying are "CB" amps, homebrew amps, or the CCI (Communication Concepts) kit amps based on Motorola App Notes, and that circuit is terrible.

    On VHF-UHF, for "FM" work, it's very common (and also allowed). But if you've ever worked SSB/CW with an RF-keyed VHF/UHF amp you know how awkward it can be, in a variety of ways. It not only wears relays out and can potentially cause exciter damage, but an RF keyed circuit that's sensitive enough to pull in on a soft syllable of SSB modulation is also sensitive enough to pull in when the connected antenna receives any kind of strong signal from a nearby transmitter that's not even connected to the amp in any way. It's almost impossible to avoid that, since the sense line for RF keying is connected to the antenna itself, as well as the exciter. The C.C.I. COS system is so screwy that if you use one in the car and drive past someone transmitting with any power on any band (including police cars, etc), the amp will key from their RF, even if they're 20 feet away. You can turn down the sensitivity to reduce that, but by doing so you make the circuit less sensitive and it won't pull in on soft modulation.

    Normally you wouldn't have to modify any radios to use with an HF amp, since all of them except the SGC do have an accessory key line output. At least every rig I've ever owned or seen did. I'm amazed the SGC doesn't.
     
  9. K9FV

    K9FV Ham Member

    That sure is a simple circuit - I'm looking for a simple COR circuit to turn the fan on for an air cooled dummy load when amp is keyed. Since this will need to activate from 100 (maybe as much as 300 watts?) watts to 1500 watts. I think at 100 watts no fan cooling will be required, but at 500 watt sure will need fan to come on. I plan to use a timer circuit to keep fan running for a couple minutes after amp unkeyed for higher power levels.

    73 de Ken H>
     
  10. K1ZJH

    K1ZJH Ham Member

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