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Thread: COR circuit in ARRL 2001 HB

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  1. #1

    Default COR circuit in ARRL 2001 HB

    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. #2

    Post

    Looking for the Carrier Operated Relay (COR) circuit in the 2001 Handbook.
    I need it for an amplifier project.
    Repeater usage -- OR -- using instead of PTT / Relay Control for an outboard solid-state RF amplifier ?

    Hamtronics COR 3 -- Block diagram
    http://www.hamtronics.com/pdf/AP%20l...%20diagram.pdf

    Hamtronics COR-3 Module: Instruction Manual
    http://www.hamtronics.com/pdf/COR-3.pdf

    w9gb

  3. #3

    Default

    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 by KB7NRN; 06-13-2011 at 11:11 PM.

  4. #4

    Default

    I've seen the ARRL COR circuit mentioned (2001 Handbook) and would like to take a look at it
    without having to purchase another Handbook
    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. #5
    Join Date
    Jul 2005
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    Safford,  AZ
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    11,934

    Default

    Something like this could work:
    Attached Images Attached Images
    We cannot tax our way to prosperity.

  6. #6

    Default

    Quote Originally Posted by KB7NRN View Post
    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.
    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. #7

    Default

    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. #8

    Default

    Quote Originally Posted by KB7NRN View Post
    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
    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. #9
    Join Date
    Aug 2001
    Location
    Fairhope, AL
    Posts
    1,693

    Default

    Quote Originally Posted by K7JEM View Post
    Something like this could work:
    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. #10
    Join Date
    Apr 2001
    Location
    north central Connecticut
    Posts
    947

    Default

    Use a thermal switch. That will provide the proper fan activity when the load reaches temperature,
    and it will keep the fan running until the load cools down.
    They are made in all temperature ranges, the lowest are 85 degree F units made for attic fans.
    Here is what they look like:

    http://www.ebay.com/itm/B1-METALLIC-...-/120714903989

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