Transmitter power output during PSK31, RTTY-45?

Discussion in 'Working Different Modes' started by KE0KDQ, Sep 7, 2018.

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  1. KC3GSV

    KC3GSV XML Subscriber QRZ Page

    Good advice. I set up my 7200 the same way.
     
    K4AGO and W4NNF like this.
  2. WA9UAA

    WA9UAA Ham Member QRZ Page

    For proper linearity, set the power out put adjustment to 100 watts then adjust the audio level from the computer/ sound card etc. such that the output is about 35 watts. This keeps the finals from over heating and keeps the signal clean. (Linear, ie. distortion free.) A better way is to watch the ALC meter and not run the audio so that any ALC shows on the meter. There are two things to do here. 1) Keep the signal clean and, 2) Keep the power at about 1/2 - 1/3 of maximum to keep from destroying the final out put transistors.
    73,
    Rob
     
    WU8Y likes this.
  3. W5DXP

    W5DXP Ham Member QRZ Page

    Just curious, why would running 100 watts PSK destroy the final output transistors in a final that is rated 100 watts for RTTY, like most of the ICOM transceivers.
     
  4. WB5WPA

    WB5WPA Ham Member QRZ Page

    Well, sometimes it's the driver stage, IF the mounting screws are not torqued/have loosened over time AND with thermal cycling (like a lot of use) ... this happened in my Pro2. Lost the both the 2SC19xx TO220 package driver devices. Screws were *not* tight. I have taken steps now to assure that the hardware in these power stages is tight. Every few years take covers off radio and check/tighten the mounting screws.
     
  5. KQ0J

    KQ0J XML Subscriber QRZ Page

    " Just curious, why would running 100 watts PSK destroy the final output transistors in a final that is rated 100 watts for RTTY, like most of the ICOM transceivers. "

    It will not hurt them. There are a lot of people that post wives tales and bad info on these posts as well as the low power pundits.. There is no reason to run 25 or 35 only - if you need more power
    to make a contact , use it. I use up to a few hundred watts if needed with an external amp ( watch the duty cycle there too ) . As you stated - follow manufacturers guidelines for RTTY.

    Also, the advice not to use filters is 100% incorrect. Use your filters, IF bandwidth and shift to optimize signals and minimize interference with the station you are interested in.
     
    WG7X likes this.
  6. WA9UAA

    WA9UAA Ham Member QRZ Page

    Hi Cecil,
    The last rig I had rated 100W key down was my old Kenwood TS 440s and that was for 1/2 hour with a similar cool down time. If the newer rigs are that rugged I'm not aware of it.
    73,
    Rob
     
  7. KQ0J

    KQ0J XML Subscriber QRZ Page

    " If the newer rigs are that rugged I'm not aware of it. "

    Yes, they can be. As he stated the ICOMs will coast at high power. Use the RTTY guidelines for your particular rig.

    And of course - your ALC settings per manufacturer. My FTdx-3000 will put out 100W digital with no ALC reading when properly adjusted.
     
  8. WA9UAA

    WA9UAA Ham Member QRZ Page

    Thanks Cecil, I'm just old school I guess, and a bit more conservative on digital modes. Thanks for the update. 73, Rob
     
  9. WB5WPA

    WB5WPA Ham Member QRZ Page

    re: "It will not hurt them. There are a lot of people that post wives tales and bad info on these posts"

    Ahem.

    Relating in a post here on Zed of an actual, real-life event (power transistor failure) that one was personally involved with is not an [old] "wives tales".

    I'll post this again in case it was missed the first time:

    Well, sometimes it's the driver stage, IF the mounting screws are not torqued/have loosened over time AND with thermal cycling (like a lot of use) ... this happened in my [Icom 756] Pro2. I lost both of the 2SC19xx TO220 package driver devices. Screws were *not* tight. I have taken steps now to assure that the hardware in these power stages is tight. Every few years take covers off radio and check/tighten the mounting screws.

    @W5DXP
    Again, let me make this perfectly clear, this happened to me while I was operating 6 meter WSPR (2 minute transmit frames) at 50 Watts sometimes 100W when band conditions were really poor and I was trying for some contacts. After a few weeks the output power was getting low coming our of the radio, and the back of the radio was getting hot, even in receive.

    TO MAKE a long story short, the driver transistors were pulling a lot of current and had failed!

    Investigation showed mounting screws were NOT tight, and had probably loosened as (1) heatsink compound flowed from underneath the transistors over the years as well as (2) thermal cycling loosening the mounting screws.

    BEAR THIS IN MIND when using a rig in a high duty cycle application, that is, check the tightness (or torque) of the mounting hardware for the driver and power amplifier transistors!
     
  10. KQ0J

    KQ0J XML Subscriber QRZ Page

    " Relating in a post here on Zed of an actual, real-life event (power transistor failure) that one was personally involved with is not an [old] "wives tales"."

    You are stating an instance of a rig not working properly. There are many faults of a rig that can cause a problem. As you can see from your own post - its not a problem with FT8 or any other mode - it was a defect in the radio. That could have manifested itself in many other modes - FM for example.

    I suppose I could have said ' Properly operating radio " but I would think that we all know enough electronics to know that design specs are for a properly operating rig - not one that's broken. Or maybe stay away from ICOM radios :)...

    So, my comments stand uncorrected. Check with your manufacturer for your specs. If you have a good radio in good operating mode you should have no problems running in stated specs. Especially with FT8 on 13 second Xmit bursts.
     
    WU8Y likes this.

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