2m Linear all-mode radio questions

Discussion in 'Amateur Radio Amplifiers' started by W7UUU, May 19, 2014.

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  1. N9DSJ

    N9DSJ Ham Member QRZ Page

    Ah, ok, not overly familiar with the TR-9130.

    The Mirages should really be called 100 watt amps; notice that they are in compression at higher drive levels. You might check what the TR-9130 puts out on SSB peaks and see where you are.

    I do know the Mirage amps will die easily if over-driven and the rx pre-amps croak often, especial if RF keyed.

    Good luck,

    73,

    Bill N9DSJ
     
  2. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    It's funny - the manual actually says they are 110 watt amps!! It's right there in black and white in the
    instructions - not the claimed 160 watts.

    Live and learn - first mistake was believing a salesman on the phone with HRO - I should have
    done more homework, and asked more questions. I'm now past the return point so it's time to
    come up with a solution. I'm not worried - I'll sort it out... even if I have to build an attenuator
    with a manual T/R switch - there are only a few 2m contests a year to contend with - rest of the
    time the rig will be mostly dormant. I'm a big boy - I can deal. :)

    Probably why they are called "mirage" :)

    Dave
    W7UUU
     
  3. N9DSJ

    N9DSJ Ham Member QRZ Page

    Dave,

    The service manual in online as a .pdf. Cant' you just adjust the ALC (VR4) to keep your SSB peaks below 15 watts ?
     
  4. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    let me look into that - I believe I have the service manual on hand actually.

    That would be the ideal solution, as long as the amp were connected.

    Great suggestion!

    Dave
    W7UUU
     
  5. KM3F

    KM3F Ham Member QRZ Page

    Many miss interpret the SS amp specs.
    160 Watt output is only for CW and FM modes.
    SSB requires the drive to be limited to about 110 W out.
    The reason is on CW and FM, linearity is of no concern since the amplifier is either on or off or on with FM deviation. Gain compression is of no consequence for those modes.
    On SSB and AM where linearity is very important, the drive needs to be kept down to run the amplifier in it's most linear portion of it's input/output curve.
    Same goes for use on AM where you would limit the carrier so it can only produce a max of 110 watts peak power. This would mean 110/4= 27.5 watts carrier or if the amplifier has an input amplifier stage, reducing drive to further to be sure peak power is not over the 110 limit. Set this drive level on CW for 110 watts then divide the drive level by 4 for final AM carrier un modulated. Under 100% modulation the drive then should rise to produce 110 watt peaks.
    The radio ALC does not put out anything, it is an input signal only. The amplifier has not enough dynamic range to make ALC worthwhile in most cases but could be done if there is a desire to build the circuit into the amplifier's input stage. The ALC range would be very short and fast acting and could cause issues with some radios from pumping so they do not include it in the design..
    To limit radio power use a 9 volt battery with a 100k pot across it to feed adjustable 'fake' ALC into the radio at the proper polarity to control power same as if an amplifier were being used that has ALC output.
    Good reasonably accurate watt meter is you friend to set this all up.. A peak reading meter would be a plus.
    Good luck.
     
  6. W2VW

    W2VW Ham Member QRZ Page

    Make sure any power lowing scheme for the exciter does not allow higher power spikes. Many do. Not good for a happy amplifier experience.
     
  7. W6RZ

    W6RZ Premium Subscriber QRZ Page

    Why didn't you just get the Mirage B-2518G? It requires 25 watts of drive. And it's cheaper.
     
  8. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    That's the plan. Remember - I just called HRO and said "I have a 25 watt radio" etc. That's what they sold me!
    Stupid on my part - should have done some homework - it was a whim while on the phone ordering an M-Squared beam.

    I'm heading down to HRO tomorrow in Portland - turns out I'm within the 30 day return period (invoiced on April 29th) after all.

    So hopefully I'll have good news to report tomorrow, and not be stupid next time - big forehead slap on my part. It's just
    the guy on the phone sounded so totally sure of what he was recommending I didn't question it.

    I'll report back tomorrow on this...

    Dave
    W7UUU
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Dave, the amp will last longer if you "hard key" it using a keying line to the phono jack on the amp, rather than "RF key" it.

    RF keying "works," but the amps don't last long if you use that, especially on SSB or CW, where they will switch a lot during every single transmission. It actually damages the relays and they eventually fail. They're not expensive, but a real PITA to replace and a bad failure can also blow the PA transistors. Hook up the "amplifier keying" line, and that saves them.
     
  10. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Forgive my ignorance Steve - so do you mean to use a keyer-driven DPST high speed keying reed-relay that keys the
    rig and the amp simultaneously? Certainly very easy to do and makes perfect sense. But if that's not
    what you're suggesting, please do some 'splainin'

    Dave
    W7UUU
     
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