2m Linear all-mode radio questions

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

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  1. W7UUU

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

    I have a newly acquired Mirage B1018G 160w linear that I want to pair with
    my Kenwood TR-9130 all-mode for CW and SSB use.

    The radio offers either 5w or 25w in CW mode, and 25 PEP SSB. However
    the amplifier wants a maximum drive of 12 watts, which means I'm going
    to have to use some sort of attenuator for SSB and CW. Any suggestions
    on the best way to accomplish this?

    Also, the amp does not require (or even accept) an ALC input from the
    radio - which in fact does have an ALC output. The Mirage manual says
    nothing about ALC, just connect radio to amp and off you go. I assume
    there will be no issues there.

    As always, thanks for any advice on this setup

    Dave
    W7UUU
     
  2. W7UUU

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

    [bump]

    :)

    Dave
    W7UUU
     
  3. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Could you (manually) use the ALC input on the radio to lower its output power, rather than using an attenuator?

    AFAIK, the reason you don't have an ALC output on the amplifier is that it assumes your radio will never go higher than 12W, only because that was the specification it was assumed you met before you bought the amplifier.
     
  4. W7UUU

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


    That's what I get for trusting the guy on the phone at HRO - yes, in retrospect, had I googled it,
    I'd have had more questions. I described the radio - he said "Oh yeah that'll work great".

    Past the 30 day return time frame.

    SO. Step 2: how to drop the radio to 12 watts on CW and SSB. Trying to accentuate the positive here :)

    Dave
    W7UUU
     
  5. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Well, I'm the wrong guy to be commenting on this, because I've only worked on a few RF power amplifiers, and I'm still learning, but:

    Assuming for the sake of argument, that the radio is expecting the ALC line to be 0V when everything is 'normal', and +10V when the signal needs full attenuation. Could you apply +2VDC at the ALC line of the radio to reduce the output power (without sacrificing linearity)?
     
  6. W7UUU

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

    Assuming I could ever locate the crazy weird oddball ALC connector that Kenwood chose. In all my 40 years
    as a ham, I've never seen that pinout or format - on ANYTHING, including all the other Kenwood rigs I've owned.

    Attenuator seems the logical step, no? 50 ohms in and out, with an appropriate loss along the way but not
    so as to interfere with receive - ugh... manual TR switching in my 2m contesting future? DOH.

    Dave
    W7UUU
     
  7. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I would try the (manual) ALC route, just because I think it would work. But, then, it might not, I wouldn't know because I haven't tried it.

    I have a similar problem. I have a 2m amplifier that has an input power rating lower than the output power of a rig I want to use it with. I've seriously thought about connecting the two with one of those 50' lengths of Radio Shack RG-8. Though, based on some testing I've already done, I might actually need to shorten it..!

    You couldn't go wrong with a manufactured attenuator, though.
     
  8. W7UUU

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


    Would I have to have it on a manual T/R switch though? I would NOT want the attenuation
    on receive of course - I wonder are there auto versions (RF transmit sensing) like preamps do...

    I'm a smart guy - done a lot of ham stuff for many years - but this aspect is new to me. So
    please forgive the utter appearance of ignorance - it's quite sincere :)

    Dave
    W7UUU
     
  9. N9DSJ

    N9DSJ Ham Member QRZ Page

    They are not that linear :)

    At 5 watts in you should have about 150 watts out (if lucky). Run it with 5 watts drive.....

    From the Mirage page, input versus output:

    Typical Power Out for Watts in:
    .25: 15.
    0.5: 30.
    1: 60.
    2: 100.
    3: 130.
    5: 150.
    6: 153.
    8: 155.
    10: 160.
    15: 160+.



     
  10. W7UUU

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

    Thanks for this, and yes I've actually tried that on the bench with CW - not 150 - more like 100-110 but
    I'm not picking nits :) But for SSB, the TR-9130 doesn't have a "low power option" - it is in 25w PEP
    mode all the time. Only FM and CW have the 5-watt option. Which probably is fine - I'm much more
    of a CW guy than SSB. But for contesting, SSB is pretty much a must - maybe I'll just "talk quietly" LOL!


    Dave
    W7UUU
     
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