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Galaxy DX-94HP from Bells... Backwards Swing

Discussion in 'CB and Export Equipment and Accessories' started by AndrewGS, May 1, 2018.

  1. AndrewGS

    AndrewGS Sandbagger

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    So I’ve been playing around with my new Galaxy DX-94HP I bought from Bells CB and hooked up my average-reading power meter to look at the output. It swings backwards. :mad:



    Do I just need to back the AM carrier settings down to 5-35W and maybe back off the AMC a little?

    Thanks!
     
    rabbiporkchop likes this.

  2. OldTech03

    OldTech03 Well-Known Member

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    Swings backward from what power setting? Do you have the power set all the way or does it swing backward at any setting? If it doesn't swing backward at all settings exactly what does it do? Give some in-depth detailed numbers so we can better help you as well as what are using for a power supply or was it hooked up in the car and what size cable are you using if it is in the car? All good things for us to know. Thanks
     
  3. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Greetings!

    Ok, turn down the power - then does is still swing backwards?

    This is a 6 of 1 1/2 dozen of the other - with 13th one for Free on Tuesdays...

    So, todays your day...

    I've taken radios like the 94 onto several different meters in the shop to show someone - and waste a lot of time getting them to understand - the differences between RMS, AVG and Peak.

    Some people understand that CARRIER power - when it's set to Proper Mid-Point for a circuit (thinking steady state) then Modulate it, some of the 50 - 50 is higher while others is lower and carrier is lost into the bandwidth somewhere...they feel they are getting gypped from NEGATIVE swing until you bring them to the Peak power meter...

    It's the shift from Carrier to Audio that seems to throw a wrench into the works - because it's not the radio - it's the METER that is trying to sort this all out...

    You really need to understand the SAMPLING circuits many SWR/Power meters have and then compare them to AVG, RMS and Peak - power meters sampling circuits - and you'll see several differences in the basic circuit.

    What does SWR have to do with this?

    Good question in a radio with a built in SWR meter - the FWD power setting is also the S/RF meter power too. So it samples, rectifies, measures and "weighs" the signal one way, while an external meter may use a different circuit method to accomplish pretty much the same thing.​

    All of them take power from the radio thru a sensor, but what that sensor does with it afterwards makes this a difficult method to talk about because not many people "Get it" when it comes to signal processing and how sampled power is weighted and measured or "bridged" and the complex vectors audio envelope adds to this...

    Some use heavy capacitance to "tame" wildly swinging envelopes full of audio and others simply rectify and let the meters own coil d'arsonval movement construction design and inertial "effect" take over and show what is going on in there...some are digitals re-worked to show analog - with that, there's Linear versus Logarithmic response...within the digital realm - and even that's open for interpretation...

    In a word, yes.

    Do what is comfortable for you. It's not the fault of your radio - nor that of the operator - the meter is not faulty either - they are all working - but just not on the same circuit ... which adds to the interpretation problem...

    IF you want a quick demonstration - locate the mod limiter "pot" in there and tweak that - one direction you have your negative swing - the other direction you start to or lessen it's swing - you'll SEE the "negative swing" is less - but you HEAR the audio is processed and "flat" - the limiter effect - you re-open the modulation limiter control to the original setting - you see negative swing again...again...nothing wrong with your equipment none of it - just how it displays it makes you think you have something wrong with it...

    Again, if you don't feel comfortable with current settings, it doesn't hurt to turn it down a little and may extend the life of the radio and your enjoyment of it - longer, if you keep the power down and back off the throttle a little bit.

    Be conservative first until you are more comfortable - then run it any way you wish...

    Regards!
    :+> Andy <+:
     
    Shadetree Mechanic likes this.
  4. AndrewGS

    AndrewGS Sandbagger

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    Thanks for the replies guys.

    First off, 30A power supply that isn't being taxed too heavily, especially on AM. It's pulling only 9A when modulated from a 15W carrier.

    Secondly, it emits a tone when it's set to key under 6W and the audio is scratchy when set under 10W.

    With the mic gain set at 3 o'clock and a 10W carrier it swings back to about 9.5W-10W average, 75W PEP. At a 15W carrier it swings back to about 14W-15W average, 75W PEP. At a 20W carrier it goes back to about 17W-20W average, 90W PEP. The maximum carrier is 25W and it runs 20W-25W average, 100W PEP. Never pulling more than 10A from the power supply.

    It sounds over modulated over the air with the mic gain set above about 1 o'clock on the stock mic.

    On SSB with the power all the way up it averages about 50W and peaks about 110W with the mic gain at 1 o'clock. It pulls about 17A set here.

    Receive seems good, but I don't have a bench to test everything properly, just a decent little MFJ-874 meter.
     
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  5. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Greetings!


    OH GOD!

    I think all bets are off...the limiters gone and the Bias on the driver and finals need to re-checked.

    Is there a Red Wire Jumper Mod in there too?!

    So sorry, thought you have the limiter still in place and it was more stock than this...

    SIGH...

    Squeals on AM below 6 watts - Oh man...On air? Or on a dummy load? Or both...?

    I don't think Bells CB would have let that leave their shop acting that way...

    WOW - what happened?

    Get it some help real quick!

    :+> Andy <+:
     
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  6. AndrewGS

    AndrewGS Sandbagger

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  7. undertaker

    undertaker Undertaker

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    If you have the radio on 11 meters the ham wire antenna is not going to work .looks like channel 39 ..
     
  8. AndrewGS

    AndrewGS Sandbagger

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    That's what the transmatch is for. Seems to work fine, but it's far from ideal. I don't think it will affect my readings.
     
  9. JoeDirt

    JoeDirt Well-Known Member

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    With a %100 modulation on an AVG reading watt meter that looks normal to me.... Only way to tell the correct modulation levels is with a scope.
     
  10. AndrewGS

    AndrewGS Sandbagger

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    Oh, and I put it on a dummy load as well to quell and doubts about the antenna. Same results.

    IMG_0905.jpg
     
  11. undertaker

    undertaker Undertaker

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    Time to call bells...................
     
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  12. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Yeah, they need some work to it, below 6 watts and then overmod - looks like this needs some TLC - it's not a big deal now that I've seen the vid. Your'e ok, just don't overdo or perform any more work to it until Bells CB has had a chance to go over it and then YOU watch them and monitor the audio WITH them, there listening, to tell-describe them the effect - if you can redo the vid with the effect and play it here - then he can determine the "Watergate" or not...

    Your reference to backwards swing - on that meter or on your radio?

    I see roughly 50% up and down and to me - that does look normal - but the reduced power consumption and envelope distortion tells me something in biasing is not right...a better way would have been to use a Monitor to demonstrate that "tone effect" better...

    I - 2nd the notion to call to Bells CB for the tuneup may be ok, but there is something fishy about the way low power is working...something needs a little more work.

    The 9 amps and 75 watts - Eeew, well ok I'll let it slide but that seems LOW - so you may have a bias with the board or with the main PCB - hard to tell but it does show some "swinging" and that is normal. It's average ok? Not peak...

    Thank you for the vid, helps me out a lot - I hope the bias is ok...

    Regards!
    :+> Andy <+:
    You can salvage the radio...
     
  13. KD8HMO

    KD8HMO Sr. Member

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    This is what the snip-n-clip hack shops call "supertune" lol
     
  14. jon666

    jon666 Sr. Member

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    bells strikes again. bet you all the limiters are removed and volted finals
     
  15. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Most people on channel 6 use backwards swing to cut through the pileups. Maybe Bells thought you wanted to be a maul dropper? It is a shame they would do that to such an expensive radio. Have you been able to contact them yet?
     
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