T680 questions

Discussion in 'CB Radio Forum' started by jjmck82, Nov 2, 2020.

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  2. Night Stalker10

    Night Stalker10 Heavy Load Member

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    When I was reading this article and I got to the Ye Olde Way, I was thinking about the diode test on any of the modern DMM. The only problem is that you are locked to a certain value of voltage and current. Not that it's really a problem, since you just try and match 2 transistors with about the same forward voltage that turns on the transistor.
    Of course for the cb perfectionist, that probably won't do. I like using my old curve tracer I built in the early 90's. It lets you see not only the knee voltage, but the linearity of the current flow of the transistor/diode. On the other hand, is maybe 5 watts difference in output with these export radios going to be that noticeable ?
     
    Timin770 Thanks this.
  3. craig_sez

    craig_sez Road Train Member

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    Nightstalker...Might be only a 5 watt difference but what else does that difference throw off elsewhere within a radio....It can become a daisy chain of differences and make an expensive radio investment #### near useless..
     
  4. craig_sez

    craig_sez Road Train Member

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  5. craig_sez

    craig_sez Road Train Member

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    To be honest,i dont put the time and $ into the hobby like most do....
    I know sweet frig all about radios and very little about the rest....$ i have into this is radio purchase,a few different antenna,analyzer and multi meter...The rest is just odds n ends kinda stuff,so no fortune spent here cause i dont have a fortune..

    Some of the stuff you just decide what you want more....Lets say smokes and booze for a few months or poker machines or bar hoppin,suddenly its a new analyzer or radio ect..
    Me for awhile i have not bothered with either of my motorcycles and prices on new pc stuff went bat crap crazy,so thats all on hold but still had $ sittin around to do stuff with....

    Some have gone to yard sales n such and picked up some deals..I see pics of some guys with 40/50 radios,not me..2 is enuf..

    The info i use is from here,cpl fellas in the states and the net,arrl or aarl what ever it is and trial n error on my part....
    Based on what i saw once im gonna tie some string to my 102" and pull to see how it affects my antenna tune if at all then likely re tune my ant to be its best when at highways speed vs sittin still....
     
  6. Night Stalker10

    Night Stalker10 Heavy Load Member

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    Well off the top of my head, I can't think of anything that a pair of slight mismatched power transistors would throw off in the RF chain of the radio. At least nothing major, mainly because these radios are technically working fine in respect to the manufactures design when they leave the factory. If a tech is doing a transmit alignment with in the specs of the transitors, it should all be good. There's a fine balance of getting all these parts in the radio to work together. Also, since these radios are being massed produced at a factory, they probably don't have time or money to pay someone to check out every transistor before they install them in the radio. Now if you are really going to push the operating limits of the parts (like a keydown competition), then it would be more critical to match them as close as you can.
     
  7. craig_sez

    craig_sez Road Train Member

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    Naw i dont do key downs n such and im no tech so i cant argue the point one way or the other..
    Im just goin by what i have seen and the tid bits i pick up here and there and what most would consider what makes sence..
    I have watched vids where brand new outta the box radios are not to bad and sound decient to some being way outta wack and sound like ####....Even saw a vid how a guy bragged about his $1000 radio onlu to get out done by an outta the box radio....
    One time i met up with a fella travelling north from deep down va way..He had a big radio,sweet 16 and a predator 30k...He was loud from about 5 mi out till he got about the same past me then i couldnt hear him....I was able to be picked up but he faded away lime he was 50 mi away....So haveing the right parts n such make a huge diff...
     
  8. Meteorgray

    Meteorgray Medium Load Member

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    To me, spending a lot of money on a radio that is used in a vehicle is like buying a $1K suit to wear without shoes.

    Without a decent ground plane, AKA the "other half" of a radio, you are largely wasting your money on perfected radios.

    It would not be surprising that a superior radio could be beat by a faulty one due to the varied RF-related attributes of the "other half" vehicles on which they respectively sit, not to mention numerous other variables such as antennas, coaxes and such. Comparing radio performance is a risky venture if you care about reality.
     
    Timin770 Thanks this.
  9. craig_sez

    craig_sez Road Train Member

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    Thats whefe the driver has to put in the work...
     
  10. rabbiporkchop

    rabbiporkchop Road Train Member

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    Every single radio coming out of China with multiple final transistors running in parallel always has mismatched finals resulting in distortion at various audio frequencies resulting in spurs adjacent to the fundamental frequency.
    They are all different but they are all complete garbage as shipped from China. This is where I agree with Ridgeline and all the ham guys that talk crap about export radios because they are correct. They just don't have the engineering skills to overcome the problem. When you follow the service manual and you cannot eliminate distortion it's always because of the mismatched transistors. It's called intermodulation distortion. For maximum efficiency those transistors must work in unison and they won't if they aren't matched.
     
    Last edited: Nov 26, 2020 at 11:28 AM
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