Amplifier: Seeking Recommendations

Discussion in 'Amateur Radio Amplifiers' started by KD2NOM, Aug 19, 2017.

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  1. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    So, I think the feed lines will be fine:

    'RG-8X power handling ratings are 3.0 KW for 5 MHz and below, and 1.2 KW through 30 MHz so you should be fine handling the 1000 watt output of the AL-80B amplifier.'

    Next question - I have an internal tuner on my FT-450D - would I still use that to 'tune up' the antenna for the band / frequency and then tune the AMP? This will be my first LA so I am asking a lot of questions so I don't have to ask 'where do I send this for repair'.
     
  2. KK4WMX

    KK4WMX XML Subscriber QRZ Page

    My understanding is that the only antenna matching done should be on the far side of the amp, so bypass the internal tuner when using the amp. The external tuner (if used) will need to be rated for the power output you will be using.

    Nick
     
  3. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Thank you Nick!
     
  4. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I've downloaded the Amplifier manual for the AL-80B and am going thru the tuning procedure - it's answering some of my questions ;-)
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Turn OFF the internal tuner in the 450D to use it with the amplifier. The AL-80B has its own tuned input circuits.

    Regardless what's printed anywhere, RG8X can be marginal even on HF, under various conditions: If SWR exceeds about 3:1 anywhere, it can suffer voltage breakdown under some conditions. On the higher bands it's easy to avoid this with matched antennas, but on 80m or 160m it's difficult to avoid this with most common antenna designs, as the bands are so "wide," percentage-wise. This isn't a "power" problem, it's a voltage problem that may or may not occur depending on other variables including how the cable was manufactured, how hot the cable is and how much ultraviolet exposure it's had (cumulative damage can occur over time). Even barometric pressure (height above sea level) is a factor in coaxial cable ratings -- they're not rated as highly at 10,000 feet as at sea level.

    One thing that causes RG8X "breakdown" is taping it or clamping it too tightly to hard surfaces like antenna booms, masts and tower legs. That compresses the soft cable and makes it more prone to break down at those places.

    In "free space" (not taped or clamped) on a cool day with minimal UV, RG8X can handle a lot of power. I use it "indoors" for jumper cables at up to 1500W PEP. But that's indoors, and it's not strapped to anything.

    All my "outdoor" coax feedlines are RG-213/U or better (heavier, higher rated) cables. We do have extreme UV here, combined with some very hot weather (>>100F), and my outdoor lines are supported by tower legs, masts and antenna booms with tape.
     
    WB1E and AF6LJ like this.
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    If you r antennas are properly matched you don't need the tuner, or the small amount of loss it introduces.
     
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    Agreed
    As I said above I don't use it.
    I wouldn't think of using it above 40 meters and only where it would be protected.
    I use RG-8 type coax (like belden 8213) on my 20 meter dipole which is currently down..
    I use 450 ohm window line for my 75 / 40 doublet. (That may change this winder)
    VHF I use 1/5" hardline.
     
  8. WF4W

    WF4W Ham Member QRZ Page

    im late to the game on this thread but thought i would throw in my experience with the ALS-600

    Its the first amp i've owned (i was out of hobby for a long time) and so far, so good. I like the no-tune setup of the SS amp. I've also added the ARI-500 for instant band switching and relize that instant band switching and no-tune is a MUST for my operating style - quick band changes chasing DX.

    I thought I needed QSK so I added the external QSK-5 unit. It runs HOT so I added a fan and now it runs LOUD. I never use it anymore. . .

    I've used this for contesting (CW) and use it a lot of digital modes (dont judge me) and have only overheated it once. I think it is b/c I had everything packed together so closely I was inhibiting airflow. The amp now sits off to the side by itself and I've not had any heating issues since.

    My next amp will have all that 'stuff' in one box - SS, Auto band switching, and QSK. Im not sure what it will be - probably the elekraft - but for now I've cobbled together a solution that takes a beating and continues to work pretty well for the cost. I do wish I had went with the ALS-1300 but oh well...
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    Where do you get that ?
     
    AF6LJ likes this.
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    :)
    half inch....
    By the way...
    they do make .141" hardline which is very close to .200".
     

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