[RTTY] AL-80B Or KPA500 for RTTY Contesting

joeduerbusch k0bx at arrl.net
Thu Aug 4 19:45:43 EDT 2016


Joe is right as always, but he failed to mention that your solid state
transceiver starts to fold back with a SWR >= 1.5 to 1.
So if you have a higher SWR, you will need a antenna tuner for your rig.
So you need to have good antenna's, low SWR at your station..
At my station I do not need a tuner for 40 to 10 meters where I operate.  I
only need the tuner for top band edge, if I ever go there.  I use the
antenna tuner mostly for the Wattmeter.
Now I still have to manually switch the coax switch between antennas and I
do need the tuner on 80 meters.

The point to question was AL80B VS KPA500.  both will work fine.  Both will
do at least 500 watts in RTTY contests.

Joe K0BX


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On Thu, Aug 4, 2016 at 8:30 PM, Joe Subich, W4TV <lists at subich.com> wrote:

> On 8/4/2016 4:02 PM, joeduerbusch wrote:
> > What do you get over the AL80B for the extra money?  Solid state no
> > tune-up, auto band switch and very fast QSK break-in.
>
> But no tuner.  Unless you have very well tuned (low SWR) antennas for
> every band (and all parts of the bands in which you operate) you will
> need a manual tuner (losing the advantage to "no tune-up") or a high
> power auto-tuner (more $$$) to make best use of the KPA500.
>
> Don't get me wrong ... I'm an Elecraft fan but I don't know of any
> solid state amplifier that will run correctly (and safely) into a
> significantly (SWR >~ 1.5:1) mismatched load.  If the impedance is
> low the devices will saturate (maximum current), if the impedance
> is high the devices will clip (require higher voltage).  In either
> case IMD and heat dissipation rise significantly.
>
> 73,
>
>   ... Joe, W4TV
>
>
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