[Elecraft] KX1 help

[Don Wilhelm]

Ed,

First welcome to a great hobby.

I would advise against using that 'old AC adapter' - those wall warts 
are usually not regulated and the no-load voltage often soars to 1.5 
times the voltage shown on it, and at high current loads, the voltage 
sags a lot. 

For home station use, you will likely accumulate several things that run 
on a "12 volt" power source - that is actually a 13.8 volt power source, 
the voltage of a fully charged lead-acid '12 volt' battery like that 
found in an automobile.  So my recommendation is that you get a 
regulated power supply that is rated for at least 3 amps (I would 
actually suggest one that is rated at 12 amps or more, you will 
eventually need it).  Put a 2 amp fuse in the power cord to the KX1 to 
protect it near its maximum current draw plus some reserve.

As for the antenna, there are several choices to make - what bands do 
you wish to use it on?  Is this an antenna for portable use or will it 
be a permanent part of your home station?  A half wavelength dipole fed 
with coax is the simplest antenna, but the coax fed dipole is a single 
band antenna. - there are ways of using it on multiple bands - traps, or 
extra half wavelength wires for the other bands spaced away from each 
other - use a 1:1 balun at the antenna feedpoint.  Alternately, you can 
feed the dipole (single wire cut for the lowest band) with ladder line 
and use a balun in the shack to convert to an unbalanced line and 
connect it to the KX1 with a short length of coax. - you will need a BNC 
connector at the KX1 end.  The KX1 autotuner does not have a lot of 
range on 80 meters, so get the antenna plus feedline as close to 50 ohms 
resistive on 80 meters as you can.  If you use a 135 foot wire and feed 
it in the center with a length of 450 ohm ladder line that is 122 feet 
long (an electrical half wavelength), you will come pretty close to a 50 
ohm load at the shack end of the feedline, and the tuner should handle 
it on the other bands.

If you want additional information about antennas and transmission 
lines, I would refer you to the ARRL Handbook (every ham should have a 
copy).  You may also find the Antennas, Transmission lines, and Tuners 
article on my website www.w3fpr.com informative.  Yes, build your own 
antenna, it is a lot of fun to experiment with antennas, and it is much 
less expensive than the prices charged for pre-built antennas.  Some 
even tout very impressive specs, but that is a stretch of someone's 
imagination, the basic laws of physics must apply, and some of the ads 
stretch that truth. (Rant off now!).

73,
Don W3FPR

Edward Doyle wrote:
> Howdy,
>
> I am new to amateur radio and just upgraded to General a few months  
> ago and have some basic questions on a power supply for the KX1 and  
> how to make a wire antenna.  I am going to add the auto tuner and the  
> optional 80 and 30 meter board later.  So as far as a power supply can  
> I use an old AC adapter as long as it is within  8 to 14 VDC and if so  
> how should it be connected to the connector for J1. Or would a  
> commercial type application be a better choice.  As far as the antenna  
> is concerned what type of wire should be used and how is connected to  
> the connector.  I hope that as I start building my kit that these  
> answers will be a little more obvious but I am trying to get as much  
> information as I can before I start building.
>
> Thanks,
>
> Ed
> KE7HGA
>   
>