[Elecraft] [KX1] 1st QSO on KX1 #2794

[Don Wilhelm]

Matt,

Yes, you will be replacing L1 and L2 with the KXB3080 Low Pass Filter 
board.  Take great care when assembling and installing that board 
because most builders' problems stem from that board.  Follow the 
instructions exactly, there is little room for "creative building".

With the KXB3080 installed, you can expect the greatest power output to 
be on 80 and 30 meters.  If that is in excess of 3.8 watts, the other 
bands should be able to be brought into range (greater than 3.0 watts 
with a 13.8 volt power source) by 'monkeying' with the turns 
spreading/compressing of L1 and L2.

My usual expectation is for 3.5 watts or greater on all bands with a 
13.8 volt power source, but that exceeds specs.  The KX1 Power Mod that 
is supplied with the KXB3080 may be required, but do not expect the 
power to exceed 5 watts (which under some SWR conditions may exceed the 
voltage ratings of the capacitors in the Low Pass Filter.

73,
Don W3FPR

On 4/10/2014 6:18 PM, Matt VK2RQ wrote:
> I just realised, the question of optimising the L1 and L2 inductors in the LPF for the basic radio is a bit academic anyway, since those inductors will be replaced when I install the KXB3080 module. Thanks also to those who replied off-list.
>
> 73,
> Matt VK2RQ
>
>> On 11 Apr 2014, at 12:46 am, Matt VK2RQ <matt.vk2rq at gmail.com> wrote:
>>
>> I just made my first contact on my new KX1 with a VK5 about 700 miles away who was running a K3 -- the KX1 is indeed a very nice rig.
>>
>> Initially I was getting about 2.7 W out on 40m and 3.2W out on 20m (13.8V supply, 50 ohm dummy load). I read in the manual that the output on 20m should normally be less that on 40m, and this can be achieved by compressing turns on the L2 inductor to adjust the LPF. I found that compressing turns on L2 reduced the output power on both bands, but 20m was still more output than 40m. By compressing the turns on the L1 inductor as well, 40m is now around 1.9W, and 20m is around 1.8W, so overall power is reduced, but the 20m output is now below the 40m output. In the KXB3080 module kit which I haven't built yet, I think there are some resistors that can be swapped in for R11 and R30 to bring output power back up a bit. Is there anything else I can check to make sure the LPF is set up properly?
>>
>> 73, Matt VK2RQ
>>
>>
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