[Elecraft] K1 Filter Board Questions

[Tom Hammond]

Hi Ron:

At 10:34 PM 9/2/04, you wrote:
>I have obtained a K1 and have a couple of questions regarding the KFL1-4
>board. Is there any reason it can't be constructed with 80 - 40 - 30 - 20
>meters? If you purchase a new one it comes with 40 - 30 - 20 - 17/15 meters.
>
>Considering the state of the solar cycle I'd prefer a board with lower
>frequency capability. So is it possible to build a board with 80 - 40 - 30 
>- 20?
>
>Second question has to do with 60 Meters. Is it technically feasible to 
>have 60 meter receive cavility on a K1, assuming the toroids and other 
>components aer appropriate to the frequency?
>
>The K1 is a super little rig and I'ce already become very fond of it. It
>would be perfect if I could get my preferred band selection on one filter
>board.

The K1 4-band board CAN be constructed for 80M, BUT then you'll have to 
give up 40M!!! Here's why...

The two 2-band filters in the KFL1-4 are designed so that the upper 
frequency cutoff of each filter is above the higher of the two frequencies, 
BUT LOWER THAN the 2nd harmonic of the lower frequency.

In other words, the 40M/30M filter cuts off above 10MHz, and BELOW 14MHz. 
If you were to build the first filter for 80/40 meters, then the filter 
would have to be able to pass both 3.5 and 7.0 MHz energy, thus allowing 
any potential 80M 2nd harmonic energy through to the antenna... this comes 
under the heading of "Bad things will happen". So, in order for the KFL1-4 
to be built to accommodate 80M, it's have to cut off at a frequency lower 
than 40M, which means that you'd have 80M, but not 40M.

Sorry pal.  Good try though...

73,

Tom Hammond    N0SS