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K1-4 on 30/20/17/15 ?

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David Toepfer

K1-4 on 30/20/17/15 ?

I am hoping to be near a point where I can actually order the K1 I decided to
get this year. And because of this I have been thinking of how I want to use
it. Now that I believe I have a better understanding of how it's working and
why I am limited to certain band choices I would just like to confirm that I
can do what I wish.

I would like to setup a K1-4 for 30/20/17/15, which I believe would need an LPF
for 20 and 15). I believe I can do this with all of the parts that come with a
K1-4 except that I don't know if it includes an LPF for 20.

Does anyone know if I can do this?

David, k3tue
.

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Mike Morrow-3

Re: K1-4 on 30/20/17/15 ?

David wrote:

>I would like to setup a K1-4 for 30/20/17/15, which I believe would need an LPF
>for 20 and 15). I believe I can do this with all of the parts that come with a
>K1-4 except that I don't know if it includes an LPF for 20.

As supplied, the K1 with KFL1-4 covers 40m, 30m, and any two of the 20m, 17m, or 15m bands. It does NOT cover ANY four of the 40m, 30m, 20m, 17m, 15m bands. Actually, K1 product literature claims that the KFL1-4 coverage is 40m, 30m, 20m, and either 17m or 15m, but the KFL1-4 is actually a little more versatile than that. I guess they thought no one would ever give up 20m coverage.

It has two LP filter sections in the transmitter output/receiver input signal path.

One LP filter section is switched in by firmware for the two lowest bands (40m and 30m), with a filter cutoff somewhere above 30m but below 20m, where the second harmonics of 40m operation would appear.

The other transmitter LP filter section is switched in by firmware for the two highest bands (any two of 20m, 17m, 15m), with a cutoff somewhere above 15m but below 10m, where the second harmonics of 20m operation would occur.

Thus, as supplied, the KFL1-4 won't cover 30m, 20m, 17m, and 15m because you'd be trying to put 30m and 20m signals through the same LP filter that cuts off below 20m.

Additionally, it would be hard to juggle around the values of the fixed capacitors in the pre-mix and the RF band-pass filters to accomodate 30m and 20m operation for the firmware-programmed bandswitching relay latching action that takes place for 30m and 40m operation.

Of course, KFL1-4 firmware could be modified to select one LP filter section for only one band (30m), while selecting the other LP filter section for the other three bands (20m, 17m, 15m), but we don't have the option of altering the KFL1-4 firmware.

Your combo is not impossible, but it would take some study, BP/LP filter redesign, and additional parts (fixed capacitors). But be careful. The K1 has the best spurious output specs of any Elecraft rig, and re-design could sacrifice that spec.

IMHO, it would be best to choose a combo of bands that the KFL1-4 already supports. Trading off 17m for 40m isn't much of a penalty. It gives you a good night-time band any time of the year or solar cycle.

73,
Mike / KK5F
K1 No. 175 (Nov. 2000)
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David Toepfer

Re: K1-4 on 30/20/17/15 ?

Well, that just sways me back to the 'I won't bother with a K1 (since I have a
KX-1)' position and just get a K2 next (even if it is not quite a
unquantifyable pure sounding as a K1). Thank you for the help in deciding
(again).

dt
.

--- Mike Morrow <[hidden email]> wrote:

> David wrote:
>
> >I would like to setup a K1-4 for 30/20/17/15, which I believe would need an
> LPF
> >for 20 and 15). I believe I can do this with all of the parts that come
> with a
> >K1-4 except that I don't know if it includes an LPF for 20.
>
> As supplied, the K1 with KFL1-4 covers 40m, 30m, and any two of the 20m, 17m,
> or 15m bands. It does NOT cover ANY four of the 40m, 30m, 20m, 17m, 15m
> bands. Actually, K1 product literature claims that the KFL1-4 coverage is
> 40m, 30m, 20m, and either 17m or 15m, but the KFL1-4 is actually a little
> more versatile than that. I guess they thought no one would ever give up 20m
> coverage.
>
> It has two LP filter sections in the transmitter output/receiver input signal
> path.
>
> One LP filter section is switched in by firmware for the two lowest bands
> (40m and 30m), with a filter cutoff somewhere above 30m but below 20m, where
> the second harmonics of 40m operation would appear.
>
> The other transmitter LP filter section is switched in by firmware for the
> two highest bands (any two of 20m, 17m, 15m), with a cutoff somewhere above
> 15m but below 10m, where the second harmonics of 20m operation would occur.
>
> Thus, as supplied, the KFL1-4 won't cover 30m, 20m, 17m, and 15m because
> you'd be trying to put 30m and 20m signals through the same LP filter that
> cuts off below 20m.
>
> Additionally, it would be hard to juggle around the values of the fixed
> capacitors in the pre-mix and the RF band-pass filters to accomodate 30m and
> 20m operation for the firmware-programmed bandswitching relay latching action
> that takes place for 30m and 40m operation.
>
> Of course, KFL1-4 firmware could be modified to select one LP filter section
> for only one band (30m), while selecting the other LP filter section for the
> other three bands (20m, 17m, 15m), but we don't have the option of altering
> the KFL1-4 firmware.
>
> Your combo is not impossible, but it would take some study, BP/LP filter
> redesign, and additional parts (fixed capacitors). But be careful. The K1
> has the best spurious output specs of any Elecraft rig, and re-design could
> sacrifice that spec.
>
> IMHO, it would be best to choose a combo of bands that the KFL1-4 already
> supports. Trading off 17m for 40m isn't much of a penalty. It gives you a
> good night-time band any time of the year or solar cycle.
>
> 73,
> Mike / KK5F
> K1 No. 175 (Nov. 2000)
>

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Mike Morrow-3

Re: K1-4 on 30/20/17/15 ?

In reply to this post by David Toepfer

David wrote:

>Well, that just sways me back to the 'I won't bother with a K1
>(since I have a KX-1) position and just get a K2 next (even if
>it is not quite a unquantifyable pure sounding as a K1).

Well, David, I'm sorry to hear about anyone foregoing a K1. It is my favorite QRP rig of the nine that I own, eight of which were put out by three other outfits. In fact, it's my favorite of any QRP rig I've ever heard about.

The first technical hurdle you'd have to overcome wouldn't be all that hard: Re-designing the lower-frequency receiver input/transmitter output LPF so that you could have 30m and 20m on that filter.

The existing third-order elliptical filter rolls off steeply just above about 10.5 MHz. You could use the "Elsie" freeware found at:

http://tonnesoftware.com/elsie.html

to come up with something similar that rolled off near 14.5 MHz instead.

With a little head-scratching and thought, the re-arrangement and value changes of fixed caps in the two other band-pass filters shouldn't be impossible for supportting 20m and 30m as band 1 and band 2.

My point was not that it would be impossible to do what you wanted, but just that it would take some work and re-design.

Good luck, what ever you decide.

Mike / KK5F
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David Toepfer

Re: K1-4 on 30/20/17/15 ?

Well then, perhaps I'll just get back to thinking as to how much effort I wish
to put into it. Thank you for clearing up my confusion over your reply.

David, k3tue
.

--- Mike Morrow <[hidden email]> wrote:

> David wrote:
>
> >Well, that just sways me back to the 'I won't bother with a K1
> >(since I have a KX-1) position and just get a K2 next (even if
> >it is not quite a unquantifyable pure sounding as a K1).
>
> Well, David, I'm sorry to hear about anyone foregoing a K1. It is my
> favorite QRP rig of the nine that I own, eight of which were put out by three
> other outfits. In fact, it's my favorite of any QRP rig I've ever heard
> about.
>
> The first technical hurdle you'd have to overcome wouldn't be all that hard:
> Re-designing the lower-frequency receiver input/transmitter output LPF so
> that you could have 30m and 20m on that filter.
>
> The existing third-order elliptical filter rolls off steeply just above about
> 10.5 MHz. You could use the "Elsie" freeware found at:
>
> http://tonnesoftware.com/elsie.html
>
> to come up with something similar that rolled off near 14.5 MHz instead.
>
> With a little head-scratching and thought, the re-arrangement and value
> changes of fixed caps in the two other band-pass filters shouldn't be
> impossible for supportting 20m and 30m as band 1 and band 2.
>
> My point was not that it would be impossible to do what you wanted, but just
> that it would take some work and re-design.
>
> Good luck, what ever you decide.
>
> Mike / KK5F
>