10 meters on K1 - component values

[Stephanie Maks]

Hi everyone,

I've finished (for now) my experiments in getting 10 meters on my  
K1.  It seems to be working pretty well, both on receive and  
transmit.  I have it up to about 4.5 watts output.  I'm sure that can  
still be improved but I've decided to give it a rest for now.

Here are all the component values I have used, with 10 Meters as Band  
2 of a 2-band filter board.  Where I've used two capacitors to make  
up the final value, I've indicated that, along with the value I would  
have used had I had the capacitors handy.

C6, C10 = 90pf (68 + 22 in parallel; intended to use 82pf)
C7, C9 = 47pf
C8 = 1pf
C16, C20 = 220pf
C17, C19 = 33pf
C18 = 2pf (1 + 1 in parallel; intended to use 1.5pf)
C24, C26 = 68pf
C25 = 150pf
L11, L12 = approx. 0.26 uuH (8 turns of #26 on the supplied yellow  
cores)
X2 = 36.000 MHz fundamental

Three additional modifications have been made to the radio to  
increase the output on 10M:

#1:  220pf capacitor added to filter board, on the top side, on P2  
between pins 7 and 8.  This could also be done on the RF board, at  
pins 7 & 8 of J7.  I had more clearance though on the filter board.

#2:  On the RF board, R11 has been changed from 82 ohms to 33 ohms,  
to increase the gain of the Buffer.

#3:  On the RF board, T3's turns have been compressed as tight as  
possible.  The windings now occupy about 130 degrees of the core.  
Experimentation showed that the tighter the windings, the higher the  
output on 10 meters.  This did not seem to affect the other bands at  
all, i.e. no noticable effect even down at 80 M.  Next time I feel  
like experimenting, I might try rewinding T3 to make it even tighter.

As I said, with those modifications I'm seeing about 4.5 watts  
output.  The bandwidth is excellent; I've got my K1 set to tune about  
270 kHz (using 200pf for RF-C2) and I'm seeing the full output power  
all across that range.  I've had good success copying a couple  
beacons, from 28.217 to 28.258.

The only thing I haven't really addressed yet is how the KAT1  
performs with 10M.  I tried it briefly and found that the output  
power seemed much lower even with the KAT1 set to bypass (ATU set at  
CLP) but that may just mean that the KAT1 needs to be recalibrated  
for 10M.

Hopefully this info will be of use.

73 de Stephanie
va3uxb

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[Akinori Harry SHIBATA]

Hi, all.

I built my KFL1-2 as a 12m/10m board.

I thank Stephanie VA3UXB for his suggestions on component values.

Values of components I used are as follows:

Band 1: 24.8MHz
  C1, C5   - 100
  C2, C4   - 47
  C3       - 1
  C11, C15 - 270
  C12, C14 - 33
  C13      - 2
  C21, C23 - 68
  C22      - 150
  L9, L10  - 0.26uH (T37-6 yellow core; 8turns, 16cm)
  X1       - 32.8000MHz (fundamental)

Band 2: 28.0MHz
  C6, C10  - 82
  C7, C9   - 47
  C8       - 1
  C16, C20 - 220
  C17, C19 - 33
  C18      - 2
  C24, C26 - 68
  C25      - 150
  L11, L12 - 0.26uH (T37-6 yellow core; 8turns, 16cm)
  X2       - 36.0000MHz (fundamental)

Additional modifications as Stephanie did:

On Sun, 1 Jan 2006 12:57:13 -0500,
Stephanie Maks <[hidden email]> wrote:
>Subject: [Elecraft] 10 meters on K1 - component values

>#1:  220pf capacitor added to filter board, on the top side, on P2  
>between pins 7 and 8.  This could also be done on the RF board, at  
>pins 7 & 8 of J7.  I had more clearance though on the filter board.
>
>#2:  On the RF board, R11 has been changed from 82 ohms to 33 ohms,  
>to increase the gain of the Buffer.

I added 56-ohm in parallel with R11 (82 ohms).

>#3:  On the RF board, T3's turns have been compressed as tight as  
>possible.  The windings now occupy about 130 degrees of the core.  
>Experimentation showed that the tighter the windings, the higher the  
>output on 10 meters.  This did not seem to affect the other bands at  
>all, i.e. no noticable effect even down at 80 M.  Next time I feel  
>like experimenting, I might try rewinding T3 to make it even tighter.

In additon to above mods, I added a 0.001uF capacitor in parallel
with R30 on the RF board.

My K1 got the output power as follows:
  24MHz = 7+ watts @ 13.8V
  28MHz = 4 watts @ 13.8V


VFO range must be "150kHz", not "80kHz".  The 12-meter begins from
24.890MHz but K1 covers this band starting 24.800MHz.


Best Regards,

harry
--
Akinori Harry SHIBATA, JL3AMK http://jl3amk.net/ http://jl3amk.org/
Elecraft K1/Mod (160-10m CW 5W) & KX1 (40-20m CW 4W) + Whip Antenna
A1C#311 FISTS#15002 G-QRP#11804 NAQCC#540 QRP-ARCI#12260 RU-QRP#110


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[wayne burdick]

Harry,

Thanks for your 10/12 meter modification details. (And thank you, too,
Stephanie!)

Given your success on these bands, there's the possibility of a future
KFL1-4H option ("H" for "high bands"): a version of the 4-band K1
module that covers some combination of 10, 12, 15, 17, and 20 meters.
But I digress  :)

I'd like to offer a suggestion for those considering either 10 or 12
meters. I think I posted this information earlier regarding 10 meters,
but it applies to 12 meters as well. I've also corrected the math in
the examples to reflect a VFO tuning range of 150 kHz -- necessary to
go above 24.900 on 12 meters.

When I designed the Norcal/Wilderness Radio Sierra, which uses the same
I.F. as the K1, I realized that 10 and 12-meter crystals would be
expensive (especially 36 MHz in the case of 10 meters). So I came up
with an alternate mixing scheme where the LO is below the band rather
than above it. The RX and TX image rejection isn't quite as good with
this technique, but that doesn't matter, in most cases, since the
band-pass filters are narrow.


Here's the normal conversion scheme on 10 meters (high-side injection):

    RF   28.000 to 28.150
  + IF    4.915
------------------------
  = LO   32.915 to 33.065
+ VFO    3.085 to  2.935
------------------------
  = XO   36.000


Here's the alternate scheme on 10 meters using low-side injection:

    RF   28.000 to 28.150
  - IF    4.915
------------------------
  = LO   23.085 to 23.135
+ VFO    3.085 to  2.935
------------------------
  = XO   26.170


And on 12 meters:

    RF   24.800 to 24.950
  - IF    4.915
------------------------
  = LO   19.885 to 20.035
+ VFO    3.085 to  2.935
------------------------
  = XO   22.970


Advantages of these lower-frequency crystals include: (1) more power
output from the premix NE602 (both the crystal oscillator and mixer
output); (2) cheaper; (3) possibly available from Wilderness Radio. If
Wilderness doesn't have any, you might try ICM. I think the ICM part
number for the basic crystal type (not including frequency) would be
#436162.

Low-side injection results in one additional minor issue: the sideband
gets inverted. This just means that the CW pitch will change in the
opposite way from the other bands as you tune. But VFO readings should
still be accurate, since the VFO can be individually calibrated on each
band.

If there's enough interest, Elecraft will supply the crystals and other
parts needed to cover these two bands.

73,
Wayne
N6KR


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[Stephanie Maks]

That's great news Harry!

Just one small correction:
> I thank Stephanie VA3UXB for his suggestions on component values.

That's "her suggestions" - I'm a YL, not an OM ;-)

73 de Stephanie
va3uxb
K1 #02132

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