Last Up Date:   11/ 04/2010


Drawing Corrections:

It has been noticed that there is inconsistency in component values between the circuit board and the schematic and parts placement drawings supplied with early kit shipments.

Please take note of these Adjustments:

Capacitor Values:

  1. The capacitor from Pin 1 to ground on U3 should be 0.1 mfd.
  2. the capacitor value going to the base of Q3 from the VFO should be 0.1 mfd.
  3. The correct value from U1, Pin 4 to ground is 0.01 mfd.

Resistor Values:

  1. Your kit includes a 510 ohm resistor that may be used in place of the 1K value shown as R19



The 510 ohm and the 1 meg ohm resistors have the same colors but in reverse order. Be sure to use 1 Meg at R4. The 510 ohm value at R4 will kill the receiver audio.



Diode D6 is drawn backwards on some schematic drawings that came with some board kits

It is shown correctly on the ARRL schematic found on the binary file for the

Rockless QRP. The Binaries are found at

Diode D6 is a 5 volt zener diode used to regulate voltage to U3.



If any kit arrives missing parts please email me immediately and I will send what was missing. I recently found that a package that was marked 120 pfd was actually 100 pfd. This was corrected kits shipped after November 7, 2009



Most kits have shipped. I am waiting for one part to complete the last of current open orders. All orders

now received should ship within a week.


Caution When Wiring Multi-Turn Tuning Potentiometer:

Be sure to check your 10 turn potentiometer with an ohm meter to determine which connections are the ends of the 10K protion and which terminal is the wiper contact. The wiper contact should go to the 100K resistor that connects to the varactor diode. When measured against ground the resistance at the wiper increases with clockwise rotation. Likewise voltage to the varactor diode should increase with clockwise rotation.of the control. The higher the voltage to the varactor, the lower the capacitance that it exhibits, hence you tune up in frequency as capacitance becomes lower. Check this out before you get it all together.


Reported Source for MV209 Varactor Diode:

K8RRH reports that he has found the MV-209 Varactor diode for the VFO at the following site:

Hosfelt Electronics.


Thanks K8RRH, this should be of great help to many searching for this part. Search the site for diodes, “other” and you will find it.


VFO Inductor and VFO Stability:

I have had reports that when first applying power to some oscillator boards, that the frequency drifts for some time. Recently I built an oscillator board using parts supplied in recently shipped kits and found this same problem. I have traced it to a substitute 8.2 uHY inductor used in the VFO which was recommended as a replacement for the original coil when I re-ordered the inductor. The coil in question has multi-stripes, with gray on the end and then red. (Color code for 8,2 uHY). The original shielded inductors for this value were all black in color and were very stable. Running a sample test on on the replacement coils I had in stock I found the substitute parts had poor consistency of value and many were out of tolerance. The original Black color shielded coils all test consistently in value and operate well in the oscillator.

If you have trouble with oscillator stability and your kit included the multi-striped coil, contact me at and I will send you a replacement inductor.

I have recently changed this part number in the Parts List to an unshielded 8.2 uHY coil made by Delevan.. The unshielded coil is Delevan part 1025R-42K. It has a Digikey part number of DN7692-ND, and it is immediately available in small quantities. Either this unshielded 8.2 uHY coil by Delevan, or the Black color Delevan Shielded coil give good stable operation in the oscillator.

The shielded inductor is Delevan Part 1641-822K. Mouser lists their part number as 807-1641R-822K, and this part appears to be immediately available from them.

The unshielded coil is smaller in diameter and is solid sandy yellow in color. The value is stamped on it.

Kits shipped after 12/28/2009 will have either the black shielded or sandy yellow colored unshielded coils for the VFO.


Volume Control Suggestion

I have found another Volume control that will ship with all future CK-1 kits. The 9mm square volume control had been used because it would fit in both size cases, and at the time I couldn’t locate a better one to do the job.

However, I have recently found Mouser Part number 313-1500F-1M. It has audio taper and performs very well in the Rockless. The body is about 16 mm (.63 inches) in diameter, not counting the terminals, which you can face to the side. The terminals are solder lugs. Remember to short the center wiper to one of the end lugs so that zero resistance is in the full counter clockwise position.



Read this Great RF Probe Tutoral:

If you don’t already have an RF Probe for testing your Rockless and other projects involving RF, you can find a great tutorial for building one at this web page: N5SE’s Classic RF Probe Just click this link and it will take you to the site. This is a simple item to build, which every “building ham” should have in his shack.

The Article includes a great discussion of how it works.


Alternative Audio Chip for LM1450:

The OP Amp chip LM 1450, 8 pin dip has been getting difficult to locate. I have found a substitute in the Dual OP Amp KA4558. Mouser stocks this chip as part number 512-KA4558.

No change in operation was observed when using the KA4558 as the audio chip in the “Rockless Qrp”.



Setting the Offset Frequency:

It has been pointed out to me that I mistakenly show the offset frequency in KHz rather than Hz as it should

  1. be. Note that this has been corrected on the web page under the Building Hints link for “Setting the Offset”.