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Yes, the capacitance change of a varactor per volt decreases as voltage increases. But remember that the capacitance change has more "worth" at low levels. For example, in a tank with only a varactor

Most QRP CW transmitters get by with just the output low pass filter because the oscillator is working directly at the desired transmit frequency. There is no mixer to create spurious products. The

John, Why offline? Perhaps we can all learn something. I have no experience with this particular design. But I don't think you have a layout issue. Most CW transmitters are broadband all the way out

To make a long story short, I am have a problem with the output power varying a couple watts over the tuning range depending on where I peak the filter (T3 T5).? I built the rig using ugly

As someone who has endured graduate level math... Don't overthink the math when designing or troubleshooting a radio. As someone else commented, high school algebra is almost overkill for the amateur

two CR2032 batteries Roy WA0YMH

William, Oooops, That should have been Vrms ?^2 I never could get comfortable with RPN.? I had one of the TI programmables.?That worked good for me for a while.? I *loaned* it to my son when he

Chuck, Thanks! I had discovered that a long time ago and was using it in my previous message to illustrate my relative Business Administration degree ignorance of electronic theory. But, coincident

Here's a thought on a minimalist si5351 vfo: Could turn on a second channel at 600 hz away from the primary channel, weakly coupled into that primary channel. This should come through on most

The si5351 is a great part, and only costs $1. You do need a processor to communicate with the si5351 via its i2c bus, but a low end msp430 these days is $0.50. With that, a 25mhz reference crystal,

It is stable enough because of the use of the crystals. However, if this was an LC circuit, you definitely want voltage into that pot to be regulated. The voltage applied to the diode is always some

Jerry, The capacitance beyond 10V changes very little.? The plotted curves by k7qo?in the attached chart show that. The MV209 is similar to the BB910 that I used. Note too that the curve for the

Would it be of any value to use a Si5351 module like the Adafruit module ($7 from them or Mouser or Digikey) or a homebrew one like VK3PE makes that is a drop in replacement for the Adafruit

William, Try this:? Vrms = 0.3535 * Vpp? then, Po = Vrms*2 / 100 That's the simplest approximation. -- Chuck, W5USJ (ex K2OFN) Point, Rains Co, TX? EM22cv

Thanks Chuck

Would not be an issue with the tuning range limited to 3khz.. However, the frequency determining pot for the varactor diode is operating directly from the power supply.

this is the vfo I made from Solid State Design

I built a simple regenerative receiver awhile ago using VK3YE design Rob mentioned and linked http://www.learnmorsecode.com/716/index.html Stable, sensitive.? Two transistors, a resonator, and an

Tried to add two attachments at a time --- Didn't work...8^( -- Chuck, W5USJ (ex K2OFN) Point, Rains Co, TX? EM22cv

Jerry, I get about 3 kHz with a pair of crystals on 7MHz using the "fixture" in the picture.? I measured that with a 10V tuning range. The SA612?oscillator is running from the 6V regulator circuit