Sulaiman wrote ...

I don't know if it helps but for simple amateur radio h.f. power amplifiers
IRF510s are popular because they are cheap, have relatively low capacitances,
and I've had them working at 14 MHz (20m).

They are only 100v, 4A cont., 20A peak but would be a cheap intro to h.f. Class-E
cheap enough to blow up a few whilst learning :)

ZakWolf wrote ...

Can I use my sn74hc14 to find the Res frequency of my secondary? Since I dont have a function generator or the money to get a worthwhile one I was wondering if the hex inverter would be able to do the trick.

300khz-~6Mhz sweep ability at 5.6v peak. Connected like this:



Would that supply an accurate reading? I havent dont much tuning before.

Also Im not this far along in my project yet but I was wondering if there was any good site for how to layout RF boards. From what I have read a good layout can do wonders. I noticed that just used through hole parts. Just looking for food for thought.

GrantX wrote ...

You can set up the 74HC14 as a variable frequency oscillator, which can sweep a rather large frequency range. But for 350kHz all the way to 6MHz the 74AC14 may be needed (the online calculator I found just then for the 74C14 tops out at 2.5MHz if you stay within the recommended values). You may also need a few different sized timing caps, with a switch to select the range you want. With one of the Schmitt gates set up as an oscillator with potentiometer and timing caps, the other 5 gates can be wired in parallel for a bit more current (probably a good idea to include a resistor in series with each output to ensure even current sharing).

This page has the relevant info on the 74C14, including the schematics and calculators for setting up the oscillator:

And this schematic I just found on google images shows roughly how to connect the oscillator to the parallel bank of gates (the gate with pins 3 and 4 is unnecessary and can be included in the parallel bank. Resistors in series with the output of each gate in the parallel bank are advised for current sharing purposes as I said before. Its also a good idea to include a resistor in series with the potentiometer so you can't turn it all the way to 0 Ohms):

That method of tuning seems reasonably accurate. I've had successful measurements by leaving the scope ground and signal-gen ground unconnected, but when using my lower power battery operated signal-gen I had to connect it to the scope ground to get a large enough signal.

As for RF layouts, it kind of depends what construction techniques you want to use or avoid. If you want to have some PCB's made up, a two layer board with generous ground planes and short thick traces will be beneficial. If you want something cheaper and easier, "point-to-point" or "dead-bug" techniques built on a copper ground plane will probably be the easiest to solder. Its mostly all about the shortest possible connections to avoid stray inductance, decoupling caps on all DC rails and shielding or ground planes everywhere possible.

For the handmade approach, these 3 Youtube videos may give you some inspiration:
- Construction and prototyping techniques:
- Building a RF crystal oscillator:
- Building CW transmitter and low pass filter:

ZakWolf wrote ...



Those videos were perfect you guys are batting 1000.

So I havent settled on a set frequency yet, Whats the trade off of higher Mhz's? I think ball park around 4Mhz will be good. Also read about not having a coil former for the secondary, something about winding it and gluing it then removing the secondary former to reduce losses in the coil former.