Re: Hilltopper 40 Power Out at 12 VDC

KB9BVN - <kb9bvn@...>

This is a fun and very learned group..I learn more every day I am here. 


On Thu, Mar 14, 2019 at 9:17 AM Dave Benson <davek1swl@...> wrote:
re class-C vs class E

There's another straightforward way to looking at the schematic.

The components on a class-E amplifier's collector/drain circuit should be resonant at the operating frequency. This primarily includes the collector/drain's RF choke and a capacitor to ground. (The PA device's output capacitance also needs to be factored in. )

If there's a capacitor to ground on the PA drain/collector, chances are good it's designed for class-E.


On Thu, Mar 14, 2019 at 6:18 AM David Wilcox via Groups.Io <> wrote:
OT I know.

Still looking for a Palm Pico Paddle.  Thought one of the listeners here might have one to sell.

Thank you.

Dave K8WPE. Djwilcox01 at gmail dot com

David J. Wilcox K8WPE’s iPad

On Mar 13, 2019, at 11:02 PM, Charles W. Powell via Groups.Io <doctorcwp@...> wrote:

Oh good.  Some more fun with the scope!


Chas - NK8O

On Mar 13, 2019, at 8:30 PM, WA0ITP <wa0itp@...> wrote:

Correct!  Put your scope probe on the collector of the finals  If it is in Class E, You should see only positive rectangular pulses, such as the ones below.  The LPF filters out the harmonics making it sign wave. 

Dave has mentioned that the HT runs in Class C.  The second graph below show most classes and their conduction angles.  Class C is sinusoidal but is biased off for most of the cycle.  It can be very efficient too.


I love this radio stuff.
On 3/13/2019 6:32 PM, Charles W. Powell via Groups.Io wrote:
Question:  Can one tell from the waveform of the output of the BS170s what class amplifier is in operation?  If I understand correctly, Class E would show only a series of pulses, whereas class C would show a “round topped” upright square wave.

Any guru comments on this?


Chas - NK8O

On Mar 8, 2019, at 4:25 AM, Dave Benson <davek1swl@...> wrote:


Good question!  (and nice going on all the kit building)

There shouldn't be much difference in power output between the two bands. There's plenty of drive from the paralleled logic gates. As a result, the PA devices should be in saturation either way.  As an aside, I'd heard from someone who tried the scheme on 50 MHz. He got 4W out.

From what I've heard, the QCX may be more prone to low power output. I don't know if that's a common occurence, though.  The QCX is configured for class-E but the component values don't make sense to me.  In the case of the Hilltopper, I was concerned about peak voltages (4*Vcc) and tolerance stack-ups. As a result, the Hilltopper runs class-C and not class-E.

73- Dave, K1SWL

On Thu, Mar 7, 2019 at 8:45 PM StanWB2LQF <sjl219@...> wrote:

I'm about to purchase a Hilltopper 40 but first I would like to know how close to 5 watts output I can get from 12 VDC?  I built five QCX transceivers and not one of them ever approached 5 watts on 12 VDC and they also use three BS170 transistors.

In fairness to QCX Labs, they do indeed specify that the QCX transceivers operate on approx 6 to 16 volts and, of course, output varies directly with voltage.

Followup question:  For whatever power out 12 VDC provides for the Hilltopper 40 should I assume it will be EQUAL or LOWER for the Hilltopper 20?

Thanks in advance for some enlightenment; I'm a new group member.

72, Stan WB2LQF

73 de KB9BVN
Brian Murrey

Join to automatically receive all group messages.