Hi
One consideration:
If you do signal injection for calibration, you have the amplitude
uncertainties on
both the “carrier” and injected signals. The slope at zero on the beat note is
likely
to be *much* more accurate ( even if gain measurement at audio gets thrown in …)
Bob
> On Jul 7,
Hi,
A well established method is to use a separate offset RF generator that
you can steer frequency to form suitable offset and amplitude to form
known level. You can now inject this ontop of a signal to measure.
Consider that you steer your offset frequency to be +1 kHz of the
carrier you
Hi
The idea is partly to lock the two devices. The bigger objective is to hold
the mixer output at the correct zero volt operating point.
Cabling things to a different device and then doing phase correction to keep
things at zero would be a major pain.
Bob
> On Jul 7, 2022, at 5:52 AM, Mike
On 7/7/22 8:55 AM, Bob kb8tq via time-nuts wrote:
Hi
Yes, you do need to know the system gain. Since we are talking about
gain at audio, measuring the gain directly is not a crazy thing to do. One
of the things that makes audio spectrum analyzers a nice tool for this that
they eliminate the
Thanks Gerhard, for putting up the schematic. After a quick look, I'd
recommend trying the following changes. Of course, I don't know the fine
details, so this is just from a general circuit perspective - could be
all wrong versus the actual situation.
1. Delete the Q7 circuitry including R10
Hi
Yes, you do need to know the system gain. Since we are talking about
gain at audio, measuring the gain directly is not a crazy thing to do. One
of the things that makes audio spectrum analyzers a nice tool for this that
they eliminate the “variable gain to the sound card” issue.
Some sound
Hi
> On Jul 7, 2022, at 12:09 AM, Gerhard Hoffmann via time-nuts
> wrote:
>
> Am 2022-07-07 7:22, schrieb Bob kb8tq via time-nuts:
>> Hi
>>> On Jul 6, 2022, at 1:53 PM, Richard Karlquist via time-nuts
>>> wrote:
>>> The 2N5179 has high base spreading resistance (decreases isolation).
>> As
Hi
The tube cascode has it’s own issues. Setting up a tube circuit for
the sort of isolation we are talking about here is very difficult.
Bob
> On Jul 6, 2022, at 9:46 PM, glenlist via time-nuts
> wrote:
>
> how about grounded grid ?
>
> Bob can you get better isolation with a vaccuum
Hi,
On 2022-07-07 07:22, Bob kb8tq via time-nuts wrote:
Hi
On Jul 6, 2022, at 1:53 PM, Richard Karlquist via time-nuts
wrote:
The 2N5179 has high base spreading resistance (decreases isolation).
As does sticking a resistor (even a small one) in series with the base …. Yes,
inductance
is
Bob, others.
It has been explained that for the best phase noise level calibration on
should use a signal with one radian phase modulation and measure the
output voltage.
The problem with this approach is the unknown gain of the path into the
PC. And due to the gain one can not modulate with
All good comments about the isolation issues, but remember we're talking
about a desired 200 MHz amplifier system here, not a 10 MHz one, so RF
transistors are appropriate. This is a little different from the
original DIY PN test discussion, which is why I replied in a different
thread title.
I assume with grounded grid, that you mean a vacuum tube with heated
cathode. The cathode will have a noise P = kTB, where T is the red hot
cathode, and B is your bandwidth. k is as usual Boltzmann constant.
That said, if you could cancel the capacitances inside the tube, then you
could get a
You wrote:
> Mike.
> One concern I have with active components as mixer is noise. For an SA I
> designed only a passive DB diode mixer had low enough output noise. Would a
> PF detector as being an active component, not create more noise as output?
> Erik
Eric, you do not have to give up your
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