That was a possibility I totally overlooked, Nick. Let me try that this weekend. Thanks.
Ram
On Tue, Nov 12, 2019, at 5:04 AM, Nick Kennedy wrote:
I've sometimes seen counters display harmonics. It could be a matter of overloading the counter. Try attenuating the signal to the counter a bit, possibly just be using a very small coupling capacitor.
73-
Nick, WA5BDU
Hi Ram,
Do you have an oscilloscope? If so look at the waveform from your
crystal test oscillator--I bet it's more of a square wave than a
sine wave and if so your counter is looking at the stronger 3rd
harmonic component and reading that instead of the fundamental.
73,
Steve AA7U
On 11/11/2019 9:52 AM, Ramakrishnan
Muthukrishnan wrote:
I am very early into the
project. As a first step, I thought of building a G3UUR
crystal tester to select crystals for the filter and the
oscillators. I have got about 100 4.9152 MHz crystals that I
got from aliexpress. Last weekend I built the G3UUR Colpitts
Oscillator (straight out of the EMRFD book and also described
in many other webpages). I also have a counter with a 1 Hz
resolution, again obtained from Aliexpress specifically to
hook up into the Oscillator.
Unfortunately, when I plug in the
4.9152 MHz crystal, I get a reading of 14.742475. Looks like it
is 3x the frequency of the crystal. I tested many from the lot
of 100 crystals, which came in lots of 50 from two different
vendors and they all read the same. I had a 28.04 MHz crystal
which seem to be oscillating at the correct frequency. I don't
know what to make out of these readings. Is the crystal, a 3rd
overtone crystal? Or is it that the colpitts oscillator is
designed to operate at a higher frequency and the 3rd harmonic
is where the tuned circuit that comprise the crystal (which is
inductive?) and the two capacitors are getting tuned?
73
--
Ramakrishnan Muthukrishnan