Testing quartz crystals with an HF receiver
Testing quartz crystals with an HF receiver
Sometimes you can destroy crystals with high power crystal oscillators. Here’s a way of testing them with an HF receiver.
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— Interesting! I have a pile of old crystals that I am not sure are working or even what frequency they are oscillating on.
I tried it on a long wire antenna while getting a lot of background noise and I noticed the signal level dropped by about 1-1/2 dB at resonance and much more on just off frequency. So I’m wondering if it also improves the signal-to-noise ratio on signals at that frequency. If it does, it may be a useful add-on for simple receivers matched with QRP transmitters using the commonly available 3.579 MHz TV color-burst crystals.
So, some more experimenting to do. Now I’m also wondering how the arrangement passes harmonics of the fundamental frequency.
Hi there vk3ye i’ve resently made a loop antenna but it does not work for my reciver since it only takes normal dipole or monopole. Is there a way we can convert the loop antenna output to make it a dipole/monopole output?
Brillant! Thank you for sharing.
The RISE in noise is because you hit the series resonance of the Xtal. At Parallel there should
be a dip.
There is a SIMPLE regen. circuit with no coils but a Xtal from grid to ground for a single freq
RX, The Hi impedance at parallel resonance acts a very high Q coil. Just carry rocks for your required QRG and shift channel pronto.
73 G3NBY.
How much power can this Xtal handle?
Yes
Typical the pencil marks are normal.
Peter, I am sorry you have destroyed your crystal. I have destroyed a crystal myself in the past. It was one of these hc-49s tiny ones, like the ones you have and they were getting very hot and very chirpy like in your transmitter. But this was at a 0.5A to 1A of total current draw. The small crystals transfer easily the heat from the die to the external can and you can detect it more easily, but the larger ones like the one you cracked do not, so it is more difficult to detect. Lesson is, Do not use a crystal for quite long, if it sounds too chirpy with this transmitter. This means it is overheated inside.
However, I have never destroyed a crystal that sounded chirp-free on the air. Cracking a crystal, seems believable, but removing the plating material from it, seems too extreme. I do not think this has been happened in your big crystal due to heating.
Sir can we using a xtal as a receiver??
I’m always learning something from you… Thanks.
Long ago I noticed that if you put one wire of a crystal on the antenna of a super regenerative receiver then it will go quiet with no static at all when its tuned to the crystal frequency. (Super regenerative receivers typically make very loud noise when there is no signal being received.)
I love it good
Keep uploading videos like this
Used this method to check crystal filters found at a Hamfest. At least you can tell that it’s not open. Also tap it to see if it’s microphonic (thats bad).
The pencil mark on the xtal is how they "calibrate" or adjust the xtal to get it to the desired freq. Old timers used to use this trick to "move" xtals to a more desirable freq at times. In fact Rex W1REX at QRPme has a kit to allow you to grind and check your own xtals. You could probably make up one like it easy enough out of parts and microcomputers laying around the shack. 73
Sometimes you have to sacrifice an xtal. In the name of science.
R.I.P. old quartz.
A second stage would have been cheaper. But then it’s no longer a one-transistor circuit.
No risk, no fun.