Dear forum,
The problem of my crystal measurements has solved :-).
Thank you for your advice :-).
I try change the transistors from BC547B to 2N3904.
(maybe I got 2nd grade quality of BC547B)
Then vfo works with crystals : 3.5 ~ 14 MHz,
and frequency could also displayed at my pc monitor counter.
Yours,
Milarepa
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----- Original Message -----
From: Arv Evans <arvevans@...>
To: <BITX20@...>
Sent: Friday, July 16, 2004 11:19 PM
Subject: Re: [BITX20] CRYSTAL MEASUREMENTS
(2) If the transistor you are using for the Crystal oscillator is not
capable of operating at 10 MHz or above, it may be not oscillating with
the higher frequency crystals. The solution for this is to use a better
transistor. In the US we have 2N2222 and 2N3904 available for very
reasonable prices so this is what I use for most of my HF work. These
devices are rated to 150 MHZ, and will usually oscillate at even higher
frequencies.
I hope this helps.
Arv - K7HKL
_._
On Fri, 2004-07-16 at 04:30, MILAREPA wrote:
Dear forum,
==About Crystal Measurements==
At the time I mail to BITX about this subject,
'actually' I was using a 3.579545 MHz crystal, that available
at my junkbox and drifting is in this frequency.
( not 12 MHz... ).
After that email I buy some crystal,
each 10.00 MHz, 12.00 MHz, 12.288 MHz, and 14.00 MHz.
and make some test for each crystal, using my vfo and socket
as Hans's suggest, then connect / monitor at :
shortwave rx, counter 8 leds, counter one-7segment, and
rs232 - pc monitor ( this rs232 is part of one-7segment counter's add
on )
here are the results:
The measurements stop at 10.00 MHz on 8 led cntr,
since the 8 led accuracy is 10.xxx MHz, and I need to
check them on rs232-pc but happened not displayed.
Please suggest what is possible here.
-Why for 10 MHz higher the circuit doesn't works normally ?
I have read that for a higher frequency, the vfo gain could be drop.
-Does vfo design limit is at 10 MHz ?
-How to fix this ?
Thanks.
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