EMRFD Message Archive 6718
Message Date From Subject 6718 2011-10-06 15:20:09 Lasse Where to find crystals for converters I'm about to start designing a small multi band converter
(50/137/144/432), but realized higher frequency crystals seems to be
made out of unobtainium!
I.e. tried to find 116 MHz crystal... but no one seems to stock. Odd,
years ago they were all over the place. Do anyone have a good source
for these type of crystals? BTW came up short on E-bay too.
Yes I could use the Si570... but prefer crystals. Should give better
performance at a lower price!
6722 2011-10-06 21:13:32 michael taylor Re: Where to find crystals for converters 6723 2011-10-07 07:41:09 Thomas S. Knutsen Re: Where to find crystals for converters Hei Lasse.
I have good experience ordering QT crystals via Eish-Kafka electronics in
73 de Thomas LA3PNA.
2011/10/7 Lasse <email@example.com>
> I'm about to start designing a small multi band converter
> (50/137/144/432), but realized higher frequency crystals seems to be
> made out of unobtainium!
> I.e. tried to find 116 MHz crystal... but no one seems to stock. Odd,
> years ago they were all over the place. Do anyone have a good source
> for these type of crystals? BTW came up short on E-bay too.
> Yes I could use the Si570... but prefer crystals. Should give better
> performance at a lower price!
> /Lasse SM5GLC
Please avoid sending me Word or PowerPoint attachments.
[Non-text portions of this message have been removed]
6724 2011-10-07 19:52:13 Mike Re: Where to find crystals for converters In line with WA3TIX's suggestion to use a 16 mhz crystal with X7
mulitplication: KangaUS offers a 144.2 mhz signal source that is based
on X7 multiplication of a 20.6 mhz crystal oscillator, using a KK7B
design (and the schematic is available on KangaUS's web site). So you
might be able to easily modify the KangaUS schematic and/or kit to get
your 116 mhz signal source.
6725 2011-10-08 11:58:45 KK7B Re: Where to find crystals for converters A number of experimenters have successfully used the Kanga US signal source on frequencies from 30 MHz to 222 MHz, multiplying the fundamental oscillator by integers from 3 to 7. All it takes is understanding the block diagram and schematic posted on the Kanga web site, study of the 50 MHz and 144 MHz versions, and an evening of calculations with pencil, paper, and slide rule. Those who complete the above steps find the modifications for frequencies other than 50 and 144 MHz rather trivial.
In contrast, I've observed that a significant number of SDR folks and those who automatically run to a simulator rather then pencil and paper have a devil of a time getting the things to work.
This has nothing to do with age--my experience is with a general population of mostly college-age students. I estimate that around 10% of them think slide rules and paper Smith Charts are cool and enjoy designing and building one transistor solutions to interesting problems. Many of their peers don't do anything that can't be displayed on a computer screen, and instantly grab a PIC for the even the simplest electronic tasks like turning on an LED.
I encourage students to develop a complete skill set, including both non-linear analog electronics, DSP, and circuit simulators. But as amateurs we have the luxury of embracing ignorance of things we find uninteresting and focusing exclusively on problems that fascinate us.
If you are fascinated by DDS, DSP and the latest highly integrated PLL signal sources, there are amazing new circuits to play with that are now good enough to replace overtone crystals in almost every application.
If you would rather mess with the simplest non-linear analog solution, enjoy playing with oscillators and tuned circuits, and you prefer to work
6726 2011-10-08 14:17:42 kb1gmx Re: Where to find crystals for converters 6727 2011-10-08 14:17:48 kb1gmx Re: Where to find crystals for converters 6728 2011-10-08 21:28:20 Tim Re: Where to find crystals for converters Years ago, VHF rigs with a crystal labeled 116 MHz were really near - 6.44MHz fundamental crystals used on their third overtone, 19.33 MHz in an oscillator.
The 19.33 was typically tripled and then doubled to reach 116 MHz.
In the US if you hang out at the right hamfests it is easy find buckets of VHF crystals from commercial/public service VHF radios from the 50's through the 90's. (Literally: buckets.) The labeled frequency is always a harmonic (plus an IF offset if a receive crystal) of the actual frequency.
The above scheme is actually kinda simplistic compared to the "tank radio" crystal relations used in the first BC-604 tank radios. These are known as "channel 0 through 79" and marked with a frequency from 20 to 28 MHz, which is 54 times the fundamental which is in the 370 to 516 kHz range. The high multiplication was an advantage with early FM modulators.
Today fundamental microprocessor-type crystals are available up to 50 Mhz and in some cases 100+ MHz. But many microprocessor crystals at 24 MHz or above are actually intended for operation on the third overtone.
The advice others are giving you to find a 5th or 7th harmonic relation starting from a microprocessor crystal is very good. The more traditional way of tripling/doubling your way up is very good too. e.g. 24 MHz third overtone crystal, doubled then tripled puts you
6729 2011-10-09 13:34:31 Lasse Re: Where to find crystals for converters KK7B skrev 2011-10-08 17:35:
> ----snip---Thanks for comments and thoughts...
> If you are fascinated by DDS, DSP and the latest highly integrated PLL signal sources, there are amazing new circuits to play with that are now good enough to replace overtone crystals in almost every application.
> If you would rather mess with the simplest non-linear analog solution, enjoy playing with oscillators and tuned circuits, and you prefer to work on electronics that you understand all the way down to the individual component level, the VHF signal source from Kanga might be a good choice.
> Whichever approach you choose, don't make the mistake of thinking that the other is simple. As with everything else in life, advanced skills require practice. Basic skills require even more practice.
I just want to give my reasoning for going for a high freqency resonant
The conveter will be used as a front end to my wide-band SDR, allowing
me to "see" a 1.6 MHz chunk with roughly 100 dB dB DR. Having played
with multipliers many times I know for sure that it is hard work to get
all spurs down to less than -100 dBc, and if you start at say 6 MHz I am
pretty sure I WILL have ghost signals showing, living in an urban area.
Using the highest possible frequency resonant oscillator will ease the
design of both the input filtering and the oscillator chain, but
apparently causing problems in finding the crystal :D
Doing some serious digging in my rather big junk box, I found both a 115
MHz crystal and a 80 MHz crystal which should work for some of the bands
I want to convert.
If I would use a 10 MHz crystal to generate 80 MHz, this is pretty
basic. If use this for a 50 MHz conveter with an IF (inverted) of 28-30
MHz will have to spend some time make sure the mirror at 108 does not
cause problems (FM BC), still if I had started with a 10 MHz oscillator
I am sure the very high power BC stations would show up. Not to mention
the overtone at 50 MHz....
In this specific case, having a lower f LO (non-inverting if), might be
better, but with my older 50 MHz conveter the usage of 28MHz showed not
to be optimal. Maybe I have to do a spur chart to find the optimal
LO/IF. Using a 0-30 MHz SDR as back end allows me to optimize in a
better way than just beeing restricted to HF ham bands.
It's all about compromizes and what is important to your desing and usage
6730 2011-10-09 13:34:46 ha5rxz Re: Where to find crystals for converters Nice!!
So far I've taught four young people how to use a slide rule. They were fascinated to learn that the wooden slide rule in the case on the wall was an instrument that could actually do something. In one instance I managed to do a calculation before his calculator had started up.
6731 2011-10-09 21:36:31 dan edwards Re: Where to find crystals for converters my math teacher called them 'slip sticks' in the 7th grade....1968...ha...73, w5xz, dan
6732 2011-10-10 06:34:18 Dean Blake Re: Where to find crystals for converters I used a slide rule in my electronics classes in college... wow... think about it, it took us to the moon!
A slide rule in the hands of an experience users is an awesome sight..
Date: Sun, 9 Oct 2011 16:40:41 -0700
Subject: Re: [emrfd] Re: Where to find crystals for converters
my math teacher called them 'slip sticks' in the 7th grade....1968...ha...73, w5xz, dan
6733 2011-10-11 06:41:13 sm0gns Re: Where to find crystals for converters Hello Lasse
You could try at Barend Hendriksen HF Elektronica BV
Under crystals, they have one at 116.00 MHz.
You need to contact them for the price.
73 de Peder, SM0GNS