[ARC5] Added detail re 1700kc xtal ask

[Bob kb8tq]

Hi

Depending on what you are designing, a “high IF” may have some advantages. These days, you can get a wide range of crystal frequencies dirt cheap. They might be on some odd frequency related to computer networking. That’s fine as long as they are stable and cheap. 

Related story: Walked into a computer store about 3 decades ago. Mentioned crystals. The guy popped up with “I remember back when we bought them by the piece rather than by the pound”. Seems that as the price dropped below some magic point, counting them cost way to much.

Crazy !!!!

Bob

> On Jun 18, 2024, at 4:40 PM, Michael Kana via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> Hi Tom
> I saw Steve’s response and yours and that convinced me to rethink the IF.  I also listen to the Soldersmoke podcast and they also bring up using the more widely available and low cost xtals for determining the IF. I could order a handful and cherry pick the best for the desired bandwidth. 
> I already have a couple 9MHz xtal filters also as an option.  This would allow designing to take place a lot sooner than lucking out and finding a “vintage” surplus xtal
> Thx 73
> Mike
> 
> Warning!  This is transmitted over a non secure medium
> 
>> On Jun 18, 2024, at 3:01 PM, Tom Lee <tomlee at ee.stanford.edu> wrote:
>> 
>>  Hi Mike,
>> 
>> You may wish to consider a different IF for which rocks are more readily available (as I was typing this, I saw Steve J's reply pointing out yet another reason for considering a different IF). For instance, there are tons of chroma subcarrier crystals for NTSC and PAL. I see these going for $0.20 in quantities of 10 from Digikey, making it easy to buy a bag from which to find a good set of matched ones. A higher IF would also give you improved image rejection as an additional benefit. Would that be an option at all for you?
>> 
>> --Tom
>> -- 
>> Prof. Thomas H. Lee
>> Allen Ctr., Rm. 205
>> 420 Via Palou Mall
>> Stanford University
>> Stanford, CA 94305-4070
>> http://www-smirc.stanford.edu <http://www-smirc.stanford.edu/>
>> On 6/18/2024 11:43 AM, Mike Kana wrote:
>>> Hi all
>>> This is for a crystal filter. The RX designs I’m looking at are th HBR Rx or the 6-4 from the 1964 hand book
>>> If the xtal isn’t exactly 1700, a few KC either side would require some VFO trickery. 
>>> Thx
>>> Mike
>>> 
>>> Warning!  This is transmitted over a non secure medium
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