[Boatanchors] [Glowbugs] WTB - REAL FT-243 80 Meter crystals

Sat Aug 29 17:34:12 EDT 2015

Yes Howard, the smaller crystals will not work well in a single tube 813 power oscillator 
transmiter.  However, most hams are not doing that, and if someone is using a sensible 
circuit they work fine. There are tens of thousands of them in use around the world in fact. In 
everything from 6V6 oscillators (like in the BC610 transmitter) to DX60s, Globe Champions, 
DX100s and HT40s. All working great. No drift unless I guess if someone abuses them by 
holding the key down for 4 or 5 minutes straight.

Draw more than 40 mA through a small crystal and yes, it will sometimes heat up and may 
drift a little. That depends on what band you are on, and what the ESR is at that frequency. 
There are many other factors too. The same may be said of full-sized FT243 crystals that are 
run at more than 60 mA too. By the way - our crystals were scrutinized in the lab and 
reviewed at length in Electric Radio Magazine by Dr. David Gordon-Smith, G3UUR who 
demonstrated that they could often reach 200 mA crystal current before actually failing. 

You mentioned early crystal circuits. There is one crystal oscillator type that overheats  
crystals.  The famous TRI-TET "crystal cracker" oscillator. Run it at the crystal frequency and 
yes, there goes the crystal, even a full sized one.   The oscillator circuit you describe is called 
probably a "Tri-tet" and it is historically (and notoriously) known as a "crystal cracker".  It was 
invented in 1933 at a time when crystals were relatively large slabs of very expensive quartz 
and with maximum current ratings of over 100mA, and when hard-to-drive triodes were the 
tube of choice for a ham's final amplifer.  So the high-harmonic-output Tri-tet circuit was 
hailed as one of the best things to come along since "sliced quartz".  Now a ham could get by 
with just one expensive 80 meter crystal that would also work on the 40 and 20 meter bands.  
A 40 meter rock could be used up to 10 meters with enough drive for a triode final even 
without a buffer stage.  Ham bands at the time were all harmonically related.  Then, as 
crystals became more available at reasonable prices and high-power-sensitivity tetrode and 
pentode RF power tubes became the norm for finals the Tri-tet's popularity waned.

To keep a tri-tet from cracking crystals, the two important things to do are 1) keep the screen 
voltage under 150 volts (use large value screen resistor) and 2) make the resonant frequency 
of the cathode L-C tank no lower than 1.5 times the crystal frequency.  The L-C resonant  
frequency has not much to do with output power but everything to do with crystal current.

All that said and despite its historical acuracy, it is a poor circuit choice if it is only going to be 
used at the crystal's fundamental frequency. (info from Al, AE6CM)

I see this is also crossposted to a QRP group. The anxiety about crystals would definitely not 
apply to QRP rigs.

I have known far more crystal failures due to a screw being put through the face plate to VXO 
them than from any failures such as were described here. I have a few remnants of old 
busted crystals here. They ended their life that way, with a novice anxiously tweaking them 
for "just a few hundred Hz more VXO!"

Our remanufactured crystals were endorsed by no less than DAVE INGRAM, K4TWJ who 
wrote most of the tube radio homebrew articles for CQ Magazine over the past several years. 
He wouldn't have recommended them if they were unsuitable. 

Sincerely - Brian Carling AF4K

On 29 Aug 2015 at 11:31, howard holden wrote:

> Just a caveat on the "stuffed" FT-243 crystals: they DO NOT work in higher current xtal circuits! They drift badly, and will most likely fail quickly from the current. Later (late 50's and 60's) circuits should be ok but beware if you are going to try and use them in early crystal circuits! From dismal first hand experience with a couple of different transmitters! 
> 
> Howie WB2AWQ
> 
> Sent from my iPhone
> 
> On Aug 29, 2015, at 11:24 AM, "Bry Carling" <bcarling at cfl.rr.com> wrote:
> 
> > Hope to hear ALL of you this fall and winter on 3579!! The much rumored new "COLORBURST COMMANDOS" GROUP is poised to spring into action soon!!!
> > 
> > Keep watching for more updates!!
> > 
> > Best regards - Brian Carling
> > AF4K Crystal Co.
> > http://af4k.com
> > 
> > Tel: 321-262-5471
> > 
> > 
> > 
> > 
> >> On Aug 29, 2015, at 1:56 PM, Bill Stewart <cwopr at embarqmail.com> wrote:
> >> 
> >> Howie, I have found, that the 'stuffed' FT-243 holders from AF4K work fine in about
> >> all of my BAs...less pricey than eBay too. If you are able to make some hamfests, keep
> >> an eye out for 'em there too. And, the HG-10B vfo works well with the DX-60. I also
> >> expect the little 'color burst'...think that's what they are called...xtals would probably
> >> work fine and usually they are on eBay real cheap...and other places as well. 
> >> GL...73 de Bill K4JYS
> >> 
> >> From: "Howard Weinstein" <wa3mck at gmail.com>
> >> To: "QRP-L Mailing List" <qrp-l at mailman.qth.net>, "Glowbug Tetrode" <tetrode at googlegroups.com>, "Boatanchor group" <boatanchors at mailman.qth.net>
> >> Sent: Saturday, August 29, 2015 12:31:58 AM
> >> Subject: [Glowbugs] WTB - REAL FT-243 80 Meter crystals
> >> 
> >> Gang,
> >> 
> >> Getting ready to get on 80 CW as the weather cools. I'd like to purchase several REAL FT-243 80 Meter crystals to use with my DX-60 HR-10B station. No specific frequency - just close to the bottom of the band.
> >> 
> >> Prices on that "watery place" are out of control... 
> >> 
> >> Thank you
> >> 
> >> 73 de Howie WA3MCK 
> >> -- 
> >> -- 
> >> ZCZC
> >> This is a transmission from the Glowbugs list 
> >> To unsubscribe from this group, send email to 
> >> tetrode+unsubscribe at googlegroups.com 
> >> For more options, visit this group at 
> >> http://groups.google.com/group/tetrode?hl=en 
> >> NNNN
> >> 
> >> --- 
> >> You received this message because you are subscribed to the Google Groups "Glowbugs" group.
> >> To unsubscribe from this group and stop receiving emails from it, send an email to tetrode+unsubscribe at googlegroups.com.
> >> For more options, visit https://groups.google.com/d/optout.
> >> 
> >> -- 
> >> -- 
> >> ZCZC
> >> This is a transmission from the Glowbugs list 
> >> To unsubscribe from this group, send email to 
> >> tetrode+unsubscribe at googlegroups.com 
> >> For more options, visit this group at 
> >> http://groups.google.com/group/tetrode?hl=en 
> >> NNNN
> >> 
> >> --- 
> >> You received this message because you are subscribed to the Google Groups "Glowbugs" group.
> >> To unsubscribe from this group and stop receiving emails from it, send an email to tetrode+unsubscribe at googlegroups.com.
> >> For more options, visit https://groups.google.com/d/optout.
> > ______________________________________________________________
> > Boatanchors mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Boatanchors at mailman.qth.net
> > 
> > List Administrator: Duane Fischer, W8DBF
> > ** For Assistance: dfischer at usol.com **
> > 
> > 
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to holden7471 at msn.com