EMRFD Message Archive 10861

Message Date From Subject
10861 2015-03-17 04:56:10 jmlcs2000 Source for crystals

Hi all, I'm at a loss as I can't find the post. I believe it was on this group, but not for sure. Within the post I'm looking for was a  web link to someone who sells crystals for all the Ham Bands.  Any help is appreciated. I'm looking for a 40 meter crystal around 7040 or so to make a signal source to measure the MDS of a 40 meter Receiver just completed.... Apparently Kanga doesn't sell them any more. Many thanks, John

10862 2015-03-17 06:22:15 Ephemeral Re: Source for crystals
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10863 2015-03-17 06:57:04 farhanbox@gmail.c... Re: Source for crystals

why not use an LC oscillator? 

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10871 2015-03-17 08:05:48 William Martin Re: Source for crystals
John,

Try here.

http://qrpme.com/?p=parts

Bill N7EU
10872 2015-03-17 08:17:49 Dale Hammer Re: Source for crystals

John,

 

The place I purchase crystals is:

http://www.expandedspectrumsystems.com/prod4.html

 

Price seems very reasonable and they have most of the values people would want.

 

73,

Dale   K9NN

 

10873 2015-03-17 08:33:46 Gene W5DOR Re: Source for crystals

QRPme.com has a 40m crystal pack

 

Good quality crystals can be found at ESS   http://www.expandedspectrumsystems.com/order.html

 

You can get crystals on eBay but sometimes they get the freq wrong.  For instance, someone just ordered some 36 MHz crystals on eBay and they turned out to be 3.6MHz.

 

Good luck,

Gene, W5DOR

gene@w5dor.com

 

 

10874 2015-03-17 08:34:33 Jim Strohm Re: Source for crystals
All,

While we're on the subject of crystals, does anybody know of a good source for FT-243 rocks OTHER than Bry Carling?  These would be for ham frequencies, of course, both fundamental and overtone.  Alternatively, has anybody experimented with making adapters to use more modern crystals in plug-in FT-243 applications without performing mods to the radio using the crystal?

Yes, I am well aware that a vintage rig puts much more power through an FT-243 than a newer rig puts through an HC-49, and just a series resistor or two might not be sufficient.

Thanks and 73
Jim N6OTQ

10876 2015-03-17 08:52:29 Gene W5DOR Re: Source for crystals

Are u using the suggested osc from EMRFD?   We all would be interested in the results of your testing.   I have an old Collins 75A-4 that I've restored and want to test MDS..  I think it's supposed to be around -140dBm but I want to measure it.

 

Thanks,

Gene, W5DOR

gene@w5dor.com

www.5dor.com

 

 

10878 2015-03-17 09:29:29 Kevin Timm Re: Source for crystals
halted.com and qrpme.com both sell sets of crystals that include 7.040
10879 2015-03-17 09:57:24 Dennis Anderson Re: Source for crystals
Are you talking about Kanga US or kanga UK ?

Kanga UK has a full listing of all crystals stock on the website which includes all 40m frequencies

Regards

Dennis G6YBC
Kanga Products UK

10880 2015-03-17 10:04:51 Jim Kortge Re: Source for crystals
10884 2015-03-17 13:51:03 John Lawson Re: Source for crystals
Hi all, first a Big Thank You for all the helpful responses as it's appreciated. Now to answer a couple of questions that surfaced in the suggestions.

First I'm looking for a rock solid stable signal so the LC Osc will not fill the bill. Also the Kanga I'm referencing is here in the USA.

Finally, Gene I'm not for sure what the MDS Osc I will build yet. However I did build that 14 MHz Osc that appears in EMRFD Figure 7-31, page 7.18 when it appeared in Wes's Dynamic Range QST article many years ago. I still use it on occasion. It works great along with my step attenuators. One thing that was suggested to me a few years ago was a Xtal Osc that has a output of around +4 dBm or so, then build a 80 dB attenuator......I built two 40 dB attenuators using 1% Resistors, shielding the input from the output of each pad then boxed it all up in one box RF tight. It does the trick to get down around -76 dBm for use with my step attenuators. Glad to see your post on the white lettering as I need some too. Looks like Office Depot carries them. Thanks again for the helpful suggestions. John, K5IRK

Sent from my iPad

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10896 2015-03-19 14:19:51 Gene W5DOR Re: Source for crystals

The osc I'm looking at is by Jim, K8IQY on his test equipment page.   http://www.k8iqy.com/testequipment/-20dbmsource/-20dbmsource.htm  He refers to it as a   "precision" test osc.

 

I have a step attenuator and some 50ohm BNC 20dB pads to use to get the signal down to where it needs to be.  I also have a HP 8640B signal generator that goes down to -130dBm but I don't know how long it's been since it was calibrated.   This exercise will at least confirm that my 8640B is close to accurate.

 

The osc in EMRFD is spec'd at -100dBm so it's closer to where you need to be.  I might just build it instead of Jim's.   Or better yet, build both of them and compare jim's, the one in EMRFD and my 8640B.

 

OH, wait a min.   This conversation was started by Jim    (grin)

 

Gene, W5DOR

gene@w5dor.com

www.w5dor.com

 

 

 

10897 2015-03-19 19:07:36 w7zoi Re: Source for crystals
Hi Gene,

That oscillator from EMRFD Fig 7.31 really needs to be calibrated once built.    Don't merely believe the amplitude result that is in the book.   The original was in my July 1975 QST paper and then appeared in SSD.    It used a 7 MHz crystal and there was a quite a bit of second harmonic, so I calibrated it on both the 40 and 20 meter bands.   The important thing for this discussion is to NOT just believe the level from what appears in EMRFD, but to do some sort of a calibration.    Find a signal generator and do a transfer calibration.   Or these days find someone with a spectrum analyzer and use that.

The oscillator of Fig 7.31 is biased for a mA or two, as I recall, with 6 volts on the collector.   The guys at Elecraft have done a clever thing.   They have built crystal oscillators with a 2N3904 (or similar) biased down at 50 uA or less, and only a volt or so.   As such, the output from the oscillator is way down, so less attenuation is needed to get the level down to the -100 dBm ballpark.     This gives you another route to follow.    They sell some kits if you want to go that route.

Even if you can't get a good calibration, the weak signal oscillator is still useful.    Do the best you can do and then fill in the details when you can get to someone with generator that you have more faith in.   I suspect that you 8640 will be surprisingly accurate for power, even if they are decades out of calibration.

Remember that a casual measurement is still orders of magnitude better than no measurement.

Good luck.

73, Wes
w7zoi

10906 2015-03-20 22:34:43 Gene W5DOR Re: Source for crystals

Thanks Wes,

 

I'm old and forget stuff.   What I forgot was that I purchased that osc from Elecraft several years ago and now I've got to figure out where I put it.

thanks,

Gene, W5DOR

gene@w5dor.com

www.w5dor.com