Eamon Skelton's 'Building a Transceiver' - UK Vintage Radio Repair and Restoration Discussion Forum

Newshound68 · 17th Apr 2016, 2:11 pm

The book refers to building the home-brew receiver with two crystal oscillators, one at 10.7MHz and another at 10.697MHz.

Where does one get a crystal as specific as 10.697MHz

Thanks in advance,

David

boxdoctor · 17th Apr 2016, 3:03 pm

Possibly you could "pull" a 10.7 Mhz to that frequency. I am not familiar with this project, but 10.697Mhz is very close to 10.7Mhz.
If you look here http://www.af4k.com/mega/xtals.htm you will find a list of crystal suppliers. The U.K. sources are towards the bottom of the list.
You may just be lucky there.
The problem is (as always with these things) being able to get just a "one off", and not have to order hundreds!

. Tony.

Amraduk · 17th Apr 2016, 3:20 pm

Hello Tony,

Quote:

Originally Posted by boxdoctor

The problem is (as always with these things) being able to get just a "one off", and not have to order hundreds!

QuartsLab and IQD in the UK will supply one-offs, but they'll be expensive!

Regards,

Dave.

Newshound68 · 17th Apr 2016, 3:51 pm

thanks both

Radio Wrangler · 17th Apr 2016, 5:13 pm

There are commercial filters at a number of standard IFs (455kHz, 1.4MHz, 9MHz, 10.7MHz and 21.4MHz to name a few) Some of these filters are of widths forAM, NBFM, SSB, CW. The latter two need crystals offset about + and - 1.5kHz to reinsert the carrier for SSB, and about 800Hz offset as a BFO. Offset crystals for 10.7MHz IFs are kicking around out there.

Eamon's email is published, and he does reply so you could ask him.

Oh, you don't just ask for an XX.XXXXXXX MHz cystal, you have to spicify whether it is for use in a parallel or series mode oscillator circuit, and what load capacitance it has to run with. You need to get this right just to be able to trim it to the right frequency. further questions are what 'adjustment tolerance' you want (IE how close do you need them to get it to the ideal frequency?) and what temperature range do you need, and how much can it vary over that temp range.

David

FrankB · 25th Apr 2016, 10:36 pm

Just remember this old time Ham Radio trick: If you get one of the older crystals that comes in an openable holder, you can take out the quartz blank and:
A. Lower the freq. by carefully rubbing pencil lead on the blank.
B. Raise the freq. by carefully grinding it with an abrasive cleaning compound. (I use Comet Cleanser here.)
Clean the blank carefully, and re-insert into the holder and check the freq.
Best to wear rubber gloves, as to keep finger oils off the blank.
With either method, re-assemble and re-check often to see that the freq. is either dropping or increasing.

dsergeant · 26th Apr 2016, 7:10 am

Eamon doesn't discuss a source of the 10.697kHz crystal. In the circuit as shown (which is in RadCom Dec 2010) the trimmer capacitor across the crystal would be insufficient to pull a 10.7MHz crystal 3kHz but if you reconfigured it as a VXCO with a suitable inductor in series with it that certainly would be possible - there are plenty of circuits for VXCOs out there. Alternatively I wonder if you replaced that crystal with a 10.7MHz ceramic resonator (widely available and cheap) whether that would do the job - ceramic resonators are very pullable.
But yes, a custom made crystal would make it uneconomic.
You could email Eamon via the address given at http://homepage.eircom.net/~ei9gq/index.html

73 Dave G3YMC

G6Tanuki · 26th Apr 2016, 1:20 pm

10.697MHz is a frequency often used in SSB CB transceivers.

17th Apr 2016, 2:11 pm	#1
Newshound68 Pentode Join Date: Jul 2015 Location: London & East Sussex, UK. Posts: 118	Eamon Skelton's 'Building a Transceiver' The book refers to building the home-brew receiver with two crystal oscillators, one at 10.7MHz and another at 10.697MHz. Where does one get a crystal as specific as 10.697MHz Thanks in advance, David

17th Apr 2016, 3:03 pm	#2
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: Eamon Skelton's 'Building a Transceiver' Possibly you could "pull" a 10.7 Mhz to that frequency. I am not familiar with this project, but 10.697Mhz is very close to 10.7Mhz. If you look here http://www.af4k.com/mega/xtals.htm you will find a list of crystal suppliers. The U.K. sources are towards the bottom of the list. You may just be lucky there. The problem is (as always with these things) being able to get just a "one off", and not have to order hundreds!. Tony.

17th Apr 2016, 3:51 pm	#4
Newshound68 Pentode Join Date: Jul 2015 Location: London & East Sussex, UK. Posts: 118	Re: Eamon Skelton's 'Building a Transceiver' thanks both

17th Apr 2016, 5:13 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,899	Re: Eamon Skelton's 'Building a Transceiver' There are commercial filters at a number of standard IFs (455kHz, 1.4MHz, 9MHz, 10.7MHz and 21.4MHz to name a few) Some of these filters are of widths forAM, NBFM, SSB, CW. The latter two need crystals offset about + and - 1.5kHz to reinsert the carrier for SSB, and about 800Hz offset as a BFO. Offset crystals for 10.7MHz IFs are kicking around out there. Eamon's email is published, and he does reply so you could ask him. Oh, you don't just ask for an XX.XXXXXXX MHz cystal, you have to spicify whether it is for use in a parallel or series mode oscillator circuit, and what load capacitance it has to run with. You need to get this right just to be able to trim it to the right frequency. further questions are what 'adjustment tolerance' you want (IE how close do you need them to get it to the ideal frequency?) and what temperature range do you need, and how much can it vary over that temp range. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

25th Apr 2016, 10:36 pm	#6
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: Eamon Skelton's 'Building a Transceiver' Just remember this old time Ham Radio trick: If you get one of the older crystals that comes in an openable holder, you can take out the quartz blank and: A. Lower the freq. by carefully rubbing pencil lead on the blank. B. Raise the freq. by carefully grinding it with an abrasive cleaning compound. (I use Comet Cleanser here.) Clean the blank carefully, and re-insert into the holder and check the freq. Best to wear rubber gloves, as to keep finger oils off the blank. With either method, re-assemble and re-check often to see that the freq. is either dropping or increasing.

26th Apr 2016, 7:10 am	#7
dsergeant Octode Join Date: Mar 2006 Location: Bracknell, Berkshire,UK. Posts: 1,174	Re: Eamon Skelton's 'Building a Transceiver' Eamon doesn't discuss a source of the 10.697kHz crystal. In the circuit as shown (which is in RadCom Dec 2010) the trimmer capacitor across the crystal would be insufficient to pull a 10.7MHz crystal 3kHz but if you reconfigured it as a VXCO with a suitable inductor in series with it that certainly would be possible - there are plenty of circuits for VXCOs out there. Alternatively I wonder if you replaced that crystal with a 10.7MHz ceramic resonator (widely available and cheap) whether that would do the job - ceramic resonators are very pullable. But yes, a custom made crystal would make it uneconomic. You could email Eamon via the address given at http://homepage.eircom.net/~ei9gq/index.html 73 Dave G3YMC

26th Apr 2016, 1:20 pm	#8
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Eamon Skelton's 'Building a Transceiver' 10.697MHz is a frequency often used in SSB CB transceivers.