[time-nuts] Oscillator temperature compensation

[Max Robinson]

In my opinion you are expecting more of the transmitter than it was designed 
to give.  A carrier current transmitter wouldn't have to maintain the 
broadcast standard of plus or minus 20 Hz.  A drift of 200 Hz would never 
have been noticed on an all American five radio.  Given a strong received 
signal beats with other stations on the same channel wouldn't be an issue 
either.

Regards.

Max.  K 4 O DS.

Email: max at maxsmusicplace.com

Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site 
http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html
Music site: http://www.maxsmusicplace.com

To subscribe to the fun with transistors group send an email to.
funwithtransistors-subscribe at yahoogroups.com

To subscribe to the fun with tubes group send an email to,
funwithtubes-subscribe at yahoogroups.com

To subscribe to the fun with wood group send a blank email to
funwithwood-subscribe at yahoogroups.com

----- Original Message ----- 
From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
To: <time-nuts at febo.com>
Sent: Friday, June 21, 2013 1:32 PM
Subject: Re: [time-nuts] Oscillator temperature compensation


> On 06/21/2013 06:59 AM, Joseph Gray wrote:
>>> Can you show some pictures of the oscillator?
>>
>> The wiring is point-to-point, so I don't think a picture is going to tell
>> you much.
>>
>>> Is there a tunable inductor in the oscillator circuit?
>>
>> As I mentioned, nothing tunable there.
>>
>>> Who makes the unit?
>>
>> It is an LPB RC-6A carrier current AM transmitter. It was used at the 
>> local
>> university many years ago. I was told they used to have several. I am
>> rescuing it from oblivion.
>
> The closest to a schematic I find is this:
>
> http://i30.photobucket.com/albums/c343/1073Dave/Schematics/LPBRC-5ATransmitter.jpg
>
> Hooking a trim-pot to either of the caps next to the crystal should allow 
> you to trim it, should be a good start.
>
> If you really need temperature compensation, a first degree compensation 
> should help. I haven't seen anything matching the X or Y cut crystal you 
> most probably have. The only plot I have for an X-cut shows a mostly 
> linear shift. A simple trimable first degree compensation should not be 
> too hard.
>
> Otherwise you might just as well lock it up instead. Divide 10 MHz down to 
> 20 kHz (divide by 500) and 660 kHz to 20 kHz (divide by 33) and then a 
> phase-comparator of choice. The varicap is just inserted under the foot of 
> one the caps around the crystal oscillator. Use a PI-active loop.
>
> Cheers,
> Magnus
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.