Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
At 5/23/2006 02:06 PM, you wrote: >If you decide to use an 85 deg C oven, you must get the crystal cut for >that temperature. Yes, I've noticed some short-term aging problems with crystals run at 50 C. In one case the crystal was held at 35 C for a couple of years, then sat on the shelf for a few more. When put back into service at 50 C, it drifted up about 2 PPM over a period of a couple of days. So it seems that even moderately heated crystals need to be aged at their operating temperature. Bob NO6B Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
If you decide to use an 85 deg C oven, you must get the crystal cut for that temperature. I have plenty of GE ovens here if you need one6 or 12 volts. 73 John VE3AMZ - Original Message - From: <[EMAIL PROTECTED]> To: Sent: Tuesday, May 23, 2006 11:51 AM Subject: Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change? > > Or use a Motorola crystal oven @ 85 degrees C ... > > Neil - WA6KLA > > > Original Message > From: [EMAIL PROTECTED] > To: Repeater-Builder@yahoogroups.com > Subject: Re: [Repeater-Builder] midland 13-509 tx freq stability... > cap change? > Date: Tue, 23 May 2006 08:43:33 -0700 > > >At 5/23/2006 07:20, you wrote: > >> > > >>One other thing you might try - tape a 100 ohm 1 watt resistor to > >the > >>side of the crystal and put 12 VDC across it. Not a pretty sight, > >and > > > >If you're going to heat the crystal, might as well use something that > >will > >keep it at a more or less stable temperature: a 50 ohms 50 degree C > >PTC > >thermistor. Digikey has them for $1.68 each (manufacturer part # > >RL3006-50-50-25-PTO). Desolder one of the leads & solder the disk > >directly > >onto one side of the crystal, ground the crystal case & apply a > >regulated > >voltage to the other side. > > > >Bob NO6B > > > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: Re: [Repeater-Builder] midland 13 -509 tx freq stability... cap change?
I bought a used 220 Maggiore Repeater a number of years ago and it had this setup for xtal. temp. control on both the TX and RX xtals. Not sure the manufacturer of the thermistors, but they look like what Bob is describing. Roger W5RD >If you're going to heat the crystal, might as well use something that will >keep it at a more or less stable temperature: a 50 ohms 50 degree C PTC >thermistor. Digikey has them for $1.68 each (manufacturer part # >RL3006-50-50-25-PTO). Desolder one of the leads & solder the disk directly >onto one side of the crystal, ground the crystal case & apply a regulated >voltage to the other side. > >Bob NO6B Roger White Murphy, Texas Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
Or use a Motorola crystal oven @ 85 degrees C ... Neil - WA6KLA Original Message From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change? Date: Tue, 23 May 2006 08:43:33 -0700 >At 5/23/2006 07:20, you wrote: >> > >>One other thing you might try - tape a 100 ohm 1 watt resistor to >the >>side of the crystal and put 12 VDC across it. Not a pretty sight, >and > >If you're going to heat the crystal, might as well use something that >will >keep it at a more or less stable temperature: a 50 ohms 50 degree C >PTC >thermistor. Digikey has them for $1.68 each (manufacturer part # >RL3006-50-50-25-PTO). Desolder one of the leads & solder the disk >directly >onto one side of the crystal, ground the crystal case & apply a >regulated >voltage to the other side. > >Bob NO6B > > > > > > > >Yahoo! Groups Links > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
At 5/23/2006 07:20, you wrote: > > >One other thing you might try - tape a 100 ohm 1 watt resistor to the >side of the crystal and put 12 VDC across it. Not a pretty sight, and If you're going to heat the crystal, might as well use something that will keep it at a more or less stable temperature: a 50 ohms 50 degree C PTC thermistor. Digikey has them for $1.68 each (manufacturer part # RL3006-50-50-25-PTO). Desolder one of the leads & solder the disk directly onto one side of the crystal, ground the crystal case & apply a regulated voltage to the other side. Bob NO6B Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
At 5/22/2006 10:48, you wrote: >Working on my midland 220 box, with new international crystals. >Crystals are standard delivery, not "rushed", so they should be pretty >stable. They always are in my other rigs... > >Question: Is it worth swapping out the fixed value cap that is >paralleled across the ceramic trimmer on the transmit side? >Mine seems to drift around a bit more than I like. My guess is it's the crystal that's drifting. Hit just the crystal with a bit of freeze spray, or the tip of your soldering iron for just one second & see if it takes off. Bob NO6B Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
> > >Dave, > >Keep in mind that the Midland 13-509 was built for the Amateur Radio market, >and the transmit crystals are only specified to maintain .001%, which is 10 >PPM. There is no temperature compensation in the crystal circuit, and you >may make the drift worse by using an NPO capacitor. If you have the time >and the test equipment to do it, you can determine a crude temperature >compensation by finding out how much the TX crystal drifts for a given >change in temperature, then using a capacitor whose TC has an equal but >opposite effect. This capacitor will definitely not be an NPO type, which >is stable over a wide temperature range. In fact, you want an "unstable" >capacitor that exactly balances the crystal drift. > >Commercial radios of the same vintage often used bare crystals with a color >dot on the side of the can, and you were instructed to install the >appropriate color TC capacitor with that particular crystal. Not perfect, >but adequate. > >You might also consider replacing the bare TX crystal oscillator with a >small TCXO unit from any of several sources, including ICM. > >73, Eric Lemmon WB6FLY > > One other thing you might try - tape a 100 ohm 1 watt resistor to the side of the crystal and put 12 VDC across it. Not a pretty sight, and Eric will probably really bad mouth this one, but it can move the crystal temp into an area of its temperature range that stays more stable frequency wise with external temperature changes. I have had good luck and bad luck with this scheme. Sometimes it makes the frequency stability better from a temperature change standpoint, and sometimes makes it worse. It all depends on just how your crystal is cut. 73 - Jim W5ZIT Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] midland 13-509 tx freq stability... cap change?
Dave, Keep in mind that the Midland 13-509 was built for the Amateur Radio market, and the transmit crystals are only specified to maintain .001%, which is 10 PPM. There is no temperature compensation in the crystal circuit, and you may make the drift worse by using an NPO capacitor. If you have the time and the test equipment to do it, you can determine a crude temperature compensation by finding out how much the TX crystal drifts for a given change in temperature, then using a capacitor whose TC has an equal but opposite effect. This capacitor will definitely not be an NPO type, which is stable over a wide temperature range. In fact, you want an "unstable" capacitor that exactly balances the crystal drift. Commercial radios of the same vintage often used bare crystals with a color dot on the side of the can, and you were instructed to install the appropriate color TC capacitor with that particular crystal. Not perfect, but adequate. You might also consider replacing the bare TX crystal oscillator with a small TCXO unit from any of several sources, including ICM. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of na6df Sent: Monday, May 22, 2006 10:48 AM To: Repeater-Builder@yahoogroups.com Subject: [Norton AntiSpam] [Repeater-Builder] midland 13-509 tx freq stability... cap change? Working on my midland 220 box, with new international crystals. Crystals are standard delivery, not "rushed", so they should be pretty stable. They always are in my other rigs... Question: Is it worth swapping out the fixed value cap that is paralleled across the ceramic trimmer on the transmit side? Mine seems to drift around a bit more than I like. I have to assume the stock cap is an NPO type. Schematic does not state capacitance of this cap. Anybody know what it is? RF Parts sells NPO's, but is it worth it? Better ideas, if any? tnx and 73, Dave NA6DF Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
