[Repeater-Builder] Re: midland 13-509 tx freq stability... cap change?
The first fix might be to put a non conductive insulator over the crystal (xtal). A foam pad or rubber sheeting is sometimes used by various mfgrs. Just floating a crystal to relative exposed cabinet/box air is not so great if the air temp changes more than a small amount. Second item which might help would be to seal the box and possibly insulate it from larger thermal changes as mentioned above. If things get really out of hand, you could find/buy a typical Ovenair Crystal unit from various places (like Hamtronics) along with the proper Ovenair type crystal. I would not put a standard room temp crystal in an Oven air unit, nor would I try the xtal heater (resistor) trick on a xtal not spec for operation in a heated loop/oven circuit. Chances are it's not going to be anywhere close to the desired frequency when you heat it to normal xtal oven temps... Keeping in mind the Ovenair unit draws a lot a bit of serious current in operation... ie not so great for solar only radio sites. Also note the crystal pins often plug into a tin plated holder. It might be prudent to swap the crystal holder pins for something better. I use older gold plated transistor sockets that can be found surplus or removed from vintage salvage. The cheaper xtal socket/pin metal doesn't help much as well as the xtal floating in air and the exposure to mechanical vibration. I have seen heard of numerous examples where you could modulate a transmitter with modest hits to the outside equipment case. A most funny college example was a friend actually using a BK VFO for Two-Meter operation. Sitting on a firm thin table you could actually yell close to the table surface and hear the audio on the air. Your results will probably vary... cheers, skipp [EMAIL PROTECTED] wrote: 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/
[Repeater-Builder] Re: midland 13-509 tx freq stability... cap change?
I have a few Ovenair ovens, physically identical to the hamtronics unit. They seem to be 60 deg C (140 deg F) ovens, but not verified, other than with my finger. Just as an experiment, I stuffed the other transmit rock on a closeby frequency (from ICM) in the rig, put the oven down over it, and let it cook for about 20 minutes. It was still pretty close to on frequency, so I zeroed it, and kept checking every so often. It is now very stable. I do have a call in to the crystal engineers at ICM to determine the safe tempurature range for the standard midland cut rocks, though. I'll wait and see what they say, and post it here. I wasn't gonna risk my repeater TX rock for this experiment, so I just used another that was in the repeater when I got it... na6df dave --- In Repeater-Builder@yahoogroups.com, skipp025 [EMAIL PROTECTED] wrote: The first fix might be to put a non conductive insulator over the crystal (xtal). A foam pad or rubber sheeting is sometimes used by various mfgrs. Just floating a crystal to relative exposed cabinet/box air is not so great if the air temp changes more than a small amount. Second item which might help would be to seal the box and possibly insulate it from larger thermal changes as mentioned above. If things get really out of hand, you could find/buy a typical Ovenair Crystal unit from various places (like Hamtronics) along with the proper Ovenair type crystal. I would not put a standard room temp crystal in an Oven air unit, nor would I try the xtal heater (resistor) trick on a xtal not spec for operation in a heated loop/oven circuit. Chances are it's not going to be anywhere close to the desired frequency when you heat it to normal xtal oven temps... Keeping in mind the Ovenair unit draws a lot a bit of serious current in operation... ie not so great for solar only radio sites. Also note the crystal pins often plug into a tin plated holder. It might be prudent to swap the crystal holder pins for something better. I use older gold plated transistor sockets that can be found surplus or removed from vintage salvage. The cheaper xtal socket/pin metal doesn't help much as well as the xtal floating in air and the exposure to mechanical vibration. I have seen heard of numerous examples where you could modulate a transmitter with modest hits to the outside equipment case. A most funny college example was a friend actually using a BK VFO for Two-Meter operation. Sitting on a firm thin table you could actually yell close to the table surface and hear the audio on the air. Your results will probably vary... cheers, skipp no6b@ wrote: 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/
[Repeater-Builder] Re: midland 13-509 tx freq stability... cap change?
You probably got them years ago from my same source. HSC Electronics had them pretty cheap in a cardbord bin. They are long gone now... sold out. Also keep in mind you could run the Ovenair unit un-powered as an insulator... an expensive one but the thermal insulating properties might be very helpful. See you at the super secret lunch in an hour... skipp Glad to be back in one piece from IWCE and Dayton... na6df [EMAIL PROTECTED] wrote: I have a few Ovenair ovens, physically identical to the hamtronics unit. They seem to be 60 deg C (140 deg F) ovens, but not verified, other than with my finger. Just as an experiment, I stuffed the other transmit rock on a closeby frequency (from ICM) in the rig, put the oven down over it, and let it cook for about 20 minutes. It was still pretty close to on frequency, so I zeroed it, and kept checking every so often. It is now very stable. I do have a call in to the crystal engineers at ICM to determine the safe tempurature range for the standard midland cut rocks, though. I'll wait and see what they say, and post it here. I wasn't gonna risk my repeater TX rock for this experiment, so I just used another that was in the repeater when I got it... na6df dave --- In Repeater-Builder@yahoogroups.com, skipp025 skipp025@ wrote: The first fix might be to put a non conductive insulator over the crystal (xtal). A foam pad or rubber sheeting is sometimes used by various mfgrs. Just floating a crystal to relative exposed cabinet/box air is not so great if the air temp changes more than a small amount. Second item which might help would be to seal the box and possibly insulate it from larger thermal changes as mentioned above. If things get really out of hand, you could find/buy a typical Ovenair Crystal unit from various places (like Hamtronics) along with the proper Ovenair type crystal. I would not put a standard room temp crystal in an Oven air unit, nor would I try the xtal heater (resistor) trick on a xtal not spec for operation in a heated loop/oven circuit. Chances are it's not going to be anywhere close to the desired frequency when you heat it to normal xtal oven temps... Keeping in mind the Ovenair unit draws a lot a bit of serious current in operation... ie not so great for solar only radio sites. Also note the crystal pins often plug into a tin plated holder. It might be prudent to swap the crystal holder pins for something better. I use older gold plated transistor sockets that can be found surplus or removed from vintage salvage. The cheaper xtal socket/pin metal doesn't help much as well as the xtal floating in air and the exposure to mechanical vibration. I have seen heard of numerous examples where you could modulate a transmitter with modest hits to the outside equipment case. A most funny college example was a friend actually using a BK VFO for Two-Meter operation. Sitting on a firm thin table you could actually yell close to the table surface and hear the audio on the air. Your results will probably vary... cheers, skipp no6b@ wrote: 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/
[Repeater-Builder] Re: midland 13-509 tx freq stability... cap change?
[EMAIL PROTECTED] wrote: Or use a Motorola crystal oven @ 85 degrees C ... Neil - WA6KLA Neil, Don't you mean Rock Stove? It is the same thing! 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] Re: midland 13-509 tx freq stability... cap change?
Depends on the vintage ... Neil Original Message From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: midland 13-509 tx freq stability... cap change? Date: Tue, 23 May 2006 19:53:24 - [EMAIL PROTECTED] wrote: Or use a Motorola crystal oven @ 85 degrees C ... Neil - WA6KLA Neil, Don't you mean Rock Stove? It is the same thing! 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/
[Repeater-Builder] Re: midland 13-509 tx freq stability... cap change?
Yeah, makes sense. I was just thinking along the possible lines of the cap causing the drift... at least I could eliminate that issue, if it was an issue.. df --- In Repeater-Builder@yahoogroups.com, Eric Lemmon [EMAIL PROTECTED] wrote: 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/
