Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
I know it's a quick and dirty way to go about it, but after nearly 20 years of operation, I can't complain. Besides, I had the parts in my junk box. Today, I'd go with an LM317. With age comes wisdom. And the money to do it right LOL! Bill KB1MGH From: n...@no6b.com n...@no6b.com To: Repeater-Builder@yahoogroups.com Sent: Sat, February 27, 2010 6:25:09 PM Subject: Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement? At 2/25/2010 12:36, you wrote: Build it yourself. Use an LM7808 and and series two 1N4001's to lift the ground lead up by 1.4 volts. I know 7809's are around but the 7808 is much more common and cheaper. One thing to watch out for in lifting the ground pin above ground on the 78xx series devices is that a momentary short of the output to ground can destroy the device, IOW the integral short circuit protection is effectively defeated. You'll also need to use insulating hardware if you want to heat sink the regulator by mounting it to the (grounded) chassis. The cleanest, easiest solution may simply be an LM317 set to 9.6 V output. Bob NO6B Yahoo! Groups Links http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
In a station, the 9.6 volt circuitry *could* be run from 12 volts, as long as its regulated. I'm not suggesting someone does that, because the circuits were optimized for 9.6 volts, but I'm trying to make a point. Point taken, but to add to your cautionary note, there are some circuits that will not be happy at 12V. I remember trying to run a Micor PL decoder off 13V and it did some strange things (i.e. didn't work right/reliabily). If it were me, I'd just use a 9 or 10 volt three terminal regulator (7809 or 7810) and skip the whole LM-317 or diodes in the ground leg deal. It only serves to make the circuitry more involved , harder to mount, and for NO advantage whatsoever. In general I don't like raising the ground on 7xxx series fixed regulators by adding diodes to what would normally be the ground lead. 7xxx series regulators can (and will) oscillate, which is why adding caps per the datasheets' recommendations isn't just a good idea, it's mandatory. My concern is that putting a diode in series with the ground lead results in the filter/bypass caps being at a different ground potential than the device, which may increase the chance of oscillation. --- Jeff WN3A
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
Hi Jeff, In general I don't like raising the ground on 7xxx series fixed regulators by adding diodes to what would normally be the ground lead. You're right, the diode trick is not recommended. National recommends putting a voltage divider across the output of the regulator and connecting the ground lead to the tap. See: http://www.national.com/ds/LM/LM340.pdf. 73, Bob, WA9FBO -Original Message- From: Jeff DePolo j...@broadsci.com To: Repeater-Builder@yahoogroups.com Sent: Sat, Feb 27, 2010 9:32 am Subject: RE: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement? In a station, the 9.6 volt circuitry *could* be run from 12 volts, as long as its regulated. I'm not suggesting someone does that, because the circuits were optimized for 9.6 volts, but I'm trying to make a point. Point taken, but to add to your cautionary note, there are some circuits that will not be happy at 12V. I remember trying to run a Micor PL decoder off 13V and it did some strange things (i.e. didn't work right/reliabily). If it were me, I'd just use a 9 or 10 volt three terminal regulator (7809 or 7810) and skip the whole LM-317 or diodes in the ground leg deal. It only serves to make the circuitry more involved , harder to mount, and for NO advantage whatsoever. In general I don't like raising the ground on 7xxx series fixed regulators by adding diodes to what would normally be the ground lead. 7xxx series regulators can (and will) oscillate, which is why adding caps per the datasheets' recommendations isn't just a good idea, it's mandatory. My concern is that putting a diode in series with the ground lead results in the filter/bypass caps being at a different ground potential than the device, which may increase the chance of oscillation. --- Jeff WN3A
RE: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
The diagram for the adapter box also shows +13 Vdc is also routed to one of the pins in the same plug (as well as ground) so I have to figure out if that's a requirement or just an addition to the adapter package. I did see where +13 Vdc was supplied to another location on the repeater back-plane. Yeah, the regulated power supplies come to the station backplane via that multi-wire harness and the microphone style plug. I don't think unregulated DC is in that harness; that connection is usually made by a separate two-wire (red/black) harness with an in-line fuse holder to two screw terminals on the backplane. I'm thinking of something mounted right on the Repeater Back Plane so the leads are short and there's not a requirement for another box to take up rack space. I was envisioning mounting it to something metal for heatsinking purposes, but I guess you could probably use one of the screws on the backplane plus a little TO220 heat sink. Whatever works...and doesn't make smoke. --- Jeff
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
How about a 7809 regulator IC with a 1N4004 diode in the ground leg to raise the output voltage to 9.6V? I was envisioning mounting it to something metal for heatsinking purposes, but I guess you could probably use one of the screws on the backplane plus a little TO220 heat sink. Whatever works...and doesn't make smoke. --- Jeff Yahoo! Groups Links
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
Hi all. Built up a copy of the DC supply that was in a old Micor manual. Used the caps and filter choke from an old supply. Add a LM 317 with heat sink. Added MOV's and additional hf caps. Seemed to work fine. This fed a full micor repeater with all the normal modules. Worst case 9.6 volts current was about .75 amps. Have this on a repeater up in Montana. Ralph, W7HSG - Original Message - From: DCFluX dcf...@gmail.com To: Repeater-Builder@yahoogroups.com Sent: Friday, February 26, 2010 2:59:59 PM GMT -07:00 US/Canada Mountain Subject: Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement? How about a 7809 regulator IC with a 1N4004 diode in the ground leg to raise the output voltage to 9.6V? I was envisioning mounting it to something metal for heatsinking purposes, but I guess you could probably use one of the screws on the backplane plus a little TO220 heat sink. Whatever works...and doesn't make smoke. --- Jeff Yahoo! Groups Links
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
DCFluX wrote: How about a 7809 regulator IC with a 1N4004 diode in the ground leg to raise the output voltage to 9.6V? There is nothing mysterious about 9.6 volts. It could be 9.00 volts 10.00 volts 11.00 12.00 volts or *anything* in between. The part that is critical is that it is stiffly regulated. Something less than 10.6 volts was chosen because that is the point where a lead acid battery is technically totally depleted. This means the critical circuitry (oscillators, multipliers, etc.) are always fed with stable power to the point where the battery is dead. In a station, the 9.6 volt circuitry *could* be run from 12 volts, as long as its regulated. I'm not suggesting someone does that, because the circuits were optimized for 9.6 volts, but I'm trying to make a point. If it were me, I'd just use a 9 or 10 volt three terminal regulator (7809 or 7810) and skip the whole LM-317 or diodes in the ground leg deal. It only serves to make the circuitry more involved , harder to mount, and for NO advantage whatsoever. Kevin Custer
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
In that case Just a straight 7809 or 7810 also would not require isolating the tab and can be mounted straight to the metal chassis. If it were me, I'd just use a 9 or 10 volt three terminal regulator (7809 or 7810) and skip the whole LM-317 or diodes in the ground leg deal. It only serves to make the circuitry more involved , harder to mount, and for NO advantage whatsoever. Kevin Custer
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
DCFluX wrote: In that case Just a straight 7809 or 7810 also would not require isolating the tab and can be mounted straight to the metal chassis. If it were me, I'd just use a 9 or 10 volt three terminal regulator (7809 or 7810) and skip the whole LM-317 or diodes in the ground leg deal. It only serves to make the circuitry more involved , harder to mount, and for NO advantage whatsoever. Kevin Custer Folks might consider using an LM2940-9 or LM2940-10 (or another LDO regulator) instead of the 7809 / 7810 as the dropout voltage is much lower (0.5V on the 2940 versus 2V on the 78xx typical). This would allow regulation to continue down to an input of 10.5 (-10) or 9.5 (-9) volts. The 7810 will lose regulation at around 12V and the 7809 at around 11V input. Not overly important if the system is being powered from a regulated supply, but if via batteries.. Ed Yoho W6YJ
Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?
Build it yourself. Use an LM7808 and and series two 1N4001's to lift the ground lead up by 1.4 volts. I know 7809's are around but the 7808 is much more common and cheaper. Bill From: skipp025 skipp...@yahoo.com To: Repeater-Builder@yahoogroups.com Sent: Thu, February 25, 2010 9:58:50 AM Subject: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement? A'tank u viry much Less than 1 Amp is the good news... Now instead of building a 3 terminal LM-317 regulator circuit do we want to instead buy a pre-made complete regulator board off Ebay for about $7 and shipping? A main switcher power supply or off a site DC source and the electric bill from the Micor Power Supply should drop at least $20 per month. thank you! skipp
