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In: , "Lucky" wrote:
Is it safe to use a 12v 3A PSU with the my radio even though is only requires 500Ma? In other words the excess potential Amps won't fry the radio? As everyone else pointed out, it's safe (and perhaps even slightly better) to use a higher amp power supply than is actually needed. It's the voltage you need to be concerned about. Think of voltage as water pressure and amperage as water volume. Hooking up a pipe 3" in diameter to a shower won't blow the head out, but, if you took a pipe say .25" in diameter from a high pressure pump... you'd likely blow a hole through your shower stall. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
In: , "Unrevealed Source" wrote:
In general, is it better to run a receiver off a good external DC power supply, or using AC power and the built-in transformer? It would seem to me that I might get less noise using an external DC power supply, but what is the general concensus here? Thanks. I find batteries to be the best results. 'Course, that is not very practical. I use a cheap wal-wart, but I cut the wires and put a capacitor in the circuit, that seems to help a little. (Had at one time a HUGE capacitor, but it was too much trouble to carry around) I suppose it all depends on how the respective power supply is built and how OLD it is. Electrolytic capacitors dry out over time, (especially older tin-can ones) which I believe explains the "hum" often heard in antique radios. As equipment ages, I believe an external supply could help in this area. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
The Best DC supply is a car or motorcycle battery. It is completely
noise-free, has enough power to eliminate audio clipping, and can supply many hours of listening. The drawbacks are the need to be recharged and the need to keep it well clear of electronic equipment because of corrosion caused by ions. Of course, you cannot use it with the charger when listening as most battery chargers are quite noisy, but I have used a motorcycle battery with a 2 amp charger that was not too bad (Schumaker Mity Mite). To repeat, do not keep a lead-acid battery near (within 10 feet) of any electronic equipment: it will eat hell out of the boards. But it will give you the best DC supply and it need not cost too much, either. |
wrote: The drawbacks are the need to be recharged and the need to keep it well clear of electronic equipment because of corrosion caused by ions. Is this correct? I'd expect this sort of corrosion to be pretty minimal, even with little separation. Steve |
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Gotcha, but I don't see why anyone would choose to power their receiver
off such a battery. There are plenty of sealed lead-acid and gel cell batteries on the market that are safe for indoor use and that produce negligible emissions. Steve |
wrote Gotcha, but I don't see why anyone would choose to power their receiver off such a battery. There are plenty of sealed lead-acid and gel cell batteries on the market that are safe for indoor use and that produce negligible emissions. Steve Hi Steve, I power two transceivers (1 VHF, 1 HF) off a 12vdc deep cycle battery, and the Drake R8B is powered from the computer's UPS. Other radios and tuners that can accept external DC get it from non-switching DC power supplies. Price was somewhat of an issue in a battery that is required for both normal and stand-by use, and the only reasonably priced deep cycle's were vented lead-acid types. Once a month I use a powerful charger and only in an outside vented area. But the 1 amp float charger produces very little gasses and would not overcharge unless left on for days with no draw on the battery. For some very high operating temperature receivers such as the older Icoms, external DC is the only way to go, unless you can provide constant air movement over the radios. It has zero effect in reducing noise in my opinion, but heat is the enemy of all electronics and definitely shortens their lifespan. Unless the receivers have a narrow-band stabilizing ceramic oven oscillator option, the receiver will drift less when external DC power is provided. Jack Painter Virginia Beach, Virginia |
In article ,
dxAce wrote: Lucky wrote: wrote in message oups.com... From: craigm wrote (in part: There is also the belief that removing the heat generated by a supply by using an external supply improves the reliability of the radio. However, I have only seen anecdotal evidence to support this. Aside from reliabiltiy issues, the main reason I run my R2000s and other radios from an external supply is to reduce heat, which leads to reduced heat. The radio exceeds it specified stability when operated from a external power source. Many built in supplies, and most aftermarket power supplies can be much noiser then many here would believe. With a decent battery powered receiver, make a noise probe, I use 10' of RG174 with a 10 turn coil at the sensor end and connector to fit the radio. Please be certain to use insulated wire and have all he solder connections covered. I used "liquid tape". With the radio or external power supply to be tested move the probe around the supply, over the AC mains input an DC output. For some reason very few companies include the very usefull ~1000pF caps across each diode in a bridge. This cap can really help quiten a noisy supply. The probe is also usefull to find noise leaks from a PC/monitor.VCR etc. I use a DX398 because A:It is a smal,sensisitve and easy to use receiver, and B: I own one. My main +12V DC supply is a Lambda 12V 20A linear supply, my backup is a 12V 8A Lambda linear. Both were much quiter then the often touted and extremly popular Astrons. After a few additions, feritte beads on the input/output to the bridge, 100pF micas with very short leads across the bridge, 1000pFs across the junctions in the pass elements, some 1uF tantalums added across the 723, the noise was gone. For most of us, including me, the minor noise from a decent power supply, either internal or external, is way below the local noise floor, but while these mods may be waste for operation ~50MHz, they really helped remove some noise from my NOAA APT weather satellite reception. But even on HF during some early morning quite times, I think the lowered noise helps. And with the borrowed AR7030+, it is clear that with a good (quite) enough receiver all the noise you can reduce is well worth the extra effort. I will only have the AR7030+ for about a month, so I will be listening a lot more then posting. And the stock wall wart suplied with the AR7030+ just sucks. Very noisy. Terry Hi Terry I have a Lowe 150 and I'm using a crappy Radio Shack 12v 500mA wall wort. I'd like to purchase a Lambda PSU. My question is this. Is it safe to use a 12v 3A PSU with the my radio even though is only requires 500Ma? In other words the excess potential Amps won't fry the radio? Can you recommend a certain model Lambda for my radios? I also have a Icom R75 and some others. I'm thinking even though the PSU can put out 3A or even 20A, the radio will still only draw 500Ma and it will be safe????? Yes, it will be safe. The radio will draw what it will draw. Under normal circumstances yes but for a failure of some kind that can draw more power so you should use a fuse. The fuse should be near the supply end in case of a short in the cord. -- Telamon Ventura, California |
"Jack Painter" wrote in message news:msAee.731$It1.406@lakeread02... wrote Gotcha, but I don't see why anyone would choose to power their receiver off such a battery. There are plenty of sealed lead-acid and gel cell batteries on the market that are safe for indoor use and that produce negligible emissions. Steve Hi Steve, I power two transceivers (1 VHF, 1 HF) off a 12vdc deep cycle battery, and the Drake R8B is powered from the computer's UPS. Other radios and tuners that can accept external DC get it from non-switching DC power supplies. Price was somewhat of an issue in a battery that is required for both normal and stand-by use, and the only reasonably priced deep cycle's were vented lead-acid types. Once a month I use a powerful charger and only in an outside vented area. But the 1 amp float charger produces very little gasses and would not overcharge unless left on for days with no draw on the battery. For some very high operating temperature receivers such as the older Icoms, external DC is the only way to go, unless you can provide constant air movement over the radios. It has zero effect in reducing noise in my opinion, but heat is the enemy of all electronics and definitely shortens their lifespan. Unless the receivers have a narrow-band stabilizing ceramic oven oscillator option, the receiver will drift less when external DC power is provided. Jack Painter Virginia Beach, Virginia Reasonable heat is not a significant factor for modern electronics. Humidity and moisture are more of a factor and heat lowers both. On/off cycles are the most damaging. |
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