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#11
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On Mar 1, 3:17 pm, Phil Kane wrote:
On 1 Mar 2007 03:18:49 -0500, wrote: Oh by the way... found out that the powersupply is 48V! (my bad!) Well, it won't work from a 12V battery then... g The only 48V supplies that I am used to are ones that take up, a whole wall in a communications vault...not quite the same! Wow.. I have FIOS here in Texas and I don't have excessive noise from it. 48 Volts? That seems strange because it has only a 12V battery for backup power. Are we sure that the problem is not the network wires or something else? I guess, I'm asking how did we determine that the power supply was the problem? (Aside from the fact that this is normally the problem..) -= Bob =- |
#12
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Call Verizon and complain to get the problem fixed! The noise also may be
interfering with other people (for example, short-wave radio listeners) who, because they don't have technical knowledge like you, wouldn't have a clue what's causing all the noise. On 1 Mar 2007 03:18:49 -0500, wrote: Thanks guys! I'm going to play with some filters and beads. See if that works first. I agree that it actually is Verizon's problem (and I will inform them when I can't get it resolved.) but I want to see if I can avoid the headace of trying to explain them the issue. $5 worth of filter/beads might not be so badly spend if it works. Oh by the way... found out that the powersupply is 48V! (my bad!) 73 de Dick, AC7EL |
#13
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On Feb 28, 1:26 pm, wrote:
I have the (incredible fast and reliable) Verizon fiber optic into the house for my internet connection. So far so good. However at the access point there is a battery backup unit for the fiber-Copper converter. This battery unit is kept charged by a powersupply that makes an ENOURMOUS amount of RFI that radiates onto the (15 feet) lead into the unit and from there into the shack. (S6) Does anybody have any suggestions on how to silence this? Or... a suggestion for a cheap and 'quiet' powersupply? (It's output is a regular 12v) Over the years, I have seen a number of posts that cite strong RFI from various sources. In most cases, where I have obtained a unit and made measurements, the units have complied with the FCC limits. Most of these devices are switchmode power supplies. In the US, because they intentionally generate signals above 9 kHz internally, they are classified as unintentional emitters and must meet the FCC Part 15 conducteed emissions limits below 30 MHz and the radiated emissions limits above 30 MHz. (The premise is that on HF, small chasses don't radiate much, while the wires they are connected to do.) Unless they are used as part of a computer system, they are "verified" as described in the Part 15 rules. This means that the manufacturer is required to test them and keep the results on file. Switchmode power supplies used in computers are authorized under a Declaration of Conformity (tested by the manufacturer as verified devices, but only by labs the FCC has approved) or, rarely nowadays, under certification, where the manufacturer sends test data to the FCC, which then authorizes the product. The manufacturer must meet the limits and authorization requirements; the operator of the device is responsible for harmful interference. In most of the interference reports I have seen, someone is interfering with themselves. If the device meets the FCC rules, and it is likely that it does, the FCC not, of course, offer much sympathy. The premise that boxes don't radiate much on HF, but wires do, points to the cure. The easiest thing to try is a common-mode choke on the wires going to and from the box. Below 30 MHz, ferrite beads usually don't have enough inductance to function well as ferrites. You will need to get a toroidal core that is big enough to pass the connector(s) through, and wrap about 10 turns of wire onto it. For lower HF, -73, -75, -77 or -J material is probably best. For upper HF, I would use -43. The nomenclature of most cores sold to hams has the size in the first part of the part number and the material in the second part. For example, an F-240-43 core has an outer diameter of 2.4 inches and uses -43 material. That may solve the problem, but with a switch-mode supply, it is likely that differntial-mode noise is also being coupled onto the line. For that, you need a "brute-force" AC-line filter that uses inductors and capacitors. I don't know if is still a good number, but Radio Shack's catalog # 15-1111 is a suitable filter. Others are sold by Industrial Communications Engineers (http:// www.iceradioproducts.com/). You may need a combination of brute-force and common-mode filtering. 73, Ed Hare, W1RFI ARRL Lab |
#14
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Oh, one other point I wanted to make.
Typically, from the house next door, a device that complies with Part 15 will be about S7 on HF. If hams know of devices that are significantly louder than that, I would like to test them. If you can, provide me with a model number and source and/or the unit itself, which I can return to you. Ed Hare, 225 Main St Newington, CT 06111 Tel: 860-594-0318 |
#15
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"Ed Hare, W1RFI" wrote in news:1173461308.258188.233550
@t69g2000cwt.googlegroups.com: Oh, one other point I wanted to make. Typically, from the house next door, a device that complies with Part 15 will be about S7 on HF. If hams know of devices that are significantly louder than that, I would like to test them. If you can, provide me with a model number and source and/or the unit itself, which I can return to you. Ed Hare, 225 Main St Newington, CT 06111 Tel: 860-594-0318 One of the loudest sources of RFI I ever had was a UPS that almost oblitereated the AM radio band making it near impossible to tune an old 5- tube 'all american' style GE receiver. When I localized the source it quickly became misc. parts never to bother me again. Sorry I can't send it to you to play with. cheers, chuck... |
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