Re: ANSI C63.4
The ferrite loaded mast cable is obviously there for common mode rejection. As such, the CM can only be sourced form unbalanced baluns at the antenna, or from the imbalanced complex impedance variance caused from the mutual inductance of the antenae over the ground plane. An antenna expert such as Bob German or Roger McDonnel can shed more analytical light onto this. Hans Mellberg EMC Consultant - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: ANSI C63.4
A1. Since concrete is partly conductive and varies with mositure content and ambient conditions, the reflected path with vary substantially. The solution is to place a screen mesh over the top of the concrete. A2. The specified size is that of the elipse which is 2d by root3d. A practical size is 20m by 17m rectangle. A3. running coax on the top surface most likely will not affect the measurements but for NSA measurements, to obtain maximum repeatability ferrite cores are placed every 1m on the mast cable. It would be best to feed the cables diametrically opposed from each other so as to minimize any effects. A4. Theoretically the conrete curbs, the hedges and metal object can cause additional unwanted reflections. Those may or may not be a problem. Metal objects will have the greatest effect since most of the wave will be reflected. Hedges will most likely act as absorbers at certain frequencies, and the curb will cause reflections or absorbtion at certain microwave frequencies. Hans Mellberg EMC Consultant - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
New CISPR 22 limits 1GHz
There is a round of voting ongoing at this time for a new set of CISPR 22 limits for measurements above 1GHz. They are rumoured to be quite interesting and substantially different from anything the FCC has been doing for years, including the required anechoic chamber (vs semianechoic most of us use frequently) a 20 dB difference from FCC limits and more. If anyone can get a copy (they are apparently a controlled distribution item) study them and contact you country representative to CISPR for you opinion. My opinion is that the FCC methods, procedures and limits were quite adequate and here was a chance for CISPR to adopt the FCC rules. Now, if the CISPR limits are voted for in favor, we are in for dual rules that will eventually cause EU-US commerce friction. Hans - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Fwd: dB limits and Stats
---BeginMessage--- when using a log value, A +/- xdB, the tolerance is a percentage of value A rather than an absolute range independent of A. Makes sense to me! Hans ---End Message---
Re: Ce versus FCC
I have encountered certain European agencies requesting that not only are the conducted emissions required to be performed at 230V 50Hz but radiated emissions as well. I agree that for conducted emissions it may make a difference but I have not seen radiated emissions change when the power source is changed from 60 to 50 Hz (while keeping Voltage the same). I did, however, see recently a product change emissions when the voltage was changed from 120 to 230 V. And, it did not matter if it was 50 or 60 Hz, only the voltage was significant. Go figure! Hans
Re: Tantalum Capacitors
Tantalums give you the advantage of a high Capacitance per unit volume. Their reliability is proportional to the applied voltage versus rated voltage, operating temperature versus rated temperature and power dissipation (Vripple*2*pi*f*C) The do most often fail in a short circuit. They should be derated to a maximum of 60% but no less than 40% in a hi-rel circuit. If there are a lot of spikes on the bus they are attached to, then of course, their reliability will be significantly lower, especially if the spikes are 50% OV or higher. If you have a lot of spikes, then go for the aluminum electrolytics. Hans
Re: 60 to 50 Hz Motor Generator Set in Santa Clara CA USA
This M-G set is located in Santa Clara CA USA. Shipping costs are anticipated to be high. Hans
60 to 50 Hz Motor Generator Set
If anyone is in need of a 150KVA 3-phase Motor-Generator Set please contact me for details. Hans Mellberg
Re: Emissions or not?
What if the little green Italian sports car, happened to resonate at 433. MHz? And, with a reasonable Q? Then, your weak 3rd harmonic, will retransmit from the sports car and your receiver will pick it up. I contend that it is your Tx output filter that is not performing. Do a conducted emissions test (not the powerline type but the RF type) using a spectrum analyzer and filters and attenuators to measure your actual output to the antenna. At a minimum you should see at least -60dBc as required by the FCC, for any spurious emission (97.307(e)) Hans
Re: isolation of TO-220 package
There used to be a special plastic shoulder washer used in exactly this application (The washer has a crossection resembling the letter T). This solved the clearance and creepage problem. It fits inside the hole of the TO-220. Hans
Re: PCI edgecard vs. compact
In general reliability terms, one connector is better than two. But, if the lack of connector allows for warpage and hence, reduced contact pressure at certain locations, then it is a toss-up. Secondly, without the use of the second connector, the pad contact material becomes significantly important as gold over copper (with a flash of nickel) has less life expectancy than gold (with a flash of nickel) over phosphor-bronze. I have assumed gold on gold on the non-soldered connections. Do not use gold on solder as this will slowly build an oxide barrier. Best to use gold on gold or tin on solder but not solder on gold. Best regards Hans
[SI-LIST] : Re: EMC-98, 1 June, Santa Clara CA
Correction: It is held next door at the Westin Hotel, not at the Convention center. (about 100 yards/meters walking distance between the two) To unsubscribe from si-list: send e-mail to majord...@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
EMC-98, 1 June, Santa Clara CA
A one day Colloquium and Exhibition on 1 June 1998 at the Santa Clara Convention Center, Santa Clara CA. 7:30 am to 5:00 pm. Sponsored by the IEEE EMC chapter of the Santa Clara Valley. Fee required for attendance, All welcome, visit our web site for details at: www.scvemc.org/emc98/ Topics include: Product Compliance, Telecom Regulations Signal Integrity, Product Safety, Troubleshooting techniques, EMC Design PCB Design, Regulatory issues, and more. Vendor exhibits, lunch and reception available too.
Re: Surge filter
The best way to design a filter is to establish the performance criteria first. Determine the source impedance Determine the load impedance Determine the attenuation required and at what frequency Determine the roll-off required Now you can determine what order filter you need and whether it is a butterworth or eliptical based on component count and cost. At this point you best use a filter design program such as FILSAP and then characterize it with SPICE. Don't forget that common mode rejection filters are a bit more tricky and require all lines to have a transfer impedance. Last but not least in importance is the topical placement of filters especially critical at high frequency. The closer they are located to the entry/exit point the better the performance. And, return path inductance and length, is not to be ignored. Hans Mellberg Director of Engineering Compliance Certification Services
