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Someone has a different opinion on this matter... http://www.levitonvoicedata.com/support/technotes/tech_note_detail.asp?tnID=175 http://www.levitonvoicedata.com/support/technotes/tech_note_detail.asp?tnID=176 As far as I know the TV signal is above 300 Mhz. Will I experience a (even small) signal reducing?

In order to give signal to two different cables, the TV technician stripped the cable coming out of my TV antenna and the two other cables. He then twisted all three cores together and all three nets/foils together. He insulated the junction with tape. This cabling is on my roof and has no protection from weather effects. Is it the proper way to do this, or are there any losses? >:( I was thinking of putting all three cables inside an electrical box and connecting the cables somehow. Which is the best (minimum signal losses) way to do this? Should I install connectors (e.g. BNC type) in order to simplify a future task? (e.g. changing antenna, installing satellite dish e.t.c.).

I have removed the TV socket in my wall and installed a BNC connector in the end of the cable. It is a typical 75-Ohm cable. The BNC connector was bought for usage with RG58 50-Ohm cables. Will I experience problems?

Are the values of the capacitors of significance? The absorbing of sharp transients in the output line is improved with the capacitance; a bigger capacitor would perform much better. Why just 1 pF? Similarly for the input capacitor (is it an RF-lowpass filter to filter out AC?).

What is self-oscillation? ;D How can a capacitor improve transient response? How can a capacitor minimise the effects of load variation?

It is mentioned in the datasheet of the LM78XX series that for the standard operation the pins 1 (input) and 2 (ground) must be connected using a capacitor of 0.33

Thanks for the feed EnigmaOne. But I am a minimalist... using Slackware and fluxbox WM. No Gnome, KDE, apt-* utils. And I will not change my distro ;)

Alun thanks for the reply. I know about the different types of ac/dc conversion, my question was how the change in load can alter the output voltage. Does it depend on the internal resistances of the AC/AC transformer itself?

Check these out: http://www.electronics-lab.com/forum/index.php?board=21;action=display;threadid=2308 http://www.electronics-lab.com/forum/index.php?board=21;action=display;threadid=2336 Regarding the slow decrease of the voltage when you unplug the adaptor, it is absolutely normal. It is a simple discharging RL circuit; L because the transformer of your adaptor has an inductor and R because voltmeters have big resistances.

Are there regulated and unregulated AC/AC transformers? Or are all transformers unregulated and the regulation of the voltage depends upon something else (a circuit, perhaps)?

gEDA sucks! A needed B, B needed C... installed 20+ different things, some would not compile, no uninstall could be done in some of them, got angry, formatted, reinstalled Linux. :( I'll try Xcirquit for now.

gotcha! :P

I have read that voltage regulators dispose of surplus power by dissipating it as heat. I have an idea, most probably something is wrong but I would like to ask you. What if the regulator supplied just a small amount (~10mA) of current to a current amplifier which would provide the "real" current for the rest of the cirquit? Thus we would not have wasted energy and big heatsinks and fans. What is your opinion on the subject?

Ante I work as a systems administrator in an informatics laboratory in the University of Athens. When I talk with the other admins I always see strong opinions - some love Win, others hate it. And most of these persons are most educated and extremely skilled in operating a variety of machines and operating systems. So it is nearly impossible to reach a justifiable conclusion in a single thread. Why has this distro war started? All I wanted to know was which is the best free soft for WinXP and which one for Linux :)

(Why was the previous topic locked, gentlemen? ???) From what I have read I have realised that the current listed on most unregulated AC/DC adaptors is the one needed for output voltage to take its nominal value. How can I determine the maximum current rating for an adaptor (without destroying it or starting a fire or something exaggerating)? What is the "saturation" phenomenon observed in an overloaded transformer and how does it affect future function? Why is it non-reversible?

Thank you all for your replies. Audioguru, I realise that high-end multimeters (and equipment, in general) need quality input voltage in order to operate properly. Though most educative, your replies do not answer the original question regarding "el cheapo" equipment. From all replies I have read I assume that powering my multimeters via DC (and using a regulator, LM317 e.g.) would be fine.

I am a Linux fan. What can I say? ::) Anyway, which one is the best fow Win XP? (free software always)

For the past few hours I have been trying to install gEDA. Does anyone know of a good scematic design & simulation program in Linux? I know some titles but I do not know which is good and which is not. I am mainly interested in small circuits and simple, analog electronics.

What is a D shell? :-[ And why "unfortunately"? Do you mean that a decent multimeter must accept voltage of a very specific and small range in order to provide the expected accuracy? What happens when we power a cheapo multimeter with a somewhat different voltage than that expected? Does it alter the values of the measurements we make? If I create a circuit with a voltage regulator to make sure that the voltage of the multimeter will always be stable and 9V, will it function properly and accurately?

What do you mean by the phrases "unregulated to boot" and "double up on" ? ::) I thought that the current listed on the device is the maximum allowable, and not the proposed value. What is the relationship between these two? I have dismantled the adaptor, it consists of an AC/AC transformer and a bridge rectifying circuit (4 diodes etc.). What could cause this alteration in voltage when changing external resistance? Could it be the internal resistance of the adaptor? One more thing: what kind of damage does a transformer receive if the current it provides is higher (say, double) than the nominal value? I suspect that the wires are heated up and they eventually melt; In any case, can we deal with this by providing extra cooling to the transformer?

I own two cheapo (~10 Euro each) digital multimeters, and have been paying fortunes for 9V batteries. Can I supply the multimeters with power coming from a DC PSU or an adaptor/transformer? What are the cons of this? possible problems?

Over the years I have collected several AC/DC transformers/adaptors. These adaptors provide higher voltage than their nominal value. Below follow some calculations I have made with one of them. The theoretical voltage of the adaptor is 3V DC. I connected several resistances in the adaptor's jack and measured the voltage in the resistance's ends. Resistance (Ohms) Real Voltage (Volts DC) no resistance 6.58 470 K 6.51 100 K 6.39 12 K 6.21 5.6 K 6.18 9.6 3.15 shorted (no resistance) 0,16 We can clearly see a pattern: the voltage lowers when the resistance lowers. But it is nowhere near 3V! What is the matter?

Hello to all. Since I am new to this forum, I thought it would be good to introduce myself. I am a pre-graduate student at the department of informatics and telecommunications of the university of Athens (yes, I am Greek :)). Until recently I had been the type of person who likes electronics but does not know where to start from. After attending a laboratory cource in my dpt. and getting to work with the oscilloscopes and circuits I realised that I really like all this ;D. My theoretical level in electronics is low and my practical level is 0. Currently trying to change both for the better. Glad to be here :) Oh, by the way, Merry Christmas to all !