### Recent Posts

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##### RF, Microwave, HAM Radio / Re: UltraWideBand antenna design write-up - pedantry required
« Last post by Kire PĆ»dsje on Today at 06:37:44 AM »
The linear scale makes it always look much worse than actual. I am generally used too seeing dB m^2 (dB square meter) plots, but I think you found a very nice way by inserting a gain line based on a fixed effective area. Effective area is (I think) a concept that will be hard to understand by the average reader of your blog and they are more used to gain.
A lot of times people focus too much on gain. Especially for these kinds of wideband antennas, it is purely physics. The antenna will only collect the power density that is 'falling' on the antenna. (P_out(av) = A_eff * S). There is little you can do to the collecting area (effective area). Therefore the gain behavior over frequency is almost fixed by nature. Your graph is a perfect example that the antenna is a very close approximation to fixed effective area.
The way you presented this (maybe move the effective area to a different graph), will be a good explanation for your blog as to why your gain rolls of at lower frequencies.
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##### Beginners / Pulse Amplitude Modulated Signals: Sampled signals.
« Last post by richard1991 on Today at 06:37:00 AM »
Okay, the results of sampling is a pulse amplitude modulated signal. And that is the type of signal that is under consideration. It's not the result of modulating a carrier.

Page 303 of ELECTRONIC COMMUNICATION TECHNIQUES by Paul H. Young says "Figure 11.1 shows an example of a sampler. The switch S1 is closed instantaneously every Ts seconds to allow the instantaneous amplitude of VAto appear at the output. The output is in fact, a pulse amplitude modulated signal."

So, I'm referring in my posts to a pulse amplitude modulated signal. And it is the result of something akin to modulation, because it has sidebands. One then thinks that sampling is a form of PAM. Because of the result, i.e, sidebands. But is it?

I am absolutely certain that modulating a sinusoidal carrier with pulses will be a form of modulation called PAM. Somewhat less certain whether chopping an analogue signal can be said to be PAM modulation (notice I did not sat PAM signal).

It seems then, that the result of sampling is a pulse amplitude modulated signal.   The result of pulse modulating a carrier is also a pulse amplitude modulated signal. However, what is being pointed out I think, is that only the latter involves PAM in the generation of the signal, that is by way of pulse modulating of a carrier.  I guess then, that where a carrier is not involved, the method producing the pulse amplitude modulated signal is,  well - sampling.

Therefore there is a discrepancy in my title. The title should have been something like Pulse Amplitude Modulated signals: Sampled signals. Where PAM is involved, the title would be something like: Pulse Amplitude Modulated Signals: PAM signals.
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##### Projects, Designs, and Technical Stuff / Re: High Humidity Design
« Last post by Benta on Today at 06:36:49 AM »
Nothing special on circuit design, but conformal coating the assembly comes to mind.
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##### Repair / Re: Rigol 1022u doesen't boot up
« Last post by Armadillo on Today at 06:36:20 AM »
My mistake, that's not you.

you have to update 2 files.

One is the bootloader.
then the other is the dsp file.

Which GEL have you upgraded?

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##### EEVblog Specific / Re: ANNOUNCEMENT: 121GW Multimeter on Kickstarter
« Last post by VinzC on Today at 06:36:06 AM »
i never understood the concept of VAT. Value Added Tax.

- it is produced outside EU
- it is sold by a non EU company
- it is shipped from outside EU.

please, enlighten me : what value is added by the EU ? if the answer is none : how can it be taxed ?
Like states needed to justify collecting taxes... In my country, VAT is paid by us, customers, regardless of where a product comes from and how many (including zero) times it has been transformed. It doesn't have to make sense, it's mandatory. And if you try to avoid it, you risk being fined for fraud.
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##### General Chat / Re: Cryptocurrency -- Is anyone on-board?
« Last post by CatalinaWOW on Today at 06:35:00 AM »

But the whole reason that the world moved away from using gold or any other currency of intrinsic value is because:

* They can be faked.   Fake gold coins where a real issue back in their day.
* They are easily stolen.
* In a lot of cases they are hard to store and hard to move/carry/ship
* they are very difficult to trade with if as the denominations are awkward to work with.  If your loaf of bread is not worth a whole gold coin what do you do?  Buy 500 loafs and let the 499 rot?

I suppose you could start scrapping off slithers and using jewellers scales to weigh out the 100mg of gold needed to buy your lunch, but if the person behind you in the queue sneezes while you are doing that, lunch could cost you twice as much.

A quick watch of "Requiem of the American Dream" is good craic.

Your list of reasons for abandoning the gold standard is bogus.  The problem of detecting fake gold coins was solved thousands of years ago by a gentleman named Archimedes.  Better solutions have been developed since and are in place in pawn shops, jewelry stores and any other place that handles gold.  Easy theft is somewhat valid, but actually it is not materially different in difficulty from other currencies.  Gold is inconvenient for transfers of large sums of money.  Not the kind of sums used in daily trade, but the kind of sums banks and countries move around.  Look into how heavy the gold equivalent of a car or house is.  It won't strain much of anyone.  The divisibility of gold coins has never been a serious problem.  From pure mechanical division (pieces of eight are an example even though those coins were silver) to use of base coinage for subdivisions the problems were easy to deal with.

The biggest single reason we went away from a gold based currency system was that the supply of gold was not increasing as rapidly as the growth of other things in the economy.  If gold mining increases the gold supply by 1% a year then economic growth is limited to 1% or other distortions occur.  BITCOIN has the same type of defect.
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##### Projects, Designs, and Technical Stuff / High Humidity Design
« Last post by cwerther on Today at 06:30:58 AM »
I'm designing some add on's for my telescope (mirror fan control, temperature sensors, etc) and depending on the time of year it can easily be operating in the 90%+ relative humidity range.  Do y'all have any suggestions for circuit design for high humidity environments?
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##### General Chat / Re: New Member, Please introduce yourself
« Last post by jouko.perkkio on Today at 06:30:22 AM »
Hi, Jouko from Finland.

I've been working with embedded systems for > 10 years for now. My work consists of both software and hardware design. My passion is in combining these two; not just making a nice piece of hardware but to make it sing too! My semi-professional hobby is within drag racing and developing a data acquisition system for the very harsh conditions.. We have currently a well working, accurate and fast data acquisition system with web & SD-card interface to bring the data to PC for analysis. Great forum, somehow never got here before.
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##### Beginners / Re: Used Oscilloscope for under 250$« Last post by rstofer on Today at 06:28:55 AM » I only linked the video as an example of why an oscilloscope with greater than the minimum bandwidth for audio is desirable. The 2467 is special for reasons other than its bandwidth and not the oscilloscope I would recommend. As always, the video was excellent. I tend to see what equipment is being used in the various tutorials and then price it on eBay. No particular reason, just curiosity. Quote There are lots of used analog oscilloscopes to be had for$250 or less and most suitable ones will be available for a lot less.  The 50 MHz Tektronix 2225 shown in Dave's video is one of the better examples because of its low cost, 500uV/div sensitivity, and lower age but I would consider any similar oscilloscope.  I've picked up Tektronix 2230s, 2232s, and 2236s for less than \$150.  The various 465 family oscilloscopes can also be had for that price or less but are more likely to have age related problems.

The problem is, those asking about 'first' scopes are in no position to evaluate the alternatives.  I suppose it already exists but a list of desirable scopes, in some kind of ordering, would be handy.  "Here's your shopping list, start at the top and work down.".

When I was in college, the Tek 454 was fairly new and one of the other fellows worked for Burroughs and he had one.  I decided that I wanted that form factor.  It was 30+ years later before I bought the 485.

Quote
The largest problem however with used analog oscilloscopes is finding one in good shape.  Novice users have difficulty evaluating them and repairing or maintaining them.

And this is the reason I don't recommend buying used <anything> but especially complex test equipment.  Yes, there are some bargains out there but there is also a lot of junk.  Repairing scopes isn't something I would think a newcomer was up to although there are forums that can help.
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##### General Chat / Re: Scientist finds UK water companies use 'magic' to find leaks
« Last post by MrW0lf on Today at 06:26:39 AM »
If you can't make it real science, why not call it quantum science and forego the evidence, claiming it's all delicate and complicated?

I have no problem with science or evidence on the subject, finding interesting paper or two every day
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