Tee he, yes that is what the woman and man at the Bus stop suggest. I no longer get involved as although these folk are not dim, explaining this in such a situation is just not going to work.
What is annoying though is at night you often hear the same station from two transmitters on medium wave with a long delay between them. Surely if they are all being fed by the same method then they should not be out of sync in this way. This never happened in the old days.
I noticed an article the other day about materials with a negative refractive index. This set me wondering if one could use something like that at radio frequencies. Brian
I don't think that is really the point. The safety critical stuff is all hard wired and well taken care of.
However, at the local level, there has been little, if any, monitoring of actual voltage, current flow and other parameters. In changed times, and with the economic need to make the best use of installed plant, improved data flow could be really useful.
I think they now use digital links between transmitter sites, with the associated coding and decoding delays. I've read somewhere that even the pips on Radio 4 FM aren't guaranteed to be right nowadays, and as for the ones on DAB...
I'm probably somewhat out of date, but ~30 years ago when I worked for GEC, the lower current breakers were air blast breakers, where a jet of air is used to blow the arc into too long a loop for it to sustain as the contacts open, and for higher power breaking, the contacts are under oil, which quenches the arc as the contacts open.
Magnets are used in some MCBs for the purpose of quenching the arc in a very confined space by increasing the effective contact gap.
I've never noticed any appreciable difference, when checking the 01:00 shipping forcast pips against my watch'es pip. My watch is very accurate, synched nightly via MSF, with no noticeable drift.
Which is why a mandatory key shaping filter is normally used.
Back in '67, before the RAE was transmuted into the simplified 'Multi-Guess' form it is today, I'm sure that was one of the questions relating to the use of a 'Key Click/Shaping filter'.
Back then, radio amateurs were largely expected to understand this stuff in detail because it was still common practice for a good portion of them to build their own kit from scratch (particularly transmitters) so it was important that they could demonstrate a working knowledge of such things so that should they operate a transmitter, whether homebrewed or not, that generated such avoidable interference, they could have their license suspended or even be prosecuted for causing interference to other more vital services and not be able to invoke "ignorance" of the rules as a defense (the basis for all licenced operations, e.g. a vehicle driving licence or any other similar licence).
I'm not familiar with the current RAE syllabus (nor even the one that was current back in '88 when I passed my 12wpm morse test and finally got around to capitalising on my '67 RAE pass to obtain a class A license) but I suspect this sort of knowledge is given far less emphasis than in days of yore simply because most 'modern day' amateurs are buying ready made transcievers which incorporate _all_ such necessary filtering built in.
That's not to say a modern ham won't be doing some homebrew work, it's just not likely to be building Tx and Rx and TRx kit from scratch so much as building their own ATUs and 400W PEP Linear amps and crafting interesting antennas/antenna arrays (steerable or not).
Even with a proper shaping filter between the key and the cathode circuitry of an 'old school' valve transmitter, you'll still hear clicks if you're right on top of the Tx site.
Turn the IF gain down on a modern synthesised LO transciever (most don't use a tunable RF amplifier stage) and switch in the front end attenuator and you should lose the key clicks and hear the shaping effect of the key filter even without selecting the CW filter setting.
Indeed, AIUI, electronics/radio engineers did play with such things in the 50's or thereabouts, athough not (as I understand it) quite in the systematic and directed way present in Veselago's
1968 paper or as modern physicists do.
Many NRI/metamaterial concepts are implemented first in the microwave regime, for instance, largely because it makes fabrication easier.
So it'd be easy to make radio frequency metamaterials, losses permitting, just as long as you have the space (on the scale of multiple wavelengths) to put them. What is it you want to do?
The more cycles, the better defined is its centre frequency. Anything sub-cycle doesn't have any sort of well defined frequency, unless, I suppose, you add some assumptions (such as: this is a small segment from a sinusoidal waveform that repeats to infinity).
The larger the bandwidth, the greater the rate that data might be transmitted for a given signal-to-noise ratio. For a given bandwidth, the better the signal-to-noise ratio, the greater the rate of data transmission. The speed of data transmission depends on the method of transission - for EM in air, you get (approx) the speed of light.
well until you examine the thing digitally when it tends to be that the delay is the size of whatever block of data you need to error correct times the time sent to send one bit of it. Plus the propagation delays as detailed above.
i.e. from the time you send the first bit to the time the far end has a valid corrected packet is longer than the propagation delay - massively in most cases.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.