Johnythree

I'm puzzled by this claim. I wouldn't call it a myth, but all the same...

I grew up on a vineyard. Each harvest time the grapes would hang down heavily and almost touch the ground. Our pet dogs would park themselves beneath and greedily consume a whole bunch.

They would also scoff any dried grapes they found on the ground.

The worst effect seemed that they all would get noticeably pudgy during the season.

AM is a type of modulation which is widely used by many different services (eg Shortwave broadcasting, CB radio, Aircraft VHF, etc).

However "Longwave and Mediumwave Broadcast" unambiguously refers to that service.

Transmitters need only be re-certified if they are to be sold in quantity.

Once-off Broadcast Transmitters need only demonstrate that they meet the relevant standards.

Many of the existing LF and MF BC transmitters were effectively custom built to meet the requirements of their transmit license (for example, the radiation pattern of the antenna were often unique for each station).

It doesn't. In both it depends on what the stations engineer chooses to transmit.

Most cheap FM receivers definitely use a PLL to detect FM. Giving automatic tuning is just a side benifit.

Most FM receivers can lock on the carrier because they have a "Phase locked loop" to cancel any tuning errors.

Many good AM receivers do exactly the same thing, especially those receivers which have "Synchronous Detectors" for AM.

It's just that the circuitry involved is simple for FM, but rather more complex for AM.

Is commonly known as "Bass Boost".

As the OP has said, it cannot give louder bass, but simulates the bass harmonics.

This is yet another myth:

The "Woolyness" of AM broadcast (at least in America) is due to the stations purposefully tailoring their audio processing to suit typical cheap AM receivers. And this in turn is because designers of cheap AM receivers fit narrow filters instead of using noise reduction techniques, eg a good outside antenna.

There was a period (in the rest of the world) where high quality AM receivers had a narrow/wide switch to give better audio response to stronger signals.

The good news is that modern SDR receivers usually have selectable bandwidth on AM so as to derive the full transmitted audio. And many of these have AM stereo decoders as well.

If you listen to a good quality AM broadcast (eg Gov AM stations in Australia) you will hear audio which are very hard to tell from FM audio.

Go back and read the many high-quality AM tuner articles in the electronic hobby magazines from the past.

Only while signals are strong. On weak signals however, AM has a considerable benefit in intelligibility over FM.

This is a myth. There is no reason that channel spacing need limit the modulation bandwidth. The only downside is that listeners to adjacent stations will hear a slight "monkey chatter" from the overlapping sidebands. In reality stations are never allocated adjacent frequencies within the same coverage area so this usually doesn't happen.

Yes, this is one of the proposed methods. It's known as "Independent Sideband".

It works, but it is a fairly expensive method to implement.

There were a number of successful AM stereo broadcasting methods proposed and trialed. These were completely compatible with conventional AM transmissions.

The conceptually simplest of course whas where the LSB and USB are used as separate channels.

Although most of the systems did work, they were not ultimately successful simply because insufficient stereo receivers reached the market.

Go search in Wikipedia on "AM Stereo".

There is no reason that the channel spacing need limit the sideband bandwidth.

The only downside to this is that listeners on adjacent stations hear a slight "monkey chatter" from the overlapping sidebands.

This is one of many reasons why station frequencies are never allocated close to stations which are physically close.

You only need glance at the waterfall display on a good SDR receiver to see that the actual audio bandwidth is often much wider than the channel spacing implies.

The pickle will shunt (steal) some signal, but the radiated power from the antenna will be very much greater than that flowing through the pickle.

Because your nerves don't respond to high frequencies, you cannot "feel" RF current.

What you do feel is the intense burning associated with the RF energy being converted to heat.

You have it backwards:

Fessenden is famous for developing a electomechanical RF generator which put out a clean sinewave (eg a coherent wave), which helped replace the earlier Spark-Gap systems (which generated wide-band hash).

Or even simpler, use a Neon bulb. or even a Fluro light.

The alternative is to do the standard sitting exercises intended to avoid DVT.

eg wiggle your toes, flex your leg muscles, rock your feet, etc.

All you need do is avoid pinch points which block blood flow.

These are routinely taught to solders on point duty, pilots on long flights, patients confined to bed,etc.

There are simple exercises that you can do while seated to avoid DVT. Just wriggling your toes help a lot, or flexing the muscles in your legs.

I fly a lot on routes over the tropics and have experienced serious turbulence multiple times. There's no way I will be wandering around the cabin unnecessarily.

Likewise "Pavane", an alternative history science fiction novel by British writer Keith Roberts.

Any Antenna designer wants to see the antenna being an elevated ground-plane or dipole mounted clear of obstructions well above the phone.

However he is stuck with a compromise design and knows that there are various effects that a nearby conductive body can have on the antenna's performance.

- Anything nearby will effect the tuning of the antenna. And if the antenna is no longer at resonance, then it's efficiency is greatly reduced.

- Anything nearby will disturb the antenna due to its missing ground plane, which will change both the tuning and the loading (eg impedance).

- And anything nearby will act as Directive or Reflective elements thus greatly effecting the radiation pattern (eg directivity).

In the early days, it was common for phones to have an external whip antenna, and also a socket so an outdoor antenna could be plugged in if required.

But forcing the designed to include the antenna within the body of the phone, (and without an effective ground plane) results in a mess of compromises.

Unfortunately the general public thinks that phone works by "magic", and is somehow exempt from the fundamental need for a radio to have an efficient external antenna.

> antenna is tuned to the maximum allowed emission power per local regulations

Actually it's not. The antenna is tuned to give a peak in output. It's either correctly tuned, or it's off tune.

It's the design of the whole transmitter/battery/antenna which chosen to give a compromise between battery life and max allowed output.

Few transmitters will come close to the max legal power, and if they did, de-tuning the antenna would result in a very inefficient compromise.

If you include a (dummy) human in the test environment you will (with luck) be close to optimum. By not including a human, you can be sure that the results will be worse in actual use.

Different body positions are going to affect the antenna tuning differently.

And of course different surroundings will also effect the directivity (eg the radiaton pattern).

So some will give better results than others. Why is hard to understand?

A more likely theory is that the fob transmitter (and antenna) is tuned to put out max signal when near the body. This is it's normal use.

If however you tested it with the fob somewhat isolated it would then be out of tune.

eg in the factory it would be tuned at a set distance from a "dummy body".

It's the same with a walkie-talkie radio. The antenna must be tuned when held in the hand, as your body provides the missing earth or ground-plane.

You can easily demonstrate this. Mount an antenna on a ground-plane with a length of coax, a SWR meter and a transmitter. Tune the antenna so the SWR is 1:1 and then move you hand close to the antenna. Once your hand gets withing a wavelength or so, the effect of the "detuning" can be readily seen on the SWR meter.

DC Currents also create magnetic fields.

And neither type are a health hazard.

You would need to forget about any Radio Communications, eg Medium Wave Broadcast.

Most grid-tie systems use multiple solar panels wired in series to give the high voltage DC needed to simplify the conversion to Mains AC.

> Solar cells' output varies greatly, hence it needs to be DC/DC converted to a fix voltage to be of any use.

This is simply wrong. It is true that modern MPPT solar regulators use PWM to extract the maximum power, but for years, a simple on/off regulator was used to prevent overcharging.

The reality is that a solar panel is essentially a "Constant Current" supply, so the panel puts out the same current over a wide range of battery voltages. It is the battery which puts out a Constant Voltage at whatever current the load requires.

I bought my first set of Solar Panels 33 years ago. Those panels are still on the roof, have had zero maintenance, and are still happily running my small fridge.

The Battery story is somewhat different. My first set of batteries finally died a few years ago. Likewise I've probably replaced three or four inverters in that time.

Whatever, my off-grid Solar power system has repayed itself many times over.

> Some places have interference but in situations where they work, they seem to be fairly well liked.

But that is the problem....

Power-line networking both suffers FROM interference, and causes interference TO licensed services. When it works, it works well, until randomly it stops working.

You can't expect to reuse allocated spectrum without encountering serious problems.