On Wed, 17 Oct 2018 14:32:20 +0000, Spike
wrote:
The clash of cultures between the open-minded out-of-the-box thinker,
and a rules-and-regulations-trump-everything engineer. We have the
latter type on UKRA too, more's the pity. Then there's those that don't
know a sideband from a sideburn, waving their 'Vouvray for our side'
banners. In all senses of the word.

I guess it's too late to put you back into your box. Yes, I'm one of
those rules-n-regs types. I've even been involved in manufacturing a
few standards. Since you have an open mind, I hope you don't mind if
I pour some reasons why we have rules-n-regs into your wide open mind.

In order to talk with someone via radio, you don't really need rules.
You could simply build or buy something that generates and detects RF,
attach a modulator, and now you're talking. The necessary ingredients
are commonly available and fairly inexpensive. Not much more than a
frequency counter or frequency standard are required so that you and
your accomplice are both on the same frequency. Tuning with a light
bulb is perfectly functional and will probably help with the tuning.

However, there's a problem. You and your accomplice are not the only
people on the air. There are others that also want to communicate
with their friends and find that spurious crap belched by badly
designed, badly constructed, or mis-adjusted transmitters are making
their communications rather difficult. Similarly, your ability to
receive transmissions from your accomplice might be limited by the
spurious junk produced by the other users of the spectrum. Therefore,
it would helpful if your receiver was somewhat tolerant to intermod,
overload, blocking, adjacent channel, spurious responses, and other
anomalies.

In order to insure a minimum level of quality, the various regulatory
agencies produce specifications and testing procedures. In other
words, they produce numbers. Manufacturers and builders of radios are
expected to test their products to those standards and fix anything
that fails to comply. If everyone complies, then there's a good
chance that you and your accomplice will be able to communicate
without either transmitting or receiving any interference.

Like you, I once had an open mind when it came to radio regulations.
At the time, I was designing marine VHF FM radios. I was faced with a
blocking (receiver overload) specification that was almost impossible.
The interfering signal was so high that my test equipment could not
produce the level required. I calculated that the interfering station
antenna would need to be about 2 ft (60 cm) from my radio antenna to
produce the required interference level. My open mind declared that
to be ridiculous. I protested the specification and waited. In the
return mail (this was before email), I received several photos of
typical marine masts, yardarms, and towers, showing dual watch VHF
antennas about 2ft away from each other. Oops. It was a real problem
that required the radio to meet the specification.

Obviously, all these specifications ultimately manifest themselves in
the form or numbers. You'll find them all over the various FCC and
Ofcom rules-n-regs. They're there to insure that you, your
accomplice, and other users can communicate without mutual
interference. There is no other way to insure reliable communications
without measurements and test equipment.

So, how do you make an RF tuning light bulb produce numbers? A light
meter?


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558