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Author Topic: Transceiver Design Priorities  (Read 12421 times)

Posts: 1604

« Reply #15 on: June 11, 2016, 04:45:20 PM »

Theres also a misreading of the EMC laws. Many manufacturers think that its only internal LED lights that have to  meet EMC standards.

The other issue is that the standards do not take into account  the radiated emissions from the house wiring especially when you have multiple LED lights on the circuit.
Theres no doubt that both radiated and conducted emissions for LED light standards have to be improved. This is before we start talking about the Chinese manufactures who ignore the standards all together.

It does not where you are, all that it takes is 1 LED floodlight even in a country area and your ham radio enjoyment is over they are powerful jammers. S9+40db on the whole HF spectrum how can such crap be even be sold?

AC powered LED lamps have switching power supplies and produce conducted RF. The amount of conducted RF allowed in the U.S. by the U.S., and other agencies in other countries, is enough to cause interference in the HF bands.

Posts: 215

« Reply #16 on: June 14, 2016, 04:06:31 AM »

A realistic and valid systems test and evaluation would be to create an artificial RF environment consisting of real-world interfering transmitters using various modulation formats summed together with a weak wanted signal at suitable frequency separations.

I cannot see any case against such an Modus Operandi, as transmitters/transceivers are a "dime a dozen" compared to high-performance RF signal generators.

A suitable way could be to establish a wanted signal reference level, for example 12 dB SINAD in an SSB bandwidth, and after this turn on one interferer after another and notice how much the levels of the interferers need to be increased until
degradation of the SINAD commences as a function of the number of interferers, their power levels and frequency separations.

This would mimic "real-world" conditions very closely, and if the number of interferers is large enough (say 10), even contest or pile-up conditions could be emulated.
When transmitters of varying quality are used as sources, there is a definite possibility to evaluate the system impact from the spectral properties (wideband noise, phase noise, "splatter" and keying artefacts) from "low-end" as well as "high-end" transmitters.

And if you used the average ham transmitter as the signal generator you will soon realize  the realities  of air receiver and transmitter performance.

 Use a clean signal generator and measure the receiver detecting the IMD product  at level X. Now use a typical ham transceiver as the signal generator and watch the IMD product disappear because the transmitter is so filthy. That is the real world ham radio on air test lab. Ignoring transmitter  performance is technical stupidity at its best.

We dont transmit with perfectly clean signal generators we transmitter with crud generators.  Since there is no splatter blanker, why worry about  receiver performance when the receiver has probably 50db or more headroom before its even stressed. Receivers in the real world get stressed by splattering hams, not ultimate IMD dynamic range problems.

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