John Curl's Blowtorch preamplifier part II

[tomtt]

Originally Posted by john curl

We wanted the case to be relatively RF and air tight, not perfectly,

necessarily, but to keep the dust out, at least.

perhaps the next, no compromise step would be,

a "pressurized electrical system" ...



"pressurized electrical system" - Google Search



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John Curl's Blowtorch preamplifier part II

Replies: 2,200

Views: 1,247,432

[syn08]

Originally Posted by john curl

Syn08, are you line of sight of an RF transmitter antenna array? I have lived in that particuliar situation, in the past. Even tubes picked up RFI demodulation. Not everyone needs the 'best of the best' just some people.

I think I already asked: out of the total sales, how many BT preamps were sold to people living on a transmitter pole?

The balance was ripped off $3,000. They were not told they are paying for such an expensive (and useless for them) feature (which, BTW, has a questionable efficiency, this was already discussed long time ago).

But otherwise I agree people love heavy equipment. It makes them feel secure and confident A simple and well known marketing fact.

[john curl]

Too noisy, Tomtt.
However, a completely independent research effort by the National Institute of Standards and Technology has published a paper:
'SUPERIMPOSING LOW PHASE NOISE, LOW-DRIFT INSTRUMENTATION TECHNIQUES ON RF DESIGN' by C.M. FELTON
Please everyone, you will see that it closely parallels the CTC Blowtorch and Vendetta Research approach to power supply regulation. Someone here posted a link, so it should be available.

[anatech]

Hi simon7000,
Interesting, and all true.

I once knew another fellow who worked at a couple AM transmitting sites, and another who surveyed transmitting sites. He also certified the ground resistance of the installations. We had some interesting conversations.

Hi John,
I was referring to RFI when I commented about AL foil. It was effective in those cases. Understand that this was a method used to prove to customers that the problem was environmental and not with the equipment. Doing warranty service can lead a person down some funny paths.

As for the weight of the chassis, it is both a selling feature and suggests value in the mind of a consumer. Like seat belts, how many people will actually need the preemptive measures of a heavy chassis? I'll guess that seat belts are used by a higher percentage these days, but the heavy construction of the case is sure nice to have - even when not required.

-Chris

[Juergen Knoop]

personally, I prefer the Blowtorch case over those of the 'chrome brigade'.
Regards

[PMA]

Chris,

as already explained many times, the thick Al case shields by eddy currents effect and is pretty effective even for low frequencies, not only RF. Al skin depth is about 11mm at 50Hz.

[kannan_s]

Originally Posted by PMA

Chris,

as already explained many times, the thick Al case shields by eddy currents effect and is pretty effective even for low frequencies, not only RF. Al skin depth is about 11mm at 50Hz.

Does it mean - kind of mangetic shielding also?
kannan

[PMA]

You may have 'static' magnetic shielding by ferromagnetic material, or shielding by non-magnetic, conductive material, that shields by eddy currents (skin effect)

Skin effect - Wikipedia, the free encyclopedia

Skin effect does not shield against DC magnetic field.

[john curl]

Thanks PMA. Everyone should learn this.

[Andre Visser]

Originally Posted by syn08

Perhaps because I (and others) listen to what I do?

Wouldn't help, you can't even hear cable differences.