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I do not have a strong foundation in RF. I have been doing some research but I still do not properly grasp what it means if a receiver/antenna can do DC to X Hz. For example this Funcube Upconverter, http://www.ct1ffu.com/site/hf-converter.pdf, can do from DC to 1700 MHz.

When they say DC do they really mean 0.0 Hz? Or would it be more precise to say 1 MHz for example?

I ask because I am interested in purchasing or assembling an SDR that can do LF (~100kHz) as well as higher frequencies. Obviously there is a big difference between 100kHz and 1MHz and I am wondering what exactly it means when the range goes from DC up to some value.

Is it a hard-value or a vague/fuzzy value/term?

Out of further curiosity, if it's synonymous with 0.0 Hz by don't list a raw number like "0.0" instead of "DC" - is there some other significancy? Is it because it doesn't radiate (i.e. technically it's not RF) - it requires a conductor like a wire?

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    \$\begingroup\$ It's a corruption of "DC to Daylight", which informally describes a receiver that can handle any frequency. When used that way it's okay; as @user27637 points out, its use in the more formal context here is not correct. \$\endgroup\$ – Pete Becker Aug 18 '13 at 15:03
  • \$\begingroup\$ In RF class I was taught that everything below 1GHz was DC ;o) \$\endgroup\$ – jippie Aug 18 '13 at 15:13
  • \$\begingroup\$ Hah, @Pete. Love that phrase, DC to Daylight. I'll have to remember that one. +1 \$\endgroup\$ – SDsolar May 12 '17 at 17:45
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The term DC is not being used correctly. The frequency converter shown in that link has an RF path that is AC coupled, so it will NOT pass DC. It will most likely cover from the below the AM broadcast band, which is typically the lowest RF frequency that most people would care about tuning.

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  • \$\begingroup\$ It is used correctly in the sense of common use of such term. :) \$\endgroup\$ – oakad Dec 17 '13 at 3:03
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"DC" in the context means that circuit in question has no internal limits on operational frequency (apart from the gain-bandwidth product of the active components, of course). In simple term it means that all couplings internal to the component are DC couplings. In more complicated circuits it may also have implications on clocking and synchronization (some components can operate with arbitrarily slow clocks, while other have certain internal limits imposed by tuning ranges of PLLs, to name one example).

Btw, the above does not mean that the component in question can be successfully used to process signals of very low frequency - normally, RF components require a sufficiently stable DC operating points to be set, and low frequency signals will require some pretty big coupling/decoupling capacitors to maintain it (which, in turn, may lead to charge/discharge currents damaging to the sensitive RF device).

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A DC capable RF equipment usually means AC coupled, and that the equipment will not be damaged by DC voltage. An example for non DC capable equipment are most spectrum analyzers, which cannot tolerate any DC input.

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