开云体育

The noise figure of a transistor from the data sheet refers to a specific test circuit under well defined test conditions. The noise figure of a transistor in a particular amplifier circuit depends on

I was looking for something else and stumbled across an article on designing with new FETS. https://www.interfet.com/jfet-datasheets/audio-electronics-jfet-new-frontier1-2.pdf I know from

Hi Dan, I downloaded your simulation of a one meter diameter loop and was able to run it without problems.? Nicely done!? Your 36 segment structure much more closely models a circular loop than my

I would expect that the noise figure of a transistor would be the same no matter what amplifier you plop it into - but with the provision that it depends on its biasing conditions (e.g., current).?

Discrete RF-Transistors ar becoming more and more extinct. For example BFQ590 BFP196 NTE278 (2N5109 replacement) PZT2222A PXT2222A are currently actively produced and widely available.. The

Thanks Everett and Simon, and to Steve I have found his comprehensive list, I should have searched better. However, are these low measured NFs just for the very low input Z loop preamps like the LZ1AQ

Yes, I swept each of the seven transistors I tried. This is typical, and the gain for the last one, 2N4401, unmarked brand: 0.2 MHz +16.1 dB gain 0.5 MHz +16.3 dB gain 1 MHz +16.3 dB gain 5 MHz

Steve, did you measure the frequency response? The properties of the output transformer and the RFC in the base biasing circuit will of course have influence on the frequency response but I am just

This circuit does not make a good preamp--it overloads too easily. As the info in the Files states, it's for making a test IMD preamp that can be duplicated with a characterized OIP3. Recent posts

Hi John Do a search on here..been covered..alot. I think it was Steve, whom did a very excellent and comprehensive list of suitable transistors exactly as you are asking. The 5551 is very good

Steve, I've built a number of preamps similar to this. I use them for low VHF to ELF and lower HF frequencies. I've measured it to be relatively flat through 30 MHz. I've typically used the 2N5109.

Raphael Wasserman <wassermanr46@...> added the photo album Short Current Mode of SMA ( /g/loopantennas/album?id=298213 ) : Equivalent Circuit of Small Closed Loop

I've uploaded to the Files a relatively simple one transistor 50 ohm preamp with +30 dBm OIP3 that can be built using common transistors and used to check your own IMD test set. I tried seven

John, The NF for the 2SC5551 transistor is 1dB. Everett N4CY

My knowledge of semiconductor theory is rather basic and I was wondering whether amplifiers like the LZ1AQ could be improved by using low noise transistors like the 2N5109, rather than 2N2222 or

Agreed.? In the context of a resistance calculation at frequency, skin effect cannot be ignored.? But, as you say, the inductive reactance still defines the overall loop impedance....at least for

Hi Mark, Yes I have similar but limited results with my MMANA models , creating a field with a dipole source, but? with this setup I cannot compare currents at different frequencies.?? I installed

Mark and All, I tried to use Mark's data of 10/4/24 where he ran a single loop model in EZNEC to ascertain whether Chavdar's test simulator is designed correctly: f = 15 MHz , Isc = 0.707 mA ( short

The induced voltage in the loop rises proportional with the frequency. The inductive reactance rises also proportional with the frequency. Both compensate each other what, in shortcut mode, results in

I reran the simulation with the load point located at three different positions: bottom side, front side, and back side.? I obtained the following results: At resonance (around 49MHz), the current