Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [hf]

HF stands for High Frequency and it is normally used to denote the range of radio frequency electromagnetic waves between 3 to 30 MHz.

24 questions
16
votes
1 answer

Analyze My Homebrew Diplexer

I'm in need of a diplexer that'll separate RF signals from a single feedline to two antennas. What I designed and built was a diplexer that would allow ~38 Mhz and below out port 1, with ~38 MHz and above out port 2. This is primarily to use a…
MarkSchoonover
  • 1,113
  • 10
  • 17
11
votes
2 answers

Purpose of bare copper perimiters on HF PCBs

I have seen many RF PCBs with a thick, rounded area of exposed copper going all around the PCB, like in this example: My intuitive thought is that this is for some kind of grounding or shielding can, however I have seen this on PCBs that had none…
Azsgy
  • 336
  • 2
  • 10
6
votes
3 answers

How does this Miniature Solid State Tesla Coil work?

Here are the schematics What is the use of> -Transformer (I assume it is providing higher voltage? and what does it do) -Transistor (Is it common emitter? and what does it do) -LED (What does it do?) I do not need this for homework, I was just…
Triak
  • 916
  • 8
  • 14
4
votes
1 answer

SMPS output noise: Why is it amplified further away from the output capacitor?

Well this is just a general question about switch mode power supplies, but i have recently built a buck converter, and read that it is very important where in the circuit you place your probes, to measure output ripple and noise. As output…
Linkyyy
  • 1,153
  • 8
  • 19
4
votes
1 answer

Arduino+2X12 LCD to emulate a defective Kenwood HF rig display unit

I have an HF rig with a bad display init (LC7582A driver and custom LCD with 9 seven-segment numeric indicators and some icons making for a total of a 100 or so segments). The input pins of the LCD driver are CE CLK and DATA. I gather from the…
Mon DU1FV
  • 41
  • 3
4
votes
1 answer

Metcal: why do they heat with HF?

I got a used Metcal station from ebay for my home-lab and everything I read about soldering with it is right, it is a completely different feeling. I understood that stuff about controling the temperature using the Curie-effect in the soldering tip.…
wollud1969
  • 494
  • 1
  • 5
  • 12
3
votes
1 answer

Why is drain-source parasitic capacitance(Cds) omitted in JFET datasheets?

I've checked several datasheets on JFETs and I cannot find drain-source parasitic capacitance. They either include only Cgs and Cdg or they only include Ciss or Crss. Here are a few high frequency JFET datasheets for an example: MMBFJ309 /…
Phill Donn
  • 367
  • 1
  • 12
2
votes
1 answer

Special considerations when designing a PCB with signals in HF band (3 -30 MHz)

I want to design a PCB which will handle RF signals in the HF band (3 -30 MHz). Are there any special considerations when designing a PCB at these frequencies? I know higher frequency PCBs require special design considerations due to transmission…
J Physics FM
  • 159
  • 8
1
vote
2 answers

HF Peak detector

This is a peak detector taken from page 21 of the opamp ADA4610: I need it to capture peaks from 500KHz sine wave. I can't understand why when the sine starts it goes above the peak and then discharge with a costant (I think determined by…
kristian_
  • 31
  • 5
1
vote
3 answers

What's the signal seeing on the output - 50 ohm?

Hi, I'm designing an OP amp circuit. I would like to terminate the output with 50 ohm because the device will be a measurement device with an oscilloscope or DUT on the iutput. Left side is basically my PCB right side is outside of it to the…
R098
  • 47
  • 5
1
vote
2 answers

How to understand EIRP, PSD for a given bandwidth?

I have troubles to understanding what is the meaning of parameters for transmitting power of RF-signal. So for RF signal in the same frequency band and same application, on one hand I see the max. allowed mean power is e.g 50dBm. On the other hand I…
BL_
  • 215
  • 2
  • 9
1
vote
2 answers

How to drive an AD9850 at 100 kHz/s sweep using arduino or rasberry pi?

The basic problem I am interested in doing is using an ADXXX chip to make a linear frequency sweep through the HF bands, from 1-20 MHz. The sweep rate I would like to achieve is 100 kHz/s, which granted is an upper end requirement. The chips I…
AD0AE
  • 11
  • 1
1
vote
1 answer

PIN-diode lowest operation frequency limitations

I have a need to implement RF switch for HF circuit (~10 - 30 MHz) and I've been browsing options for that. Electromechanical switch would of course work, but I want to consider other possibilities too. Researching the options I have determined that…
RautSa
  • 51
  • 6
1
vote
1 answer

Difficulty getting HF filter to work: maybe PCB layout?

I am trying to build a set of HF filters using the values from the Alex filters from HPSDR. I'm having difficulty getting the input impedance to be 50Ω as it should. Based on wide variations in measuring capacitance before and after installation,…
Phil Frost
  • 56,804
  • 17
  • 141
  • 262
1
vote
4 answers

Transmission Line Question

I have a question concerning reflections due to impedance mismatching. Now, assuming a lossless TL, the latter is modelled by sections of lumped L-C segments where L in a series (sub)element of the transmission line and the capacitors connect to…
Junius
  • 979
  • 11
  • 23
1
2