Questions tagged [measurement]
The measurement tag has no usage guidance.
61
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Measuring Power - Attenuators and 50 Ohm Termination
I'm attempting to measure the output power of my transceiver + linear amp combination and I would like to confirm that my measurement approach is correct. I need to get the output power down to a ...
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1
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139
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Why is my homebrew copper sulphate resistor behaving like a capacitor? [closed]
I brewed a CuSO4 resistor in a glass jar. I got the idea from here. This was done by creating a solution of Copper Sulphate in distilled water. The lid on the jar was provided with a BNC socket into ...
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2
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173
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Why measuring Voltage and Current becomes difficult at Microwave frequencies? Why measure Power?
I have been reading some Classic books viz. Techniques of Microwave Measurements - Carol Montgomery, Foundations of Microwave Engineering - Collins, and some other google searches and they all claim ...
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759
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Calculating a real antenna gain from electric field strength?
Could someone please tell me if it is possible to measure the antenna gain simply by placing a field strength meter at a selected distance to my antenna, knowing the power applied to the antenna. ...
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3
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198
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Do I need a precision wattmeter or will a $50 one suffice?
My transceiver has a built-in wattmeter but I've decided to buy an outboard one to monitor the antenna system before it reaches the ATU. I'm capable of putting out 100 Watts and I see that several ...
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Measuring effectiveness of vehicle bonding
Is there any objective way to measure the effectiveness of your bonding in a mobile HF setup? Or determining when you have "adequate" bonding? I have a hard time with just throwing straps on ...
- 411
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764
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Using a Return Loss Bridge and Nano VNA to measure amplifier characteristics
One of the difficulties of measuring active devices like LNA and IF amplifiers with the Nano VNA is the care needed to avoid over-driving the amplifier input and, more importantly perhaps, to avoid ...
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1k
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Can an oscilloscope be used as an RF voltmeter?
I just recently acquired a slightly functional Icom IC-735 HF radio, and am trying to resurrect it.
The service manual outlines procedures that specify the use of an RF Voltmeter, which I do not own. ...
user14945
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861
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Sweep times for Spectrum Analyzer
I have a basic question about sweep times and number of points.
My frequency span of interest is: $f_{span} = 30\ \rm MHz$
My resolution bandwidth is: $RBW = 10\ \rm kHz$
The minimum number of points ...
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1
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242
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Obtaining S parameters using S11 measurements?
Is it possible to obtain the S-parameters of a circuit with only S11 measurements (S11 measurement with a VNA)?
My gut tells me that it should be possible by connecting open, short and characteristic ...
- 163
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1k
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Questions about effective isotropic sensitivity(EIS)
Recently, I read something about EIS (effective isotropic sensitivity) and TIS (total isotropic sensitivity). I'm trying to understand the concept, but I find it's quite hard for me.
In the book ...
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303
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Can the parallel capacitance of a quartz crystal be directly measured?
A quartz crystal is often represented by this equivalent schematic:
simulate this circuit – Schematic created using CircuitLab
How to measure quartz crystal motional parameters using a VNA? ...
- 51.7k
7
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2
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957
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What does an antenna analyzer tell me about these coaxial cables?
Note: more measurements added after graphs below
I recently acquired a RigExpert antenna analyzer and I am trying to learn how to use it to test cables. I took two cables to start with to try and ...
- 342
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0
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181
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Problem with theory of HF detector
I'm currently trying to build my own SWR power Meter. This design is based on the so known HT detector with schottky diode BAS70. For my understanding, and for easy purpose, I'm currently focusing on ...
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6
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How to make an RF probe for accurate power measurement at QRP power levels?
Typical SWR meters don't measure forward power very accurately at the lower end of the scale, which can be a real problem at QRP power levels. Better power meters like the Bird model 43 are expensive,...
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232
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Signal power measurement
I have a radio with a nominal output of 1-30mW (frequency dependent) and amplify this with a 21.8dB capable amplifier (frequency dependent, but should be ~150mW). The signal output then passes through ...
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Do External Signals Affect Antenna S11/SWR Measurement?
Do external signals affect the S11/SWR measurement of an antenna?
For example, if I try measuring the S11/SWR of an HF antenna with a SWR meter or a Vector Network Analyzer in the middle of a field ...
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389
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How to properly measure sensitivity of the receiver?
I have Kenwood TH-D72 2m/70cm HT. According to the manufacturer the sensitivity is "Less than 0.18 uV". I would like to check this, since the radio is not new and I'm not it's first owner.
To do this ...
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What exactly was a decremeter and how did they work?
In A Century of WWV, I found this mention of an unusual sounding instrument that may have once been commonplace:
Calibration work was mainly focused on decremeters, instruments designed for ...
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298
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Most accurate way to measure signal power with (cheap) Spectrum Analyzer
I am using an USRP X310 which is unfortunately not calibrated and the specs given are only very vague.
Hence I would want characterize the device with first-order measurements. Unfortunately I only ...
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RF Bridge Problem - K6BEZ Antenna Analyzer
This question regards erroneous SWR measurements of K6BEZ antenna analyzer (links gone from Internet now) design from 2013 using Arduino and AD9850 DDS modules. There have been many variations of it ...
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1
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364
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UHF cubical quad VNA analysis interpretation
I've designed a two element UHF cubical quad. It was designed to resonate at 385 Mhz. I used 0.1mm thick and 1cm wide copper tape instead of wire to lower the antenna Q. I used PVC electrical conduit ...
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How to measuring ferrite core efficiency vs frequency
There is an unknown ferrite toroid. I would like to figure out whether it can be used in an audio transformer, or maybe in a 1:4 transformer on given HF frequency.
The experiment I came up with is ...
2
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1
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Measurements in far field for radar cross section
I have to measure the S parameter for a rectangular sample with an antenna that works from 2 to 18 GHz. I need to measure a large band from 5 to 15 GHz and I have a problem with the known F.F. (Far ...
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159
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Parasitic inductance of relay contacts
I need to switch a bank of filters operating on bands from about 2MHz to 30MHz. The parasitic series inductance of the relay contact system will have an effect on the performance of my system. ...
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Determining Impedance With An Antenna Analyzer
I need some help interpreting some information from my antenna analyzer (RigExpert AA-35). I want to use the information to impedance match my AM receiving antenna system to AM radios. No ...
- 149
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110
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Cabling question between two devices
Here is my schema. I would like to connect a device using SMA connector with RG 174 to an attenuator of 30 dB with SMA connector. On the other side the attenuator is connected to a SMA-UHF converter ...
- 23
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326
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Measuring S21 against TX-RX distance (a.k.a path loss modelling) with a network analyzer didn't give expected results
Task: Path loss modelling
Target frequency: 433 MHz;
Laboratory environment: in a basement where there were other equipment and metal shelves. A few acoustic absorbers were placed around the setup.
...
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2
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2k
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dBm signal minus dB
I've got a 27dBm signal that I'm going to put through a 6dB attenuator. How do I work out the resultant signal in dBm?
I've tried Googling that without any luck.
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199
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How to measure the power emitted from an HF antenna in near-field WPT?
I'd like to estimate the power density from a 13.56 MHz power source in a near-field WPT (wireless power transfer) scenario. Using a spectrum analyzer with a receiving antenna will give the E-field ...
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1
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78
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What is the best approach for measuring return loss of a home-made 3cm horn?
Let's assume I have built a SMA-to-waveguide transition that flares out into a horn antenna. There's no flange between transition and horn, it's made of a single metal sheet. The antenna has tuning ...
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1
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Wire dipole antenna proving ground / test bench
i am considering building two movable (concrete base with wheels) non metallic poles with hooks every ten centimeters or so, in order to test wire dipoles of various sizes at various heights with an ...
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500
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Peak envelope power should be 2:1 or 4:1 on meter?
I've always been reading my AM modulated signal on a Bird wattmeter and trying to set the carrier to 1/4 of the peak envelope power (PEP).
Recently, I was told by a CBer that you only can see it that ...
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2
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506
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Antenna design - Ground plane in simulation and in practice
For monopole antennas, the ground plane acts as another arm of an equivalent dipole antenna. I'm wondering how we can expect the behavior of that antenna in practice, because the ground plane is ...
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272
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Why is the insertion loss of my coax cable higher than expected?
I am testing a long cable run (about 90m). This cable has been used outside and inside, for temporary setups.
I've set up my VNA with the correct values (velocity factor,...) and the distance to ...
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2
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485
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How were 1920s hams able to measure megahertz frequency?
I was reading 200 Meters and Down but one thing that was unclear to me was that hams in the 1920s were operating on the 200 meter frequency, which is around 1.5 Mhz .... or 1500 kilocycles to use the ...
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3k
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Input and output impedance of antenna/circuit: theory and measurement methods?
As illustrated in my previous post, I got stuck with the matching circuit between an receiving antenna and my circuit, including a rectifier and sensory circuits. I got confused with input and output ...
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1
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103
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How should I measure RFI on the headset cable from a hand-talkie?
I'd like to build an audio interface cable from my smartphone to my Yaesu FT-60 which incorporates VOX (since the Yaesu doesn't have VOX functionality) for APRS apps on the phone.
I'm having problems ...
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2
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356
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Measuring dBs with software defined radio
If the "floor" of the graph in my SDR is at -110dB, and when I key up, it goes to -70dB, and the wattage is 5W....is there a direct correlation between dBs and wattage?
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336
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Seeming conflict in the definitions of dynamic range
As I understand it, dynamic range is the difference in dB between the strongest and weakest signal discernible by your receiver. So, the larger the dynamic range, the better, which seems intuitive.
...
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3
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1k
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Ferrite rod or core permeability determination
Is there a simple empiric way of determining the permeability (mhu) of a ferrite object (be it a ring, rod or any form)?
I've been thinking this for a rod: if I wind coils with different number of ...
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votes
1
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867
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How to probe a dipole antenna?
I want to start experimenting and tinkering with antennas, starting with ½ wave dipoles. I will be measuring the AC voltages on both the transmitter and the reciever antennas simultaneously. And by ...
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Is it possible to measure antenna trap with MFJ225 without help of PC?
I have MFJ225 antenna analyzer. I measure coax trap filters by connecting this analyzer to PC and using IG_miniVNA application. That works fine.
But, sometimes I need to make such measurements in ...
- 870
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Why Coaxial Collinear Antenna Gives Strange Graph of Frequency Sweep vs SWR?
Antenna Analyzer gives a understandable results for a Quad Antenna (photos 1, 2 & 3), but gives strange results for Coaxial Collinear Antenna (photo 4)
Photo 1 of 4: Test setup for Quad Antenna
...
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crt TV emissions
I have my Hack RF plugged in my TV antenna to have a cheap setup and I have observed on the spectrum analyser a signal (Bandwidth: ~400Khz) that is emitted by my old analog TV from 80ies. These are my ...
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158
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Measurement/calibration error after OSL calibration on VNA
Purchased a HP 8711A some time ago to learn how to make better measurements.
I've tried doing an OSL calibration with a 75ohms Agilent cal kit.
When reconnecting the short after succesful ...
3
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1
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203
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Portable radio antenna measurement
Just purchased a HP 8711A and have "upgraded" the bootrom to enable vector measurements. I am now trying to learn more about how to make better measurements and understand what's going on.
One of the ...
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1
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952
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Measuring energy density of 2.4 GHz and 5.0 GHz signals
I'm a math and computer science student, starting to mess around with using amplifiers and antennas to build long-range wifi hardware in my spare time.
Calculating the expected power density of a ...
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8k
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How should this SWR meter's directional coupler work?
I'm wrapping up a "home build" of the MFJ-941EK antenna tuner kit and having trouble getting the wattmeter calibrated. I can't use C4 to get the reflected power reading calibrated down to 0 as is ...
- 7,411
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4
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880
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Recommended way to analyze spectrum output of a high-power amplifier?
I have a small collection of "software defined RF lab" equipment, notably a HackRF and a VNWA3. I am almost done building a 35W HF amplifier and once I've done some other testing, would like to look ...
- 7,411