Questions tagged [rf-power]

Questions about power ratings and restrictions, including maximum power by law or for certain components, or about calculating power in certain situations.

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RF Coax Termination Question

I am looking to terminate a line with the below characteristics and having a hard time locating an RF coax terminator. Can anyone help? I have an FPGA HW that is feeding multiple receivers. The input ...
Newb's user avatar
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348 views

What is the antenna design and gain for the WA1 U/V band antenna on the ISS?

My son KJ7NLL is working to contact the ISS using an antenna we built together, and we were wondering the approximate minimum transmission power to reach the ISS. If I understand correctly (and ...
KJ7LNW's user avatar
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Low power indicated on tuner

Please forgive my extremely basic question, I am brand new on HF and have issues with my setup. I have a Chameleon MPAS antenna in vertical configuration connected to an AT-100 ProII tuner with a 50 ...
kataik's user avatar
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2 answers
298 views

Waveguide size for 2.4 GHz

I'm thinking to make a wave guide that has diameter 1/8 of the wave length. At 2400mhz the full wave length is about 125mm. I have aluminum pipe that is 16mm. So 8*16 = 128mm (very close to 125mm). If ...
Svetoslav's user avatar
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1 answer
142 views

What happens with LNA in bidirectional communication? [closed]

I want to ask that if you have a cable that has started with 40dbm source signal and has reached -10dbm then you put LNA (the end of the cable will be plugged to RFIN), then attach the RFOUT to ...
Svetoslav's user avatar
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193 views

Coaxial cable loss, dbm, db correlations

I am very confused how ham operators deal with all this, because most of the information in internet is controversial. I have coaxial cable with loss of 34dB at 100 meters at 2400mhz. People say that ...
Svetoslav's user avatar
2 votes
1 answer
94 views

What this E(EL) symbol does mean?

I can't understand what this E(or EL) symbol does mean. I know that Zo means impedance and I can calculate trace width according it, but what E symbol does mean?
Alatriste's user avatar
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Extracting radio signal strength from multiband TIFF file

I have N number of TIFF files corresponding to each radio stations in my data, and I am trying to measure the approximate signal strengths from each of these stations at K geographic locations(say for ...
Parijat Maitra's user avatar
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How do you protect your radio when testing custom RF circuits at ~100W?

We are designing a UHF/VHF diplexer for a satcom project and targeting support for 100W. Our radio can transmit near 100W but of course we want to protect it in case there is a failure of some kind. ...
KJ7LNW's user avatar
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9 votes
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436 views

How do you choose an inductor wire gauge for high-power RF?

At 100 watts in a 50-ohm system, the current flowing through an inductor would be about 1.41 A, thus a 26-AWG wire should be plenty since they are chassis-rated for 2A and for just a few windings that ...
KJ7LNW's user avatar
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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 ...
eecs's user avatar
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Does ERP power depend on transmitter duty cycle?

I’m building a transmitter and I’m trying to stay under the ERP power limit of my country , which is 0.5 Watt at the frequency I’m working on . I was thinking about increasing the transmission range . ...
Alessandro Mini's user avatar
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Ferrites losses calculation

I am new on RF design. I would like to know more about ferrites. I am looking for information about how to calculate ferrite losses and saturation points for a given application. I also would like to ...
Drod's user avatar
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Design of an LNA housing box for a UHF/VHF satellite ground station

I'm currently designing a waterproof metallic case to house LNAs, power cables, and RF switches for a UHF/VHF satellite ground station. As shown in the diagram below, the antennas are connected to an ...
Moses Browne Mwakyanjala's user avatar
4 votes
3 answers
468 views

What is the difference between antenna input impedance and its radiation resistance?

I got to know that the input impedance of the halfwave dipole antenna is given as: Zin=1/Im* sin(β(H-|Z|)) where Im is the maximum current on the antenna( when excited with a 1 volt supply), H is the ...
Moulee's user avatar
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What power levels do the Baofeng UV-5R/5RA/5RE have? [closed]

What are the power settings of handheld radios of the Baofeng UV-5R series in watts?
manarinian's user avatar
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1 answer
87 views

Does a filter or inductor's power rating matter in its passband, or only in the attenuated frequency range?

I would like to build a high-pass filter that would block reception of signals from the United States' FM broadcast range (88–108 MHz) while still allowing me to transmit VHF ham signals (around 146 ...
natevw - AF7TB's user avatar
1 vote
3 answers
515 views

What can be used to protect an SDR receiver against bursts?

I am using a USRP B205 to detect electromagnetic pulses. Sometimes the signal power bursts to 100 dB, average power is around 10 dB. What can be used to protect the SDR receiver against bursts?
kittygirl's user avatar
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6 votes
2 answers
352 views

Power rating of a selfmade air coil

A colleague was winding an air coil himself. It's a 110µH coil with 200 windings for an 80m antenna, intended to be used on a 600 W transceiver. He used a copper lacquer wire with 0.6mm diameter. ...
Thomas DK3TU's user avatar
3 votes
2 answers
576 views

How do you calculate peak voltage given VSWR caused by impedance mismatch in a 50-ohm system?

I would like to choose a feedline that is safe for the wattage at a given VSWR to avoid coax arcing. How do you calculate peak voltage given a peak power in watts and maximum expected VSWR from ...
KJ7LNW's user avatar
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3 votes
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149 views

What safety procedures should be followed when developing and testing a high power amp?

I'm designing a 300W power amplifier using the MRF300AN from NXP targeting a center frequency of 146 MHz. Obviously I need to keep my fingers out of it and test into a dummy load, but generally ...
KJ7LNW's user avatar
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2 votes
1 answer
385 views

What is a "feed-through load" and how does it work?

While browsing some miscellaneous RF test equipment supplies I stumbled across a two-port component sold as a "feed-thru load". Take for example the Pasternak PE6026 (datasheet), which looks ...
natevw - AF7TB's user avatar
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2 answers
251 views

Why is there so little difference in the gains of Yagi Uda antennas with omnidirectional antennas? Shouldn't the power at the back be at the front?

Consider an omnidirectional antenna with X dBi gain. Intuitively I understand that the power that would have been dispersed in now-dead directions is directed around the antenna. What I don't get is ...
Mister Mystère's user avatar
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How do you take into account the SNR of a transmitter in a fade margin?

I have a fade margin for a RF bridge, but it only compares the sensitivity of the receiver to the received power - or alternatively calculates the Eb/N0 from the net received power divided by the ...
Mister Mystère's user avatar
-1 votes
1 answer
75 views

Acoustic Communication issues [closed]

[![I've attached schematic, I am connecting transducer directly to that header pins on receiver side. On transmitter side I am connecting op-Amp to boost voltage to +10v -10v.][1]][1]I am working on ...
Gaurang Solanki's user avatar
1 vote
2 answers
154 views

Is power output or something else to blame for my duplexer failing?

A Ham buddy of mine and I were trying to setup a UHF repeater in our area due to a lack of them. We had two Motorola CDMs, one a 1250 and one a 1550, and we purchased a $200 or so reject only duplexer ...
Caleb Krajnak's user avatar
5 votes
1 answer
92 views

Acceptable RF radiation exposure to electronic equipment

I'm wondering if there are any general guidelines or rules of thumb about the exposure of electronic equipment to RF transmissions, 150 MHz - 900 MHz. The background is that we are looking to install ...
Frank's user avatar
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3 votes
1 answer
656 views

Troubleshoot ICOM IC-745 intermittently shows no power on transmit

I have an old IC-745 I bought used last year. Recently it seems to be malfunctioning intermittently. It is receiving well on all bands as far as I can tell. Sometimes when transmitting, there is no RF ...
elplatt's user avatar
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6 votes
2 answers
1k views

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. ...
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4 votes
2 answers
328 views

Is the 1.5kW power limit per antenna? What about antenna arrays?

My son KJ7NLL just got his general, and while we don't (yet?) have plans to transmit at 1.5kW, he asks if the 1.5kW limit is per-antenna? If it is per-antenna, and you use an antenna array of 8 ...
KJ7LNW's user avatar
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0 votes
2 answers
164 views

Repeater design using round robin transmitters to increase duty cycle?

I would like to build an FM repeater using a short stack of Kenwood TK-890H rigs adjusted to 70cm USA amateur band, but the model has a 100W rating with a duty cycle of only 20%. 20% isn't nearly ...
Jason W7DM's user avatar
1 vote
2 answers
320 views

Increasing communication range by boosting output and input power

ORIGINAL QUESTION I am trying to increase the range of communication between two SDRs to simulate near space communication. The output power of TX is 10dBm but I would need 37dBm for near space ...
wei's user avatar
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2 votes
2 answers
317 views

Output power from the TX/RX port of the USRP N210 decreases as the frequency increases

I am trying to build an FMCW radar using a USRP N210 with a CBX40 daughterboard. I generate a sweep from 1.5GHz to 5GHz. According to their respective datasheets, the daughterboard and the USRP should ...
Fati's user avatar
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2 votes
5 answers
375 views

Does 3 W vs 5 W TX power make a huge difference in QRP CW operation?

I've bought the QCX+ 40 m band radio. I will be powering this off a 12 V battery. I read on the manual the RF power at 12 V is just 3 W whereas on 15 V it is 5 W. Should I buy a boost converter for ...
rsn's user avatar
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0 votes
2 answers
554 views

Where can I find a table listing the maximum PEP per band?

I'm building myself an Excel Cheat Sheet.
NonYaBidnezz's user avatar
1 vote
1 answer
188 views

What is the maximum antenna cable length allowed in GNSS application?

I am beginner in designing GNSS receiver design and facing concern while testing the high precision GNSS survey.I am using GNSS survey grade antenna for my GNSS receiver application testing, the ...
BalkisMM's user avatar
9 votes
2 answers
3k views

Importance of Ferrite Size in Coax Choke Balun

The question is quite simple: When making a coax choke balun, does the size of the ferrite matter, and if so, why? I have seen design notes that say to use a single FT240-43 toroid for powers up to ...
M1GEO's user avatar
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1 vote
2 answers
1k views

Power vs. Bandwidth

A 10 watt transmitter is transmitting a 700 hz tone in a 3 kHz wide band. If the power is increased to 1000 watts will that not increase the bandwidth if the data (700Hz tone) remains constant? What ...
John Harvey's user avatar
2 votes
6 answers
4k views

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,...
rclocher3's user avatar
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1 vote
1 answer
232 views

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 ...
user2497's user avatar
  • 125
2 votes
2 answers
212 views

Estimating near-field electric field strength at LF (137 kHz)

I'm experimenting with low frequencies, but due to the inherent nature of LF, I strive for more transmit power and bigger antennas. Now of course I want to comply with regulations, which allow (in my ...
kernash's user avatar
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0 votes
1 answer
462 views

Calculating receive wattage given transmit power, antennae dBi and path loss

I would like to understand how to calculate receive wattage given the following (excluding feeder loss and SWR): Transmit 50 dBm (100W) => 24 dBi directional antenna => 30 dB path loss => 24 dBi ...
KJ7LNW's user avatar
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2 votes
3 answers
2k views

How safe is 100 watts on 2-40 meters?

So I have the misfortune of being an apartment dweller. I know that 50 watts is pretty safe as it is what first responders use on 2 meters. Am I really going to have to run around with an analyzer ...
NonYaBidnezz's user avatar
0 votes
2 answers
352 views

measures for quantifying non-linearity of a HF linear power amplifier

I am DIYing a class-AB HF Linear Power amplifier. How to quantify the non-linearity of this amplifier. What are the common measures of non-linearity as applicable to RF power amplifiers? How to ...
SRK's user avatar
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1 vote
2 answers
1k views

What kind of filter should be used at the output of HF linear amplifier?

I am looking for a output filter to use with a HF linear amplifier called miniPA70 which is available through several online auction sites. The circuit is available here : http://iu3idf.blogspot.com/...
SRK's user avatar
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0 votes
3 answers
1k views

Can a carrier operated relay be used for T/R switching in a HF linear amplifier?

I am building the T/R switching circuit for an HF linear amplifier covering 80m band to 20m band. The current circuit takes a potential-free contact from the exciter and use this contact to turn on/...
SRK's user avatar
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1 vote
1 answer
1k views

SO-239 (UHF) vs N connector power handling on 160m

I am curious how much CW power an N connector or SO-239 connector will handle on such a low frequency like 160m band. I know on VHF they will probably handle about 800W before getting too warm. I ...
Synaps3's user avatar
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2 votes
1 answer
861 views

Legal aspects of the HackRF one / SDR in Switzerland?

I would like to know, what I can legally do with SDR / a Hack RF One in Switzerland? What are the limitations concerning sending and receiving? Do I need any licenses for that? If so, which ones, ...
wdjpng's user avatar
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5 votes
3 answers
2k views

Cheap antenna for new HF HAM

I just got a 100W HF radio and I am new at this. What is the cheapest antenna I can hook up without burning up my radio or shocking myself?
Pugz's user avatar
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-4 votes
1 answer
148 views

Wifi inside a rocket

I want to understand, as most rocket uses LAN cable and switches to communicate between stages. Is it possible to replace with WiFi? Although it's will be complex system but one idea to make each ...
shahid mobin's user avatar