Questions tagged [amplifier]
Questions about amplifiers, typically RF power amplifiers. For low-noise amplifiers (LNAs) consider using the "lna" tag.
51
questions
-4
votes
0answers
38 views
Does a UHF amplifier exist that will boost 5 mW? [closed]
I need to boost my 5 milliwatt HackRF to a jammer level power. Is anything like this available?
Ideally portable and self contained. I expect a 45kg amplifier or something but it has to be powerful ...
-1
votes
2answers
61 views
What is an optimal amplifier arrangement with ham radios?
As I am settling on a design for a radio I need to figure out one thing:
Should I modulate on low power and boost it up with a post amp, or should I go on full power right out of the gate?
0
votes
0answers
12 views
What configuration of a BJT IF amp can I use for a superhet receiver?
I am making a superhet SSB CW receiver with a crystal filter on the input after the mixer.
Do I have to use IF transformers as the coupling method?
Or can I use capacitor coupling with resistors as ...
3
votes
1answer
61 views
What is unique about a Low Noise Amplifier (LNA)?
What is so special about a low noise amplifier? If I were to design an amplifier, I would always design an amplifier with low noise anyway.
Why is it emphasised as being “Low Noise”?
What are the ...
0
votes
0answers
33 views
How to calculate combined power of two amplifiers
If I have 1 amplifier running at 95%, and another identical one running at 60%, how may I calculate the output power of the combiner? I believe this combiner is a "Magic T", but if there is a ...
2
votes
3answers
137 views
Under what circumstances does intermodulation become an issue in a filter after LNA setup?
I'm reading about using software-defined radio for picking up ADS-B signals at 1090MHz. There is this blog which considers (among others) a setup as follows:
...
1
vote
3answers
120 views
How does the Maximum Power Transfer Theorem relate to RF power amplifiers?
The Maximum Power Transfer Theorem says that maximum power transfer occurs when the source impedance equals the load impedance, when the power transferred to the load is 50%, the other 50% being ...
4
votes
4answers
205 views
Why does an RF Amplifier fail when the SWR is high?
Exactly why does an RF output transistor fail if the SWR is bad ?
Is it A because the impedance mismatch between the transmission line and the antenna results in maximum power not being transferred ...
0
votes
3answers
109 views
How to make simple AM detector using an LED?
I'm new to amateur radio, and as a beginner project, I wanted to use some of the basic components I have to create an AM receiver.
Anyway, what I'm trying to do is create a simple AM receiver that ...
4
votes
2answers
106 views
Pi Matching circut for tube PA - what values?
I am working on my 80m and 40m CW transmitter and ran into a problem:
I need to match the high impedance of PL504 to 50ohm coax, a Pi match seems to be the best, but I don't know how to calculate ...
7
votes
1answer
202 views
Double power-handling ability of RF amplifier output transformer
I want to base the output network for a 500W push-pull HF amplifier on "A 250W Broadband Linear Amplifier" described in Chapter 17 of the 2014 ARRL Handbook. I need advice on whether and/or how the 1:...
1
vote
0answers
63 views
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. ...
1
vote
2answers
71 views
Toroid Coupling Issue in Common-base Amplifier
I'm working on an old school VFO for the 15 meter band based on a JFET Hartley oscillator. The plan is to follow the oscillator section with a JFET buffer, then a CB amplifier (for increased reverse ...
0
votes
3answers
73 views
Voltage Converter for Amp
I have a chance to get a 1 kW amplifier with a 220V plug dirt cheap from a friend of mine, but I only have a 110 outlet. The 110 outlet is on its very own 20A breaker with no other outlets. Could I ...
1
vote
0answers
85 views
2GFSK 9600bps Transmitter and amplifier for 433 MHz
I'm looking for a reliable, however cheap solution for ground-space communication. I need at least 50W of transmitted power with 2GFSK modulation at 70cm band (433 MHz). Transmission will be done ...
1
vote
1answer
86 views
is KPA100 a good amplifier for Yaesu Vx-8Dr
I am interested to explore what a Yaesu VX-8DR radio can do and would like to add an amplifier to it. One of the AMPs that seems to work with a 5W input is KPA100, I am still doubtful how the Yaesu ...
7
votes
2answers
167 views
Water cooling a GS-35B in lieu of air cooling?
Does anyone know how to --or have any experience with-- water or oil-cooling the anode? Since forced-air cooling is required, the sound from the blower and the exhaust air would be too noisy for my ...
2
votes
2answers
518 views
Why does a Class-C non-linear power amp distort SSB but does not distort AM?
Can someone tell me why exactly a transistor non-linear power amplifier will amplify an AM signal without noticeable distortion, but will distort an SSB signal, giving the familiar scratchy sound ...
8
votes
0answers
144 views
UHF FM power amplifier design without expensive software
I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application ...
2
votes
2answers
242 views
How to supply high voltage to an amplifier in a safe way?
The grounded-grid amplifier that I am looking at requires 1100 volts Max.
How do I safely deliver this rated voltage without getting hurt?
Should I consider a alternative amplifier?
By request here ...
5
votes
3answers
396 views
Impedance Matching between RF Amplifier Stages
I'm in the process of building a RF buffer-amplifier chain for a VFO and I'm experiencing a design issue trying to impedance match between the sections.
The issue I'm having is that many (most) of ...
2
votes
1answer
148 views
Power Amplifier Balun Question
Second (and last hopefully) question on the classic Solid State Design for the Radio Amateurs (SSDRA) book by Hayward et al. Again it's a power amplifier circuit (Chapter 4, pg. 66), and again it's ...
7
votes
2answers
278 views
What is the purpose of the transformer at the input (and output) of this RF push-pull amplifier
Firstly, feel free to move this to Electronics SE if it's not on-topic, but it's strongly related to ham radio and RF circuitry.
Reading Hayward's classic "Solid State Design for the Radio Amateur" ...
0
votes
2answers
3k views
HackRF + Amplifier = HF/VHF QRP Radio?
Do you think it would work to combine a HackRF One and an amp like the following to create a QRP SDR?
Link to eBay
Output of HackRF is approximately 10dBm, which fit's this amp nicely...
What is ...
1
vote
3answers
110 views
I just got this RF equipment but i don't know what's for
I got some RF equipment for free (it was going to the trash and I 'rescued' it). It's almost new, and seems expensive, but i don't know it's purpose. Googling the model numbers yields very little ...
0
votes
1answer
69 views
RF Coverage range doesn't improve inspite of increased Tx power
I built an RF power amplifier with about 10 to 13 dB gain operating at about 100 MHz. It amplifies signal from about 50 to 100mW to about 1W. Inspite of the amplification, I don't see a real ...
1
vote
1answer
203 views
building a relay for 5.8Ghz?
I'm interested in building a relay for analog video sent from an R/C aircaft. The idea is to get around obstacles like hills and increase distance a bit.
Rather than just applying more power, I ...
1
vote
1answer
98 views
Parallel tube amplifier power supply using 6DE4 tubes [closed]
I’m looking to build a vacuum-tube based linear amplifier. I’d like to do it all tube based, including the power supply. The original ARRL design I’m looking at (from the 60s) has two paralleled 807s ...
8
votes
1answer
221 views
How can I do direct digital synthesis of a 630m WSPR signal?
I want to do direct digital synthesis of a 630m band WSPR signal.
Specifically I'd like to use an Atmega 328 chip running at 20 MHz to produce such a signal.
I will use standard phase accumulator ...
2
votes
1answer
200 views
FET for low voltage class E amplifier
I'm building a small APRS radio for a high altitude balloon, and I'm thinking of using an Si570 (3.3 V CMOS) at 144 MHz to drive a small class E amplifier. I'm looking for about 1W output power. I'm ...
2
votes
3answers
1k views
Will an Internal Antenna Tuner work with an external HF amplifier?
I am a new General and don't quite understand how Antenna Tuners work other than changing the impedance ratio between the radio and the antenna.
So my question is -
Do I need to buy a new tuner if ...
0
votes
2answers
712 views
what are the alternatives to LM387 and SA602AN?
I am building a 20 Mhz RF receiver out of the NASA radio JOVE instruction manual and they have recommended the use of LM387 as an audio amplifier. SA602AN as mixer IC:
1
vote
1answer
137 views
UHF Into VHF Power Amplifier
What would be the result of accidentally applying a UHF signal to a VHF power amplifier? Say a 70cm transmission from a dual-band 2 meter / 70 cm radio into a 2 meter PA, assuming the input power is ...
2
votes
1answer
960 views
33cm 5W(effective output power) tx amplifier for ATV (HamTV)
I am searching for a 5W effective output power TX amplifier that I can use with my BladeRF to send DVB-T Signals for ATV (33cm band).
Can someone tell me on what things I have to look for when buying ...
5
votes
4answers
543 views
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
votes
2answers
467 views
How to calculate if low-pass filtering is sufficient?
An answer on this question Suggested method for boosting 0.05 watt transmitter up to 10+ watts? suggests putting a filterless 19dB amplifier between the HackRF (or similar general-purpose SDR) and a ...
9
votes
3answers
3k views
Why does “high SWR” damage transmitters, instead of “impedance mismatch”?
In the audio realm, where cable lengths are insignificant compared to the signal wavelength, I would understand an impedance mismatch damaging an amplifier as follows:
Take an audio amplifier that ...
1
vote
2answers
266 views
RF6886 high power amplifier maximum reverse power
I'm designing a circuit which uses the RF6886 amplifier IC. What is the maximum reverse power that the amplifier can sustain? At what reverse power will the amplifier die?
2
votes
1answer
228 views
AN762 Amplifier Transistors
According to the MRF421 or MRF454 transistor datasheets, used in the AN762 HF amplifiers say that the transistors are "100% tested for load mismatch at all phase angles with 30:1 VSWR".
Further, in ...
0
votes
1answer
195 views
How can I reduce power consumption and thermal dissipation in power amp?
I am designing a Class-E power amplifier in UHF band using ADS. Now I have 20dBm fundamental output power with 13% PAE, which is low for this class of PA. The problem is that I have thermal ...
3
votes
1answer
490 views
Receiving through a linear amplifier
I want to build a simple amplifier using those Mitsubishi modules (like the RA30H1317M or other RA parts). I know this might seem like a very obvious question, but I am unable to find the answer after ...
1
vote
1answer
86 views
Is preheating required before replacing an old valve?
I have a Drake transceiver. I want to replace the valves in the final output stage. The valve in question is a 6jb6.
I was told by elmers that the valves need to be preheated (cooked) before ...
3
votes
2answers
90 views
Link margin calculations with two antennas and two low noise preamplifiers
Background -
UHF - 434-438MHz
Two identical crossed Yagi's mounted on rotator.
Currently, I have a low noise preamplifier after combining cables from the two antennas (T connector + matching stub).
...
0
votes
1answer
141 views
audio amplifier as fm amplifier possible?
Is it possible? I know it depends on legal issues; it is just for testing.
I will "transmit" from RPI (Raspberry pi as fm transmitter).
6
votes
1answer
1k views
Suggested method for boosting 0.05 watt transmitter up to 10+ watts?
Long time ham operator here, new to this particular challenge -
I have a software defined radio transceiver that I'd like to try and use to make contacts on HF, in particular 20-meters. Tuning ...
7
votes
1answer
124 views
Efficient BPSK31 amplification
I'm looking at making a portable system that can transmit BPSK31. I have a limited power budget, so I'm looking at trying to make my final power amplifier as efficient as possible. From my ...
2
votes
2answers
266 views
What is the difference between Rf Gain Blocks & IF Gain Blocks?
As advertised on websites of large manufacturers like Analog Devices And Texas Instruments
I am aware of the difference between an IF stage and an RF stage, however, I was curious if there was any ...
4
votes
1answer
311 views
What is the average fade margin required for proper operation at 2.4 GHz?
I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect?
I want it to be somewhere near about 2-3 km. Is it possible?
9
votes
3answers
6k views
What is dBm and why is it used rather than watts?
Reading through an RF power amplifier datasheet, I found the sheet only referenced dBm output power, rather than watts.
What is dBm?
How do I convert it to watts?
Why, or when, would you use dBm to ...
1
vote
1answer
1k views
Is transmission wattage calculated using RMS?
I understand (and correct me if I'm wrong) that transmission power follows Ohm's law ($I = \frac{V}{R}$), that is that if I have a 50 Ω antenna that I know is transmitting at 1 W, then the current is:
...
