Questions tagged [amplifier]
Questions about amplifiers, typically RF power amplifiers. For low-noise amplifiers (LNAs) consider using the "lna" tag.
7
votes
2answers
91 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 ...
1
vote
2answers
197 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 ...
6
votes
0answers
63 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
182 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 ...
4
votes
3answers
102 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
94 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
126 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
594 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
99 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
64 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
167 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
68 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
0answers
159 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
172 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 ...
1
vote
3answers
880 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
525 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
119 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
812 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
389 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 ...
6
votes
2answers
358 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 ...
8
votes
3answers
2k 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
197 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
192 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
174 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
352 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
81 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
87 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
115 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
822 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 ...
6
votes
1answer
118 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
197 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
276 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?
8
votes
3answers
5k 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:
...
12
votes
3answers
2k views
What is a linear RF amplifier?
Most of the RF amplifiers advertised, and most of the questions about amplifiers, are "linear" amplifiers.
What is a linear amplifier, and what other common amplifier type(s) exist that requires ...
