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Questions tagged [mixer]

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5 votes
2 answers
771 views

How to design a Local Oscillator for a radio receiver?

I have decided to design a Medium Wave radio with discrete parts which won't include much complex ICs or schematics . I am thinking of designing the radio in Heterodyne mode. Which requires an ...
CoderBittu's user avatar
8 votes
1 answer
304 views

What will the *amplitudes* of mixer products be?

The key fact about mixers, which iirc is even part of the FCC amateur radio exam(s) in the USA, is that they output "the sum and difference" of the input frequencies. And iiuc in practice it'...
natevw - AF7TB's user avatar
2 votes
3 answers
372 views

Explanation of VFO as one part of the the tuning variables in mixers

I do apologize if this has been answer previously, but the term "VFO" seems to have become overloaded over the years. I think I have a handle on the notion of multiple VFOs on device for the ...
user avatar
3 votes
1 answer
264 views

How to balance a mixer?

I have read about double-balanced mixers and as far as I got the theory right they should suppress carrier frequency. I am trying to build my own transceiver project and I cannot suppress the carrier. ...
k1zmt's user avatar
  • 337
4 votes
1 answer
167 views

SSB Single Conversion Superhet 2nd Mixer IF Termination on Transmit

I have a question about "best practice" in regards to how the 2nd mixer IF port is coupled to (in my case) a 20m double tuned filter on transmit. I'm currently building out the transmit ...
Buck8pe's user avatar
  • 989
5 votes
1 answer
128 views

MF band mixer - feasible parameters

Trying to build an homebrew receiver for MF band broadcast (Navtext). Usually working on VHF, where all parts are easily found as an IC, but here I'm trying to get back to roots, so I may be missing ...
gusto2's user avatar
  • 153
9 votes
7 answers
2k views

How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...
John B's user avatar
  • 191
3 votes
2 answers
882 views

SSB Transceiver Architecture - USB with Crystal Filter

I'm planning to build a 20m SSB transceiver and I want to get the overall architecture straight in my head first. Here's what I'm thinking so far, a single conversion superhet design with a 9MHz IF ...
Buck8pe's user avatar
  • 989
4 votes
1 answer
184 views

How to track down and neutralize this apparent mixer creating noisy emissions around my signal?

When I transmit, it there seems to be something mixing and reflecting my signal. For example, when I transmit on 14.300 MHz, I see signals above my transmitted signal at at 14.500, 14.700, 14.900, etc....
Rosa's user avatar
  • 191
2 votes
1 answer
266 views

What would a "crystal mixer" have been in an 1960's radio telescope at 960 MHz?

In a paper cited in comments to this answer to In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)? ...
uhoh's user avatar
  • 543
7 votes
4 answers
786 views

How can quadrature mixing adjust the phase of all frequencies by the same amount? Can it be done in the digital domain?

This came up in some feedback I got when I tried to answer What is IQ in the context of SDRs? and revealed some of my own misunderstanding. Initially, I gave an answer something like (paraphrasing): ...
natevw - AF7TB's user avatar
8 votes
4 answers
2k views

DIY SA612 + RTL-SDR HF receiver: good on laptop, but huge wideband noise on Raspberry Pi

I recently built a SA612 mixer for HF reception. I used an USB-frequency oscilator to shift the incoming frequency up by 28.8 MHz. I used a random wire antenna outside my balcony and connected it to ...
比尔盖子's user avatar
0 votes
1 answer
141 views

mixing frequency of intermediate frequency (IF) and radio frequency (RF)

AM broadcast signal covering 995-1005 kHz radio frequency (RF) range is to be down-converted to an intermediate frequency (IF) range of 395-405 kHz where main amplification takes place in AM receivers....
natasha's user avatar
  • 61
1 vote
1 answer
120 views

Frequency mixing products

I encountered the following question on a test, and I'm not sure of the theory behind it. Could someone please explain? When a signal with spectrum ranging from 13 MHz to 15 MHz is mixed with (i.e.,...
natasha's user avatar
  • 61
1 vote
4 answers
280 views

Finding an Intuitive Explanation of Mixer Theory

I don't know about you guys, but I've always been somewhat confused by fundamental mixer action. I've always been left unsatisfied by the standard trig identity explanation as one that's a tad too ...
Buck8pe's user avatar
  • 989
8 votes
3 answers
5k views

What exactly is a "balanced modulator"?

While studying for his U.S. General class license, my son wondered about the "balanced modulator" referred to by a few questions in the FCC pool. Quoting KB6NU's General Class study guide to give a ...
natevw - AF7TB's user avatar
1 vote
1 answer
183 views

BFO locked synchronous AM detection

I am fixing up an old classic Yaesu FRG7 general coverage AM/SSB/CW HF receiver. The BFO section is a rudimentry 455 kHz IFT configured as a carrier reinsertion oscillator that that is made to run USB ...
Autistic's user avatar
  • 469
9 votes
1 answer
433 views

How Could Superheterodyne Receiver Ever Work?

I am surprised how the Superheterodyne Receiver still works and is still in use after coming to realise the impact of Image Frequencies on its performance. Basically, I'm curious how engineers make ...
Denis's user avatar
  • 702
2 votes
2 answers
130 views

What function do high-pass filters in a direct conversion receiver perform?

Use case: I'm considering hacking into my SoftRock RXTX to bypass the filters, then add external filters. I'm wondering if I can use just the low-pass filters I've already built, or if there's a ...
Phil Frost - W8II's user avatar
5 votes
2 answers
455 views

In the context of the mixer in my radio, what does balanced and unbalanced mean?

I'm trying to understand how the mixer in a radio actually works, at a physics level. When looking at this article and studying the first schematic I realized I really don't understand what balanced ...
flickerfly's user avatar
2 votes
4 answers
3k 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:
Mathav Raj's user avatar
3 votes
1 answer
683 views

What might this "spreading" interference be?

Any idea what might be causing this signal to appear in the "panadapter" spectrogram of my Omnia SDR around the 40m band? Every twenty seconds, I get a strong "focused" signal that then rapidly ...
natevw - AF7TB's user avatar
3 votes
2 answers
345 views

Building an IQ mixer using an in-phase LO splitter

There are many examples of IQ mixers on the internet; all use 90 degree hybrids to split the LO to the mixers with the outputs being combined in-phase. I'm curious, could both mixers be fed an in-...
Sam's user avatar
  • 161
1 vote
1 answer
358 views

Homodyne vs heterodyne

Im not sure what is true, when I want to calculate it. First, the fact is that classic homodyne is used only in receivers. (I'm not talking about quadrature homodyne.) But I can't understand how the ...
Przemek Lewandowski's user avatar
3 votes
1 answer
349 views

SSB modulation image rejection

I'm trying to figure out how SSB transmitters manage to get rid of the images created when mixing up audio frequencies. For example, when mixing a 1KHz signal with a 7MHz one you will end up with two ...
s3c's user avatar
  • 837
10 votes
1 answer
3k views

How does a switching mixer multiply the two signals?

I understand what a mixer does, and when I see it in a block diagram it's obvious what purpose it serves and how it fits in the overall design of the radio. However, when I look at the schematics and ...
Adam Davis's user avatar
  • 12.1k
4 votes
1 answer
3k views

What advantages does dual-conversion have over single-conversion superheterodyne?

I've seen a variety of radio block diagrams, and some have two mixers inline with the signal. If the signal is already in a frequency range suitable to work with, what does the second conversion/...
Adam Davis's user avatar
  • 12.1k