Questions tagged [superheterodyne]

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2 votes
3 answers

Loss of information and aliasing in superheterodyne receivers

For a radio / SDR that downshifts a signal to an IF / intermediate frequency band, wouldn't information be lost in the case that the original signal is above the IF sampling rate? For example, the ...
7 votes
1 answer

Is there anything special about 4.9152 MHz intermediate frequency?

I noticed that there are several QRP transceivers that use 4.9152 MHz intermediate frequency. For instance, John Dillon, WA3RNC uses it in Penntek TR-25, TR-35 and TR-45 transceivers. Also a very ...
2 votes
2 answers

What are best practices against spurious frequencies (birdies) in the superheterodyne design?

One problem I observe with my homebrew superhet receivers/transceivers is the constant presence of several "birdies". From what I know this happens due to the great sensitivity of the ...
6 votes
3 answers

What is a "direct sampling superheterodyne" receiver?

Browsing the specifications for the IC-7300, I noticed it says the receiver system is a "Direct Sampling Superheterodyne" with an IF of 36 kHz. I was confused by this, since I thought "...
2 votes
0 answers

IF derived AGC: how to choose the best block diagram?

I've built several transceivers in the past. I never implemented IF derived AGC, so I decided to give it a try in the next project. I choose to build a superheterodyne receiver, which will probably ...
6 votes
4 answers

Can SDR receivers be detected remotely?

It's my understanding that active superhet receivers can be detected by looking for the emissions from the local oscillator, particularly because the LO's frequency is usually set at some fixed offset ...
3 votes
3 answers

What causes an AF amplifier to make popping sounds in a superheterodyne receiver?

Recently I've made a simple single IF superheterodyne SSB receiver for 40 meter band. The schematic is available here [PDF]. VFO and BFO are based on Si5351, the AF amplifier is LM386. It works OK but ...
0 votes
1 answer

Combining two CFU455IT +/-2kHz (4kHz) ceramic filters to get a +/-1.25kHz (2.5kHz) filter for SSB

Can I put two of these cheap (less than 3USD) and common CFU455IT +/-2kHz (4kHz bandwith -6dB ) ceramic filters in series to get a lower bandwidth good for SSB TX? If I'm correct I will get -12dB at +/...
2 votes
1 answer

Frequency Display for Old Tube Radio

I have a Hallicrafters S-120 1960s vintage vacuum tube receiver (an "All American Five" superhet with solid state rectifier replacing one of the "five" tubes). It works well, doesn't have excessive ...
  • 3,967
9 votes
1 answer

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 ...
  • 682
4 votes
2 answers

Can a Digital Down Converter, at the same time, generate I,Q streams & Downconvert?

A Digital Down Converter (DDC) is usually used to convert Real Digital Signals at a high frequency to baseband (centered around 0Hz). DDC does this so by producing negative and positive frequencies. ...
  • 682
3 votes
1 answer

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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4 votes
1 answer

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/...
12 votes
1 answer

How is the IF for a superhet selected?

There seem to be almost as many choices for the intermediate frequency (IF) as there are superheterodyne receivers and transceivers out there. The ones I have come across are 455 kHz, 452 kHz, 1.6 MHz ...
  • 2,794