Questions tagged [receiver]

Use this tag for questions about the theory and structure of receivers.

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3 votes
3 answers
73 views

Serial Inductors in Tuned Circuit - Elenco AM780K AM Radio Kit

I'm trying to understand a component of an AM radio kit that I have. (There is a document available here: https://www.elenco.com/wp-content/uploads/2017/10/AM-780K_REV-K-2.pdf describing the build ...
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0 votes
0 answers
32 views

FT-991A CODEC Microphone low volume on WSJTX

I have just installed WSJTX to work with my FT-991A. I noticed that the volume bar is always very low ~2db. Changing the CODEC microphone setting on the PC sound card from 24 to 100 for volume gain ...
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5 votes
2 answers
114 views

How can AM radio work differently when approaching the true frequency from different directions?

I bought a very cheap world band receiver, Nedis RDWR1000GY. It has MW, SW and FM reception. MW is useless where I live (no MW stations nearby and signals don't propagate far), but I was primarily ...
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1 vote
1 answer
155 views

Why is the Air Band distorted at times with SDR Sharp?

I am using SDRsharp to monitor air band with an RTL-SDR dongle. Sometimes I receive ATC voice clearly but at times it's distorted, I am using RTL AGC gain of 29dB with no tuner gain. My filter ...
1 vote
2 answers
48 views

Phase detection accuracy with USRP N210 and CBX-40

I have designed a simple TX/RX system in GRC with a single USRP N210 and CBX-40. I am transmitting sinusoidal signals at various frequencies within the 2-6GHz range and detecting the amplitude and ...
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3 votes
2 answers
115 views

Antenna reciprocity how does an antenna increase receiving range?

According to Wikipedia antennas are reciprocal unless they're constructed of nonreciprocal materials. There are a multitude of mathematical formulas which unfortunately I'm unable to understand due to ...
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9 votes
3 answers
2k views

Would it be possible for a software-defined FM receiver to demodulate two signals on the same frequency?

When two FM signals are transmitted on the same (or about the same) center frequency, either you hear only one or you hear that noise I'm sure most of you have heard. Would it be possible for a ...
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2 votes
2 answers
920 views

Why do Baofeng radios have such poor reception reliability?

What is the nature of Baofeng radios' poor receiver performance? This brand of handhelds has somewhat notoriously poor receivers. I hadn't noticed this much when using them for short distance simplex ...
2 votes
2 answers
297 views

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 ...
2 votes
0 answers
108 views

Why the Receiver Sensitivity theoretical value doesn't match its experimental value when using USRP B200mini in GNU Radio?

I'm using a USRP B200mini SDR card for my GNU Radio energy detector project. I wanted to measure its Receiver Sensitivity ($RS$) experimentally and compare the experimental value to the theoretical ...
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0 votes
4 answers
330 views

Does an RF amplifier allow us to receive a signal from further away?

From my understanding a RF amplifier boosts the transmission power of your antenna, this will in turn give you a higher gain. However I've read that this only will give you a further "...
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2 votes
1 answer
341 views

Performance gain when turning off CTCSS/DCS?

By turning of CTCSS/DCS can there be an increase in performance*? *Performance: Battery life Latency Range Voice quality From what I understand CTCSS/DCS is extra work for the IC inside the radio. ...
0 votes
3 answers
105 views

How to transmit computer audio to a wireless microphone receiver? [closed]

I'm currently trying to broadcast my computer's audio output to a wireless microphone system receiver so that I can accompany my school's coming presentation with music. The frequency range is 480-598 ...
0 votes
1 answer
82 views

Frequency division multiplexing FM Radio stations

Can someone help me with this I'm confused on what it is supposed to look like?
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12 votes
1 answer
2k views

What is a "roofing filter"?

What are roofing filters? Are there different kinds of things that are called roofing filter? Why would a circuit or component be called a roofing filter instead of just a IF bandpass filter? Why ...
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5 votes
2 answers
533 views

Phased array (rx only) with separate complete receivers

Is it possible to have a network of separate (but co-located) 'receivers' (antenna + adc) act as a phased array receiver? Supposing one can get very precise timestamping on each receiver, couldn't all ...
2 votes
0 answers
79 views

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 ...
-1 votes
1 answer
74 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 ...
0 votes
1 answer
67 views

How to analyse the distribution of the noise being received by my RTL-SDR device?

I'm very new to RTL-SDR and signal processing in general, but have managed to get my device (NOOELEC NESDR Mini) working and data into Python (via the pyRTLSDR library). I am able to output a complex-...
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0 votes
1 answer
75 views

How to Measure Bandwidth using just your receiver [closed]

How do you measure the two to one bandwidth of an antenna using a Bird Watt meter? Tom Planer KJ9P
1 vote
2 answers
124 views

Can a smartphone with single antenna receive signals modulated by different schemes

I am working on a system whereby a smartphone may receive signals simultaneously from different sources. As we know, the fading and pathloss will make the transmitters send their traffic with ...
0 votes
3 answers
531 views

Where can I find a service manual for the TECSUN PL-660 to replace the failed circuit board flex cable myself?

Diagnosed three nonfunctional TECSUN PL-660 radios (one from eBay Anon-CO, and two from Amazon) where can I find a service manual to replace the failed circuit board flex cable board assembly part? ...
3 votes
1 answer
106 views

Why is my experiment to produce 3rd order harmonics by saturating a receiver not working

I've been trying to devise an experiment to produce a third order harmonic in radio receiver that's been saturated, but I'm not seeing the expected results. My understanding of the theory is that when ...
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3 votes
1 answer
302 views

Globar resistor repair or alternative(s)?

I am restoring a Hallicrafters S-120 receiver and when trying to unsolder the wires, from the electrolytic capacitor, I noticed that one of the terminals of the Globar resistor (880-100 Ohm / 023-...
0 votes
2 answers
195 views

Receiving range of ham radio on SSB with a portable radio receiver

I'm learning about shortwave listening. I want to listen to amateur/ham radio on a portable radio (eg a XHDATA d-808) with SSB, I hear SSB is the main place hams would be on. I know it's hard to give ...
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2 votes
1 answer
235 views

Receiving shortwave frequencies from different countries (e.g. North Korea)

This question may be a little strange, but how can I receive radio waves from a country like North Korea (when I live in Poland)? I am interested in this topic, but I don't have that much knowledge. ...
0 votes
2 answers
76 views

universal 433 MHz test lamp (receiver)

I was wondering whether quick testing of various commercial ISM band transmitters for operation can be accomplished with some sort of off the shelf universal receiver which only turns on a led upon ...
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2 votes
3 answers
109 views

what is the baseband for CATV?

I was reading on wikipedia this: the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency (baseband) But when I ...
3 votes
2 answers
164 views

Why am I receiving a local tv channel on a CMB frequency

I am using a simple Baofeng H6 dual band radio and I programmed weather channels. Well, on frequency 161.77500 I am actually picking up WGN, a local tv network. This frequency should be reserved to ...
3 votes
3 answers
201 views

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 ...
4 votes
1 answer
118 views

Modeling a regenerative receiver

What is the signal processing model of a simple regenerative or super-regenerative receiver? Is it just a linear 2-pole IIR filter with gain? How does a single regen control knob control both ...
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3 votes
1 answer
208 views

WWV interference all over the band!

I have a mid-era Hammarlund HQ-129-x. It sounds great if I don't count the motorboating. But the problem is in the middle bands. I got the radio way out of alignment, and managed (I think) to get ...
5 votes
3 answers
475 views

SDR: How are I and Q determined from the incoming signal in quadrature sampling on the receiver side?

I'm new to digital radios and signal processing, so I apologize if this question is trivial but I haven't been able to find an answer here or by googling. Also, some terminology might be off, please ...
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2 votes
3 answers
250 views

Receiving multiple signal

Maybe this is a really silly question even from me, a completely amateur... But I like to know about how's the antenna output when its receive multiple signal Is it possible different signals on ...
1 vote
2 answers
588 views

Benefits of AGC?

I note that many popular kit and QRP radios do not include any AGC capability. Thus it must be possible to operate successfully without AGC. Are there difficulties involved in manual gain control? ...
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0 votes
2 answers
68 views

Detecting receiver intermodulation distortion?

On some (most?) receivers, if the RF gain is turned up too high, intermodulation distortion increases due to increasing non-linearities (maybe even clipping, etc.) Is it possible, just by examining ...
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3 votes
1 answer
116 views

Tradeoffs: varicap vs. air variable capacitor for Rx bandpass?

What might be the tradeoffs between choosing varicap diodes versus air variable capacitors in the design and construction of tunable bandpass filters for HF receivers?
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2 votes
1 answer
198 views

Receiving an Coded Odd Signal at 137.25MHz but don't know what it might be. It can affect my detection on NOAA 19. Need help

I am a newbie trying to detect NOAA 15, 18, and 19 satellites, which have downlink frequencies between 137 MHz and 138 MHz. I am using an SDR dongle and attached a photo of it to this post. Of course,...
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13 votes
1 answer
3k views

Why does the audio on my FM transceiver cut out every 5.5 seconds?

Specifically, my Icom ID-4100a. What's interesting, is that this happens in MR and VFO modes... but NOT when using the built-in WX stations. For example listening to WX-01 (162.550 MHz), no problem. ...
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4 votes
2 answers
471 views

Does the output of a BFO for a short wave receiver have to be exactly a sine wave?

I want to build an external beat frequency oscillator (BFO) for an old valve Eddystone receiver I have. There are many circuits for BFOs on the internet, they are mostly similar, the idea seems simple ...
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5 votes
2 answers
760 views

How to calculate power transmitted by monopoles?

I only studied monopole in sending mode or receiving mode alone but never in both modes together, I have this question which says: Two vertical λ/4 monopoles are parallel to each other with 20 ...
user avatar
2 votes
1 answer
106 views

Buzzing FM interference

What kind of interference or other receiver issues can cause a constant buzzing noise (picket fence lines in the audio spectrum) in the demodulated audio of a received NFM VHF signal? With AM, it ...
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0 votes
1 answer
55 views

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
93 views

Baofang uv-5rA/ repeater trouble

I programmed my Baofang UV-5RA radio to my local repeater about less than a 1/4 mile away. When I cue the mic and release, I get a signal from the repeater. However, I can only hear people if I have ...
1 vote
1 answer
219 views

PSR500/Pro106/WS1040 Phase II Upgrade?

I want to know if one can upgrade the hardware chips/ the CPU/DSP inside police scanners to do Phase II. I know they cannot do Phase II due to hardware/software limits but if whistler can upgrade ...
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5 votes
1 answer
187 views

Looking for a book that contained a circuit for receiving (literally) underground amateur radio transmissions

In this comment in Earth Science SE I've said: This is a really cool question! I remember (a long time ago) reading about electromagnetic waves inside conductive soil that travelled near but below ...
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4 votes
1 answer
175 views

Commercial Loopstick Antenna Manufacturers?

I am an electrical engineer working on a product that needs a loopstick antenna. I had thought that AM radios were so commoditized that I'd be able to find an off-the-shelf vendor. However the closest ...
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3 votes
2 answers
814 views

Advantages of IQ mixer versus direct sampling SDR architectures?

What might be the advantages, if any, of HF SDR architectures that use a mixer between the ADC/DAC and RF, versus those that sample or generate RF directly (at 0 Hz on up) with a fast ADC or DAC? Are ...
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2 votes
3 answers
1k views

What causes my direct conversion 80m receiver to receive AM broadcasts?

I am making a Direct conversion receiver from this circuit at this website. I made it for the 80m band and I changed: The frequency of VFO to about 1.75 MHz L1 and L2 to a bandpass filter for 80m ...
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0 votes
1 answer
265 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 ...
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