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

1
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1answer
30 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 ...
4
votes
1answer
152 views

What is this odd data/screeching/fuzzy signal?

I was listening to a commercial FM radio station on 100.9 MHz, and this intermittent weird sound kept coming through it. Here is a recording of it. The audio starts at about 15 seconds. It sounded ...
0
votes
1answer
71 views

Ultrasonic FM receiver

I need a FM receiver that is capable of receiving ultrasonic audio frequencies above the standard wide band FM range of 15 KHz. I'd like something that can receive signals up to 60 kHz if possible: I'...
7
votes
1answer
123 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 ...
3
votes
1answer
54 views

What's the use case behind long AGC constants?

So my shortwave radio has adjustable AGC constant with settings between 0.1 s to 8 s. I always find myself using the fastest AGC settings. Often, I experience 20-30 dB fades and if I use the slower ...
2
votes
1answer
35 views

Poor reception on single AM channel

My car stereo has terrible reception on a single AM station. Other cars get the signal fine and other channels on radio are received fine. I have contemplated some sort of booster for the antenna or ...
5
votes
2answers
615 views

IQ imbalance after quadrature mixing

What is IQ imbalance in the output of complex or quadrature downconverter/demodulator/mixer? What are the causes and effects of IQ imbalance? (A spike in the spectrum display of RF noise?) Are there ...
4
votes
3answers
197 views

Can an antenna be too powerful for certain receivers?

I'm brand new to shortwave radio and have been researching what kind of a receiver to get. I'll use it on the antenna I'll build (longwire, 50-100 feet) for shortwave listening; no transmitting. Right ...
1
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2answers
281 views

What are some equivalents of a BF199 transistor?

I'm planning to build an FM radio receiver using the instructions on http://www.instructables.com/id/Build-your-own-Crude-FM-Radio/ The schematic uses a BF199 transistor which is marked "obsolete" by ...
4
votes
2answers
81 views

Use noise figure and gain to calculate weakest signal radio can receive?

An FM radio receiver, using a 1 kHz tone at 3 kHz deviation has a 12 dB SINAD (Signal To Noise and Distortion) of -116 dBm. I would like to increase the 12 dB SINAD sensitivity of the receiver to at ...
3
votes
1answer
59 views

Carrier wave timing

I'm not really too technical when it comes to radio, but I understand that in AM, a shortwave radio generates the carrier frequency so that it can mixed with the received station and then removed, ...
2
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0answers
47 views

What is this sound on FM radio? [closed]

When tuned around 87.5-88 FM, a strange repetitive sound can be heard. The title 'Les Professionnels' from 'Air' start with this sound.
4
votes
2answers
280 views

Understanding WFM modulation

I am using "HDSDR" software to demodulate a WFM broadcast ("Classic FM" in the UK, on 100.1 MHz, 192 KHz bandwidth). I'm using an "SDRPlay RSP1" software defined radio and a cheap indoor discone ...
1
vote
1answer
141 views

SDR - discone antenna setup

Here's a picture of my SDR receiver setup... This entire setup lives indoors as I'm not able to put anything up on the roof right now. My understanding of a discone antenna is that the downward ...
0
votes
1answer
57 views

Are there receivers and transmitters that can be tuned to multiple frequencies at once? [closed]

What kind of hardware/circuitry would be needed for a device to be able to transmit and receive over a range of frequencies at once?
4
votes
1answer
86 views

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. ...
2
votes
1answer
246 views

What parts / procedure do I need to build a UHF receiver that can connect to a standard pair of headphones

I have a low power wireless microphone (10 - 50 mW) with a large receiver designed to connect to a mixer/sound system. The mic transmits in the UHF band between 530 and 860 depending on the band (see ...
1
vote
1answer
95 views

Can my portable radio receive amateur radio?

http://memorex-ce.com/product/amfm-pocket-radio/ Yeah, I guess it's cheap and probably won't pick it up but...
1
vote
1answer
143 views

Recommendation for noob

I don't yet have any radio equipment but I find this hobby interesting and would like to learn more. I'm looking for something that isn't too basic and will keep my interest without spending too much. ...
1
vote
1answer
190 views

What is pinout for headphone FM radio antenna?

My Android phone (as many others) have FM radio receiver on-board. But apparently, it has no internal VHF antenna at all, since there is no signal at all w/o headphones plugged in and sound quality ...
2
votes
1answer
678 views

How to find or derive the maximum safe input power to a receiver?

A number of my RF devices have a specified safe maximum input power, for example: "The maximum RX power of HackRF One is -5 dBm. Exceeding -5 dBm can result in permanent damage!" source "If you look ...
2
votes
2answers
115 views

How to safely connect a digital output to a receiver's antenna input?

Suppose I have a 3.3 or 5V GPIO digital signal (from an Arduino or Raspberry Pi, etc.), periodically toggling at some HF or VHF frequency. Since it has such a "dirty" spectrum, I don't want to hook ...
1
vote
2answers
154 views

Intermittent receive on FT-990

My FT-990 often does not receive well after it powers up. i.e. Tuning across various bands, changing from one VFO to the other, few if any signals are heard. Briefly tuning up (CW) with low power ...
0
votes
1answer
112 views

DRM standard receiving on shortwave

What's the particularities of receiving SW-broadcasting, that uses DRM standard ? Every SW-receiver can directly receive this kind of signal?
4
votes
1answer
302 views

Detecting the listeners

I wonder, if a broadcasting radiostation can detect, how many receivers are tuned on it, and if it possible - how exactly this detection is happening? Thanks.
6
votes
1answer
157 views

What would be the typical received power of an “S9” signal?

Obviously, I would expect the amount of power at a receiver would vary greatly based on distance from, and the power/efficiency of, the transmitter. But I don't really have a good sense for what "...
1
vote
2answers
80 views

different digital modulations interference. Does it happen?

Bottom line is I have got a very strange (but regular) reading on a < $1 type of ASK 433 MHz receiver. Have a look at it - those 3 spikes are sometimes caught by my receiver, don't know their ...
4
votes
2answers
274 views

How to make a “you're getting warm/cold”/“fox hunting” game based on RF signals

I would like to build a system in which the emitter emits omnidirectional RF signals, and the receiver gets a stronger signal (it does not have to be accurate) with a) closer distance from the emitter ...
0
votes
2answers
458 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:
5
votes
1answer
1k views

SDR with the Raspberry Pi

I wanted to explore digital modes by connecting a Raspberry Pi via audio cables to a transceiver. However, I realized that thanks to the clock generator, the raspberry pi can produce RF signals ...
4
votes
3answers
1k views

Good FM receiver single-chip IC for simple VHF receiver?

Is there an IC out there that implements all, or most all, of a simple FM receiver in the VHF range? I'm interested in doing some experiments with using DTMF over the air for tele-commands and the ...
2
votes
1answer
85 views

feasibility of wireless passive crystal earphones

I just learnt about such a thing as a crystal radio receiver and the following idea came to my mind. I have no background knowledge on electronics nor anything related. What if battery-less earbuds ...
2
votes
3answers
276 views

Is it normal for mini shortwave radios to not have any reception in a major city?

I'm new to radios. Just bought the mini Eton which has FM/AM/SW and while FM & AM work I have never received a single station on SW1 (5.9 - 10 MHz) or SW2 (11.65 - 18 MHz). Is that normal? Will ...
10
votes
4answers
5k views

How To Join Packet Radio BBS

I'm a complete newbie here, and on the Southeast Coast of the USA. I don't even own a ham radio yet. Some preppers and I got to talking about a dystopian time of Internet collapse where shortwave ...
2
votes
1answer
308 views

What's the difference between the normal and S-meter squelch in IC-2730?

I recently obtained an IC-2730E and can't figure out the difference between its squelch options. Unfortunately, the user manual isn't very helpful. The squelch option had 3 types: off, attenuation and ...
1
vote
2answers
263 views

Scanner radio purchase advice for someone that's nosy but not technological?

If it sounds like a stupid question, it probably is. My mom loves being nosy... When she hears the police siren, an ambulance, firefighters, or something like that, she's the first one to run to the ...
2
votes
2answers
180 views

SkyStar S2 has a mac address, for what? [closed]

Hy just a "stupid" question, I bought a technisat skystar s2 pci card. Can any body tell me why this thing has a mac address printed on it? ^^ And the mac address can even been looked up. (00-08-c9-xx-...
1
vote
2answers
288 views

What is an adequate antenna for a JRC NRD-545?

I live in an attic apartment, just acquired a JRC NRD-545, and am somewhat limited to what I can put outside (within reason). I have an old folded dipole CB antenna that I might get away with ...
3
votes
2answers
936 views

Scanner radio for 433MHz locator beacon

I am looking for a recommendation of an inexpensive scanner radio that should be used to locate animals equipped with 433MHz locator beacons. The beacons (based on DRA887TX) will send periodic tones. ...
2
votes
3answers
500 views

Any SDR radios that receive FM BCB

Are there any software defined receivers capable of receiving Regular FM broadcast band stations and displaying a waterfall of the band from 88 MHz to 107 MHz or a significant portion of that range?
1
vote
1answer
126 views

How will I improve my portable radio reception

I listen in a close room. I have this kind of radio, but it doesn't give a clear sound... it has "shhhhhhh" sound. There's a certain position where it will give out a clear sound but that position ...
2
votes
1answer
483 views

Square wave vs. sine wave timing reference

Some RF receivers accept square wave clock reference (10MHz, 1pps, etc) and others accept sine wave. Most of the GPS do devices are outputting 10MHz sine wave timing signals. Are there practical ...
3
votes
4answers
3k views

Shortwave Antenna Listening with Portable Receiver Like TECSUN PL-660?

I have a Tecsun PL-660 (link is to the manual) has the usual AM/FM radio telescoping internal antenna, and a 1/8th-inch jack for an external shortwave antenna. There appears to be no facility for ...
1
vote
2answers
100 views

Does a station that's only going to receive require grounding

So I'm looking at building a satellite receiving stations (amateur bands). I know that a station that is transmitting requires grounding of the RF components due to the high power of the transmitter, ...
0
votes
1answer
95 views

List of capturable data services (diy)

Looking for a list of capture-able data services. By browsing some sites I accidentally discovered that it is possible to receive NOAA satellite weather images with DIY receiver (link) or (here), ...
3
votes
2answers
840 views

In SSB how do receivers calculate the frequency offset without a carrier?

On page 2-9 of the ARRL Ham Radio License Manual, it discusses how in SSB one of the side bands and the carrier are suppressed to conserve power and bandwidth. Given the explanation of how AM works, ...
1
vote
1answer
143 views

Reception for FM stations is offset, but AM stations aren't

I have a Realistic STA-78 AM/FM Stereo receiver I recently rescued from my grandmother's attic. It hadn't been played in a while, but it appears everything is in working order except the FM dial. It's ...
3
votes
4answers
320 views

Low power long distance wireless data communication

I am looking for a communication solution with the following requirements: wireless unidirectional, point to point low power (li-ion battery powered, should operate at least one hour on the single ...
6
votes
3answers
844 views

Why do I only hear broadcasts from 150 kHz to 29.999 MHz?

I am currently studying for my amateur radio license. Until I'm licensed, I'm trying to use a Sony ICF-SW7600GR receiver to listen in on amateur radio "phone" transmissions. No matter what I do, ...
1
vote
1answer
239 views

Is this simple description of SSB correct?

I was recently asked to explain why a "carrier injection oscillator", or CIO is needed in an SSB receiver but not in a transmitter. This is the explanation I gave, and I would be grateful for comments ...