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14 views

Dipole increased CM current using choke balun

My 20 meter inverted vee dipole is fed with 56 feet of 50-ohm coax. The SWR measures 1.2 at the center of the band. According to http://arrl.org/grounding a balanced antenna doesn't need a ground, so ...
0
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0answers
15 views

Request your expertise on ohm values from two identical headphone speakers [on hold]

This stackexchange was the closest match for this question, not fit for sounds design. Dropped my headphones and left speaker stopped working. I've set my multimeter on ohm 200. The left none-working ...
0
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0answers
15 views

uhd_packet_rx do not work

I was trying to set up packet communication using examples in gr-digital/examples/uhd_packet_tx and rx. uhd_packet_tx is doing fine, but on receiver side(uhd_packet_rx) is freeze when i check up the ...
1
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0answers
39 views

Capturing Bluetooth / WiFi on an SDR

I have a question, right before purchasing SDR for some tests: Commercial hardware for bluetooth (even Ubertooth) allows you to receive packets on a 1MHz channel. Which practicaly means that if you, ...
-1
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0answers
17 views

Can a butler matrix have variable phase shifters instead of fixed ones?

If not, why are fixed phase shifts required?
1
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1answer
20 views

Baofeng UV-9R Chirp Pinout

I'm searching the pinout of the Baofeng UV-9R to programm it with Chirp.
2
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0answers
38 views

First linear power supply build - design questions

I have decided to build my own linear regulated power supply to provide the power for an upcoming build. Since I'm no pro, I was hoping I could get some feedback on my design before building it, just ...
2
votes
0answers
24 views

Fetching data from APRS-IS.net

I would like to fetch the data transmitted by a specific radio station from APRS-IS.net servers. I've read the documentation on their site and it is not clear how you would do it, if you are fetching ...
0
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0answers
65 views

communication with underground mines?

I have a meter that will analyze limited RF spectrum in my area. One frequency that keeps coming up is 2.498 kHz. An FCC site listed that as the frequency used to communicate with underground mines. ...
1
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3answers
67 views

How does the Maximum Power Transfer Theorem relate to RF power amplifiers?

The Maximum Power Transfer Theorem says that maximum power transfer occurs when the source impedance equals the load impedance, when the power transferred to the load is 50%, the other 50% being ...
4
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4answers
92 views

Why does an RF Amplifier fail when the SWR is high?

Exactly why does an RF output transistor fail if the SWR is bad ? Is it A because the impedance mismatch between the transmission line and the antenna results in maximum power not being transferred ...
2
votes
1answer
45 views

Received a QSL card with signal reports transposed. What to do?

I received a QSL card with the signal reports transposed, at least according to my log of the contact. He says I sent a 44 and that he sent a 55, but I wrote down the opposite in my log. If I send a ...
2
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0answers
43 views

I/Q demodulation of DSBSC-AM signals

I was looking at some Stereo FM demodulators on the Internet, and I can't understand the use of the complex to real block for demodulation of the L-R signal (DSBSC-AM) which can be seen in different ...
0
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1answer
44 views

What is the minimum legal requirement for logbook keeping in Ireland?

The question came up during a club event, and obviously we checked the regulations. references: "Amateur Station Licence Guidelines" page 22 From this document the details in regards to required ...
1
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3answers
72 views

Frequency for UHF hot spot in the US

Approximately what frequency should my UHF Pi-Star be set on in the US? Is there a standard?
0
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0answers
23 views

Isolator Frequency Range

If I have an 1.8-30MHz isolator on my multiband antenna (80m-6m), should I still be able to transmit 6m?
3
votes
1answer
44 views

Antenna testing, minimizing feed-line radiation?

Assume that one does not have access to a multi-million-dollar RF anechoic chamber. When testing an amateur radio HF or VHF antenna, how would one absolutely minimize the amount of any RF radiation ...
0
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0answers
28 views

What the difference preamble and access code?

gnuradio packetize using access code for start sync packet, but another example attach the preamblee, so what the differences preamble and access code ?
2
votes
3answers
62 views

Will a “crystal set” work with an untuned RF amp stage?

In my ongoing process of building up to a homebrewed general coverage receiver/transceiver, a first step might reasonably be a crystal set, where a tuned circuit and simple, or even improvised, ...
3
votes
1answer
87 views

How does a higher antenna reduce rain static on a lower antenna?

I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
3
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0answers
31 views

How to simulate two antennas in 4nec2

I need to simulate 2 helix antennae placed side by side, and see the resultant radiation pattern. But after adding the second antenna with a separate and when I try to simulate 4nec2, only simulated ...
3
votes
1answer
37 views

Antenna system components in the rain

An antenna system often consists of more than the feedline and radiating wires: such as fixed or tapped loading coils, LC traps, baluns, toroids, air variable capacitors, roller inductors, feed horns, ...
0
votes
3answers
84 views

Synchronizing HackRF Ones at a distance

I am using four HackRF One devices that will be situated ~1000ft apart, and that must be synchronized. Running 4000ft of cable to connect their clocks is obviously not feasible. I am wondering what ...
1
vote
3answers
53 views

Improve AM reception on an old Walkman that has no external antenna

I have an old Philips walkman that has AM/FM radio. I tried AM radio. Really I can get clearly 2 country radios. I catched very poorly 4 foreign radios or different countries, but they do lots of ...
3
votes
1answer
55 views

How does a 1:4 current balun work?

I'm having little difficulties understanding the following schematic: I understand the part regarding current distribution. I understand why this schematic suppresses common mode current. Also I ...
3
votes
4answers
126 views

How does the thickness of the radiator affect an antenna

Another question (Metal for antenna construction?) covered some aspected of this question, but the answers didn't exactly answer it, so I'll make it specific. Given 2 dipole antennas, resonant at the ...
0
votes
1answer
52 views

How can I determine the possible damages of transmission with detached antenna in portable ham radios?

Premise: I had a Baofeng GT-3 TP Mark III 8W stored and never used, this morning my nephew has found It and He tried to "play with It" transmitting at maximum power(8 Watt) despite antenna wasn't ...
5
votes
1answer
47 views

What does a receiver's noise reduction function do?

Some receivers contain a noise reduction button or function. What does this noise reduction do? Is there more than one type of noise reduction? How does the circuit or software know what part of ...
1
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0answers
49 views

GNU Radio does not run flow graph

I am sorry but yet again a question about GNU Radio. (I just started following some tutorials a couple of months ago and am learning about it. I am unfortunately not that proficient in it yet, but I ...
1
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1answer
74 views

Can anyone identify this military radio?

Hoping someone can identify this military radio... I spotted it at the curb and decided to make it a land-fill diversion project...
0
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3answers
518 views

Why aren’t emergency services using callsigns?

I’m super new to radio with nobody I know knowing it, so noob alert - plus some extraneous details in case you can comment on any of those. I got a pair of BaoFeng BF-F8HP radios with recommended ...
1
vote
1answer
74 views

Can I use a QFH antenna for transmission?

I've seen a lot of videos and tutorials on using the Quadrifilar Helix Antenna for receiving signals, but I haven't seen any material for transmitters. I'm just starting right now, but can a QFH ...
0
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0answers
31 views

A gnuradio program that can output some arbitrary waveform read from a file containing I/Q values

I am trying to figure out how to create a gnuradio program that can output some arbitrary waveform read from a file containing I/Q values. I would highly appreciate any guidance in this topic. Simple ...
0
votes
1answer
35 views

How to output a CW tone or a Broadband Noise in GnuRadio?

Kindly, can anyone show me how to output CW tone or a Broadband Noise in GnuRadio in a sort of simple flowgraph if possible? Update: So, what I did is I tried not to overthink the whole issue here ...
1
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0answers
35 views

How FEC works on GNU Radio

I am new to GNU Radio. I need some reference to how to use FEC block in GNURadio. When I try to make encoder and decoder without modulation, its work as well, but when I using modulation and add ...
1
vote
1answer
61 views

Is this antenna “system” really work? [closed]

I posted yesterday asking how can I have signal inside my house which my house is obstructed by a hill from direct signal from the cellular's operator' Base Transceiver System (BTS). The schema of the ...
0
votes
2answers
67 views

How much power does an RTL-SDR draw?

Background: Last night (and the night before) I was playing with my RTL-SDR and GNU-Radio again. Working with my FM Receiver, (which was working previously by the way), I detected that last night I ...
0
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0answers
52 views

Can I make a simple Tx/Rx antenna (Radio System) which will receive signal from BTS and broadcast/transmit it, and vice versa? [duplicate]

Consider a situation as below. I am stay in a farm field, which my house is 9.4km distance from the nearest and the only one BTS (Base Transceiver System), a cellular antenna for transmit and receive ...
1
vote
0answers
52 views

How do I Construct a Simple FM Antenna?

I recently bought a cheap stereo amplifier with built in FM receiver from Amazon at the first link below. Testing it out today I found the FM reception to be sub-par. All of my local stations that I ...
3
votes
1answer
51 views

CW skimmers and spotting networks?

What are CW skimmers, especially with regard to spotting networks? Are there more than one (of each)? How do the skimmers interface with spotting networks? (Or are they combined into a single ...
1
vote
2answers
58 views

Direwolf sends APRS transmission but it isn't being picked up by local digipeaters

I'm new to APRS and trying to setup a RaspberryPi APRS GPS Tracker. I've installed Direwolf and configured it, my transceiver transmits the signal, and I've decoded it with GQRX via an RTL-SDR and I ...
0
votes
1answer
54 views

Understanding RG6-75 ohm Cable Impedance

Here is my measurement to a piece of RG6 cable. It is around 30cm cable. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. From my measurement I got data as below: From that table, we can see that ...
2
votes
2answers
476 views

Can I use my US callsign to transmit while in El Salvador?

I am traveling to El Salvador later this fall, and was wonder if there is any reciprocal agreement that would let me use a US callsign while there? If so, what privileges would I have there based on ...
1
vote
1answer
82 views

Design/Build a DIY Audio Attenuator and Splitter

I’m trying to be less of an appliance operator. To that end, I recently came up with a simple project that I thought I could figure out and build entirely on my own. I was wrong. My goal was to ...
1
vote
0answers
36 views

Problem to paralel tv digital reciever [closed]

Here is my C-Band parabolic tv digital receiver. As shown by the pictures, the incoming coax cable (INPUT) connected both the outer and the core. One goes to digital receiver 1 (receiver 1), and ...
1
vote
1answer
21 views

Can the transmit and receive functions of a boat anchor transceiver share the tank circuit?

I'm starting design work on a two-tube (two-valve, for those who prefer that term) reflex-regen receiver that I hope will cover AM broadcast through 160m-10m -- both amateur bands and those "in ...
1
vote
2answers
95 views

Is the Relay in ARRL still relevant?

The second R in ARRL stands for Relay, but is that still as relevant in the 21st century? Has it been relevant since broad damped-wave spark transmitters were supplanted with tube-generated CW, which ...
1
vote
3answers
109 views

How to calculate impedance in antenna design's practice?

I would like to make a match half wave length (λ) dipole antenna (or probably a short dipole antenna). So I would like to make it by measure using LCR meter. What I am still confuse is about what is ...
2
votes
4answers
139 views

What is the maximum and minimum of antenna gap of dipole antenna?

Consider the picture below is design of half wave length (λ) dipole antenna. I read some explanations saying that it is the best design to get the optimum transmit power. Half wave length (λ) is from ...
4
votes
1answer
45 views

How can I decode SSTV with only macOS software?

Have you used an SSTV decoding application on an up-to-date version of macOS? Which one, and if you built from source, can you share the steps you took to do so? I do not know of a single working ...

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