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2
votes
1answer
8 views

Can an ultra-wideband system transfer data at high speed without precise clock synchronization?

Recently, ultra-wideband technology has been in the news again. From the Wikipedia article: UWB transmissions transmit information by generating radio energy at specific time intervals and ...
0
votes
1answer
44 views

Center-frequency parameter for gnuradio noise generator flowgraph

Can I add a center-frequency parameter for my noise generator flowgraph, is there a different noise source that has this parameter other than the generic noise source block?
-1
votes
0answers
50 views

i need help from Hong Kong protester, i got a code from HK police behind the window [on hold]

i got a morse code , someone can translate for me , i come from HK. link : https://www.facebook.com/1107747729381260/videos/3027350677292028/ many thanks !
8
votes
4answers
75 views

Practical limits to maintaining coherence in an HF channel

Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve. It would be nice if one could simply take any existing modulation and slow it ...
3
votes
0answers
19 views

What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

I am working on space-ground networking for a Cube Satellite, and one of our candidate Layer 2 protocols is AX.25. We haven't settled on a physical layer, but it's likely to be some form of quadrature-...
2
votes
3answers
63 views

Can a person in Portugal get an amateur radio license in another country?

In Portugal to transmit one must take a cat 3 exam then wait for 2 years to take the cat 2 exam. While this 2 years go by one cannot emit on his station. I find this rather annoying. Is there any EU ...
0
votes
2answers
35 views

Local Relay with static

On our local Relay there are from time to time transmissions, where only static can be heard. Most transmissions via relay can be heard clearly. What could be the cause of this?
-4
votes
2answers
73 views

Wifi inside a rocket

I want to understand, as most rocket uses LAN cable and switches to communicate between stages. Is it possible to replace with WiFi? Although it's will be complex system but one idea to make each ...
0
votes
1answer
51 views

Passive antenna system as a Wi-Fi repeater [duplicate]

I want to extend WiFi signal using a passive repeater between two isolated boxes (have to make both box wireless). Transmitter antenna from box A is placed in the gap between box A and B. In the same ...
3
votes
1answer
55 views

Help understanding transmission loss of trivial circuit

I was trying to DIY a VHF/UHF diplexer, and got some weird readings from the VNA. By debugging I reached this trivial circuit: Which has the following frequency response: I'm trying to figure out ...
1
vote
2answers
61 views

Beam antenna changed directivity

My Hy-Gain TH6DXX antenna has been up on a tower about 20 years, with excellent results. Suddenly, the gain of the antenna is off the side; in other words, when the boom is broadside to the ...
5
votes
3answers
134 views

ARRL handbook as a reference for all your radio learning needs?

Looking to take up learning understanding everything from basic electronics to how today's wideband radios work, so that I can build my own radio systems (not just ham radios), and talk radio concepts ...
1
vote
1answer
47 views

New quad-band mobile receives while transmitting?

I've got a week-old TYT TH-9800, a quad-band (10/6/2/70cm) mobile, Chinese knock-off of a Yaesu HT-8900. So far, I love it -- several times the power of my HT, and a better antenna actually outside ...
2
votes
0answers
32 views

Demodulating ISO14443 (part of NFC) using SDR?

I'm looking for info on demodulating both sides of an ISO14443 communication using a cheap SDR, preferably an RTL-SDR (R820T2+RTL2832U). The application is passively monitoring an NFC exchange for ...
2
votes
1answer
59 views

How much field strength to blow out a receiver?

I was wondering what calculations would need to be performed to find out if a receiver will blow out in the given conditions. Portable AM receiver with ferrite rod antenna 200 ft away from MW antenna ...
0
votes
2answers
91 views

Strong but unreadable signal received on 2m FM voice, transmitter less than 2km away. What could be the cause of the readability problem?

I conducted an experiment today using a prototype copper wire 2m dipole at a ground level base station (noted on images) and a FT2D HT with an SRH77CA antenna. I recorded my transmissions using a ...
1
vote
3answers
104 views

Does the impedance along a transmission line change when there are standing waves?

I know the characteristic impedance can't change because it's determined by the physical properties of a transmission line. But the impedance seen when there are standing waves changes along the ...
1
vote
2answers
41 views

How is frequency selection (tuning) accomplished in a direct conversion receiver?

How is frequency selection (tuning) accomplished in a direct conversion receiver ? A crystal filter can't be used is that correct ? Because there is no IF to mix with the incoming frequency band ...
3
votes
2answers
83 views

What are the advantages for a receiver that uses an IF compared to direct conversion?

What are the advantages for a receiver that uses an IF compared to direct conversion ?
0
votes
2answers
48 views

How should i go about building my first transceiver?

So i want to build my very own transceiver, not looking for anything worldwide, just local but i do have a background in arduino and some electrical engineering, what tutorials would you recommend?
2
votes
1answer
61 views

Do Buried Radials for Vertical Monopoles Need to be No Longer than the Monopole Itself?

This is a rather common belief among amateur radio operators, but is it true? A NEC analysis provides some insight on this concept.
0
votes
1answer
30 views

Using dvb-t device as rtl-sdr

I am wondering if I can use that dvb-t device to listen 48-836 mhz? if it's no, why? thanks..
1
vote
1answer
61 views

Is there a practical way to triangulate a signal?

Around my location, there is an odd signal near 50.145MHz (at this moment it seems centered around 50.14735MHz but that changes as the day progresses). Other amateur radio operators in this city also ...
7
votes
4answers
2k views

What fraction of 2x2 USA call signs are vanity calls?

I found out a while back that, as things currently stand with the FCC, if you take and pass all three license class exams in the same sitting, you get a so-called "two by two" or 2x2 call -- two ...
4
votes
1answer
57 views

How do I evaluate and use a toroidial core for my HF double-balanced mixer?

Last year, I planned to make a double-balanced mixer covering the entire 3-30 MHz band as an upconverter for my RTL-SDR receiver, mainly for learning RF circuits and ham radio. Naturally, it requires ...
4
votes
3answers
82 views

Do resonant antennas actually resonate?

Do resonant antennas actually resonate (in the lumped circuit sense, exchanging stored energy between inductive and capacitive elements at a natural oscillation frequency)? If so, can this resonance ...
4
votes
1answer
346 views

Does an antenna tuner remove standing waves from a transmission line?

Does an antenna tuner remove standing waves from a transmission line ?
4
votes
2answers
175 views

How is a crossed-ellipse display generated from FSK?

What is the algorithm or circuit needed to generate a (vintage?, retro?) crossed-ellipse display from RTTY and/or 2FSK signals? (as per the (obsolete?) questions in some FCC exam pool) (assume ...
2
votes
2answers
61 views

resonance vs resonator in antenna

Resonance in electronic means: reactance of zero. (maybe wrongly/correctly someone's calling the minimum VSWR, the resonance of antenna! and this cause confusion) I've heard in Antenna Design for ...
0
votes
0answers
33 views

Gnuradio loopback flowgraph is not working

I found the below uhd_two_tone_loopback example (which is one of the gnuradio provided examples) and I am trying to run it, it runs but I can't receive signal. EDIT: I mean when I run the program I ...
0
votes
1answer
82 views

Locate a ball 1000 times a second

I want to locate a small ball in the air 1000 times a second. The ball is thrown from the ground and then flies in the air for 0.5 seconds until it lands. Distance from the location instrument is 1 ...
2
votes
1answer
42 views

how to select an SDR stick remotely from gqrx via soapysdr

I have a raspberry pi 3b on my roof (in a plastic box) with two SDR sticks attached to it. On the raspberry pi the "soapysdr" program runs. ...
2
votes
2answers
85 views

Buying used tower

I'm thinking about buying a 70' self supporting tower that I can see had a little rust here and there. Besides minor rust is there anything I should ask the seller before I buy?
9
votes
2answers
124 views

What is the decimal in Morse Code?

The ITU's International Morse Code recommendation ITU-R M.1677-1 specifies a "Full stop (period)" as ".−.−.−", however it falls short of specifying a decimal point. Even the examples, though they ...
4
votes
1answer
120 views

Does a UHF/VHF handheld transceiver kit exist?

I am a licensed ham looking for a UHF/VHF handheld transceiver kit. Unfortunately so far I was only able to find broken links, i.e. Ten-Tec used to produce exactly such a thing but they just don't ...
7
votes
2answers
145 views

Do lightning rods attract or do they help prevent lightning?

I'd read that the current theory of how lightning rods protect a house, antenna tower, or other structure is by preventing lightning from striking -- that is, the sharply pointed rod lets charge ...
0
votes
1answer
91 views

Vertical Antennas

I have just changed from a ground mounted Vertical antenna , to a MFJ-1796 Vertical antenna, due to not having big enough ground to bury as many verticals as recommended. So far what I have found is ...
4
votes
2answers
68 views

How to design constant impedance tracks on pcb

I have designed PCB's in the past, but need to draw a constant 50 ohm impedance track on the project I'm planning. I know the calculations for (for example) a coplanar wave and how to get a straight ...
1
vote
2answers
90 views

If I parallel two crystal filters together, will that double the bandwidth? [closed]

Will the bandwidth be doubled ? And will the impedance be halved ?
2
votes
1answer
93 views

Do these magnetic field measurements of end-fed and center-fed half-wave dipoles corroborate measurements made by antenna experimenters?

Using a sensor and procedure discussed in my article, I made the following plot comparing the magnetic field strength along a 30m-band half-wave dipole fed at center and one end. Key points include: ...
1
vote
1answer
55 views

Controlling the number of samples

In the below simple qpsk_tx_uhd flowgraph I am trying to create a slider to control the number of samples but got a bit confused with which parameter I should be ...
1
vote
0answers
17 views

How to identify the mic connection pins in Heathkit SB-102?

One of the things I need to do to put my Heathkit SB-102 into service is connect a microphone. I've got a suitable crystal mic, with four conductors in the cable -- two for the mic element, and two ...
1
vote
1answer
37 views

Wiring a CW paddle and straight key to a TRS connector?

Some transceivers come with a TRS plug input labeled "key". When wiring my paddle or a straight key for these TRS connector inputs, is there any current standard for which key connection goes to ...
1
vote
0answers
34 views

Error in an attempt to simulate SDR frontend hardware in GRC

I was reading these lecture slides: https://web.mit.edu/6.02/www/f2006/handouts/Lec9.pdf and I tried to implement some of the schematics shown there in GNU Radio. On page 3 the author describes how ...
2
votes
3answers
113 views

Under what circumstances does intermodulation become an issue in a filter after LNA setup?

I'm reading about using software-defined radio for picking up ADS-B signals at 1090MHz. There is this blog which considers (among others) a setup as follows: ...
3
votes
1answer
375 views

What is Spectral Subtraction for noise reduction?

I previously asked a general question about noise reduction, but none of the answers mentioned this specific method or algorithm. (the noise reduction button on some radios and DSP software seems to ...
3
votes
1answer
41 views

UHF cubical quad VNA analysis interpretation

I've designed a two element UHF cubical quad. It was designed to resonate at 385 Mhz. I used 0.1mm thick and 1cm wide copper tape instead of wire to lower the antenna Q. I used PVC electrical conduit ...
4
votes
2answers
74 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 ...
1
vote
0answers
23 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
vote
0answers
63 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, ...

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