All Questions

0
votes
0answers
3 views

Why my new RTL-SDR dongle does not work with GQRX? [migrated]

I just bought a new RTL SDR dongle, so I was excited to test it immediately. So, I installed the drivers on ubuntu 18.04 and i tested it using rtl_sdr -t command ...
5
votes
2answers
1k views

Is it legal to transmit with HackRF one?

Is it legal to transmit using HackRF one (in Germany), the purpose is to do some Lab research and Academic experiments. for example i want to broadcast an FM signal using HackRF one and try to ...
1
vote
0answers
32 views

DVMega / DVDongle with a TNC connection to radio

What I want to do is add digital voice (DMR, D-Star, Fusion) capability to an existing dual band mobile or HT. Similar to adding APRS functionality using APRSDroid and a bluetooth TNC. Reading here, I ...
2
votes
1answer
74 views

Can my laptop pick up CB radio frequencies?

I was on my laptop watching a show and I paused to look something up and since there was no sound I could hear a voice talking. It sounded distorted like it was coming over a radio and I couldn't make ...
0
votes
1answer
42 views

Is there any way in which elevation *does* affect medium frequency (AM radio) transmissions?

This is a followup to this question of mine. From reading the wiki article, I get that: Radio waves at MF wavelengths propagate via ground waves and reflection from the ionosphere ( called skywaves)...
1
vote
3answers
117 views

Finding an Intuitive Explanation of Mixer Theory

I don't know about you guys, but I've always been somewhat confused by fundamental mixer action. I've always been left unsatisfied by the standard trig identity explanation as one that's a tad too ...
1
vote
2answers
52 views

Ground radials: Electrical difference between 14 gauge and 18 gauge? Lifespan difference?

I am starting the process of installing a vertical ant (6BTV) and radial ground system. I am ready to buy the wire. I would like to know if there is an electrical difference between 14 gauge and 18 ...
3
votes
2answers
60 views

It it really useful to terminate unused 75Ω outputs on a coax splitter?

When discussing improvements to my home HDTV Antenna/distribution system a colleague brought up the need to terminate all coax, even unused splitter ports. My understanding of the way terminator ...
0
votes
5answers
62 views

Are cold temperatures harmful for ham radio equipment?

I'm getting ready to build an HF / CW kit and just finished setting up a workbench in my garage. While I was wrapping up, I started wondering if the cold temperatures this winter might be harmful to ...
3
votes
5answers
54 views

Gain difference between half-wave and infinitesimal dipole?

In discussion around another Q&A here, Glenn W9IQ commented: The directive gain difference between a half wavelength dipole and an infinitesimal dipole is only 0.39 dB I'm curious where this ...
6
votes
3answers
89 views

What should I put on a QSL card for a repeater contact?

From time to time I'm a new ham's first contact - usually on a repeater. If I want to send the new ham a QSL card, how should I distinguish a repeater contact from a non-repeater contact? Is there a ...
5
votes
2answers
104 views

Can this 960 MHz CelWave fiberglass antenna be retuned for the 70cm band?

I recently inherited a CelWave fiberglass antenna pictured below. It is marked that it's for 959.9875 MHz. The model number appears to be either 339 or 359. It is 96 1/2 inches from base to tip. I ...
3
votes
2answers
84 views

Impedance matching: Why do components behave totally differently from theory?

I got stuck with impedance matching for an antenna. Any added components in the matching network gave a result totally different from what a Smith chart predicts. Let me explain this clearer. First, ...
-4
votes
0answers
32 views

About WiFi antenna on outside TV antenna on RV

How do I put a WiFi Booster Antenna on the TV antenna on my Motorhome. I will then be able to rotate the beam antenna for the best signal for my devises. Thanks from N5CHW.
0
votes
1answer
27 views

Can timing information be used to compress data for LoRa transmission?

I have a course challenge. It involves calculating an FFT of an audio signal of 2 combined frequencies (up to 20KHz) then sending it over LoRa through to a fixed receiver. There will be an interferer. ...
1
vote
2answers
60 views

Wiring questions: grounding, attic antennas, BNC connectors

I am upgrading from an HT to a Kenwood TM-V71A. Yay! But this means I need to install some antennas and run feed lines into my shack. I'm going to be installing antennas in my attic (the feed lines ...
4
votes
1answer
66 views

How do I have a full signal of noise on a handheld?

I'm new to ham (although I've had a license for a long time) and I'm having issues with receiving on a basic handheld. I have a cheap BaoFeng UV-82HP and I keep getting full signal noise at random ...
2
votes
1answer
28 views

In HLDC framing/Bell202 encoding, are the flag bytes NZRI encoded?

I have previously implemented an APRS transmitter from scratch by manually generating the modulated sine wave. In this implementation, I did NZRI encoding over the entire packet (including postamble ...
1
vote
2answers
100 views

Can I reflect a radio wave by receiving it with one antenna and then sending it back out with another?

An outside source is broadcasting an RF signal at 406 MHZ. I want to know if it's possible to receive this signal with one antenna, and then simply send the signal to another antenna that sends it ...
1
vote
1answer
61 views

Repeater for 1/4 square mile campus

I am a noob to a lot of amateur radio and I am investigating and planning a repeater setup to be installed in my workplace. We are on a hospital campus in Chicago, IL and have many tall buildings ...
1
vote
2answers
66 views

Repeating UHF Handheld via UHF vehicle transceiver

I have recently taken on programming radios for my workplace in Chicago, IL. We have an old base station (Kenwood TK863G-1) that I wanted to know if it would be possible to use as a repeater similar ...
-4
votes
2answers
46 views

Transmission distance of PSK31 on various HF band [closed]

Would appreciate insight on efficiency of PSK31 on various HF band. Would 300 to 1000 km generally achievable if suitable band are chosen, according to day night and sun spot cycle using low power ...
0
votes
2answers
80 views

If one were to add reflector elements above and below a dipole would it change the direction to horizontal?

Since adding a reflector and a director horizontally to a dipole (as in a three element Yagi) causes the beam to reflect horizontally, what should happen if reflectors above and below the dipole were ...
2
votes
1answer
71 views

Stacking DB8 “bedsprings”

I'm trying to receive a UHF TV signal 86 miles away. Considering the height of the transmitting antenna and the height of the receiving antenna, I should be able to just make line-of-sight between ...
4
votes
2answers
93 views

100MHz to 1000MHz Antennas for Transmit and Receive

I am building a ground and wall penetrating frequency modulated continuous wave radar. The only components that I have not been able to track down are the antennas. I need two antennas (one for ...
2
votes
1answer
81 views

Power Amplifier Balun Question

Second (and last hopefully) question on the classic Solid State Design for the Radio Amateurs (SSDRA) book by Hayward et al. Again it's a power amplifier circuit (Chapter 4, pg. 66), and again it's ...
2
votes
2answers
158 views

Using approximate signal strength at a distance to estimate reception strength of a radio station

I have some historical data on radio stations, but unfortunately, the dataset only has these variables: the power of the transmitter, in watts the coordinates of the radio tower Unfortunately, I don'...
3
votes
1answer
53 views

Running mag loop feedline INSIDE the loop tube

We are building a 4 ft diameter mag loop using 1" copper tube. The coupling loop will be at the top of the loop (we are using a large vacuum cap in a weatherproof box and it is too heavy to be ...
3
votes
1answer
79 views

Radial length for vertical antennas?

I plan on installing a vertical antenna soon. I expect it to cover from 80 meters to 10 (or perhaps 6). I plan on putting down 32 radials. I am wondering if 16 66' and 16 33' radials will be just ...
1
vote
2answers
77 views

antenna theory for beginners [closed]

I am new to amateur radio and am having trouble getting my head around antenna theory. Can anyone suggest a good 'introduction to antennas' that doesn't get too technical? Thanks.
4
votes
1answer
70 views

A question about callsign formats

I just passed my technician exam (yay!) and received my callsign from the FCC (KC1KHV). I was surprised by the two letter prefix, which seems to come from the class D group. According to the FCC ...
4
votes
1answer
69 views

Do Loading Coils Supply “Missing Degrees” to Electrically Short Radiators?

References are made on this and other websites to the effect that loading coils can/will supply "missing degrees" to electrically short radiators. But do they?
1
vote
2answers
74 views

Using a common-mode choke on symmetrical antenna system

I am curious as to what happens to a symmetrical dipole center-fed with balanced feeder-line. Let's assume the dipole is arranged as a sloper - that means it's not parallel to ground (horizontal). ...
7
votes
3answers
345 views

Understanding power supply requirements

I have a basic question about power supply requirements for typical transceivers. I'm looking at the specs for a Kenwood TM-V71A, which is a 50W mobile transceiver. I figured that a 50W transceiver ...
9
votes
3answers
175 views

Capacitive hats on wire dipoles?

Capacitive hats seem to be advertised as an option for mobile vertical antennas. One mentioned advantage is the they can widen the SWR bandwidth, making the antenna easier to tune. What might be the ...
2
votes
1answer
62 views

What does co-phasing of cross-polarized antennas mean?

I was working with the 3GPP release 14.6, and it mentioned that modern communication systems have cross polarized antennas, and in order to perform beam-forming we need to co-phase our pre-coder. Pre-...
2
votes
2answers
97 views

Deep-cycle marine battery life question

I just installed a brand new deep cycle marine battery. It goes thru a charger-inverter and will switch over automatically if the power goes down. My question is what to do with the other two (old) ...
2
votes
2answers
214 views

78.5MHz AM receiver self-oscillation

Circuit appears to be working but very easily breaks into oscillation - sometimes just getting up from my desk triggers it, or while tuning, and sometimes after a few seconds with no disturbance that ...
4
votes
2answers
52 views

What are the effects of different feed-line incidence angles?

Consider a dipole antenna fed by a coax (say, longer than the antenna) with a signal reasonably close to the dipole's resonant frequency. Various sources say that the feed-line should approach the ...
2
votes
1answer
63 views

Receiver using a NE602 oscillator-mixer not working

I built a CW receiver using NE602 for the 20m band. Unfortunately, I do not receive any CW or SSB signals, only some noise and sometimes broadcast stations. The schematic here shows the circuit that ...
1
vote
1answer
38 views

FTDX3000D SWR Meter

I just bought a Yaesu FTDX3000D and would like to see the SWR. Is it possible to display the SWR on the FTDX3000D? If so, what menu option would that be? I'm not finding it. I searched for this ...
2
votes
1answer
36 views

Wire dipole antenna proving ground / test bench

i am considering building two movable (concrete base with wheels) non metallic poles with hooks every ten centimeters or so, in order to test wire dipoles of various sizes at various heights with an ...
2
votes
2answers
56 views

Effective area of a dipole

Effective area of a dipole is $\lambda^{2}/4*\pi$. Consider 1 GHz em waves. Consider two antenna of length 15cm ie half wave length and 1 cm. Both have same effective area. This is very non-intuitive ...
3
votes
3answers
347 views

The right antenna size

I'm preparing for the USA Technician exam and I was reading in the manual that the ideal size for a dipole is following this strange formula: 1/2-lambda. But based on what I read after, it seems it ...
1
vote
2answers
66 views

How Can I Remove a Password From a TYT MD-UV390 (Non-GPS)?

I just purchased a TYT UV-390 (Non-GPS) on Amazon. It arrived, I unboxed it and charged it and turned it on and it's asking for a password. The same goes if I try and read or write to it using CPS ...
6
votes
5answers
155 views

Are there formulae to calculate capacitance and inductance of an antenna?

How to calculate internal impedance of a dipole antenna? Its resistance has two components ie wire resistance and radiation resistance, both these can be calculated using formula. Are there formula to ...
7
votes
2answers
110 views

What is the purpose of the transformer at the input (and output) of this RF push-pull amplifier

Firstly, feel free to move this to Electronics SE if it's not on-topic, but it's strongly related to ham radio and RF circuitry. Reading Hayward's classic "Solid State Design for the Radio Amateur" ...
0
votes
0answers
38 views

Are there audio cables for sale to connect e.g. a Baofeng UV-5R to a computer? [duplicate]

I'm referring to this connector with one 2.5mm and one 3.5mm socket. I found this on how to make one, but I would have thought they'd be for sale in a compact form at a decent price. (also the one I ...
4
votes
3answers
164 views

Efficiency of short dipole receiving antenna

For a transmitting dipole antenna, its length is important. If it is close to half the wavelength, it will be efficient and most of the input power will be radiated. How important is the length of ...
6
votes
3answers
104 views

What exactly is a “balanced modulator”?

While studying for his U.S. General class license, my son wondered about the "balanced modulator" referred to by a few questions in the FCC pool. Quoting KB6NU's General Class study guide to give a ...

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