# All Questions

2,299 questions
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 ...
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 ...
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 ...
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 ...
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)...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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, ...
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.
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. ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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'...
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 ...
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 ...
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.
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 ...
69 views

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?
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). ...
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 ...
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 ...
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-...
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) ...
214 views

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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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" ...
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 ...