# All Questions

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161 views

### EFHW works only on one band - what am I missing?

I tried to build a multiband EFHW antenna as described in articles by PA3HHO, PD7MMA, G0KYA and many others. I decided to start with a short 40/20/(15?)/10 meters version without any loading coils. ...
163 views

### How long would a radio last in storage?

For a modern rig, any rigs that come out within the last 20 years. How long would it last in storage? By that, I mean "dust it off and plug and play". Assume it is in a dry and cool place, without ...
147 views

### Required SSB sideband and carrier suppression?

Is there a legal (U.S. FCC) or a commonly accepted standard requirement for SSB opposite sideband and and carrier suppression for either manufactured or kit built transmitters? Does the 43+ dB down ...
135 views

### Why have knife switch storm grounds for antennas vanished?

Long ago, it was fairly standard to provide lightning protection for outdoor radio antennas by installing a large double-throw knife switch -- antenna leads to the center, radio on one side, ground on ...
56 views

### Trouble with osmocom source

I'm having trouble running a simple flowgraph with an osmocom source and a qt gui sink. If I run the file with a waveform generator instead of the osmocom source, all is well, the plots appear as they ...
48 views

### Unusual modulation

I've been writing a SciFi story, and it calls for something very unusual to happen. I'd like to check this idea for plausibility, but as I'm not a radio ham myself, I don't know if this already exists ...
52 views

### Microwave kiln for glass [closed]

I am building a 1000W microwave kiln for glass jewelry. The internal capacity needs to be around 5 litres. What internal dimensions of the cavity should I avoid, or strive for, to ensure even heating....
98 views

### How to make simple AM detector using an LED?

I'm new to amateur radio, and as a beginner project, I wanted to use some of the basic components I have to create an AM receiver. Anyway, what I'm trying to do is create a simple AM receiver that ...
54 views

### What should I take into consideration when choosing a new antenna? [closed]

I am trying to choose a new antenna for the HackRf One, but there are several variables to consider, such as the frequency, threading, resistance etc. In general, what things should I take into ...
96 views

### Can a WiFi antenna be used for other 2.4 - 2.5 GHz applications?

I am looking for a few long range antennas that can pick up signals from recreational drones in the 2.4-2.5 GHz range. I have done a lot of looking online and most of the results I find are for WiFi ...
169 views

### Voltage vs. Current Balun for Dipole

I'm a new radio amateur setting up a half-wave 10-meter inverted vee antenna fed by 50 ohm coax. I understand that the inverted vee lowers the normal 72 ohm dipole closer to 50 ohms, so I only need to ...
145 views

### How is working on DC high voltages as in a tube radio different from 120VAC?

Suppose that I am familiar with the safety procedures for working on 20 A 120 VAC 60 Hz household lines. What should I be prepared for before working on high voltage DC circuits (say, 800 volts) as ...
54 views

### Need help understanding the gain on antenna pattern plots

My understanding is that the value of the axis (like -10 / 0 dB) refers to the maximum antenna gain (e.g. 12dbi). So, if a ...
49 views

### Understand Radio Pattern of a WIFI antenna

I have a Fortigate AP, and need to understand its radio pattern for optimal positioning. I've already understood the E-plane and H-plane representations and also that number on the circumference of ...
61 views

### Heathkit SB-102 Plate Current out of control

I bought a "technician special" Heathkit SB-102 transceiver. Everything seems to work well until I attach a dummy load and try to go through the "initial tune up" procedure in the manual. At the ...
65 views

### How does the height above ground of a VHF/UHF receive antenna affect the r-f voltage at its output terminals?

It is commonly known that greater antenna heights usually improve the performance of these point-point terrestrial paths. Here's a NEC study showing the relationship of receive antenna height AGL to ...
53 views

### Somewhat-directional (cardioid?) antenna for receiving ADS-B?

I recently set up my own RTL-SDR-based ADS-B receiver. I live in a Manhattan high-rise with an eastern view, so I do not get any signals from behind the building (almost: I get the occasional ...
85 views

### Mismatched Radios: A Baofeng UV-5R & a Cobra ACXT 645 [closed]

I've got a Baofeng UV-5R and a Cobra ACXT 645, and I'm trying to get them to communicate. The Cobra transmits and the Baofeng (programmed with CHIRP) receives, but not the other way around. I've ...
62 views

A single inductive loading coil in a vertical or a pair of loading coils in a dipole are commonly used to match a given total antenna length parameter to a given frequency wavelength (where the ratio ...
46 views

### advice needed for balanced line terminals

I am designing a portable antenna with a radiating element and a balun that are not close to each other. The impedance has been designed to be close to 50 ohms. ...
97 views

### House wiring as an antenna on HF and 2 meters?

The apartment I live in is a 1970s type without access to the outdoors. It does have a balcony. A 2m transceiver is the only radio which will enable me to reach the ham world. Would be possible to ...
74 views

### How do I design a dual band LPDA antenna?

Im not sure if this is the best place to ask a question like this but its the best place i could find. My goal is to build a dual band antenna similar to this one. That covers ...
67 views

### Frequency Display for Old Tube Radio

I have a Hallicrafters S-120 1960s vintage vacuum tube receiver (an "All American Five" superhet with solid state rectifier replacing one of the "five" tubes). It works well, doesn't have excessive ...
38 views

### What's the issue with stainless steel antenna elements? [duplicate]

New ham, here...getting motivated to build some antennas to experiment with and so far my research has shown that stainless steel is not a desirable metal for creating antenna elements - which is a ...
60 views

### Can I connect a 75 ohm antenna to a 50 ohm radio?

I have been looking for an affordable yagi antenna to use with a dual band handheld radio and I came across some very inexpensive VHF/UHF (HDTV) antennas. They are all 75 ohm though. Is it ok to use a ...
92 views

### Audio being sent over ground pin on audio jack

I just bought a QYT KT-8900D mobile radio. One of the first things I've noticed is that I cannot use my mixer to completely lower the volume of the radio's 3.5mm TRRS output. When the fader is all the ...
88 views

### What type of antenna is this?

I have very little knowledge about antennas (I just read about simple dipoles and monopoles recently) and I need to buy a directional antenna for my wireless device. I have found a cheap antenna (I ...
709 views

### Why is my calculation for added length of coax for a double cross antenna different to everyone else's?

I'm an amateur amateur radio enthusiast finally building my own antenna, and have decided on a double cross antenna, with the goal of pulling data from NOAA satellites. Four coax cables, two of ...
57 views

### Relative computational requirement for various digital modes?

What might be the relative computational performance requirements for the various popular digital modes? (FT, JT, WS, PSK31, etc.) I seem to recall FSK modulation/demodulation being done with 1 or so ...
31 views

### Propagation Analysis with WSPR / RBN

I would like to analyze data from the Weak Signal Propagation Reporter (WSPR) and/or the Reverse Beacon Network to understand the propagation mode(s) of the recent welcome spate of CW and SSB contacts ...
63 views

### No module named 'analog_swig' [duplicate]

I know guys you gonna tell me tat there is something wrong about GnuRadio or Pybombs installation. Well, this is my third time during the past 48 hours I reformat the OS of my mini pc fitlet2 mint ...
113 views

### Can I capture stereo IQ signals from WebSDR?

When I set my sound device to record from the monitor/loopback source, I can capture the signal from WebSDR in my browser in an application like Audacity. Looking at the captured signal more closely ...
75 views

### Where did the LP to BP transformation $\frac{\omega ^{2}-\omega_0^{2}}{\omega\cdot BW}$ come from?

I'm not sure this question is appropriate for this site, but I feel that if anyone knows about a filter, a radio ham knows! And as a ham myself I feel I need to understand this important area better. ...
74 views

### Better SWR bandwidth

Good day, I have a Kenwood TS-480HT with a Wolfriver coil and a stainless steel whip in my car. I find that on 40 meters I can get the SWR at around 1.4 (using an MFJ 269) at 7.1000 MHz. But the SWR ...
55 views

### SDR as an oscilloscope

Can a SDR be used as a general purpose AC oscilloscope with appropriate attenuation at the front end. Have in mind a capacitor to block DC voltages, large resistor say 10 Mohms to limit current and ...
119 views

### Is it possible to have multiple people talking on the same radio channel at the same time?

I understand that my question is not desireable for ham radio communication at all, but bear with me. I want to use long range walkie talkies whose microphone is attached to an underground acoustic ...
106 views

### How does a Faraday cage block an EMP?

If you search the Internet for Faraday cages, you'll find a lot of information about using homemade cages to protect radios from EMP damage while in storage. A lot of that information is either ...
42 views

### No module named _osmosdr_swig [duplicate]

I am trying to run GnuRadio python code in my python web server and got the "No module named _osmosdr_swig" error. Please, what is the cause for this error? I know it sounds like so obvious that I ...
51 views

### Can my neighbors ham radio station be preventing my TV antenna from proper reception? [duplicate]

I have a winegard 8200 series antenna and it worked flawlessly in getting me reception of more than 70 stations. The wind blew it down and I couldn't replace it for about 6 months due to the fact that ...
238 views

I encountered with the "No module named 'gnuradio'" error while I was trying to run GnuRadio python code in my python web server. And this is my gnuRadio generated code: ...
74 views

### How should two loopstick antennas be placed w.r.t each other to maximize transmission?

An engineer working in the RF industry told me something which left me very confused: He said that a pair of emitter-receiver beacons get the clearest signal when loopstick antennas in the receiver ...
118 views

### Merging gnuradio generated python code into the Python web server

I am trying to figure out how I control a Software Defined Radio over a network, and stream the received baseband samples from my remote hardware back to the gnuradio. What I'm trying to do here is, ...
189 views

### Will transmitting on this antenna cause problems?

Inspired by this discussion, I wanted to check if this is something I can get away with. I've got an old FM Broadcast antenna that came with a home stereo receiver -- it's 75 ohm flat cable, in a T ...
90 views

### Why does no one use a Buddipole as an Inverted V?

I have been looking at the Buddipole, and I've seen the most popular configuration is as a standard dipole with the arms parallel to the ground. I've also seen it configured as an upright V, as well ...
72 views

### Presumably working FT-8900R doesn't turn on. What can be a reason?

I bought a pre-owned Yaesu FT-8900R. Sadly turned out that the radio doesn't turn on. When I hold the power button (the right bottom one) the speaker pops briefly but nothing else happening. The ...
79 views

### Simple Gnuradio TX/RX loopback example/tutorial

I'm looking for some sort of simple and a beginner level instructions on how to build TX/RX loopback flowgraph using GnuRadio software and B200 USRP with an attenuator FW -10 + 10dB. Kindly, help me ...
26 views

### Unsure how to assemble Shakespeare SSB antenna; not working [closed]

Have 23 foot Shakespeare SSB antenna. Can not connect through the side feed termination band? Antenna not working? What is the band supposed to look like? Is the termination band supposed to be ...
728 views

### VHF 50 Ω Antenna Over 75 Ω TV Coax

I have a 50 Ω VHF airband antenna which I’m planning to install in my loft, for use with a RaspberryPi-based RTLSDR scanner/receiver. I already have a UK-standard UHF/Freeview antenna using standard ...