# All Questions

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1answer
95 views

### How hard to send files [duplicate]

How hard and expensive would it be to send a file from my house in London to a coastal area in Spain? It would most likely be software I want, so it must transfer perfectly, however if it is feasible ...
1answer
72 views

### What are the parameters and necessary features of a Gunn diode oscillator cavity?

There are a ton of old USSR Gunn diodes available on ebay and I'm looking for a cavity that can make use of them. I am willing to machine one myself if necessary, but I'm unable to find any decent ...
2answers
141 views

### Restricted line-of-sight communication

Why do line of sight communication links have a restricted range for a given tower height? Is it only because of the Earth's Curvature?
2answers
423 views

### Multiband vertical antenna not working as expected

I built a vertical out of a 5M aluminium pipe. It tunes fine (and wide!) on 20M. I decided to add a loading coil to operate it on 40M, and it also worked fine, albeit not so wide. While I was at it, I ...
1answer
143 views

### Dominant speeds of Morse Communications

5 wpm is easy to learn and better than nothing in emergency. Speed Morse Coding is fine for "sport competition" I am trying to find out which is the typical speed for what I call "conversation" and ...
1answer
132 views

### What are the effects of a ground plane under a horizontal dipole?

What are the effects on signal propagation if this ground plane is just a metal object and what are the effects if the ground plane is actually grounded? I am asking this question because someone ...
0answers
73 views

### Uplink-limited vs. Downlink-limited

What is the definition of these terms? Would a system with signal to noise ratios of uplink 100dBHz and downlink 80dBHz be downlink-limited?
0answers
61 views

### Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

If I'm building a vacuum tube HF transmitter (say, 40 m band), obviously the simplest mode to build is CW; it's common to key the oscillator input to the final (in order to keep the oscillator running ...
1answer
56 views

### How narrow-band can a DVB-S2 signal be?

Using software defined radios I can generate and demodulate a DVB-S2 signal live. I'm wondering if I can use this to send single pictures over the air using as narrow BW as possible. Using QPSK and a ...
3answers
707 views

### Impedance ratio vs. SWR

The specs of the Elecraft T1 tuner say, that it can match a 10:1 SWR. What does that mean in terms of impedance ratio? What antenna impedance can it match to 50 Ohm then? Or is it not that easy?
2answers
78 views

### Voltage wave in transmission lines

The solution for the voltage in a transmission line can be written as: $$V(z) = V_o^+ e^{-jkz} + V_o^- e^{jkz}$$ The voltage $V(z)$ is the difference between the conductors of the line at a certain ...
0answers
58 views

### Building a ray tracing path-loss propagation model of LTE for small cells (pRRus) [closed]

Phones will receive signal from many pRRus. Should I average the antenna gain and all the path-loss (both line of sight and no-line of sight)? Or should I sum them all together?
2answers
171 views

### Can I use a amateur license to experiment with radar?

If I get a German Amateurfunklizenz, will I be allowed to experiment with non-communication radio technologies like radar? Obviously, I'd still adhere to using allocated ham bands, stay within power ...
1answer
160 views

### Can I use CHIRP for programming a Baofeng DM-5R?

I can't find my Baofeng DM-5R in the CHIRP list of supported radios. I've been told that I should try by telling CHIRP to assume a different radio from the DM-5R - perhaps the UV-5R!? Do you know if ...
0answers
58 views

### Are jammers relate to electronics or electrotechnics , why? [closed]

Are jammers relate to electronics or electrotechnics , why ? Please ,tell me the main difference between electronics and electrotechins and why we can classify jammers as electrotechics or ...
3answers
147 views

### Only noise, no signals whatsoever on HF

Last night there was a power outage at home. I was able to see a LOT of stations on 20M (FT8). As soon power returned, all of them disappeared. You can see in the waterfall very clearly when power ...
1answer
91 views

### Mounting antenna on a metal structure? Tower/Antenna insulator?

If an antenna needs to be mounted on a metal structure what would be needed to avoid interference? Are there just some specific length to avoid or it is better to be separated by some insulator? As I ...
1answer
66 views

### My radio and audio output keep changing using WSJTX on FT8

TL;DR Laptop keeps switching between Signal Link audio output and speakers. Problem goes away when I turn TX knob down far enough on Signal Link. I just bought a SignalLink and have it connected ...
1answer
132 views

### help identifying a vacuum tube

I recently bought this tube for use in an art project and would like to know what it is and what it was originally used for. Unfortunately, the silkscreen labelling on the glass envelope was worn off ...
2answers
70 views

### Matching a 188 ohm antenna to an unbalanced input that expects a 50 ohm antenna

I am new to RF field and trying to use an Archimedean Spiral Antenna design from this paper to capture 915MHz RF for the P2110B power harvester chip. The estimated antenna impedance is 188 Ohm (see ...
2answers
552 views

### How much current can Baofeng UV-5R provide on +V pin?

I noticed that the pinout for cheap Baofeng connectors has +V available. I'm interested in powering some electronics directly from this connector. When unloaded, this seems to have about 3.3V on it, ...
2answers
148 views

### Is there any practical advantage to a parabolic reflector over a high-gain beam antenna?

I've been looking at options for a high-gain directional antenna recently, and I've noted that there are commercially available parabolic antennae for the shorter bands -- specifically 70 cm, with an ...
1answer
632 views

### Difference between antennas for Wi-Fi vs. ham repeaters

I understand that Wi-Fi transmits on 2.4 GHz or 5 GHz whereas local ham repeaters transmit around 147 MHz or 450 MHz. What differences would be needed in antennas tuning into either of these ...
1answer
73 views

### Should I run RG8x / mini8 zip tied to a cat 5e ethernet cable?

I'm running a feed line from the end of my amplifier to the antenna for HF transmissions. I'm using RG8x / mini 8. There's an existing pathway through my house I'd like to use that has a cat 5e ...
2answers
155 views

### Bad squelch on a TYT MD-380: user error or hardware?

I have a new TYT MD-380; it works well for DMR channels, but on analog, the squelch doesn't seem to open when it should. I'm relatively new to ham and my first suspicion is user error, but it's ...
1answer
64 views

### SWR characteristic changes when lifting coax off the ground?

I was at Anaheim HRO and few guys there were talking about an MFJ all band vertical antenna that does not need radials. I forget what model number it is but it is one of those "wife pleasing antennae" ...
1answer
137 views

### Would a ham license allow me to use an uncertified radio on other (non-ham) bands I have permission to use?

I just purchased a UV-5R to hopefully integrate into business class radios my company uses. Do I need a technician or other class FCC license to operate these only on the frequencies I already access ...
2answers
95 views

### Pi Matching circut for tube PA - what values?

I am working on my 80m and 40m CW transmitter and ran into a problem: I need to match the high impedance of PL504 to 50ohm coax, a Pi match seems to be the best, but I don't know how to calculate ...
3answers
221 views

### Is there a public standard for 8 and 10 character grid locators?

We have a question about the algorithm for conversion from coordinates into grid squares here, and this is an extension of that. I've noticed that there are several web-sites (for example here, or ...
3answers
185 views

### Passively reducing ground loss?

Would a disconnected wire or conductive mat below a low height antenna reduce ground losses? A tuned length of wire under a wire antenna might be suitable for NVIS gain. But would a bunch of space ...
2answers
106 views

### Does scanning take much more battery than listening on one channel?

I have a couple of HTs with channel scanning features. I imagine setting the radio to scan mode takes more power than just listening to a single channel, but what rough order of magnitude? Will I lose ...
1answer
43 views

### How to record fixed number of samples in gnuradio

Is it possible to set a gnuradio flowgraph to record with a File Sink a fixed number of samples? I would like to use this wave as a reference. Thank you!
1answer
105 views

### Double power-handling ability of RF amplifier output transformer

I want to base the output network for a 500W push-pull HF amplifier on "A 250W Broadband Linear Amplifier" described in Chapter 17 of the 2014 ARRL Handbook. I need advice on whether and/or how the 1:...
2answers
95 views

### What types of materials increase the inductance of a coil when inserted inside it?

I'm asking this because of the comments in this answer, that imply that steel (mostly iron) has similar characteristics to ferrite. Specifically, it is implied that inserting solid steel into a ...
1answer
66 views

### How to match crystals using NWT?

I want to build an ladder SSB filter using 8 MHz quartz resonators. I don't have frequency meter but I have NWT-70. How can I match crystals to build a good filter? What kind of parameters should I ...
2answers
265 views

### How do I listen to the amateur radio satellites?

I'm new to amateur radio, and I would like to listen to those satellites in the orbit. Where do I start? What types of amateur radio satellites exist?
6answers
271 views

### Are transmit antennas the same as receive ones?

Are transmit antennas the same as receive ones? I am making a extended Wi-Fi comms CCTV camera.
3answers
209 views

### Do I have to disconnect antennas during thunderstorms?

lightning damage can be extensive and costly, its even life-threatening. If I have properly grounded the equipment and have a Surge protection device, do I have to disconnect the antennas during the ...
0answers
36 views

### Looking for a formula used by VE6YP trap calculator

I wonder whether the source code of VE6YP (Tony Field) coaxtrap design program (link 1, link 2) was ever published or described. As a Mac user I'm having little difficulties using this software and I ...
1answer
205 views

### How come wifi repeaters aren't just amplifiers?

Not sure if in scope for ham SE. I'm very new to this. Most wifi repeaters contain an actual router and two radios set up to receive and transmit at different frequencies. Why can't we have a wifi ...
3answers
415 views

### What is the proper way to electrically wire in a loading coil to a vertical antenna?

I am trying to put together a vertical pole style antenna with a loading coil housed at the base using a plan very similar to the one described in this ARRL article. I am trying to understand how to ...
0answers
48 views

### Qt application freezes after a fixed time period

I have an Ettus E310 from which I send some data via ZMQ to a computer. On the remote computer I am running a Qt GUI in which I am displaying a FFT and a variable. After about an hour, the GUI needs a ...
1answer
49 views

### Find the right COM to setup Winlink

I managed to successfully install Winlink on my Ubuntu operating system but it is not completely functional yet. I don't know which COM my computer is set up to use, and there are a lot of them ...
3answers
243 views

### Testing blind license applicants

My friend is blind and would like to take the amateur radio license exam. I understand that the question and the four possible answers can be read to them, and that is fine. The one question that we ...
1answer
53 views

### Measurements in far field for radar cross section

I have to measure the S parameter for a rectangular sample with an antenna that works from 2 to 18 GHz. I need to measure a large band from 5 to 15 GHz and I have a problem with the known F.F. (Far ...
2answers
69 views

### Will close-loop metal hangers affect antenna radiation?

I'm working on a kite-supported antenna for an 80m QRP rig -- to be flown at beaches, on mountaintops, and possibly other places where I want to work HF but don't want to lug poles or give up ...
6answers
319 views

### Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka “antenna tuner”)?

I will soon need an antenna impedance match (aka "antenna tuner"), because I'll initially only have a single antenna for my HF rig (needs to cover 80m, 40m, 20m, 15m, and 10m). Obviously, in order to ...
3answers
164 views

### Give vertical antenna directional gain?

So here is a strange thought. If a vertical electrically speaking is a half dipole with the other half as a ground plane to balance out. Perhaps there are ways to make equivalent director and ...
0answers
59 views

### Parasitic inductance of relay contacts

I need to switch a bank of filters operating on bands from about 2MHz to 30MHz. The parasitic series inductance of the relay contact system will have an effect on the performance of my system. ...
1answer
56 views

### Unitrunker Receivers Not Displaying Fields

I've been playing around with RTL-SDR and Unitrunker attempting to get a police scanner working. I followed the tutorial here: https://sites.google.com/site/policescannerhowto/ Everything works as ...

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