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4
votes
0answers
58 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 ...
2
votes
1answer
48 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 ...
7
votes
3answers
685 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?
2
votes
2answers
76 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 ...
1
vote
0answers
56 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?
6
votes
2answers
160 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 ...
4
votes
1answer
107 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 ...
1
vote
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 ...
5
votes
3answers
133 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 ...
1
vote
1answer
90 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 ...
1
vote
1answer
47 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 ...
6
votes
1answer
124 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 ...
1
vote
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 ...
7
votes
2answers
525 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, ...
5
votes
2answers
108 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 ...
2
votes
1answer
624 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 ...
2
votes
1answer
72 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 ...
2
votes
2answers
99 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 ...
1
vote
1answer
60 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" ...
2
votes
1answer
129 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 ...
4
votes
2answers
91 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 ...
6
votes
3answers
199 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 ...
7
votes
3answers
180 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 ...
8
votes
2answers
105 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 ...
2
votes
1answer
41 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!
7
votes
1answer
81 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:...
8
votes
2answers
91 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 ...
1
vote
1answer
62 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 ...
3
votes
2answers
254 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?
1
vote
6answers
257 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.
1
vote
3answers
165 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 ...
1
vote
0answers
33 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 ...
2
votes
1answer
204 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 ...
5
votes
3answers
273 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 ...
0
votes
0answers
46 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 ...
3
votes
1answer
47 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 ...
12
votes
3answers
235 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 ...
2
votes
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 ...
1
vote
2answers
66 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 ...
6
votes
6answers
269 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 ...
3
votes
3answers
140 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 ...
1
vote
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. ...
1
vote
1answer
55 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 ...
3
votes
3answers
146 views

How to splice RG-174 coax?

I'm pretty good at repairing broken regular coax, but I recently had an RG-174 cut and it's too small for me to solder the center wire and keep the braid away from it. What's a good way to do this? ...
3
votes
2answers
77 views

Determining whether signal meets the 12 dB SINAD voltage

The specification for a certain radio receiver says: Typically 12dB SINAD NBFM for 0.15uV at 145MHz. If I understand correctly, this means that the received radio wave should have a voltage level of ...
2
votes
3answers
92 views

Weakly directive VHF/UHF antenna

Most resources around the internel discuss common antena types, classifying them between directive (like Yagi) and nondirective (like a simple dipole). Directive antennas are good when you know from ...
1
vote
3answers
52 views

Temporary/Portable station coax pl259 connector water proof?

Currently, I am running a semi-portable setup at home. I have a spool of 100ft of lmr400 coax outside in the porch where it free from most weather and rain. I only drag it out to the yard when I am ...
2
votes
1answer
65 views

Why SWR significantly changes with adding 10-30 meters of coax in presence of RFI choke?

I've build a verical for 40M band using a fishing rod as a mast, 6 radials and an RFI choke (FT240-31 ring, 8 turns of RG58, W1JR winding according to the article by Steve Hunt). When I measure SWR ...
2
votes
6answers
2k views

Is this strange Morse signal type common?

I, just as a hobby project, am writing a program for decoding Morse code. I am not a ham, but generally interested in radio and programming. I have a first version of the project, but it failed to ...
3
votes
2answers
156 views

Can I use a 1:1 current balun to feed a 1/4λ vertical?

I have an LDG RBA-1:1 current balun, and I was wondering if it behaves as a common-mode choke that I can use for a ground-mounted quarter wave vertical w/ 16 radials. The other choice I have is a 4:...

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