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0answers
21 views

Baofeng 888s side key didn't work and solved [closed]

Thanks. Solved. Baofeng 888s, programmed with chirp, worked great. I hit the device with CHIRP many times, Everything was ok., but moni button after a month, didn't work. First I thought that the ...
4
votes
2answers
56 views

Propagation effects of noctilucent clouds

I know auroras are a propagation mode, but I was wondering with the recent outburst of noctilucent clouds (as reported on www.space.com) brings with it any interesting propagation modes, either on HF ...
2
votes
1answer
42 views

How do I interpret the FCC ground conductivity files

The FCC has .seq files that show ground conductivity which it makes available for download. Unfortunately, there doesn't appear to be any documentation that comes with the files, or even headers. I ...
4
votes
4answers
2k views

How does a receiver know the exact frequency in the channel to “listen to”?

I am reading about how radio communication works and I have an unanswered question. We have wideband channels with 25kHz of radio spectrum. The transmitter modulates a signal and sends it. The ...
1
vote
1answer
36 views

Clarification: What are Fixed and Mobile services intended for in frequency allocation documentation?

Question Does a band allocation to "Amateur", "Fixed", and "Mobile" mean that it's for amateur radio use by fixed and mobile services, or does it mean that all these services are separate but equal? ...
1
vote
0answers
27 views

Baofeng 888s sidekey (moni) don't work

Baofeng 888s, programed with chirp, worked good but maybe at change channels during pushing moni button or something else (I don't know), don't work. I tried to change side key options by programming, ...
2
votes
1answer
54 views

Transferring old callsign to a club?

A new vanity callsign will be granted to me (currently in pending level 2 stage). Can I transfer my current soon to be cancelled callsign (vanity) to a club which I am trustee without waiting the ...
1
vote
1answer
54 views

Combining/splitting three different RF signals

Not being so fluent in RF, I decided to ask here if my current approach seems doable or how one would try to achieve something like this: I'm doing research and deciding on an approach for my proto-...
8
votes
4answers
135 views

Why are there so many coaxial cable impedances?

Why do we have 50, 75, 62 and 92 Ω coaxial cable, to name a few? Why not just one standardised cable? Is there some technical reason or did Mr. Coax and Mr. Cable have a disagreement, like Mr. Tesla ...
5
votes
3answers
95 views

Is Field Day a contest?

Is the ARRL Field Day a contest, or is it not a contest? Kindly explain the reasoning behind your answer. A non-ham could not tell the difference.
1
vote
3answers
108 views

Using 75 Ω instead of 50 Ω coax feed

Can I replace my old 50 Ω coax with RG6? It's cheaper and less loss at VHF/UHF. I would match by L/2 multiples of coax to repeat input and output impedance or L/C matching networks at each end. Is ...
5
votes
1answer
445 views

What does “THREE ALPHA in Virginia” mean?

I'm listening to the 40m band during Field Day and I keep hearing things like "You are THREE ALPHA in Virginia," or "do you hold me ONE ALPHA in Eastern Pennsylvania?", or "you are TWO ALPHA Maine." ...
5
votes
1answer
99 views

How do Field Day participants protect from lightning?

I'm planning to attend Field Day this weekend, and the forecast calls for thunderstorms. I can picture a serious issue with a bunch of temporary antennas set up in an open area when a thunderstorm ...
3
votes
3answers
118 views

Applications for 100 GHz band?

I was reading this paper and I found it very interesting and the following question came up, What are the main applications (what is used for) 100 GHz band? I couldn't find any reference on what is ...
1
vote
1answer
77 views

Colinear Vhf antenna

Textbook colinear vertical antenna designs show coax cable with alternating braid to centre configuration. Commercial whips seem to utilise a single wire as the radiating element with .66 velocity ...
2
votes
1answer
94 views

How does one know how a signal has been modulated

I am trying to intercept signals from a drone remote controller and decode them. Before I can do this I need to demodulate the signals. All I have is radio data from the transmitter's operating ...
1
vote
2answers
82 views

How to plot transmitter coverage area?

As an Extra class licensee, I should probably know this... I am working on a web application for repeater owners. I would like to include an estimated coverage area, provided they have entered all of ...
2
votes
3answers
89 views

FD Battery Stations… How Do You Log?

I'm part of a small team that runs 3AB with a few Kx3 radios. We've been struggling a bit with logging. First year was all paper and that was messy. Next couple of years one of the guys put together ...
2
votes
3answers
93 views

Add capacitor to unload antenna?

So add inductor coil(loading coil) is to cancel out capacitive reactance to make the antenna electrically longer. But what if a capacitor is placed on the antenna, to make the antenna electrically ...
2
votes
1answer
45 views

Dielectric Constant of Insulation/RF Permeability

I recently purchased a 500-foot roll of military surplus 14 AWG stranded copper wire at a hamfest for next to nothing . It is Prestolite M13486/1-6 (spec sheet). It has very thick chlorinated ...
1
vote
1answer
36 views

Are stainless steel studs acceptable as a feedpoint connector for an aluminum loop antenna?

Similar to Will stainless steel bolts work with my copper antenna? however my concern here is with electrical properties. With copper antennas I never gave it much thought... just solder the wire. I ...
3
votes
1answer
62 views

Why is GNU Radio “stuttering” with this flow graph?

I have a GNU Radio Companion flow graph, where I have the following connections: 440Hz cosine wave throttle block audio sink All of the above blocks use the same sample rate (48KHz). When I ...
4
votes
3answers
130 views

Feeding a folded dipole

Can I feed a folded dipole constructed of hollow tubing by threading coax through the element to create both an impedance transformation and balun? I have fed coax through the tubing of the dipole ...
3
votes
2answers
76 views

Grounding a chimney mounted antenna

I'm installing a new antenna mast to hold one or more antennas. The new mast will be strapped on to a chimney near the center of my house. Coax will run down the mast, across the roof, down the side, ...
0
votes
1answer
92 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 ...
3
votes
1answer
63 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 ...
2
votes
2answers
133 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?
5
votes
2answers
380 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 ...
8
votes
1answer
129 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 ...
3
votes
1answer
93 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 ...
1
vote
0answers
64 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?
4
votes
0answers
56 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
45 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 ...
6
votes
3answers
672 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
75 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
54 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
154 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
89 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
57 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 ...
4
votes
3answers
125 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
89 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
44 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
118 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
65 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 ...
6
votes
2answers
511 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, ...
4
votes
2answers
91 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
618 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
70 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
86 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
56 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" ...

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