# All Questions

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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 ...
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 ...
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 ...
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 ...
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? ...
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, ...
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 ...
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-...
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 ...
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.
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 ...
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." ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
93 views

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 ...
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 ...
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 ...
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 ...
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 ...
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, ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...
64 views

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

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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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, ...
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 ...
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 ...
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 ...