# All Questions

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31 views

### what is the baseband for CATV?

I was reading on wikipedia this : the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency (baseband) https://en....
31 views

### Is spacing of parallel dipoles necessary?

Is spacing of parallel dipoles necessary. Could they be banded together and then trimmed or is there some consideration, other than tuning, requiring separation.
2k views

### 3 Band (80-40-20 Meter) Fan Dipole Tuning Question

I built a fan dipole according to the basic instructions in the SRI publication describing the theory and basic design. My questions is about next steps in tuning for the various bands. I am ...
71 views

### Why am I receiving a local tv channel on a CMB frequency

I am using a simple Baofeng H6 dual band radio and I programmed weather channels. Well, on frequency 161.77500 I am actually picking up WGN, a local tv network. This frequency should be reserved to ...
9k views

### How do I power my radio in a vehicle mobile install?

I want to install a 30W mobile UHF radio in my car. I already have an antenna and mounting bracket - but how do I get power to this radio? It has an SAE bullet connector on the back - do I just need a ...
123 views

### What does ALC do on a transceiver?

What is ALC on an HF transceiver? What are the disadvantages (if any) of operating using a rig without ALC? What might be the difference between a good and bad implementation of ALC?
23 views

### Alinco DR-635 programming software

I see that RT-Systems sells programming software and a cable so you can program the Alinco DR-635's internal memory via your laptop instead of through the Alinco's cryptic and hostile user interface. ...
29 views

### Way to bypass the second of silence when changing stations? [closed]

I am trying to mod a simple AM radio to scan through stations quickly. I've got a simple 555 timer that I hook to the tune up and down buttons to do this, but the problem arises on every single model ...
44 views

### Anytone 878 UV Commercial license?

This radio has a commercial mode but no where that I can find does it describe which commercial license. Looking at the tag under the battery... FCC ID T4KD887UV https://fccid.io/T4KD878UV ...so part ...
133 views

### If receive performance doesn't depend on SWR, then how can I tune my manual HF antenna tuner by band noise?

The popular question "What is the relationship between SWR and receive performance?" asks if a receiver with a well-matched antenna (low SWR) beats a receiver with a poorly-matched antenna, ...
461 views

### Why does ARRL license examination procedure preclude students from discovering what questions they got wrong on licensing tests

I got my Amateur Extra ticket some time ago. I was able to discover what my score was (the number of questions I got wrong). However, my examiner was not able to tell me specifically which questions I ...
1k views

### Is the Kawamall DMTF 6pin microphone usable with the Kenwood TK-805D radio?

I have a Kenwood TK-805D commercial radio, which I am using for UHF ham operation. For repeater usage, with AllStar, IRLP, and Echolink, I need a DTMF mic for it. I did a search on the internet, ...
19 views

### RS41 weather balloon unable to decode data

Some times ago I tried to decode the signal from a weather radiosonde (RS41) passing in my area using a cheap RTL SDR (using both standard antenna and a home-made one, with similar result). The ...
25 views

### I have a 433MHz LoRa Dipole antenna mounted on a rocket. I am looking for a suitable Antenna to receive data from this. Any Suggestions?

The idea was to send GPS data from the rocket to the ground station at 433 MHz using a Lo Ra transmitter - mainly to help locate it once it lands and also to provide in-flight telemetry. I have a ...
25 views

### gnu-radio on Ubuntu 20.04 and AIS processing seems impossible

I have searched, installed, and tried every package there is to get AIS processing using the gnu-radio companion to no avail. I tried installing gnu-radio both with conda and apt on Ubuntu 20.04. The ...
58 views

### Modeling a regenerative receiver

What is the signal processing model of a simple regenerative or super-regenerative receiver? Is it just a linear 2-pole IIR filter with gain? How does a single regen control knob control both ...
92 views

### What causes an AF amplifier to make popping sounds in a superheterodyne receiver?

Recently I've made a simple single IF superheterodyne SSB receiver for 40 meter band. The schematic is available here [PDF]. VFO and BFO are based on Si5351, the AF amplifier is LM386. It works OK but ...
42 views

### Will Brexit have any impact on UK recognition of foreign licenses

As a US license holder (and duel citizen of the US and UK) I know that I can operate in the UK for a couple of months using the M/W2*** prefix, while holding Amateur Extra, but I cannot apply for a UK ...
121 views

### What do old unit abbreviations like “mfd” and “kc” mean, and where did they come from?

I saw a recent answer that mentioned "mfd" as a unit of capacitance, and I can recall having seen that term in old schematics and ham radio articles. I've also seen other non-SI unit ...
8k views

### Why is Morse code still in use?

Why do people still use Morse code? What are its advantages over newer voice or data communication modes?
33 views

### Excitation coefficient of a linear phased array

it's well known that in a linear and equispaced antenna array, the array factor is equal to: The array is then called uniform if $|I_n| = I$ is the same for all elements. The phase terms $\angle I_n$ ...
2k views

### Am I really receiving FT8 signals from 12,000 km away on 144 MHz?

I have been using an Ettus B200 SDR to receive FT8 transmissions in the 2-meter band (144.174 MHz) using the WSJT-X software. Signals are received using a telescopic antenna inside on a window ledge ...
82 views

### How is phone cable with iron called?

In in Russia I saw a phone cable called "field cable" (провод полевой П-274-М). It is a loosely twisted pair with some iron strains added alongside with copper ones. I tried to lookup ...
2k views

### GNU Radio does not run flow graph

I am sorry but yet again a question about GNU Radio. (I just started following some tutorials a couple of months ago and am learning about it. I am unfortunately not that proficient in it yet, but I ...
46 views

### Identical HF Horizonal Dipoles Operating in Close Proximity

I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second ...
161 views

### Is an antenna always matched to free space impedance?

In this thesis the following model for an antenna is proposed: It is seen as a 2 port network, in which only port 1 is accessible (port 2 is an imaginary connection between the antenna and the free ...
5k views

### Radio manufactured in United States

I am just beginning with amateur radio and would like to start with an entry level handheld transceiver. I would like to consider manufacturers based in the United States, but I have not found any. ...
278 views

### Looking for headset to use with BTech UV-25x2

I have a BTech UV-25x2 that I'm using as a portable base station. This radio has a "TRRS" connection (GND/SP/MIC/PTT) which I would like to get a headset for. I'm relatively new to ham radio, so don't ...
48 views

### Repeater build problems

I'm trying to build a UHF repeater using two Motorola radios. I have a cable connecting the two radios that was built for doing such a project. The radios have been programmed for the appropriate ...
4k views

### BF-F8HP: “Radio did not respond” when trying to use CHIRP

I'm trying to program my Boafeng bf-f8hp with the chirp software, but as I have to do, "Download From Radio", after I choose the appropriate maker, product and model, all I get is an error message ...
936 views

### Are QRP transceivers only meant for CW communication?

I was just thinking about making a QRP transceiver, but are they only used for CW (Morse code) communication? If it is so, can I modify a QRP for two way audio communication?
2k views

### What kind of 2 meter antenna is this?

At first glance this appears to be a simple ground plane but there is far more going on. The ham who built this back in the '80s is now SK and I can't find anything else like this anywhere. The ...
179 views

### If repeaters share the same call sign are they “Connected”

Newbe here, I was looking through repeaters in my area and I noticed that there were a few repeaters that shared the same call sign(even though they run on different frequencies). Does this mean that ...
2k 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 ...
80 views

### Obtaining input/out impedance from S-parameters for a L network

This L network intend to transform Z1 to 50ohms. The design was made using a smith chart: The s-parameters plotted (S11 red - S22 green) in the smith chart is done sweeping the frequency from 200MHz ...
81 views

### Identifying type of RFI by waterfall

I'm trying to identify the type of RFI I'm seeing on the waterfall in the picture below. It occurs mainly at night, every night, starting at about 6:30 p.m. and ending in the morning, and I have yet ...
99 views

### Is it at all possible to make a ham alert radio?

Would it be possible to make an alert radio... for shortwave? Out of something like Arduino, or RPi. Sort of like the NOAA Weather Radios. I got to thinking one day. Say you wanted to send a message ...
73 views

### Sweep times for Spectrum Analyzer

I have a basic question about sweep times and number of points. My frequency span of interest is: $f_{span} = 30\ \rm MHz$ My resolution bandwidth is: $RBW = 10\ \rm kHz$ The minimum number of points ...
37 views

### How to avoid acoustic feedback while fixing radios?

CQ CQ CQ de BH4FHO. I have been fixing some radios recently - buying used radios for cheap, fix them up and modify them to transmit in ham bands. When testing them out, I am using my Baofeng DM-1801 ...
32 views

### Troubleshooting the MFJ 1982 EFHW

I am a beginner with not much experience in HF. My shack consists of a Xiegu G90 connected with 20ft of RG-8x to an MFJ 1982 end fed half wave antenna. There is a small coil of coax next to the ...
6k views

### Single Side Band AM vs FM

I know the difference between AM and FM, but could anyone explain to me what is the differences between single side band AM and conventional FM? So far as I know the SSB modulation will reduce the ...
53 views

### Looking for origins of a crystal filter schematic used in uBITX

Here is a crystal filter used in uBITX transceiver: I've never seen such a topology in any other transceiver and decided to invest some time in exploring it. Turned out it's quite interesting. Eight ...
1k views

### Where can one find recordings of Morse code, generated by humans and not machines?

I need some recordings of CW / Morse code for use in a project. Most of what I find is either nonsense (it just exists for the 'sound of CW', but doesn't contain a message) or is generated by a ...
242 views

### What nations still require Morse code testing for Amateur radio license?

Going a bit further I'll ask, for which licenses (all or just for licenses for HF operation) and at what speed (5 WPM, 10 WPM, none specified)? The reason I ask is because every so often I'll see ...
540 views

### CB Radio Ground Plane (or lack thereof)

Notice the vertical antenna on the truck. I believe this first antenna is referred to as a "dipole", mounted vertically. CB to coax, coax to antenna. The shell of the truck is fiberglass. Even the ...
81 views

### Help getting use out of an old RC radio transmitter

I have an old "Walkera-RC 2.4ghz Radio Transmitter WK-2401" radio transmitter from an RC Helicopter. I want to use this transmitter with a receiver in order to transmit some sort of data ...
72 views

### Can a phase-modulated voice radio transmission be received and heard properly by an “FM” radio?

Not necessarily an amateur radio question (but perhaps a licensed amateur should know the answer?) - I note that the specifications for marine VHF radio operating in the 156-157 mhz band call for both ...
58 views

### Using inverted Yagi antennas to gather and cohere RF from the sky

Imagine a group of eight or more vertical masts. On each mast is a Yagi antenna pointed upward toward the sky. The elements are inverted with the idea being that the incoherent RF coming down is given ...