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2answers
18 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. ...
0
votes
1answer
26 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 ...
2
votes
1answer
49 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 ...
0
votes
0answers
17 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 ...
0
votes
1answer
23 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 ...
0
votes
0answers
23 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 ...
5
votes
6answers
120 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, ...
1
vote
1answer
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 ...
1
vote
1answer
40 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 ...
3
votes
1answer
118 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 ...
3
votes
3answers
91 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 ...
9
votes
2answers
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 ...
5
votes
2answers
117 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?
5
votes
2answers
80 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 ...
3
votes
1answer
45 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 ...
4
votes
1answer
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 ...
1
vote
1answer
32 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 $\angle I_n$ ...
3
votes
3answers
159 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 ...
4
votes
2answers
178 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 ...
0
votes
1answer
72 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 ...
1
vote
1answer
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 ...
0
votes
1answer
31 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 ...
2
votes
2answers
98 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 ...
3
votes
1answer
50 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 ...
-5
votes
0answers
48 views

Help with changing frequency [closed]

Very new to ham radio! Have install President Lincoln 2+and have been playing some, only listening!! Can’t seem to tune in 146.520 can anyone help?
1
vote
1answer
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 ...
2
votes
1answer
41 views

Total radiation pattern in antenna arrays

let's consider a simple linear uniform spaced array: We know that, from elementary array theory, the total pattern (for instance in terms of E-field) may be evaluated, in case no phase shift is ...
4
votes
2answers
70 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 ...
1
vote
1answer
78 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 ...
1
vote
1answer
75 views

What may be damaged when using an internal antenna tuner on SWR above 3?

The Kenwood TS-570S comes with a warning against using the internal antenna tuner for antennas with SWR > 3, even though it may tune (e.g. at SWR 3.5 or 4). It says the transceiver or antenna may ...
2
votes
2answers
93 views

How much of the 136 - 174 mhz spectrum is actually in use?

I know that 144-148 and 156-157 mhz ranges are in use, and various fire/ems/police, but outside of that, I see a lot of earth-to-space, weather stuff and space research allotments (talking about ...
1
vote
3answers
90 views

Why do PSK modes have “bandwidth”?

My understanding of a naive PSK scheme is that you have some frequency(s), f(n), at baseband, and you modulate information by shifting the phase (what "point in time") the signal is at. Isn'...
2
votes
2answers
140 views

How does end loops on a long wire antenna affect antenna length

I've put up a "random" length long wire antenna for HF in my yard at about 124ish feet about 15' off the ground. I got this length from an online resource. Here's my questions: How does the ...
1
vote
1answer
48 views

Baofeng's won't talk to each other - but other radios receive the signal

I'm very new to this radio stuff and I've come across a problem. I have two BF-888S', along with two other radios. (Binatone Terrain 750) All of which are on the same frequency and have the same ...
2
votes
2answers
61 views

Destructive interference between two close antennas

let's consider this two planar biconical dipoles of total length and width each one 10mm, at a distance D = 25.6mm. They are excited with the discrete ports in the picture, which corresponds in this ...
1
vote
1answer
47 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 ...
1
vote
1answer
36 views

How can I know (check or detect or analyze) which modulation using of my remote control switch?

Please forgive me, my native language is not English. I'm new to radio, but I have several years of programming experience. I have a raspberry pi 4 model B (...
4
votes
2answers
59 views

How do you calculate the number of turns for a common mode choke?

I want to build a common mode choke for my end-fed wire antenna, using turns of coax through an FT140 or FT240 ferrite. I can find various finished products for sale, but I want to make my own. I ...
0
votes
2answers
79 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 ...
0
votes
1answer
57 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 ...
1
vote
1answer
56 views

NOAA weather broadcasts

I am getting no NOAA weather broadcasts, after loading all NOAA weather channels into memory or entering the frequencies manually on a new Baofeng UV-5R?? Why? Do I need to do something else?
3
votes
1answer
51 views

Transmit filter for Amplitude-shift keying

I want to transmit an ASK signal with GNU Radio and HackRF, the parameters are: Frequency: 27.12 MHz (ISM) Sample rate: 2MSPS Symbol rate: 2000 bps Samples per symbol: 1000 The flowgraph currently ...
4
votes
1answer
108 views

Receiving the ISS SSTV: dipole antenna configuration and orientation

In short I am trying to receive SSTV Images from the ISS (145.8Mhz) and I all have is a simple "bunny ears" dipole antenna. In what configuration (straight, vee shaped, upside down vee, ...) ...
4
votes
3answers
80 views

Does Kirchhoff's current law (KCL) apply to antennas?

I think I'm having a hard time understanding HF antennas because they go against everything I've been taught about analyzing circuits. If we look at a dipole antenna, there is the highest current in ...
2
votes
1answer
35 views

UV9RTP Slow transmit to receive

When I transmit the there is a delay in the receiving. When I let off of the mic it still transmits for a few milli-seconds. The transfer to receive is not instantaneous. Which setting controls this ? ...
4
votes
0answers
129 views

WWV interference all over the band!

I have a mid-era Hammarlund HQ-129-x. It sounds great if I don't count the motorboating. But the problem is in the middle bands. I got the radio way out of alignment, and managed (I think) to get ...
3
votes
0answers
35 views

Printed Dipole Transmission Line Equivalent Model

let's consider a printed dipole on a substrate with a GND plane: I've seen many times an equivalent model which uses transmission lines like this (reference): This model is useful to understand the ...
3
votes
1answer
46 views

Phase shifts in antenna arrays

Let's consider a simple antenna array. For instance, this three-elements equispaced dipole array: Each dipole is connected to a signal voltage source. It's well known that it's possible to choose the ...
4
votes
1answer
49 views

What is the difference between an RF amplifier's DC or quiescent operating point and the RF operating point?

I chose the resistor values in the following schematic to set the DC bias point of VCE=6V and IC=5mA because the transistor data sheet gave the S-parameters at 162MHz for these values. I learned how ...
3
votes
1answer
33 views

On the Kenwood TM-D710, what is the “D” on the B band?

I can explain almost every part of the Kenwood TM-D710(G) display except the letter "D" that appears on the second line of the B band next to the power level. I've poured over the manual and ...

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