# All Questions

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73 views

### How do Radio Regulations and Frequency Allocations Apply to an Ionosonde?

An ionosonde is a special HF radio transmitter that periodically transmits a signal that sweeps across a large portion or the entire HF spectrum to identify the propagation of radio signal in the ...
163 views

### UHF FM power amplifier design without expensive software

I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application ...
84 views

### Where to find HF channel models or statistics?

When designing a waveform for packet radio usage, it'd be helpful to know a few things, mainly distribution of coherency bandwidths distribution of coherency times Whilst such statistics are ...
205 views

### Beyond Maximum Stable Gain of a transistor

I was plotting constant-gain circles on the Smith chart the other day for a potentially unstable RF transistor. I recently read on-line that for a potentially unstable transistor the maximum gain ...
632 views

### Doppler Shift Compensation in Inter Satellite Communication

I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO). I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is ±7 GHz. I ...
75 views

### How to estimate input and output impedance of an amplifier?

I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in ...
47 views

### Choice of PCB coil design for filter inductor at ca 20 to 400 MHz, 5 W

Looking at the diplexer schematic from this nice question, I realized this can completely be done in PCB-formed elements (minus the connectors). (As a kind of counter-action to the original question'...
81 views

### What causes differences in properties of ferrite cores from same material?

Why are the shapes of the impedance curves different for cores made of the same ferrite material? The impedance (Z) of an inductor wound on a ferrimagnetic core is: Z=j\omega L_s + R_s = j\omega ...
60 views

### 4NEC2 radials & grounds

Teaching myself 4NEC2 and have most of it under control, which is good. Regarding radials & grounds, i've been learning the "rules" NEC(2) has, summarised below. 4.1. Free space. In the ...
101 views

### Problem with theory of HF detector

I'm currently trying to build my own SWR power Meter. This design is based on the so known HT detector with schottky diode BAS70. For my understanding, and for easy purpose, I'm currently focusing on ...
116 views

A single inductive loading coil in a vertical or a pair of loading coils in a dipole are commonly used to match a given total antenna length parameter to a given frequency wavelength (where the ratio ...
260 views

### ISS APRS Digipeater with Kam XL and ICOM IC-910H

I am trying to use the ISS APRS digipeater which transmits at 437.55MHz. Hardware setup consists of the following ICOM IC-910H. The transceiver has been connected to a Windows PC running a HAM ...
79 views

### DIY Triplexer for HF (low), 6m (med), and 2m/440 (high)

I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas ...
99 views

### Ground-Plane radial sizing, is there such thing as too long?

I'm just trying to make sure I understand the theory correctly. I have some triband VHF/UHF/800MHz antennas, I need to mount on a tower so I plan on using a "mobile to base" conversion kit. ...
136 views

### The whole neighborhood's internet drops when I transmit on 40M

I recently built a vertical. It's 6M radiator, a coil, and 1.2M more of radiator. It sits on my roof, which is metal, and acts as a ground plane (GND from the feedline is connected to it). There is a ...
220 views

### Are there any “parrot” repeater software projects out there?

I happened across a discussion on building repeaters for Amateur radio, which lead to looking at GMRS repeaters (because apparently this is a potential source for inexpensive 70 cm Amateur repeaters), ...
122 views

### 9:1 unun material and power loss

I need to build another 9:1 unun and I start searching for my toroids... (I have build 2-3 something like 4 years ago)... In parallel I checked on Google about the correct toroid etc so I found 2-3 ...
46 views

### What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

I am working on space-ground networking for a Cube Satellite, and one of our candidate Layer 2 protocols is AX.25. We haven't settled on a physical layer, but it's likely to be some form of quadrature-...
57 views

### How to simulate two antennas in 4nec2

I need to simulate 2 helix antennae placed side by side, and see the resultant radiation pattern. But after adding the second antenna with a separate and when I try to simulate 4nec2, only simulated ...
81 views

### Where did the LP to BP transformation $\frac{\omega ^{2}-\omega_0^{2}}{\omega\cdot BW}$ come from?

I'm not sure this question is appropriate for this site, but I feel that if anyone knows about a filter, a radio ham knows! And as a ham myself I feel I need to understand this important area better. ...
100 views

### GnuRadio RF transmission, legal and safety issues

I'm trying to run some transmit/receive RF examples that I found online using GNU Radio with USRP B200. I read and heard about some cautions in terms of transmitted frequencies here in the USA which ...
250 views

### Kenwood TS-50 and USB to Serial

I paired my old Kenwood TS-50 with serial, by using FTDI TTL-232-5V-AJ USB to serial converter. I used ideas from here: http://steeman.be:8080/posts/TS-50%20USB%20Interface/ and here http://i.imgur....
893 views

### OFDM spectrum, HACKRF, and GNUradio companion

I am trying to analyze the spectrum of wifi spectrum. I getting a good OFDM spectrum with my HackRF at 2.412 GHz (from my first QTGUI Sink). But I get nothing out of OFDM Receiver. I was wondering ...
1k views

### TS-590 Antenna Tuner Protocol

I'm looking for the protocol used by Kenwood's TS-590S antenna tuner port. I've worked as far as I can with Kenwood's tech support. They know what the pins are labeled, but don't have any information ...
71 views

### CML FX919B Forward Error Correcting

I would like to decode de-interleaved demodulated 4FSK symbols that were transmitted using the CML FX919B chip. The datasheet only gives the following information: Forward Error Correction In ...
51 views

### Buzzing FM interference

What kind of interference or other receiver issues can cause a constant buzzing noise (picket fence lines in the audio spectrum) in the demodulated audio of a received NFM VHF signal? With AM, it ...
63 views

### Vertical antenna near power and cable lines

I have a 40M vertical on top of my roof. When I transmit at 100W, my internet drops. My neighbor's internet too (different cable company). At 50W it seems to be OK. As an expermient, I used a smaller ...
27 views

### What is the format of Yaesu FT3D's QSOPCTDIR.dat and QSOPCTFAT.dat files?

The Yaesu FT3D can send photos, but only if taken with the optional external mic that has a camera. I want to be able to send photos that come from elsewhere, by putting them on the SD card. But it ...
49 views

### Receiving and decoding RDS in GnuRadio

I'm new in radio, so I started with seemingly easy task - receive and decode RDS data. I use GnuRadio to understand the concept of working with RF signals. So according to standard RDS receiver looks ...
36 views

### Is it possible to show frequency and channel name at the same time on AnyTone 878UV?

On the AnyTone 878UV I can choose to display the frequency or the channel name or frequency (Settings->Radio Set->4 Ch.Name). But seems to me like there's enough screen real estate to be able to show ...
86 views

### What is happening in a gutter “antenna”?

can you explain me what is happening with RF in a iron gutter? I've tried to simulate with nec2, but I'm just a beginner and doesn't really know all the parameters to come close to reality. This is ...
57 views

### Circular polarized antenna feed changes as I rotate it?

I had a 100cm prime focus dish laying around and I thought of making a circularly polarized feed for it, since it seemed pretty straightforward from what I've been reading. Helical feeds are supposed ...
81 views

### Which digital modes are formally specified sufficiently to be implemented?

Which currently popular digital/SDR modes do not require a pre-compiled library or pre-written source code? (e.g. has actually been used for QSOs as implemented from specification or sufficiently ...
36 views

### Clocking A and N in a Dual-modulus PLL Prescaler

In an effort to "up my game" attempting to build a VFO for my DIY transceiver, I've been looking at PLL theory and circuits. Many of my research references are quite old and I understand that many of ...
64 views

### Icom 7300 low frequency broad-spectrum noise

What's causing these horizontal bands of noise? It's the middle of the day here in a low density city neighborhood. They were not present about 20 minutes ago; now they are even stronger and filling ...
98 views

### Unknown kit from DK0TV

When my father - who became a ham years after I did - passed away, I found an unstarted project (board + components), which I only re-discovered again years later. The board is marked DK0TV-001, and ...
53 views

### Demodulating ISO14443 (part of NFC) using SDR?

I'm looking for info on demodulating both sides of an ISO14443 communication using a cheap SDR, preferably an RTL-SDR (R820T2+RTL2832U). The application is passively monitoring an NFC exchange for ...
70 views

### First linear power supply build - design questions

I have decided to build my own linear regulated power supply to provide the power for an upcoming build. Since I'm no pro, I was hoping I could get some feedback on my design before building it, just ...
108 views

### How FEC works on GNU Radio

I am new to GNU Radio. I need some reference to how to use FEC block in GNURadio. When I try to make encoder and decoder without modulation, its work as well, but when I using modulation and add ...
88 views

### Has this regeneration control been done?

I'm planning to build a two-tube reflexed RF regen receiver soon. I'm examining methods of controlling the regeneration — it needs to be possible to both initiate and halt oscillation in all bands (I ...
84 views

### HackRF One and IoT overloaded?

I'm transmitting Z-Wave frames using HackRF One in loop, one frame every second. Has anyone clue why are some frames not transmitted? You can see several too long gaps between frames on Waterfall (...
70 views

### Is PC to Digital Radio possible, is there an existing solution?

Is it possible to setup up an interface from a PC to a digital radio that is able to communicate with a Hytera PD702 handheld (450-520MHz) or like type radio? Or are there off the shelf radios that ...
37 views

### Noise Floor when receiving Es'hail 2

I'm currently trying to receive the Es'hail 2 satellite using a standard TV LNB, 60cm dish and RTL-SDR. My dish is slightly offset by 2 degrees, and my SNR is only about 15dB unfortunately. My main ...
304 views

### How to decode 2FSK signal with SDR?

I'm new to radio and SDR but, as a hobby project, I'm trying to decode a 2FSK radio signal received by an RTL-SDR that I sent using an SI4463 transmitter. The record file contains 3 packets, but I'm ...
462 views

### LimeSDR Mini + Raspberry Pi 3 B+ Transmission problem

I am new at this. I would like to transmit an audio signal cleanly using WBFM but I see two signal peaks occur around my fundamental frequency when I start transmitting. In this case I am using a ...
410 views

### Does anyone repair Flex radios other than Flex Radio?

A local ham that I have an evening sked with on 75m (Paul, W0EBV) sent his Flex 5000 SDR transceiver to Flex Radio Systems to get it repaired a few months ago. However, it seems that Flex is either ...
160 views

### It is allowed to have more APRS trackers with one callsign in Europe Union

I am interested if I can set up all my automatic APRS GPS trackers with one call sign in Austria (like in the US)? Are there any restrictions on usage?
116 views

### What protocol does the Vertex VX-2200/2100 use for programming?

I have seen a number of programming cable schematics on the internet, but I couldn't understand very much how they worked. From what I picked from all schematics, it appears the protocol uses the <...