# All Questions

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2answers
46 views

### Can an end-fed be fed with an Isolation transformer?

Typical half-wave end-fed antenna kits include either a 9:1 or 49:1 toroidal balun or unun, which is a transformer for impedance matching, but with one primary winding endpoint (for the coax shield) ...
0answers
24 views

### Isolated linearly loaded antenna?

Is there a name or common descriptive term for a linearly loaded dipole or end-fed, where a (near) parallel loading element or elements are not connected (galvanically isolated) to the fed element or ...
1answer
97 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 ...
2answers
78 views

### Can timing information be used to compress data for LoRa transmission?

I have a course challenge. It involves calculating an FFT of an audio signal of 2 combined frequencies (up to 20KHz) then sending it over LoRa through to a fixed receiver. There will be an interferer. ...
1answer
91 views

6answers
229 views

### QRN: How to chase down a solid S9 noise floor on 40m only

I am new to this, having just set up my station. I have "very bad" QRN on 40m: S9. Here is the setup: High density suburb with flats and houses Yaesu FT450D with fan dipole at 6m-9m above ...
3answers
2k views

### How can I decode SSTV with only macOS software?

Have you used an SSTV decoding application on an up-to-date version of macOS? Which one, and if you built from source, can you share the steps you took to do so? I do not know of a single working ...
4answers
119 views

### What comes first, Voltage or Current?

Impedance can be defined as cause / effect or Z = E / I. This means that a difference in voltage potential causes a flow of current, the rate of current flow depending on the impedance. In a dipole ...
3answers
93 views

### Is it possible to boost WIFI signal? [closed]

Whilst strictly not radio ham question, it does fall in to the RF area so hopefully this is not too far off topic... I have BT broadband account which entitles me to use BT-WIFI hotspots. The trouble ...
2answers
73k views

### Which HF bands are best during the day and which are better at night?

I am rather new to HF operation and have recently purchased my first HF rig. I have read about bands being "open" and "closed" based on various conditions including time of day. As I have been ...
2answers
73 views

### How to figure out my car battery's capacity?

I was participating in an emergency radio training and I was asked how long I could operate. I'm using an old car battery, which was sometimes not capable of starting the car in winter, which is why I ...
0answers
65 views

### Legal unlicensed transmitters permitted where? [closed]

In what English-speaking countries is it specifically allowed by law or regulation to operate non-commercial unlicensed RF transmitters within certain bands at certain power levels? (such as within ...
1answer
83 views

### Does SWR change along the length of a transmission line?

Wikipedia says "SWR is defined as the ratio of the partial standing wave's amplitude at an antinode (maximum) to the amplitude at a node (minimum) along the line". Standing wave voltage ...
3answers
151 views

### Aren't all antennas technically dipoles?

Since all antennas require a ground, reference or otherwise, there are two poles for their operation. For a mag mount, the car body is the reference ground. A vertical cannot operate without a ground ...
5answers
283 views

### (When) does a transceiver re-reflect 100% of reflected power?

There has been a long discussion of one question here. Phil, W8II and I agreed that it's better to post a separate question. There are several sources (some editions of "The ARRL Handbook", &...
2answers
99 views

### Can a smartphone with single antenna receive signals modulated by different schemes

I am working on a system whereby a smartphone may receive signals simultaneously from different sources. As we know, the fading and pathloss will make the transmitters send their traffic with ...
0answers
36 views

### For a resonant half wave dipole, is the phase of the applied RF voltage at the feedpoint in phase with the current reflected from the ends?

For a resonant half wave dipole, the voltage and current of the standing waves on the antenna are 90 degrees out of phase with each other. At resonance, is the phase of the current reflected back from ...
1answer
39 views

### The amplifier does not work for hack rf one

Good day! I ask for help with repairing the hackrf one amplifier. Doesn't work at all. Accepts signals without amplifier, and LNA and VGA adjustment in SDR sharp works too! But when I put a tick on &...
2answers
99 views

### How much dB gain do you need from an LNA in front of an antenna for great low-signal reception from satellites in the 2m and 70cm bands?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. This LNA we are considering (Qorvo QPL9547) provides about 22dB gain in the 2m and about 27dB in the ...
1answer
100 views

### Choosing a Relay for HF Applications

As part of my 20m transceiver build I'm looking for a relay to by-pass an RF amplifier in the front-end board. So, to be clear, that's after the 20m broad bandpass filter and before the RF mixer (it'...
4answers
16k views

### 2m or 70cm FM mobile radio for digital mode operation

Are there any 2m and/or 440cm FM mobile radios that have audio inputs for supporting digital modes, like PSK31 or SSTV? I have a Rigblaster that I use with my HF radio so I could get a mike cable and ...
2answers
64 views

### At near-QRP levels should I include a balun/unun in the antenna system? [duplicate]

To my comprehension a BALUN/UNUN is an RF Transformer. If this is correct and since a BALUN/UNUN is part of the antenna system ... how much power does one expect to lose there? Specifically, how much ...
0answers
26 views

### How does the inductive reversal process of the emission of EM radiation at the receiving antenna work?

The emission of EM radiation is based on an induction process in which a periodic electrical voltage creates a magnetic field that is offset by 90° in time and space, also known as the starting near ...
0answers
29 views

### I'm trying to configure HRD for IC7300 but cannot connect / detect frequency

Got the firmware updated. Got the Driver updated. Got the software updated. Went through instructions several times.
2answers
10k views

### How to detect common-mode currents or “RF in the shack”?

Let's say we already know that if your antenna is not suitably constructed or connected then you can get current on the shield of your coaxial feed line which will flow through the shielding/grounding ...
1answer
136 views

### Using SW radio to detect Jupiter

I read here (in the ideas section) that an old shortwave radio can be used as a receiver for listening to Jupiter but am unsure about how to do it. MY radio has both a whip and ferrite antenna, ...

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