# All Questions

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4 views

### STACKING Folded Dipoles

Looking to stack 8 folded dipoles on my 100ft tower. I can not find any information whatsoever on these. Bluewave Marathon BME139FN1H0 138 - 174mhz Gain 5.5dBd I have 4 consecutive serial numbered ...
13 views

### Can I get non demodulate IQ signals from WebSDR

I want to take a non demodulate audio signal from webSDR portals (http://www.websdr.org/). In order to try to feed these in DREAM DRM Radio software or GNURADIO. Could be cool almost try it for ...
22 views

### Do External Signals Affect Antenna S11/SWR Measurement?

Do external signals affect the S11/SWR measurement of an antenna? For example, if I try measuring the S11/SWR of an HF antenna with a SWR meter or a Vector Network Analyzer in the middle of a field ...
18 views

### Advantages of IQ mixer versus baseband sampling SDR architectures?

What might be the advantages, if any, of HF SDR architectures that use a mixer between the ADC/DAC and RF, versus those that sample or generate RF directly at baseband with a fast ADC or DAC? Are the ...
38 views

### Does a UHF amplifier exist that will boost 5 mW? [closed]

I need to boost my 5 milliwatt HackRF to a jammer level power. Is anything like this available? Ideally portable and self contained. I expect a 45kg amplifier or something but it has to be powerful ...
177 views

I am making a Direct conversion receiver from this circuit at this website. I made it for the 80m band and I changed: The frequency of VFO to about 1.75 MHz L1 and L2 to a bandpass filter for 80m ...
30 views

### How to identify type of modulation from recording done by gqrx or gnu radio?

Is there a tool or some other way that would allow me to find out the type of modulation of a specific signal? What I specifically try to do is to decode signal from this remote control: http://www....
27 views

### How is gqrx producing audio?

How exactly is GQRX converting signal in any frequency to produce audio output? Is it actually done by gqrx or some other element of the stack?
11 views

### RF signal Multiplier or Chopper [migrated]

I'm trying to design a circuit that "multiplies" two signals. Here is my problem. I have an electrical unit with two separate circuits. One circuit drives the other one with a square signal. The ...
68 views

### Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?

Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
50 views

### Antenna modelling - pse check my model in EZNEC [closed]

With success I use the Fuchsantenna especially for SOTA. Now I would like to know how is the radiation (Azimuth/Elevation) I made in EZNEC a model. But I do not know whjether it is correct. Any OM ...
62 views

### Solid angle for different E/H plane beamwidths

The solid angle formula calculates the surface area on a unit sphere, from projecting a rectangular patch onto the surface of a sphere. Image source This is calculated using the azimuth angle $\phi$ ...
148 views

### Do I always need a tuner at both ends of the transmission line or is that only for certain types of antennas/circumstances?

Last night was my first night on the air as a General licensee and at HF. I've got an IC-7300 with the built-in antenna tuner. I'm pretty sure I understand how to operate the radio, for the most part. ...
34 views

### Scan and identify bluetooth device [closed]

Being a quasi-newbie in this game, I'm trying to identify a device which communicates on 2.4Ghz, a Bluetooth mouse talking to his dongle. My goal is to identify the MAC address of the device and then ...
26 views

### What should Elecraft add to thier preliminary KX4 Specification [closed]

I was sitting in a bar in Watsonville CA the other day, unwinding with a well earned beer. Some guy sitting next to me got up and left, but he forgot to take what looked like a folder of important ...
55 views

### no contacts with Rockmite

I finished building my Rockmite ][. It's running off of 3x 18650s, or 12v. I connected it to a MFJ-1840T and held the antenna horizontally in the air (also tried vertically) with my hand. I tried ...
30 views

### UK Intermediate training a not qualified newbie

I'm 99.9% certain that this will be OK, but independent verification would be reassuring. I am an "Intermediate" licence holder in the UK. This means that I am authorised to design and build my own ...
40 views

### Calculating receive wattage given transmit power, antennae dBi and path loss

I would like to understand how to calculate receive wattage given the following (excluding feeder loss and SWR): Transmit 50 dBm (100W) => 24 dBi directional antenna => 30 dB path loss => 24 dBi ...
13 views

### How do I alter the low power setting on a QYT KT-8900

There is no difference between the High and Low power settings. Both being around 25 watts. Is there an internal adjustment or do I have to re-program the radio?
97 views

### Is there a freely accessible repeater database?

The well-known repeater listings/apps don't provide a database that you can download and use freely for any use in building your own app. Is there a such a freely accessible repeater listing database ...
147 views

### Why EME with 100W and a single Yagi-Uda antenna is possible?

Recently I've been reading about EME and there was one thing that surprised me. Many sources claim that EME has path loss for 2m band about 252 dB. In the same time they claim (one, two): Recent ...
149 views

### At what watt level is it safe to use metal strips for modulated signals?

In my working design, I have a transceiver TX on low power; Then boost it in a preamp phase in the back. The way I'm sending the signals (RX and TX) through the radio is by a network of 1/8 to 1/4 ...
30 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 ...
26 views

### How to send DMR SMS using MMDVM modem or hackrf?

I have a baofeng DMR radio with SMS feature, and since there is not much DMR radio owners in my area I want to do something myself. The easiest thing I can do I thought is to send myself some SMS as ...
80 views

### Yaesu FT-817 Won't transmit on 160m to 6m

I'm having the following problem with my FT-817: 1) Receives fine on all bands 2) Transmits fine on 2m and 70cm 3) Doesn't transmit at all on 160m through to 6m 4) Keying the MIC on 160m to 6m, ...
69 views

### How to properly measure sensitivity of the receiver?

I have Kenwood TH-D72 2m/70cm HT. According to the manufacturer the sensitivity is "Less than 0.18 uV". I would like to check this, since the radio is not new and I'm not it's first owner. To do this ...
13 views

### Did I enter my digital ID in Hytera PD785G?

Some time ago, I set up my Hytera PD785G. Unfortunately, I can't remember whether I have only requested my digital ID (I can look it up on ham-digital.org) or whether I have also entered it into the ...
54 views

### How to use FE-5650A rubidium frequency standard?

I bought a FE-5650A rubidium standard reference from eBay in the hope I can readily use it: https://www.ebay.com/itm/142361240786 Unfortunately this is far from "reasily useable". First and ...
61 views

### What is an optimal amplifier arrangement with ham radios?

As I am settling on a design for a radio I need to figure out one thing: Should I modulate on low power and boost it up with a post amp, or should I go on full power right out of the gate?
69 views

### How safe is 100 watts on 2-40 meters?

So I have the misfortune of being an apartment dweller. I know that 50 watts is pretty safe as it is what first responders use on 2 meters. Am I really going to have to run around with an analyzer ...
50 views

### Small size vertical 10 m antenna with high gain

I need a directional antenna for 10 m that is less than half the size of a yagi or quad with more than about 7 dBi of gain, does anyone know if such a thing exists ?
81 views

### 2.45GHz: constructing a horn of *thin* steel, what are good ways to join the edges (at least one joint along corner?)

TL/DR: How does someone make a good horn antenna system without using expensively made parts? Welding thin steel for this is not something even pro welders can do (it's a specialty app.) What are DIY ...
152 views

### Malicious interference to repeater

Our local repeater is severely sabotaged by unknown parties. For example, broadcast radio transmissions are repeated. Other times someone will send a transmission, when a qso is in progress. Local ...
32 views

### Wide band TX capable band-pass filter for VHF and Airband

I want to share the same antenna for VHF (TX/RX 144-148 MHz) and for Airband RX-only (116-136 MHz). I live on a very congested area where filter is a must, so I'm looking for the best solution for my ...
46 views

I'm looking for an amateur radio license class in central Iowa, near Des Moines. I've been unable to locate anything through web searches.
106 views

### Why does the 60 meter band have special operating characteristics?

Why does this band have special operating characteristics and what do they mean.
39 views

### What are the most common EMI blockers for household computer cords, monitors, etc.?

Ferrite beaded cords, and especially double-sided ferrite beaded cords, seem especially uncommon. Are there other, perhaps more effective ways, which I should be minimizing the EMI of my overcrowded ...
42 views

### What are the practical differences between the different voice modes (and why aren't there any SSB Handheld Transceivers (HT's))?

It's my understanding that FM is used for UHF, VHF, and SSB is generally reserved for other bands. From my understanding, FM better audio quality when reception is good SSB: more efficient (can ...
102 views

### Transmitting as SW AM station, not ham [closed]

What if I wanted to run a radio broadcast station on a commercial SW band? Say, I am on a boat in international waters. Or say I am in a free country. I monitor the frequency for months and I check ...
64 views

### Lowest cost portable HF radio with at least 100 W output?

My use case is intercontinental HF radio, and I am frequently traveling. Lugging a big rig is inconvenient and expensive ones get you into customs trouble all the time. So, I'm looking for a low cost ...
43 views

### HF propagation prediction using machine learning

Anyone out there know of or developed s/w to predict HF conditions using ML?
69 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 ...
33 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 ...
98 views

### How do I get a ham radio license in my country?

What is the best way to get an amateur radio license in different countries? This question is a community wiki, which means that it's sort of a placeholder, an index of answers. More info Answers are ...
323 views

### CW: when I supposed to send “E E”?

I'm new to CW and one thing I couldn't figure out is when I supposed to send "E E". Let's say I'm calling CQ and somebody answers me. The QSO is almost over. Should it be ended like this: ...
12 views

### What configuration of a BJT IF amp can I use for a superhet receiver?

I am making a superhet SSB CW receiver with a crystal filter on the input after the mixer. Do I have to use IF transformers as the coupling method? Or can I use capacitor coupling with resistors as ...
43 views

### What VHF & UHF frequencies are important during an emergency?

If something bad goes down (state-wide or nationwide), what frequencies should I be tuning into? I did see this answer, but I have a BaoFeng UV-82HP which cannot do HF at all, so what are my options? ...
81 views

### Will my neighbor's amateur RF antennas effect my own utilities?

I am buying a house in the UK and the property next door has two poles for antennas. The next door lady seems to be very nice person and said her husband is an RF engineer and he used these on ...