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5 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 ...
-1
votes
1answer
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 ...
0
votes
1answer
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 ...
2
votes
3answers
448 views

Satelite dish modified for Wi-Fi (Signal Elevation Question)

I am doing a project where I will be re-purposing an old TV satellite dish as a directional Wi-Fi antenna. The dish is circular in shape, not oval. The dish has an arm coming from the bottom that ...
4
votes
1answer
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 ...
3
votes
2answers
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 ...
0
votes
1answer
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....
2
votes
2answers
177 views

What causes my direct conversion 80m receiver to receive AM broadcasts?

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 ...
-4
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0answers
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 ...
2
votes
1answer
48 views

Kenwood TH-D72A and AO-91/92

I got a Kenwood HT and using it with the Elk Antenna On the radio, there is Tone and I set it to 67 Hz. I wasn’t able to break thru to the satellite and had it in Full Duplex mode. I can hear ...
6
votes
1answer
127 views

For a resonant 1/2 wave dipole, does the reflections being in phase with the applied signal cause the zero reactance seen in the feedpoint impedance?

For a resonant 1/2 wave dipole when used for transmitting, does the fact that the reflected waves on the antenna are in phase with the applied signal result in zero reactance at the feed point, or ...
1
vote
1answer
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?
0
votes
0answers
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 ...
0
votes
1answer
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 $\phi$ ...
-1
votes
0answers
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 ...
4
votes
3answers
4k views

Antenna tuner design

In a related question about a broadband antenna for SDR it was suggested me to build or buy an antenna tuner. Since maybe it was not clear to everybody, I'm designing an antenna tuner for reception, ...
1
vote
3answers
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. ...
2
votes
3answers
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 ...
10
votes
6answers
187 views

Practical limits to maintaining coherence in an HF channel

Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve. It would be nice if one could simply take any existing modulation and slow it ...
3
votes
5answers
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 ...
-1
votes
1answer
3k views

Is it legal to use BAOFENG BF-888S 16-CH 400~470MHz 5W Walkie Talkie in India?

If not, what can be used as mode of communication for group trekking. It is very urgent and important Please suggest some better options for walkie talkies
0
votes
0answers
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 ...
-2
votes
0answers
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 ...
-3
votes
2answers
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 ...
3
votes
1answer
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 ...
1
vote
0answers
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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?
3
votes
3answers
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 ...
4
votes
1answer
1k views

How does power received by a dipole relate to electric field intensity?

Let's say there's a transmitter far away, and I'm going to receive the transmitted signal. To keep things simple let's further say the transmitted signal is a pure, unmodulated sine wave. Further, let'...
0
votes
1answer
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, ...
3
votes
5answers
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 ...
4
votes
0answers
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 ...
5
votes
2answers
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 ...
0
votes
0answers
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 ...
1
vote
2answers
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 ...
-1
votes
2answers
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?
0
votes
0answers
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 ?
5
votes
2answers
351 views

EFHW works only on one band - what am I missing?

I tried to build a multiband EFHW antenna as described in articles by PA3HHO, PD7MMA, G0KYA and many others. I decided to start with a short 40/20/(15?)/10 meters version without any loading coils. ...
0
votes
0answers
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 ...
1
vote
3answers
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 ...
-3
votes
4answers
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 ...
2
votes
2answers
46 views

Amateur Radio License classes in Central Iowa

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.
7
votes
1answer
213 views

How do I identify a genuine Nagoya antenna?

I recently purchased a Nagoya NA-771 that I believe is counterfeit given the overall feel of the antenna. How do I identify a genuine Nagoya antenna vs. a counterfeit?
0
votes
1answer
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.
10
votes
1answer
321 views

Why does the FCC put restrictions on symbol rates?

This answer claims that Mostly, on HF, the FCC has chosen to limit modes of transmission and symbol rates rather than bandwidth Why does the FCC limit symbol rates?
2
votes
0answers
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 ...
1
vote
1answer
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 ...
0
votes
4answers
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 ...
0
votes
1answer
73 views

fldigi will only start the second/third time

Starting sometimes after 2nd sometimes after 3th times. Just now PC fresh booted, then console and fldigi started. and 2. start hangs after the two messages "Silicon_Labs_CP2105_Dual_...." start ...

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