# All Questions

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20 views

### What is the signal of a receptor antenna irradiated with a plane wave?

Lets say there is a reception antenna connected to a detection system with a coax, and a transmitter sends a plane wave. What happens is that the antenna gets a certain power, following the [...
71 views

### What kind of wire would be good for a 160m - 40m fan dipole?

I want to know the best copper wire or tinned copper wire for a fan dipole for 160, 75, 40 meters. It would be coax fed and I would like it to handle 1500 watts or more. I would like 65/30 strands of ...
41 views

### Coaxial cable identification

Is there a way to identify this coaxial cable? I am interested in model and parameters such as epsilon, diameters etc. There is nothing written.
178 views

### How much attenuation (dB) from a balun is expected?

I'm building a dipole antenna for 433 MHz, first one ever. I will have to use a ferrite bead to balance the feed. How many decibels of attenuation should I expect from the ferrite bead?
36 views

### Boom length of a Yagi antenna

Apologies in advance if this question is too straightforward. I was browsing for some information about the dimensions of Yagis. This yagi listed by PEOSAT, called Cue Dee 15144AN, is stated to have a ...
59 views

### Grounding on second floor

I need to ground an upper floor shack, but I do not know very much about grounding. I have a Pathfinder dipole by Radio Wavz and I don't believe I need any RF grounding, but as for safety and ...
36 views

### Connecting Linux to Yaesu FT3D via bluetooth for audio into Direwolf?

I'm looking to connect my Yaesu FT3D ham radio to a Linux laptop via bluetooth. I understand it only does audio over bluetooth, but for my use case that's acceptable. My end goal is to run Direwolf ...
34 views

### How to apply for the ARRL WAC award?

I've managed (thank you FT8!) to have LOTW-confirmed contacts with the 6 applicable continents. However, on reading the ARRL page for the WAC award it says that you have to apply on paper and that ...
2k views

### Do these look like amateur radio antennas?

I am planning to move into a new apartment, and of course would like to install a HF antenna there, on the roof if possible. Today I noticed a small Yagi antenna on the roof of the building , more ...
55 views

### FT8 etiquette when no reply after responding to CQ?

When you respond to an FT8 CQ and the other side doesn't respond after a couple of your transmissions, what is proper etiquette? (Assuming you're working split and not transmitting on his receive ...
130 views

### Fractal antenna shapes that work for you? [closed]

I just answered this question, and I wanted to know if any particular shape has been found to be successful for anyone. There seems to be a lot of research on IEEE that indicates that there should be ...
121 views

### How to choose antenna "pigtail" pragmatically?

I'm starting to tinker with an RTL-SDR (generic, and cheap, so nothing fancy in any respect, hence the "pragmatic" in my question title). It's clear that the antenna provided (about a foot ...
58 views

### Spinning magnet in space and EM waves but how? [migrated]

If we take an iron disc in space that is spinning on its axis, no electron in sight for miles other than the disc. The disc is magnetized with 2 poles. Speaking from an electrical potential, yes the ...
45 views

### Simple AM receiver with gnuradio / RTL-SDR

EDIT: I have succeeded in getting the AM receiver to work, by replacing the AM Demod block with a Complex To Mag, and a Band Pass filter (this is noted as an alternative in the AM Demod docs). ...
58 views

### What steps to take to secure for G2 geomagnetic storm?

So I see NASA has issued a geomagnetic storm watch for a possible G2-level storm on the 11th. I’m at about 53 degrees north geomagnetic latitude. Is this something I need to care about equipment-wise? ...
101 views

### far-field in air versus vacuum [migrated]

I think the far-field is significantly different in vacuum versus air, is this true? More specifically, when we talk about far-field, we mean the electromagnetic wave as a whole etc. but in the near ...
145 views

### Why half-wave dipole is the most efficient one in comparison to other electrical lengths of that antenna?

I have a problem on the understanding of a half-wavelength antenna. Namely, why is the half-wave antenna has a highest power emission. Considering Far Field factor F($\theta$), which is known from the ...
61 views

### Link Budget - Are there any restrictions in the formula?

Depending on the parameters used in the link budget formula it seems that one may come up with a received power (dBm) larger than the transmitter output power (dBm). For example: Frequency: 50 MHz ...
211 views

### EIRP - Conservation of energy

I have a theoretical question about EIRP. EIRP is calculated by summing the power of the radio (the intentional radiator, IR) plus the gain of the antenna (dBd/dBi) minus the sum of the losses. The ...
32 views

### What modulator is used on this audio file? (it should be ASFK1200, but not recognized)

I have this audio file (WAV) that I'm trying to decode using multimon-ng (also tried Qtmm AFSK1200 Decocoder). It should be using AFKS1200 but multimon-ng can't demodulate it and by the looks from the ...
79 views

### What cause the shape of frequency spectrum convex or concave?

I use gnuradio and fosphor to view the spectrum from USRP B210, default gain set to 34, output looks like concave as below: ...
29 views

### How to record and replay the center frequency when file_sink?

Workflow as below: When file_source after file_sink,center frequency is not recorded and ...
36 views

### What would cause this RF noise pattern? (Hum with associated "flapping" and beeping)

In quite a lot of places below 7000kHz I see a repeated noise figure. A hum, then about 12kHz above it a "flapping" with beeping noise, and then about 50kHz from that whistling with three ...
454 views

### Can I power a QRP station with an USB powerbank?

I recently found out there are very cheap (down to under a dollar) adapters that convert the 5 Volts from a USB port to 12 Volts. Manny small QRP stations draw very little power. For instance, the ...
41 views

### GNURadio Guided Tutorial PSK Demodulation Example

I have been reading and doing the steps on this webpage of GNURadio : https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation In the middle of the page, there is a section: "Using ...
37 views

### Any good RF noise "libraries" out there?

Are there any good/useful "libraries" of RF noise out there? I know about http://www.arrl.org/sounds-of-rfi but it is pretty limited. (And I wish the screencaps showed the FFT rather than ...
235 views

### If I tie antenna wire in a knot, will there be damage to the wire?

I'm building HF kits 80m EFHW kit, and in the instructions it directs you to tie a knot in the antenna wire. I'm concerned of damage to the wire. I have found no source as of yet that indicates if ...
90 views

### Erratic behavior on Baofeng UV-5R Plus

I bought a UV-5R Plus (8 watt radio in the same casing as a normal Baofeng), and I've noticed some strange behaviors. Occasionally when I key up on my local repeater, the radio turns itself off and on ...
85 views

### Need advice for running coax for HF to my shack

I'm looking for advice for running coax cable to my shack on the second floor of my house. I'm planning to use this coax line for HF (recently upgraded to General!). I'm a newbie and I am very handy, ...
84 views

### Clock Recovery for 4FSK Modulation in GNU Radio

I have made a loopback flowgraph in GNU Radio companion to implement a 4FSK modulation. For the modulation section, I have simply adjusted the "chunks to symbol" block to map each 2 incoming ...
37 views

### How the ELF-VLF background noise spectrum looks like?

In the ELF-VLF frequency band,some background noise like Schumann resonances shows in the spectrum analyzer as peaks. I want to have a overview look of the background noise of ELF-VLF frequency band,...
84 views

### Google Birthday Doodle Morse Code?

Morse code in this doodle? think Interstellar (movie) https://www.google.com/doodles/googles-23rd-birthday
25 views

### Does GPS port of USRP B210 only used for GPSDO?

I try to use gnss-sdr these days with USRP B210. When I connect GPS antenna with RX port,gnss-sdr output well.But GPS antenna ...
83 views

### How to make ELF-ULF antenna myself?

I want to check the EM pulse between 3HZ-3kHZ with N9041B UXA Signal Analyzer,it seemed the only antenna I can use is Aaronia MagnoTRACKER,but the price is not affordable. Then I plan to make ELF-ULF ...
34 views

### SSB Single Conversion Superhet 2nd Mixer IF Termination on Transmit

I have a question about "best practice" in regards to how the 2nd mixer IF port is coupled to (in my case) a 20m double tuned filter on transmit. I'm currently building out the transmit ...
321 views

### What's the proper way to mount antenna mast to the side of a house?

I'd like to mount an antenna mast to the gable end of my house. I was planning for the mast to extend from ~10 feet above the roofline down to the ground. I've seen wall mounts specifically for masts, ...
62 views

### How to automatically scan a wide-band signal without manually changing center frequency in GNU Radio?

I have a USRP B210 SDR that has only 56 MHz bandwidth. How can I automatically scan a wider bandwidth (like from 80 MHz - 5 GHz) without manually changing the center frequency in GNU Radio? In the ...
112 views

### What is the minimum height required for a 60 meter NVIS antenna?

Various answers include 1/8th of the wavelength all the way down to 1/10th, but would 1/15th or even 1/20th of the wavelength be sufficient for a 60 meter (5 MHz) horizontal NVIS antenna?
41 views

### Calculating SWR for a dipole

I have a dipole wire antenna that is tuned to 14.0 MHz so that it has an SWR there of nearly 1:1. Is there a mathematical formula by which I can compute the expected SWR for other frequencies? I would,...
28 views

### For a 5'X9'balcony up 12-18 ft I need a good short antenna for 40m USB. Openings ~5x 8 ft to west 5'X4ft to south w/3' metal balustrades

Is there a 2-3 meter long loaded dipole for the USB 40m ham band that I can use on a 2nd floor balcony?
197 views

### Why is the total radiated power of array calculated by sum of square of excitation coefficients different from the result by integral of power pattern

Consider an array with same isotropic antennas, $P_{ele}^n$ is the input power of the nth antenna. As I consider antenna radiation efficiency = 1, the $P_{ele}^n$ is also the radiated power of the nth ...
64 views

### Will a HF beam antenna on rooftop building interfere with other antennas there

I am moving into an apartment on the top floor of a building and I intend to install a HF beam antenna for 20 to 10 meters, on the rooftop of the building. I notice that there are already some ...
59 views

### Increase transmit and receive frequency of handheld transceiver

I'm new to the world of ham radio so this might be obvoius, but I have a Baofeng UV-82 which can transmit and receive up to 520MHz. I need to be able to transmit and receive on frequencies up to 1GHz. ...
64 views

### Mounting a hex beam on top of a high urban building

I am moving into a new apartment in the city soon which is on the 24th and last floor of an apartment building. I will have access to the roof of the building also. I'm still trying to understand ...
309 views

### How to reduce VFO sensitivity to the hand capacitance?

I got a little tired of Si5351 and decided to build an analog CW transceiver. It's almost done and works pretty well. However, I discovered one problem. When I reach the VFO control with my hand the ...
108 views

### Common-mode choke (CMC) hurting my SWR. Live with it? Drop the choke?

I have been using a Par EndFedz Mk2 Trail Friendly 40/20/10 though using the matchbox from an EndFedz EF-QUAD (with Vibroplex’s blessing) so I could transmit at more than 25W. On all three bands I ...
289 views

### How to increase the range of the spectrum analyzer in SDRSharp?

I'm trying to visualize the frequency band utilization during a GSM phone call using SDR. Ideally, I would like to plot the whole 900 MHz range, i.e. 876-959 MHz. However, even setting the zoom to the ...
42 views

### How to do physical QSL when not operating from your home QTH?

If you have preprinted QSL cards that have your home address and grid square on them, what's considered the most proper way to do a physical QSL exchange for a contact that was made while you were ...