All Questions

What might be the tradeoffs between choosing varicap diodes versus air variable capacitors in the design and construction of tunable bandpass filters for HF receivers?

I'd like to collaborate (e.g. play together) with other musicians in my local area and/or beyond. Coronavirus has made in-person collaboration difficult. Latency makes internet-based collaboration ...

I'd like to collaborate (e.g. play together) with other musicians in my local area and/or beyond. Coronavirus has made in-person collaboration difficult. Latency makes internet-based collaboration ...

I'm pretty sure this will be fine but thought I'd ask. A Hustler 5btv antenna, the coax from the feedpoint (ground mounted) runs for 3 or 4 meters along with the radials, and am thinking of going up ...

It's understood that ground rods should be spaced by a distance equal to twice their length. I read one source that claimed reduced effectiveness if the rods are closer than that. Is that correct? ...

I'm using a USRP N210 with this GRC diagram where I'm trying to upconvert a 1kHz sinewave. I tried just upconverting the signal from the signal source to 2.5GHz. However, I keep getting the output ...

I am new at gnuradio companion and USRP and I am a little bit confused with UHD:USRP Sink block. I am trying to build an FMCW radar in USRP N210 with CBX40 daughterboard. I want to generate a sweep ...

How should a coax-to-housing connection like this be weatherproofed? It doesn't seem like taping is going to do much good here

Trying to grasp antenna phase, reading through ham.se and youtube but haven't come across a clear (enough) explanation. I understand the basics of antenna phase (i think), where E leads I that's ...

I am looking for a simple schematic for building an effective RF detector which can trigger a GPIO. The goal is to (passively?) detect a 10 mW RF signal (10% duty cycle) and have that raise voltage on ...

Are there any antenna that have disk like lobes : Or are there any antenna that have very thin directivity, say lobes be no more wide than few mm.

For a typical EFHW antenna, let's say we are in a very space-restricted environment, says a hotel room. I am thinking of the idea loop around the wire around the room, maybe even many loops. This is ...

Situation: I have an old 144MHz rig from the 2000's, an IC-271. I am trying to get it up and running. Summary of the problem: I can receive fine on the rig, except for from my HT. I can transmit a ...

There seem to be lots of descriptions and/or articles on using multiple turns of conducting element in small magnetic loop antennas (STLs). But I haven't found any information on full size full wave ...

can someone tell me what are the formulas of HPBW for a helical antenna? I've searched a lot and I saw that there are two different formulas of HPBW for the helical antenna, this one, and this one, ...

How much do transceivers drop their output power, when the SWR is high? Most amateur solid state amplifiers or transceivers are (fully?) protected against high SWR, by a circuit which reduces the ...

I have an EARCHI EFHW (40:1 unun)antenna that I used quite successfully until it fell from a tree. I wasn't able to get it back up, so ran it along my wooden fence temporarily. Unfortunately, the ...

How can I check if my CB radio is AM or AM/SSB? I know that it is a CB UHF radio but there is no information of whether it is AM or AM/SSB.

I'm trying to wrap my head around software defined radios and antennas and noticed that lots of antennas are described in terms of a frequency range. For example, this one is described as operating ...

I own a Kenwood TM-D710E. I connected it via the COM-connector on the panel to a Raspberry pi. On the panel I selected "packet12" (with the TNC button). After that, I can send TNC commands ...

I am looking for the original papers describing both MSK144 and JT4 protocols. I can easily find the corresponding papers for some other digital modes such as JT65 or FT8 (mainly at the Princeton ...

What tools can I use to study for the entry-level ham test? Are the ham tests online now?

I'm installing a transceiver in an office on the ground floor of a warehouse. The antenna will be 45 feet above the office on the roof of the warehouse. The ceiling of the office is a drop ceiling, ...

Once you program a memory name on this radio, it displays the name only. Is there any way to quickly confirm the actual frequency of a named memory?

In a communication Satellite system, there are losses that occur when the signal is received at the antenna and then passed through a communication link to the output stage which could be the receiver....

Good Morning all, I want to calculate the mutual impedance of two parallel dipole. The first hypothesis is to assume that the dipole 2 is in open circuit, nothing difficult here I knew how to do it ...

Is there a way I can connect a 2"x.025" copper strap to a 5/8" grounding rod that can be buried? I've seen the bolt-on strap clamps, but those need to be inspected periodically. I've ...

In a few weeks I'm hoping to set up a solid state linear amplifier at a remote shack that I've set up at the house of a friend who lives in a rural area. I've been connecting to this shack remotely ...

I am in the process of building a SWR meter with VNA-like features. I'd be really interested to hear from fellow hams any input, suggestions, or tips they have regarding this before I go get it mass ...

I am currently modeling a yagi antenna using Matlab and after I optimized the antenna, it gave me a director length shorter than the exciter itself (even if the optimization gave me a good gain). From ...

I’m in Sacramento and have an EFHW antenna about 30’ up. I expected to be able to hear the W6WX 14.100 beacon without issue but I cannot. The distance is about 140 miles and the beacon transmits its ...

I tried to use SA612 as a frequency mixer. Since it's a Gilbert cell, it has a high input impedance. Thus I added a pair of transformers as "Experimental Methods in RF Design" book suggests: ...

I'm looking for a good tutorial about oscillator design (electronically) for transmitter. The problems with current tutorials are almost all provide only schematics, some explain how it works. But ...

I am currently trying to observe and obtain data from the meteorological satellites. I have constructed a V-dipole specifically for the 137 MHz and was able to observe the NOAA 15, NOAA 18, and NOAA ...

I have few similar questions regarding Radio waves communication particularly FM and AM type of Radio wave communication. Please bear with the naivety of the questions. Questions: Radio waves in FM ...

I have Echolink 2.0.908 installed in the default folder C:\Program Files (x86)\K1RFD\EchoLink Every time I click on the shortcut to launch it, a copy of echolink.exe is created in the root of my G:...

Per the subject, what is the capacitors purpose on a balun? Used a lot on wire wound ferrite toroidal baluns.

I have a couple of Ferrite beads that are advertised as effective for suppressing conductive noise around 150kHz which I'm trying to monitor their actual performance with noise filtering. In my set ...

I've heard lots of contest exchanges, and the signal report almost always seems to be 59 for phone or 599 for Morse, even when the operator giving the report has to request information to be repeated ...

Every so often while shortwave listening I’ll come across a frequency where tons of hams are talking all over each other giving a call sign and a six digit number only (not a QSO). I imagine these ...

I have an antenna on a building. It is made of steel and is about 10ft long. It wobbles a bit in high winds. It is not going to do a Tacoma Narrows but it is a bit annoying. Can I tie stainless steel ...

OAM (Orbital Angular Momentum) Multiplexing is a form of multiplexing capable of high data speeds on limited bandwidth using the physical properties of EM waves. An experiment in 2012 transmitted two ...

I am a newbie trying to detect NOAA 15, 18, and 19 satellites, which have downlink frequencies between 137 MHz and 138 MHz. I am using an SDR dongle and attached a photo of it to this post. Of course,...

I have a Baofeng UV-5R and I have been using it as a police/EMS scanner. I have used it before and it has worked perfectly. I just recently moved to a new area and yet when I went to listen into the ...

I have recently started getting into wireless digital communications and I read about QAM modulation. But I am a little confused as to how the receiving demodulator would know which symbol it is ...

My understanding is a J pole is a $\frac{1}{2} \lambda$ dipole attached to a $\frac{1}{4} \lambda$ impedance matching element. How does this dual band work? What acts as the impedance matching element ...

Specifically, my Icom ID-4100a. What's interesting, is that this happens in MR and VFO modes... but NOT when using the built-in WX stations. For example listening to WX-01 (162.550 MHz), no problem. ...

The FT8/FT4 communication protocols use an 83x91 generator matrix for the low-density parity check code. I am interested in MATLAB recasting of portions of these protocols. Can anyone explain to me ...

I'm trying to analyse a signal from a HVAC remote control (864 MHz) with my HackRF, but I'm facing an interrogation about the used modulation: Is it BFSK (frequency modulation) or BPSK (phase ...

I want to get a Garmin Astro 320 (or 430) which transmits GPS coordinates to a Garmin handheld unit on frequency 151.820-ish and 154.600-ish. But I would like to have the Garmin Astro GPS collar on ...