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4 views

Tradeoffs: varicap vs. air variable capacitor for Rx bandpass?

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?
68 views

Using radio for musical collaboration — the line between conversation and broadcasting

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 ...
21 views

Using radio for musical collaboration [duplicate]

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 ...
19 views

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 ...
708 views

Why is it bad to put ground rods too close together?

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? ...
12 views

Upconvert Signal with USRP N210 in GNU Radio Companion

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 ...
27 views

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 ...
54 views

Weatherproofing coax connection to balun

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

Antenna phase explanation

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 ...
52 views

Building a low-power simple RF frequency (433MHz or 900MHz (but not both)) detector effective at 5m with a 10mW signal

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 ...
919 views

Are there any antenna that can create disk like lobes?

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.
46 views

Loop a long wire antenna or EFHW

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 ...
47 views

Old 144MHz rig can transmit/receive signal but not voice

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 ...
70 views

Multi-turn large/full-wave loop antennas?

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 ...
33 views

The HPBW of a helical antenna

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, ...
23 views

Reduction in transceiver power output into high SWR

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 ...
70 views

Multi-wire EFHW?

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 ...
123 views

How can I check if my CB radio is AM or AM/SSB?

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.
74 views

What does antenna frequency range mean in practice?

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 ...
33 views

Kenwood TM-D710E in packet mode: does not transmit

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 ...
25 views

Does anyone have any link to the original papers describing MSK144 and JT4?

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 ...
49 views

What tools can I use to study for the entry level ham test? [closed]

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

How far from a cable entry point can the lighting suppressor be installed

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, ...
28 views

Viewing current frequency on Kenwood TM-281

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?
758 views

Why does Free space have the highest loss compared to other losses like atmospheric loss, feeder loss etc?

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....
57 views

Mutual impedance of two parallel dipole

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 ...
83 views

Connecting copper strap to grounding rod

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 ...
55 views

Checklist for QRO remote setup

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 ...
38 views

Looking for criticisms on my VNA-like SWR meter I am designing

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 ...
76 views

Yagi Antenna - Elements Length

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 ...
107 views

Sanity check: Should I be able to hear this 20m beacon?

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 ...
59 views

What is an expected IF level of SA612?

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: ...
116 views

Design of oscillator

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 ...
64 views

Could not observe the Meteor M2 even though I scanned the sky at the time it passes with a high elevation degree (77). What might have happened?

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 ...
83 views

Radio Waves propagation (Intuitive Understanding of Wave propagation)

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 ...
50 views

Why is Echolink copying the exe file to another drive letter everytime I launch it?

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:...
246 views

What is the capacitors purpose on a balun?

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

How to effectively test and interpret the “working range” of a ferrite core with a signal analyzer?

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 ...
214 views

Why are contest signal reports always “59” or “599”?

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 ...
114 views

What are these serial number pileups on 20m and 40m?

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 ...
67 views

How to stabilize an antenna

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 ...
110 views

Would Orbital Angular Momentum (OAM) multiplexing work over HF bands?

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 ...
87 views

Receiving an Coded Odd Signal at 137.25MHz but don't know what it might be. It can affect my detection on NOAA 19. Need help

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,...
50 views

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 ...
75 views

How does a digital demodulator know which level it is reading?

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 ...
84 views

How do dual band J poles work?

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 ...
3k views

Why does the audio on my FM transceiver cut out every 5.5 seconds?

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. ...
37 views

FT8 low-density parity check code

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 ...