# All Questions

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192 views

### Why can I hear Morse when not in CW mode?

I don't "get" CW. I can't understand the chatter on an FM radio broadcast when my radio is set to AM. This makes sense, the signal is modulated using frequency modulation and I am trying to ...
95 views

### 440MHz collinear dipole array - suitable coax?

friends! Finally found my next antenna project..a collinear dipole array for the 70cm US ham band. The general idea: (image courtesy https://link.springer.com/referenceworkentry/10.1007%2F978-981-...
116 views

### Why does the HamQSL website say the 40m band is fair and the 20m band is poor during the day?

http://www.hamqsl.com/solar.html Why is 40m shown as "fair" while 20m is "poor" during the day. Shouldn't 7 MHz be getting absorbed by the D-layer more than 14 MHz?
84 views

### What Are the Properties of 43' Vertical Monopoles Used as Multiband Radiators?

43' vertical monopoles sometimes are used with an auto-tuner at their input as radiators in the ham bands from 40m through 10m, but are any performance compromises required to do that?
42 views

### What is the maximum antenna cable length allowed in GNSS application?

I am beginner in designing GNSS receiver design and facing concern while testing the high precision GNSS survey.I am using GNSS survey grade antenna for my GNSS receiver application testing, the ...
45 views

### Effective area of a phased array

For a $N$-element planar phased array, all the elements are same isotropic antennas. Then, what is the effective area of this array? Is it $$A_e=\frac{\lambda^2}{4\pi}GN$$ where $G$ is the directivity ...
570 views

### Do chokes at the antenna feedpoint stop the coax from receiving signals as well, or just transmitting?

It seems common knowledge that a choke at the antenna feedpoint stops the outside of the coax shield from radiating when transmitting into the antenna. But what about stopping the outside of the coax ...
169 views

### Ground-Plane radial sizing, is there such thing as too long?

I'm just trying to make sure I understand the theory correctly. I have some triband VHF/UHF/800MHz antennas, I need to mount on a tower so I plan on using a "mobile to base" conversion kit. ...
45 views

### Is a Buried Ground Rod for the A-C Mains Service Entrance to a Building Also Useful as an R-F Ground?

A NEC4.2 analysis of the performance of a buried ground rod at the A-C mains entrance of a building shows it be ineffective in removing the common-mode r-f current that can flow along the OD of the ...
69 views

### Is a 1/4 wave vertical actually better than inverted L on 160m?

Surprisingly, I am unable to find much info comparing these two antennas. Essentially, they are the same except the one is shorter and top loaded with one wire. Does anyone have any performance data ...
99 views

This is my first ever experience with GNU Radio. I am trying to implement a simple FM receiver shown below with its C++ API. I seem to have pedantically deconstructed this receiver into its smallest ...
78 views

### How to deal with foil shield when adding a connector?

I want to crimp a connector onto some RG58 A/U cable. The cable has a foil shield under the braided shield. What's the recommended way to deal with the foil? Should I treat it just like the braided ...
79 views

### How much loss is there in traps, really?

I searched and couldn't find a direct answer so thought I'd ask. We all know the mantra "traps aren't good as they have losses", but how much loss are we talking about, really? Am I correct ...
128 views

### How does this quarter-wave stub balun work?

I was searching for 1:1 balun designs that would be efficient at VHF yet could easily be made from commonly available materials when I came across these two: While the design on the right seems ...
49 views

### Choice of PCB coil design for filter inductor at ca 20 to 400 MHz, 5 W

Looking at the diplexer schematic from this nice question, I realized this can completely be done in PCB-formed elements (minus the connectors). (As a kind of counter-action to the original question'...
29 views

### 2GFSK digital filter bandwidth calculation

I'm working on a S2LP from ST and I am configuring the RX digital filter. I need to calculate the bandwidth of the signal which has 2GFSK modulation. Do you think the code below is correct for ...
75 views

### What kind of RFI is this?

I'm getting a lot of noise now that I have a dipole higher up. The pattern on the waterfall makes it seem man made. Could it be power line? Or is it some kind of motor? Here's a short video of the ...
103 views

### What is the name of a device used to detect noisy appliances?

I live in an apartment. I don't have control over all of the appliances but perhaps I can mitigate if I know where the noise is coming from and under what circumstances. If I'm shopping for such a ...
97 views

### Convincing kids to learn NATO alphabet

I'm trying to make learning of the NATO alphabet interesting for kids. I invite them to spell car plate numbers during vacation with their parents. So both, the kids and the parents will learn the ...
51 views

### Lightning protection for a vent stack antenna

I've seen ham radio antennas that slide over a vent stack. The usually way to connect them to the transceiver is to lay the feedline across the roof. However, the manufacturer provides instructions ...
38 views

### Baofeng UV-5RE shows wrong TXP icon

I bought a Baofeng UV-5RE of Alibaba for a little over \$30. It seems to work as expected, all the menu items are consistent with the YouTube videos I watched but... the little power icon at the top of ...
79 views

### How to match transmitter to Beverage antenna

Beverage antenna consist of pair of transmission lines - one being the "antenna proper", the other ground. The antenna is being fed via open feed line ( approximately 450 Ohms ) - one side ...
165 views

### How to measure quartz crystal motional parameters using a VNA?

I want to measure quartz crystal motional parameters with a VNA, unfortunately all Google searches I've done have lead me to nothing in concrete. I know how to get an impedance curve and measure the ...
136 views

### How to prevent cracking the capacitors in my diplexer?

Just made my first 2m/70cm diplexer. Important: I aim to be able to use this up to 50 Watts. S21 from the LP section: Having access to regular distributors such as Farnell/Element14, Mouser, Digikey,...
15 views

### R433A SAW Resonator

I have one of those wireless weather sensor things that stopped transmitting. Inside is one of those ubiquitous R433A SAW resonators that transmit on 433.92MHz. I've verified that the board it's on ...
94 views

### GNU Radio - Frequency parameter of Signal Source Block

I designed an analog FM transmitter with GNU Radio Companion in order to understand the tool better. The hardware I use is an USRP B200. The carrier was built with a Signal Source block and the ...
81 views

### How can I replace the NiMH battery in an old RigExpert AA230 Antenna Analyzer?

I have an AA-230 Pro Antenna Analyzer. Its similar about 5-10 years old with a failing battery. The battery will only hold a charge for a day or so, and only for minutes while in use. I tried: ...
4k views

### When would we ever want to use a voltage balun in ham radio?

In a world where common mode current is the enemy, and we're constantly doing what we can to avoid RF in the shack, why would we ever choose a voltage type balun over a current balun? I understand ...
114 views

### What is an expected SWR plot for a trap dipole?

I've build a trap dipole for 20/40m bands. Traps are made of a coil wound on an insulator of RG213 coax and 3 kV NP0 capacitors. The impedance measured with EU1KY antenna analyzer is following: This ...
106 views

### Wiring Cobra 29LTD CB for home use?

I'm a beginner trying to use one of my two CB radios as a "base station." The problem is that the power cable is just two wires (no connectors/12v car plug) and a 2A fuse along one. Is it ...
102 views

### Should I bother with a doublet if I can't go straight to the tuner with open wire?

I have two trees about 135 feet apart and about 55 to 65 feet tall. I have been trying to determine which kind of wire antenna to put up there. Initially I was considering either a fan dipole or ...
171 views

### What would be a good modulation scheme for communicating a single bit of information with no more than 4ms of latency?

This question has been suggested in the comments to a closed question a couple of days ago. I have nothing to do with the original question, but this aspect of the problem made me quite curious, so it ...
83 views

### How Does the Performance of an Inverted V Dipole Compare to a Linear Dipole?

The NEC4.2 comparison in the answer below shows one example, for a practical set of installation conditions.
179 views

### What would a “crystal mixer” have been in an 1960's radio telescope at 960 MHz?

In a paper cited in comments to this answer to In the 1950's how were radio-astrometric positions with portable dishes so precise they could be assigned to their dim optical counterparts (Quasars)? ...
110 views

### Why is a half wave dipole resonant?

Is the following explanation correct ? RF energy with a wavelength equal to twice the electrical length of the dipole is applied to the feed point at the center of the half wave dipole. To understand ...
101 views

### Confusion about dipole standing waves and feed point impedance

The animation below from Wikipedia shows the standing waves of voltage and current on an ideal center fed resonant half wave dipole in free space. The red and blue curves show the change in amplitude ...
2k views

There are various techniques for locating a radio emitter. But what are some methods to make this really difficult? There is usually a patch to every vulnerability, at least from the world where I ...
72 views

### Are circular polarized antennas on HF subject to polarization fading?

Consider the common scenario of two amateur radio operators communicating through an ionospheric channel. Typically, each station will have a linearly polarized antenna, like a dipole or a vertical. I ...
574 views

### Can left-hand and right-hand circular polarizations exist at the same time?

I read in a comment: it doesn't matter which circular polarization you choose, because they are both present, and the whole point here is to select one of them instead of receiving both and getting ...
75 views

### Would the same callsign be issued after a license has fully lasped?

My license is set to expire in a couple of days. I know there is a grace period but I'd like to know if I were to take an exam after the grace period I would be reassigned the same callsign or a new ...
112 views

### Can a receiving antenna really be “as small as you can imagine”?

I read this antenna theory statement somewhere: And, for next-step or future thoughts: a receiving antenna can be as small as you can imagine, without loss of signal to noise. Is this BS or not?
127 views

### Double Cross antenna: what's wrong with my model?

Important note: After consulting another source, I learned that the article calls for the first pair of opposing dipoles to be fed in phase, with the second pair fed in quadrature to the first pair (...
81 views

### For a center fed half wave dipole operated at resonance, are the voltage and current in phase only at the feed point?

For a center fed half wave dipole operated at resonance, the voltage and current at the feed point are in phase in time and there is zero reactance present in the impedance seen at the feed point. For ...
130 views

### How does an Airspy HF+ Discovery compare to a “real” radio?

I was looking for a secondary radio for RX only and I thought a SDR may be a better option. I read about upconverters but then I saw Airspy has a SDR with the upconverter onboard, and claims to have &...
145 views

### Transmit data over HF signal 10,000km away [closed]

I would like to transmit trinary data (-1,0,+1) on 20-30m wave to be received 10,000km away. From Europe to US. My first thought was this: https://www.researchgate.net/figure/Burst-modulation-mode-f-...
116 views

### Why do horizontally-polarized RF waves reflect better off ground than vertically-polarized waves?

It's a well-known fact among hams who use HF frequencies that horizontally-polarized RF waves reflect better off of ground than vertically-polarized waves. This explains why ground conductivity is so ...
137 views

### Long range HF polarization

Is it possible to polarize HF signal (20-30m) at long range (thousands of km)? It was commented in my over questions that polarization is not feasible at long range. However in this article is ...
101 views

### Can I transmit bit data over FM signal on 30m wave 10,000km away? [closed]

I am trying to understand if it's feasible to transmit -1,0,+1 data using FM on 20-30m wavelength to be received 10,000km away. From Europe to US. Ultimately I would like to create a solution which is ...