# All Questions

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2 views

### Talk Around vs Reverse

I thought that "Talk Around" and "Reverse" were two ways of referring to the same thing: swapping a channel's transmit and receive frequencies so that one could e.g. listen for ...
26 views

### Hunting RFI with bars every 61 khz

I realise there have been many great posts on hunting RFI, i've got pretty close to tracking mine down, but would appreciate some insights from the ham.se experts :) I've done quite a lot of work to ...
47 views

### Yagi performing far worse than a dipole

A few months ago, I built a 6 element yagi: 3 driven elements, and 3 reflectors. For 10-15-20m. I was able to tune it to SWR 1:1 for the FT8 frequencies in each band. This antenna is only 6m above ...
46 views

### How to track down and neutralize this apparent mixer creating noisy emissions around my signal?

When I transmit, it there seems to be something mixing and reflecting my signal. For example, when I transmit on 14.300 MHz, I see signals above my transmitted signal at at 14.500, 14.700, 14.900, etc....
28 views

### three-band vhf/uhf ground plane antenna [closed]

I recently saw a ground plane antenna on a mast with four radials drooped at 45 degrees and in its center instead of one vertical element there were three different length verticals mounted within an ...
49 views

### what frequencies is this antenna cut for?

I just bought a magnet-mount whip antenna at a garage sale. It has no brand markings anywhere on it. it is 32" long overall but is broken up into three segments by what appear to be two small ...
59 views

### How does PTT from one two-way radio prevent input on another?

I'm very much a beginner with radio. I have a simple set of Baofeng BF-888S radios, and in my basic use with those, I got very curious about something: when you push the PTT button on one radio to ...
35 views

### Where can I find a table listing the maximum PEP per band?

I'm building myself an Excel Cheat Sheet.
206 views

### Does the output of a BFO for a short wave receiver have to be exactly a sine wave?

I want to build an external beat frequency oscillator (BFO) for an old valve Eddystone receiver I have. There are many circuits for BFOs on the internet, they are mostly similar, the idea seems simple ...
37 views

### Resources and guidance regarding APRS

I know getting my Technician License is the place to start, however, I have in my head a clear path that I want to achieve and am looking for guidance for the most efficient way to achieve that goal. ...
100 views

### How do I know if my coax connectors are good?

In installed a couple of compression style PL-259 connectors to the ends of RG8/U FOAM coax. It's about 16 feet in length. Here is an example of one of the connectors: How do I know if the coax is &...
15 views

### how to set the CFO standard deviation in CFO models

I need some help with a simple thing. I am trying to simulate carrier frequency offset model for Bluetooth Low Energy standard in GNURadio (I am bit new to this). For this purpose, there is a CFO ...
59 views

### What is an Audio Peaking Filter?

What is an Audio Peaking Filter? And how might that be different from an ordinary (narrow) CW bandpass filter, or from tunable audio filters (with fully configurable upper and lower cutoffs)? Does a ...
92 views

### Which cable is better for ham radio antenna? RG58, RG59, or RG6? [closed]

Which cable is better for ham radio antenna? RG 58, RG 59, or RG 6? Based on [1], RG6 has lower signal loss. So, is RG 6 a better cable? Or there are no differences? [1] https://sewelldirect.com/blogs/...
75 views

### How to estimate input and output impedance of an amplifier?

I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in ...
164 views

### What are these antennas?

On a recent trip to China I photographed a number of "antennas" that I do not recognize. Are they even antennas?
73 views

### What is the difference between RIT and XIT?

What is the difference between RIT and XIT? When would one use one and not the other for split (or other) HF operation? When would one need both? Which one is more useful for a transceiver to have ...
41 views

### Omni 144 MHz antenna

I plan to build omni antenna. My goal all about better gain versus a 1/4 wave antenna. I am curious about radial position of the legendary ARX2B Ringo Ranger. Why is the position in below feed point? ...
315 views

### What is the use of dual VFOs?

What is the value of more than one VFO in an HF transceiver? Many novice rigs only have a single crystal oscillator, and a vast number of famous classic transceivers, HF kits, and QRP rigs only have a ...
71 views

### Does Improving Earth Conductivity Near a Buried Ground Rod Improve Antenna System Performance?

The suggestion has been made on various ham-related websites that improving the conductivity of the Earth around a ground rod produces a worthwhile improvement in the e-m radiation from a vertical ...
87 views

### Built a 2 meter 5 element Yagi

Straight dipoles. I can't get the Yagi to tune. I have tried the 4:1 Balun method with coax but not able to tune. With the straight unbalanced input to the dipole I get a 1:1 swr on about 129 MHz ...
49 views

### String in APRS report

Here are two messages I received: ...
79 views

### DIY Triplexer for HF (low), 6m (med), and 2m/440 (high)

I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas ...
40 views

### How to use OFDM Synch in GNU Radio?

I am transmitting OFDM 16-QAM x 6 carriers packets using the python library amodem and a HackRF. My setup is very simple for the transmission side, it takes the .wav generated by amodem from data and ...
125 views

### If the data port on a Yaesu FT-7800R only communicates FM signals, why does the manual mention the port having a bit rate?

I was wondering how the Radio interfaced with a TNC. I thought the computer sent digital data (in a serial format) to the data port on the radio, but from what I read online, it is not a data port. ...
114 views

### What nations still require Morse code testing for Amateur radio license?

Going a bit further I'll ask, for which licenses (all or just for licenses for HF operation) and at what speed (5 WPM, 10 WPM, none specified)? The reason I ask is because every so often I'll see ...
44 views

### Pondering variations on the vertical bazooka antenna

I've seen these antennas built out of coax that are called a bazooka vertical. It's a kind of 1/4 wave vertical, or perhaps a 1/2 wave dipole. Constructing such an antenna is to roll back the outer ...
100 views

### Why are many ground radials preferable to a single ground stake buried 1m deep?

Surely a 1m copper stake provides better ground connectivity for a vertical dipole?
123 views

### 50Ohm Coax presents 50 Ohms of impedance on which frequency?

Either there's a simple answer that I'm not finding in a spec sheet somewhere, or, I'm asking the wrong question!
68 views

### Frequency synchronization in GNU Radio for OFDM 16-QAM x 6

I am transmitting a 16khz data signal using OFDM 16-QAM x 6 carriers and the library amodem using a HackRF. However, I am having issues receiving this signal as the frequency the HackRF transmits on ...
46 views

### What is “allied mode” with regards to PSK31?

Wikipedia says: Colloquial usage of the term 'PSK31' in amateur radio usually implies the use of the most commonly used variant of PSK31: binary phase shift keying (BPSK). BPSK uses no error control, ...
60 views

Teaching myself 4NEC2 and have most of it under control, which is good. Regarding radials & grounds, i've been learning the "rules" NEC(2) has, summarised below. 4.1. Free space. In the ...
70 views

### Questions about effective isotropic sensitivity(EIS)

Recently, I read something about EIS (effective isotropic sensitivity) and TIS (total isotropic sensitivity). I'm trying to understand the concept, but I find it's quite hard for me. In the book ...
80 views

### How to select capacitor for diplexer use

Follow-up on this question: How to prevent cracking the capacitors in my diplexer? Short story: 2m/70cm diplexer, to be used up to 50W. Schematic from Elsie: S21/S11: I don't know exactly what to ...
64 views

### How Does the Propagation of H-pol E-M Fields Compare to That of V-pol E-M Fields (other things equal)?

A rather popular belief on this topic is that h-pol is superior to v-pol. Probably that is traceable to published "far-field" patterns over a lossy ground plane generated by Method of ...
108 views

### Can the parallel capacitance of a quartz crystal be directly measured?

A quartz crystal is often represented by this equivalent schematic: simulate this circuit – Schematic created using CircuitLab How to measure quartz crystal motional parameters using a VNA? ...
114 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 ...
66 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-...
99 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?
83 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?
33 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 ...
38 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 ...
544 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 ...
99 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. ...
42 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 ...
46 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 ...
59 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 ...
70 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 ...