All Questions
4,228
questions
5
votes
2
answers
2k
views
Can i use speaker wire as a transmission line?
Speaker wire is really cheap and available everywhere, it doesn't seem that different to 300 ohm twin lead. It seems to me it would make an excellent balanced transmission line, does anyone know what ...
- 3,393
1
vote
0
answers
38
views
Is this amount of loss normal with LMR400?
I have a run of about 150 feet of LMR400 (specifically, it's this DX Engineering "400MAX" product). It connects to an Ed Fong antenna (2m, 1.25m, 70cm tri-band J-Pole) about 75 feet up a ...
- 301
0
votes
3
answers
46
views
Linux Alternative Time Sync-ing for JS8 or FT8
I was learning about the time drift set and correct features of JS8Call and wondering about an alternative.
Assume I have a wrist watch that loses 1 second a month and that it's been sync-ed to an NTP ...
- 225
5
votes
2
answers
56
views
14dB insertion loss for bandpass filter acceptable?
I'm busy with a direct conversion receiver for the 20m band, using a VXO and a 14.060 MHz crystal.
I designed a bandpass filter with the following components, using this design calculator.
Someone ...
- 51
0
votes
0
answers
78
views
How can i make an ULF spiral antenna for agriculture [closed]
I have a 15 yrs persistent dreams to accomplish and i don’t know how. The frequency is between 7hz to 250hz TX in the physical appearance of spiral electric stove burner and a RX Whip rubber antenna ...
1
vote
2
answers
167
views
Why do ham radio operators refer to current flow on the outside of coax as common mode current?
My understanding is that the desired mode of operation for a two wire transmission line is differential, where at any point along the line the addition of the voltage or current is zero, such that the ...
- 3,393
1
vote
2
answers
68
views
Baofeng Orange Transmit light comes on by itself (triggered by sound)
I have a BTech UV-5X3 and if I yell or blow into the mic, the transmit lights (red indicator light and orange backlight) come on as though I'm hitting the PTT button. Is this normal and am I actually ...
2
votes
4
answers
102
views
Is an off-center fed dipole (and/or doublet) inherently unbalanced?
Does a balun/choke have to "work harder" in an off-center fed dipole than when the feedpoint is at the center? Or do the standing waves that develop keep the antenna balanced electrically ...
- 5,995
2
votes
1
answer
326
views
Help on identifying signal type and extract audio from a signal
I Just recorded a signal using SDR++ and RTL-SDR.
The signal seems to be normal audio but I cannot extract clear audio from it.
I can recognize speech and tones even without any demodulation so I ...
- 123
1
vote
2
answers
76
views
How to best ditch the counterpoise of a random wire antenna?
The "ground" has several effects on antennas, most of them negative (see e.g. Why does an HF "monopole" need dozens and dozens of radials while a VHF/UHF "ground plane" ...
- 5,995
2
votes
3
answers
79
views
Why does an HF "monopole" need dozens and dozens of radials while a VHF/UHF "ground plane" antenna only needs four?
It's a bit counter-intuitive that for an HF vertical antenna (such as a quarter wave monopole) the best advice is to put as many radials and as close to the proper length as possible.
The typical VHF/...
- 5,995
0
votes
0
answers
27
views
HAMRS logging app dumped all data
Anyone have this issue. HAMRS logging app on Android dumped 3 months of logs. It's an amateur radio logging app where you log your contacts. I went to open the app the other day and my profile and all ...
2
votes
3
answers
50
views
Is a UHF connector any real disadvantage off the transmitter circuit board or at an antenna feedpoint?
I have a discone antenna intended for use in the 25-1300 MHz frequency range, but it uses a SO-239 connector.
Now, we know that the so-called "UHF" i.e. the PL-259 male plug and SO-239 ...
- 5,995
0
votes
3
answers
84
views
ELF antenna receiver build instructions?
I built a vlf receiver in the nineties but good grief, that's a long time ago and have looked very little at receivers since.
I'm interested in frequencies from 12 - 18 Hz.
Looking at the following
...
- 101
2
votes
2
answers
90
views
How do I rewire a simple a.m. loop antenna that became unwound?
This antenna has been around for decades and the design is as basic as can be.
Somehow the antenna I'd been using, became unwound. The total length of the wire is 4.9ft.
I need to know the proper ...
- 21
2
votes
1
answer
42
views
How can a low-impedance load can damage a FET final amplifier?
I believe I understand how an excessively high impedance can damage a final output power MOSFET (voltage rises until avalanche breakdown). But how does an excessively low impedance do that? If the ...
- 487
2
votes
1
answer
81
views
Core mix preferences for a balun (or unun) vs a choke
Was watching a YouTube video a little while ago and an engineer from Palomar engineers mentioned that using Mix #31 cores for balun construction wasn't ideal.
He went on to mention that Mix 31 (or 43 ...
- 585
0
votes
0
answers
43
views
Direct call via the repeaters
Is it possible and if, how does it work, to establish direct DMR call between two stations through different repeaters? Does it work in the similar way as opening temporary groups on repeaters or some ...
- 111
-4
votes
2
answers
56
views
Why does CHIRP report "Frequency not supported"?
I have been trying to enter a frequency in CHIRP but every time I do it clears the frequency and issues the message "frequency not supported".
I'm trying to program a Boafeng BF-F8HP with ...
- 7
1
vote
1
answer
40
views
How do I wire an external mic and speaker to the Yaesu FT-250R without using their adapter?
I'm trying to wire up an external mic with PTT and a speaker to my Yaesu FT-250R to basically use as a VHF base station when I'm not mobile. Unfortunately, I can't find anywhere a description of how ...
- 71
0
votes
1
answer
55
views
YouLoop antenna for amateur satellite reception
I recently learned about the commercial YouLoop antenna and it seems to be quite simple to set up. They said it was possible to receive satellite signals on amateur VHF (e.g. NOAA and other CubeSats ...
-2
votes
3
answers
80
views
Radio without antenna?
Is it possible that there will ever be a radio system that does not require antennas? (Not small embedded antennas for microwave radios, but radios that actually do not have antennas)
- 239
4
votes
3
answers
182
views
What is the difference between antenna input impedance and its radiation resistance?
I got to know that the input impedance of the halfwave dipole antenna is given as:
Zin=1/Im* sin(β(H-|Z|))
where Im is the maximum current on the antenna( when excited with a 1 volt supply),
H is the ...
- 43
10
votes
3
answers
2k
views
Would it be possible for a software-defined FM receiver to demodulate two signals on the same frequency?
When two FM signals are transmitted on the same (or about the same) center frequency, either you hear only one or you hear that noise I'm sure most of you have heard. Would it be possible for a ...
- 239
-1
votes
1
answer
59
views
Transmission power of Apple Wi-Fi antennas (EMF and health)
(I hope this is the right place for this kind of question)
Background
I was looking a little bit into how Wi-Fi affects our health topic. While many people seem to be concerned about their Wi-Fi ...
- 109
3
votes
2
answers
100
views
Can someone without privileges on a band operate FT8 on it using the callsign of a ham who does and is present?
I have an Extra license. Is it legal for my dad (who has a Technician license) or my mom (who is not licensed) to operate FT8 on 20 meters using my call sign, if I am physically present at the control ...
- 239
9
votes
2
answers
2k
views
Why are longer antennas not suitable to pick higher frequencies?
I know that the length of an antenna depends on the wavelength of the frequency it's trying to receive.
A higher frequency needs a shorter antenna and vice versa.
I can see that with a high frequency ...
- 203
0
votes
0
answers
36
views
How to get channel displayed on an Anytone 868UVE
How do we get the channel displayed on an Anytone 868UVE?
I'm probably missing something in the manual that is obvious elsewhere, but how do I get the display to show the channel I'm on and not the ...
- 1
1
vote
2
answers
105
views
Is a 94' dipole antenna fed directly by coax useful for any particular known purpose?
I'm trying to figure out an old handmade antenna I picked up at a swap meet a few years back. It is a dipole (or "doublet"?) that is both made of coax but also fed by a length of built in ...
- 5,995
0
votes
1
answer
58
views
What power levels do the Baofeng UV-5R/5RA/5RE have? [closed]
What are the power settings of handheld radios of the Baofeng UV-5R series in watts?
- 109
0
votes
1
answer
45
views
Sine wave 'frequency' in recorded signals
I'm trying to replicate a signal from a remote using another wireless transmitter (a cc1101 to be exact). I got somewhere, but I am stuck, and have a fundamental question
At the top is the signal I'm ...
1
vote
0
answers
49
views
Does a filter or inductor's power rating matter in its passband, or only in the attenuated frequency range?
I would like to build a high-pass filter that would block reception of signals from the United States' FM broadcast range (88–108 MHz) while still allowing me to transmit VHF ham signals (around 146 ...
- 5,995
2
votes
2
answers
143
views
Why do Baofeng radios have such poor reception reliability?
What is the nature of Baofeng radios' poor receiver performance?
This brand of handhelds has somewhat notoriously poor receivers. I hadn't noticed this much when using them for short distance simplex ...
- 5,995
0
votes
1
answer
38
views
How do you create a DC-blocking ground-shunt that looks inductive in an "L" match?
We are optimizing an impedance match with s2p models for an LNA and found that an "L" match with a serial cap and shunt inductor will optimize to provide +3 dB of output, versus using serial ...
- 307
1
vote
1
answer
231
views
Why is there a repeater on 146.46? Isn't that a simplex frequency?
I have a commercial GE Phoenix transceiver that I sent out to be programmed on 146.460 but have been informed by a club that my transmissions are interfering with their repeater that has a 146.460 ...
- 145
-2
votes
1
answer
37
views
Can I use the Baofeng UV-5R radio with the older model RETREVIS RT-5R? They look like the exact same unit [closed]
Can I use the Baofeng UV-5R radio with the older model RETREVIS RT-5R? They look like the exact same unit.
4
votes
2
answers
298
views
VNA basics, antenna coax cable
Recently purchased my first VNA (Nano VNA) and I'm trying to learn the basics.
I have a 150MHz 1/4 wave whip antenna that I need to install on a large metal object so I was hoping to use a VNA to help ...
- 43
2
votes
0
answers
47
views
What could cause an IQ diagram to shapeshift randomly?
I'm trying to interface a DVB-S2 transmitter to a DVB-S2 demodulator - for now with a direct cable+attenuator link. Both are set up exactly with the same parameters (same carrier frequency [2150MHz], ...
- 133
1
vote
1
answer
52
views
RG-174 vs RG58 for winding toroid
I'm building a balun for a fan dipole, and this chart suggests 9 turns of RG-58 on two FT240-31 cores will give good performance over the frequency range of interest.
However, I don't feel confident ...
- 225
0
votes
1
answer
31
views
Vertex Standard VZ-28 - Unable to import settings into software due to password
I had been trying to program my Vertex Standard VZ-28 radio on my Windows-7 Machine using the VZ-28 V2.0.2 software.
I had entered the password under "General" menu for the radio and now ...
- 111
0
votes
2
answers
115
views
Does the specific frequency of a CW tone make a difference to output from a practical SDR?
I'm using a Nuand BladeRF 2.0 micro, which is based on the AD9361. I'm just trying to get a handle for how it behaves at the moment, so I was testing generation of some CW tones using GNU Radio and ...
- 176
0
votes
1
answer
43
views
Looking for an inexpensive FM downconverter for an SDR project
I do a lot of work with DSP and I am looking for an inexpensive down converter so as to down convert from the FM band to some intermediate frequency. Not necessarily to standard FM 10.7MHz but ...
4
votes
1
answer
73
views
Looking for a Mic-E APRS encoding routine [closed]
I am looking for a Mic-E APRS encoding routine that is available for reuse in free and opensource software.
I found many libraries and open source software offering Mic-E decoding, but never encoding. ...
- 1,267
1
vote
2
answers
93
views
Small shortwave (20MHz) directional antenna design
I'm trying to do some basic radio astronomy experiments, and I'm currently working on picking up radio bursts from Jupiter. These are emitted at around 20MHz; for all intents and purposes, Jupiter is ...
- 111
3
votes
1
answer
55
views
Ferrite choice for fan dipole
I am intending to build a two element fan dipole for 80 and 20m. How should I go about choosing a ferrite toroid and number of windings for the balun, to operate effectively over such a range of ...
- 225
2
votes
0
answers
32
views
Easy Digi PTT circuit with Baofeng or Kenwood HT stays on after transmitting on VHF
I got my Easy Digi all wired up correctly, believe me, it took a while because of this issue. I've ruled out the FTDI controller I'm using because I can manually activate the optocoupler but supplying ...
- 21
2
votes
1
answer
68
views
What would happen if the low noise amplifier (LNA) is saturated?
Suppose that there is a 2 dBm interference signal and a -90 dBm signal of interest (SOI) at the input of LNA (Gain = 1, in linear region). Suppose that the P1dB of LNA is 1 dBm, so the LNA is ...
- 125
5
votes
3
answers
149
views
What kind of soldering iron is best for PL-259 (UHF) connectors?
What do you use to solder connectors onto bulk coax cable?
Soldering the UHF connector to the coax shield on a PL-259 is described as requiring a bit of "experience and skill" in Dave Casler'...
- 145
2
votes
1
answer
86
views
Phase-tuning Yagi-Uda antennas
Related to my earlier question around the TET-Emtron HB35C antenna. It is advertised as a:
The HB35C is a full size tri-bander, efficiently utilising the DUAL
DRIVE HB9CV system with the ...
- 585
0
votes
1
answer
75
views
Dual driven-element Yagi-Uda antennas
Came across the TET-Emtron HB35C antenna which is a:
"The HB35C is a full size tri-bander, efficiently utilising the DUAL DRIVE HB9CV system with the revolutionary “PHASE TUNED” VK2AOU multi band ...
- 585