All Questions
4,265
questions
1
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11
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What lengths of counterpoise is suitable to support a 58 foot "random wire" antenna?
I am a technician interested in building my first antenna. I want to explore HF bands, 160m - 6m. Quick impedance calculations indicate that a 58 ft "random wire" antenna could work for this....
- 111
0
votes
0
answers
14
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Descrambling/dewhitening in GNURadio
I am currently working on project which utilizes RTL-SDR for capturing packets. I know that those packets are whitened with x^9 + x^5 + 1 polynomial. No matter what I do the descrambling each time ...
- 1
1
vote
1
answer
34
views
Feedpoints for stacked antennas?
I'm considering building some stacked 70cm quad antennas (home brew / DIY build) -- and... I'm having a devil of a time trying to figure out how/where to feed these antennas. For a single home-brew ...
- 11
1
vote
1
answer
51
views
Multiplayer game over ham radio digital link?
Would it be legal to play a multiplayer video game over a ham radio link? Both players are hams, and their call signs will be transmitted in the link.
- 271
0
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0
answers
15
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What is the best monoband VHF HT 2 Meter Antenna [closed]
I'm looking for the best VHF monoband antenna for my handheld (ICOM IC-V86).
My goal is to significantly increase my talking distance.
I would prefer a flexible antenna over a telescoping antenna if ...
- 1
0
votes
2
answers
46
views
Understanding Coax Impedance when Connected to Reactive Load
The 50 ohm characteristic impedance of my coax is only "characteristic" if it's terminated with $ 50 + 0j$ load. So when the coax is connected to an antenna that is fairly reactive like $ 23-...
- 261
3
votes
2
answers
1k
views
Putting up a tower on my residential property
I live in upstate South Carolina.
I contacted the city and the person who answered the phone call said it would be a new structure and can't be higher the the house on the property.
I looked at the ...
- 31
0
votes
3
answers
68
views
Extend transmit range of my HT
Based on comments and new information I have rewritten this question entirely:
I need advice on a simple, inexpensive, and non invasive (no holes being drilled in walls) way to talk to repeaters in my ...
- 23
2
votes
1
answer
49
views
What are the qualities of a good field day site?
What are the qualities of a good field day site? Specifically what do you or your clubs look for or use as criteria for site selection?
- 123
3
votes
2
answers
206
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DIY Short Vertical Wire Loaded Antenna: Using 20 Ohm Resister to Widen Q
I've been working with Xnec2c to model a 40 meter vertical antenna I want to build for field QRP. This antenna is short at 25 feet and uses a 1:1 unun at the base with 4 radials.
The model has the ...
- 261
3
votes
1
answer
61
views
Is there a list of public datacasts?
I know several datacasts which are free to almost free to receive.
Like there is the outer(other-)net, which can be received using a lora module - it contains a subset of APRS messages and weather ...
- 31
0
votes
1
answer
61
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Can the 902-928MHz ISM band be used in Kazakhstan?
My team is planning to test an IoT sensor in Kazakhstan. This sensor normally sends data to an Edge device (a tablet PC) using the ISM radio band ranging from 902 to 928MHz.
Is this band allowed in ...
- 103
2
votes
0
answers
29
views
DVB-T gnuradio loopback
I have recently had access to two SDRs a hackrf and a Plutosdr through my university.I am now trying to experiment and learn more about wireless communications and how to implement some examples on an ...
- 21
3
votes
1
answer
69
views
Is a club call sign with a suffix (i.e. /GOTA) permissible for a Field Day GOTA station?
The 2017 Field Day GOTA Station FAQ states "The GOTA station uses a callsign different from the call used by the group’s main Field Day operation. The GOTA station must use the same, single ...
- 183
1
vote
2
answers
67
views
What is the name of this connector?
It's the TTL connector on an MFJ-1270. The pins are 1/10" spacing, but I don't know what it's called so I can order another one.
- 847
1
vote
1
answer
66
views
Link budget validation for a UHF satellite ground station
I built a UHF satellite ground station. It has a yagi with G=16.1dBi and an LNA with G=20.1dB. It’s a 430 - 450 LNA with NF=0.68. The RF cable, rg174/u has I think close to a 1dB/m, which would mean ...
-1
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0
answers
46
views
What is the type of Data Stored on GNU Radio File Sink
I am working on storing the data transmitted by AM Transmitter using GNU Radio. I used file sink to do that I'm here by attaching block diagram.
So, I want to know what type of data is stored in file ...
0
votes
1
answer
59
views
Identify format of the files with ".cap" extension [closed]
I have recently inherited a ham radio, and with it several IQ files with ".cap" file extension. They have "IQ capture" in the name. What formats might I be looking at and what ...
- 1
3
votes
3
answers
102
views
Why is analog TV vestigal side band and not SSB?
Analog TV signals have one sideband cut off to reduce their (very wide) bandwidth and save frequency space in the ether. The lower sideband is cut off, but not completely, the lower 1.25 MHz is kept ...
- 385
2
votes
1
answer
49
views
New Amateur Radio User - UK
I am new to this hobby and was wondering if anyone could point me to some easy to digest beginner friendly materials that are relevant to the UK (A lot of my searching has returned US specific ...
- 21
1
vote
1
answer
103
views
Would a transmitter similar to "The Thing" be legal on ham bands in the US?
The Thing was a listening device used by the Soviet Union to eavesdrop on US government officials. It was basically an AM transmitter if I understand correctly, but it required another transmitter on ...
- 271
1
vote
0
answers
16
views
RigExpert AntScope2 is missing Data popup
I recently started using AntScope2 and everything was great. But all of a sudden the Data popup has disappeared. The missing popup is circled in the photo.
How do I turn it back on or get it back? ...
- 11
4
votes
2
answers
159
views
Can an 'ugly balun' be too long?
Will an ugly balun exhibit adverse effects if more coax is wound onto it than the recommended 18 - 21 feet?
The antenna in this instance is a 40 Meter Delta Mono Loop that suggests using 22'-6" ...
- 187
3
votes
1
answer
90
views
Is an Icom radio’s model ID info available via a CI-V command?
I have built a prototype device using an Arduino Nano Every which communicates (using CI-V commands) with Icom radios, to augment control of them. Currently I use the default addresses of the “target ...
4
votes
1
answer
86
views
Digital Protocols, Public Documentation, and Encoded Messages
When is a new digital protocol considered "documented publicly" enough to be used for amateur radio transmissions?
Part 97 states the following about prohibited communications:
(a) No ...
- 43
3
votes
6
answers
95
views
Do changing sidebands have their own sidebands?
An amplitude changing carrier wave causes sidebands to appear next to it when viewed in the frequency domain. But if those sidebands themselves also change with time (because the modulating signal is ...
- 385
3
votes
1
answer
81
views
Using PVC coated solid-core wire for a small number of turns on toroid
I'm researching making my own 49:1 unun using an appropriate mix ferrite toroid and some reasonable gauge solid-core wire. (This is for an experimental HF end-fed antenna, though this detail probably ...
- 1,417
1
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0
answers
50
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What is the point of using LNA if the SDR can increase the gain itself [duplicate]
Usually there is a LNA next to antenna, while SDR devices also have gain setting so we can increase the gain.
As i know LNAs are amplifying all signals with same gain (Am I right?)
So i wonder what is ...
- 133
2
votes
3
answers
74
views
RF switch for half-duplex sequencing on amateur UHF satellite ground station
I need a 3-port RF switch illustrated below. The idea is to use this switch with a sequencer to enable half-duplex communication on a UHF antenna. The switch has three ports: port A connected to the ...
0
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0
answers
29
views
Is there a console client for spyserver?
I am currently using multifm to monitor a few frequencies in the ISM band with a RTL-SDR dongle. I can pipe the resulting demodulated data to other tools.
This works well enough, with a few ...
- 276
1
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2
answers
69
views
What band did walkie-talkies use in Europe before PMR446 was allocated?
The PMR446 band, now used for walkie talkies in Europe, was only allocated after 1997. I'm sure walkie talkies existed before that. What radio bands did those use?
- 385
5
votes
2
answers
111
views
Understanding Impedance (R+jx)
In a typical antenna (lets say dipole for this discussion), the pattern below is observed in the impedance (R+jx) graph:
I'm trying to wrap my head around this graph.
Why does the resistance spike, ...
- 637
-1
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0
answers
93
views
Major 2.4GHz interference disrupting communications
I need help to determine what is causing significant interference with my communication devices, such as Bluetooth, router, and phone calls. I always use a Bluetooth headset when I'm on the phone. I ...
- 1
2
votes
2
answers
44
views
Fox & Hound or regular FT8 for ARRL International Digital Contest?
So I'm thinking about casually working the ARRL Int'l Digital contest this weekend to try to pick up (hopefully they'll confirm!) a couple of new DCXX entities so I can get my DXCC (almost there).
...
- 873
1
vote
1
answer
74
views
How is it possible for a halfwave dipole antenna to be resonant?
I've been learning about antennas recently and I have some questions about the halfwave dipole antenna.
My first question is about its resonance; as I understand it
everything that oscillates has a ...
- 113
2
votes
1
answer
41
views
Yaesu FT817ND + (Bluetooth) CAT control + ESP32 microcontroller: reading SWR "programmatically"?
I am building a wireless control system for a magnetic loop antenna. The system uses an ESP32 microcontroller (that has Bluetooth and WiFi) that
automatically drives the magloop capacitor by means of ...
- 31
4
votes
1
answer
253
views
Using threaded rod for VHF radials
I've been thinking about building a VHF antenna using stainless threaded rod for the ground plane's radials to mate with a hub I already have. My theory is that will make life easier than trying to ...
- 1,657
4
votes
1
answer
65
views
Any way to get LOTW "credit" for a paper QSL card?
I have some QSOs with hams who will send paper QSL cards but do not use LOTW.
I know that if I manage to get a paper card from them I can submit it to ARRL for DXCC credit. But will that QSL show up ...
- 873
5
votes
2
answers
2k
views
Can I use speaker wire as a transmission line?
Speaker wire is really cheap and available everywhere, and it doesn't seem that different to 300 ohm twin lead. It seems to me it would make an excellent balanced transmission line.
What would the ...
- 3,409
1
vote
0
answers
70
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 ...
- 300
0
votes
3
answers
92
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 ...
- 261
6
votes
2
answers
82
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 ...
- 71
1
vote
2
answers
206
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 ...
- 3,409
1
vote
2
answers
89
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
132
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 ...
- 6,007
2
votes
1
answer
351
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 ...
- 133
1
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2
answers
116
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" ...
- 6,007
2
votes
3
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101
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/...
- 6,007
0
votes
0
answers
34
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
57
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 ...
- 6,007