Newest Questions
4,999 questions
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What is this signal?
https://drive.google.com/file/d/1pCUDjJbDJVGmmnhp-jYk_vXjfm_KxK6V/view?usp=sharing [18kb .m4a file] (Note: The file was edited to remove the 30 seconds of silence between bursts.)
Heard on 7-May-2025 ...
- 949
1
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1
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98
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How to match 5w radio output to 0.005 watt input on amplifier
Found a 50-ish watt amplifier kit online that looked like a good challenging build.
It says it provides 40dB of gain, and specifies maximum input power of 0.005 watts.
The candidate radio I'd like to ...
- 111
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0
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33
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Hopelessly Lost on BFO Island
I am picking up some low ssb somewhere I think on the 160meter band (1800 -2000 khz) on one of my homebrews. I can also pick up much higher ssb bands, but this low stuff I was concerned because I ...
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2
answers
52
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Capacitance between two parallel wires with a cylinder of a dielectric added
A open twin feeder or a Lecher line is two parallel wires, both the inductance per meter and the capacitance per meter affect the impedance and the velocity factor of the line. While the polythene of ...
- 151
1
vote
1
answer
74
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Reverse protection for PA
I am designing an RF transceiver for TX RX at 435MHz. I have the module working fine without any issues with PA TX at 2W.
The only issue is the reverse power from the antenna if both units are placed ...
- 69
3
votes
2
answers
433
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Is this an unintended short circuit in my Moonraker GPA-80F vertical HF antenna?
I'm a newly licensed ham and purchased this Moonraker antenna from DX Engineering as my first HF antenna.
I noticed that there is continuity between the inside and outside of the SO-239 connector at ...
- 133
3
votes
4
answers
185
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dBi gain of random wire antennas
All antennas are a compromise. Are there any antennas that in free space perform strictly worse than an isotropic antenna would? Or a simple flat ground model?
This is what has been bugging me. I am a ...
- 131
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0
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77
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Help Identifying RF Data Protocol
I hope this is the correct place to ask. At my university, we've been picking up some strange transmissions on 146.66625 MHz in the engineering buildings. The noise persists at nearly full strength ...
- 11
1
vote
1
answer
89
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Dual-watch implementation
I would like to know if there is an implementation of dual-watch (AKA split mode?, tri-watch in some brands) more extended than others, for both station equipment and ht, in case they differ. I'm ...
- 133
2
votes
1
answer
57
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What is the authentication response algorithm in Winlink protocol?
I am writing a program that should integrate a Winlink client. All elements of the protocol used in Winlink network seem to be described well, but I cannot find the algorithm to calculate ...
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1
answer
63
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Receiving P25 on a Ham Rig
I found this question: Receiving commercial / public-safety on a general-coverage HAM transceiver that has the same topic, but it's from 9 years ago and doesn't answer my question. I have an Icom IC-...
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2
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89
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Converting mobile radio to portable use -- Will any whip antenna work?
I'm still a newbie amateur radio licencee (but slightly less newbie than before).
I have the AnyTone 578UVIII PLUS Tri-Band Mobile Radio
I'm seeking to make it into a portable use-out-of-a-bag radio ...
- 105
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1
answer
77
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Yagi antenna design fails with short dipole elements – why?
I am trying to design a directional antenna with compact dimensions and considered using a Yagi antenna with a short length ($l < λ/4$). I ran an optimization algorithm in Matlab, where I maximized ...
- 11
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1
answer
52
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Is my backup battery charged? Using my battery meter, how can I know?
I'm still a newbie amateur radio licencee (but slightly less newbie than before).
I have the AnyTone 578UVIII PLUS Tri-Band Mobile Radio and I use the DuraComm power supply unit from an accessory ...
- 105
0
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1
answer
77
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Antenna matching for a dipole
I am working on a research project involving antenna design for a HAM payload on a deployable drone. The drone includes a deployable dipole antenna. After antenna deployment, the dipole antenna spans ...
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4
votes
3
answers
167
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Does a transceiver radio have a "receiving range"?
I'm familiar with the fact that a transceiver radio has an effective transmission range that is affected by several factors, such as the antenna, transmit power, obstacles, etc. I'm wondering if a ...
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2
answers
62
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Midland G7 Pro charging voltage (Ni-MH battery)
I've found contradictory information about the voltage and current fed by the original charger (using a PB/ATL-G7 Ni-MH battery), and I'm trying to use a generic one through its mini-jack port, ...
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3
answers
108
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does "CW signals" still mean the same since 1960s vs. today?
I think my 1964 my CW transmitter was just an on-off carrier. I think today's CW is a modulated sideband with no carrier. (This makes tuning today's CW signal non-intuitive to my old paradigm.)
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2
answers
84
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Extending the range of PMR446 power-limited equipment
I'm looking for workarounds that may be well-known by the community, to extend the range of units such as Midland G7 Pro, which operates in the PMR446 band and is also limited in power by this ...
- 133
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votes
1
answer
48
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Output from Constellation Modulator different from Demodulator output
I'm just comparing the IQ plots from the output of a QPSK Constellation Modulator and comparing to what I get on the reciever end via the Costas Loop output. Note that data transmission is working ...
3
votes
2
answers
163
views
3 ferrite rod antennas in close proximity
I want to control a trio of radio controlled clocks. DCF77 (77.5kHz), JJY (40kHz), and WWVB (60kHz). Suitable signals can be generated with a microcontroller or Raspberry Pi. I will use ferrite rod ...
- 159
0
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1
answer
82
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Poor SWR on short coax line
I have build an antenna for 446mhz I have used 15mm copper tube for the dipoles and RG-58 for the coax. On the horizontal centre line I have created a coil 9 turns around a 25mm former. The feed line ...
-1
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2
answers
249
views
Balancing Currents in Coaxial Cable
The basis for the two questions that follow, is that I have always been dissatisfied with the reasons given for the cause of the balancing currents in a coax cable, since as far as I could tell, ...
- 1,002
2
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2
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245
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Prudent power limits for SSTV on my Yaesu FT-710
I recently added a Yaesu FT-710 to my setup. I do some FT-8, and I found guidance from Yaesu posted online that said that 50 watts is an appropriate power level for FT-8 on this radio, but that more ...
- 177
3
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1
answer
141
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Repeating signal every 0.185 MHz on 1400 MHz region
So I’m analyzing the spectrum from my RTL-SDR setup and noticed a periodic feature repeating approximately every 0.185 MHz. I don’t use any LNA, just a simple RTL-SDR dongle and a Wi-Fi grid antenna. ...
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1
answer
88
views
How can I get any reception from my new baofeng?
I have a new out the box baofeng AR 5RM. I also have three different antennas. The original "rubber duck" antenna, an abbree ar 895s VHF uhf and an abbree ar 771 VHF uhf antenna. No matter ...
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95
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How long do I have to wait before I get a letter from the fcc about my callsign?
How long do I have to wait because, I just paid and am waiting.
4
votes
4
answers
1k
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Is there really a shielding of low-level audio frequency signals (e.g. for microphones) in the factory-made cables with (plastic) RJ45 connectors?
There are several schematics that show, for example, a MIC signal line in a 6- or 8-conductor ribbon cable for crimped RJ45 connectors that is marked as shielded. The shield is shown as the adjacent ...
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1
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77
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Constructing a dual whip dipole antenna
I am wanting to put two 20-meter 17' telescopic whip antennas on a dual 3-way mirror mount, one to one side of the mirror mount and the other one in the opposite direction on the mirror mount.
Should ...
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1
answer
151
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does lease restricting "ham radio" apply to "amateur radio" legally?
the legal language of my lease uses the term 'ham radio' (a colloquial term) prohibiting 'installing' it. would this legally prohibit my 'amateur radio' (FCC term)?
is my HT 'installed' as it rests on ...
- 107
1
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1
answer
237
views
How do you construct a 6:1 balun
I want to run 50 ohm coax from a tuner through the wall of my house to 300 ohm ladder line to an 80 meter dipole. How can I construct a 6:1 balun from 50 ohm coax?
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3
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1
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156
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HF 49:1 toroid unun same ratio more windings
I've been looking for an answer, but no luck so far finding it. It's about windings, and it's effect on HF. 49:1 UNUN transformer. What will happen if we keep the ratio 49:1 and increase the number of ...
- 31
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1
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63
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Dealing with alkaline cells "welded" into an alarm clock with weather radio [closed]
I have a half forgotten alarm clock with weather radio that has had the alkaline back up AA cells leak to a point that it effectively "welded" the plastic cover to replace them shut. It ...
- 379
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1
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52
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What options do I have for a V/U 4 way 90 degree divider/combiner for satcom
I have a AV2011 satcom antenna that has a Merrimac QHF-2-.312GN power divider/combiner that's good for 225mhz to 400mhz and I'd to replace it with a wider bandwidth version buuut this series doesn't ...
3
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1
answer
93
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Measuring losses from reactive near-field interactions in simple antennas
Question:
How can we measure the total losses due to reactive near-field interactions relatively simply, without far-field strength tests or mapping out the entire near field distribution?
I've ...
- 2,610
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1
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79
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VHF Handheld radio not charging after replacing battery
I recently replaced the battery of this SIMRAD HS35 handheld radio as it was dead. I bought a new that matched the description, replaced the old one and the radio works fine. The problem is that it no ...
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0
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105
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Programming software for YINTAI YT-588 radio
I am looking for the programming software for the YINTAI YT-588 radio. Thanks. Marco
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4
votes
1
answer
625
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Antenna - vertical & beam antenna transmit at the same time?
Is it possible to use a vertical antenna and a vertical polarized beam antenna at the same time?
I have a friend that lives about 7 miles away & I can talk to him on 220MHz FM just fine on a ...
- 41
1
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1
answer
102
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EFHW With a 0.05 Wavelength Counterpoise - Use CP for Tuning?
If an EFHW antenna with a 49:1 transformer & a 0.05 wavelength counterpoise, can be considered an OCF Halfwave antenna, why can't I place a LC network somewhere in the counterpoise wire length to ...
- 51
0
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0
answers
52
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Loop Back test - GNU radio - USRP mini B200
I am new to working with radio and currently attempting to transmit a sinusoidal waveform from the transmitter directly to the receiver port. I found a flowchart online to set this up, but since I ...
1
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1
answer
69
views
changing bandwidth from wide to narrow on my SW 3B transceiver
On my SW 3B I tend to scan the band (usually 40 metres) looking for a CQ call using the wide (2Khz "USB")) filter. Having tuned in I then change to the CW narrow filter (400 Hz "CW"...
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4
votes
1
answer
140
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How to tell if a vacuum tube has gone bad?
Because it was $5 on my local classifieds, and I have a bit of a weakness for old junk, I bought myself a Heathkit HW-30 "Two-er". I've been going through the alignment procedure in the ...
- 161
2
votes
2
answers
125
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Correcting impedance at the feedpoint vs. at the radio
Recently I have been trying out some upgrades to my station. For all of 2024, I was using a Xiegu G90 (20W PEP) with 50' of RG-8 connecting it to a balun with a 5:1 transformer and a stainless steel ...
- 177
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1
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55
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CB Antenna (Jetfon AB/02 Base CB antenna) connection and grounding
I am trying to get into CB world and have couple of questions if some good soul could help out,
Radio is CRT 2000H and antenna is,
Jetfon AB/02 is a CB-27 base antenna with 3 radials.
FEATURES
Band: ...
- 103
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1
answer
58
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Distance to and type of objects affecting radiation pattern
Mostly interested in metallic / plastic objects.
do far field metallic objects influence radiation pattern ?
do plastic objetcs in the far / near / reactive fields influence the radiation pattern ?
...
- 287
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96
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Can an isolation transformer be considered a balun / Can you feed dipole with isolation transformer
I'm trying to wrap my head around a concept of unbalanced and balanced transmission lines, baluns, ununs etc. to properly understand how to feed symmetrical (e.g. dipole) antennas.
Currently, i'm ...
- 121
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1
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103
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Limiting Frequency for Alinco DJ-VX50
With my Alinco DJ-VX50 which supports frequencies 136-174 MHz and 400-470 MHz I am trying to limit the frequencies between 144-146 Mhz and 434-438 MHz in VFO mode.
For this I used RT System's ...
- 119
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1
answer
154
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GNU Radio block selection window is missing!
I am trying to use Gnuradio but am unable to add new blocks after "find blocks" (blue magnifier icon) button of Gnuradio stopped functioning. I can execute flowgraphs but can't use find ...
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1
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76
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Eliminating the ground: two back to back helicals
Do we get any other benefits aside from the obvious by replacing the big ground pour with another identical helical antenna ? Normal mode operation, not axial, eg. this one
Expecting the radiation ...
- 287
2
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4
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203
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Software to decode Morse transmissions including explanation of abbreviations (like Q codes)
I am not very good at decoding Morse transmissions. Therefore I am looking for a software assist me. The software should work in real time.
Supported morse codes:
regular morse codes (like A, B, C, .....
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