Amateur Radio Stack Exchange
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1500 questions
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3 answers

Call sign ID for a "homebrew" or improvised repeater?

I saw a couple YouTube videos last night about setting up a repeater using a pair of cheap hand-held radios and, at its simplest, an audio patch cable to connect the speaker output of one radio to the mic input on the other. Set frequencies…
Zeiss Ikon
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Is it safe to run two barefoot rigs on one antenna with an AB switch?

I have a Daiwa CS-201A two position switch. The single side is connected to by quarter wave vertical (40m). The A and B sides are connected to an IC-7300 and TS-830S. The switch is claimed to have 60dB of isolation. It also shorts the unused port to…
Paul
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What are contests? What do I need to know about them being new to ham radio?

I have heard about radio "contests" but I haven't seen a real explanation of what they are and what they entail. What do I need to know about contests before getting a technician license for the first time? Is there any particular etiquette…
Rob Rose
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Why does adding 50-ohm BNC Ethernet terminator(s) in parallel to my 4-element yagi improve my radio's reception? (70cm)

I have this radio, with a rubber duck antenna, and a repeater twenty miles away to my north-northwest. If I set my radio on the top of a cabinet in my bathroom, I receive the repeater fine. I can't hit it from there, but I can hear it, which for…
CJ KE4EDD
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1 answer

What should I look for in an antenna for a DVBT Dongle used for SDR?

I use a cheap DVBT dongle that I control via RTL-SDR. Right now a very basic setup. The general consensus seems to be that a long usb cable should be used (to keep noise from the computer away from the dongle) and the antenna directly plugged into…
mart
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6
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3 answers

Coax or bifilar windings for a choke?

Making a common mode choke out of bifilar windings has proven rather difficult. For me the difficulty lies in getting the impedance to remain a constant 50 ohms from on the HF bands. I've tried 14 gauge enameled and I've tried 18 gauge PTFE. The…
Paul
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6
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2 answers

What are some good options for covert dual band vehicle antennas?

Would like to have a 50W mobile in my SUV, but I'm not allowed to have a big whip on the outside. What 2m/70cm dual band antennas are available that don't say, "Ham Radio Operator"? Are there three band antennas that replace the radio antenna? I'd…
Adam Davis
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6
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How far do radio waves travel?

I have read that radio waves just keep traveling but the signal gets weaker because of how the wave spreads. OK, I get this, but what confuses me is that satellites emit signals from space that our phones and GPS modules pick up regardless of…
sirshakir
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2 answers

Why can I receive a vertically polarized signal on a horizontally polarized antenna on HF and vice versa?

One explanation I found is that a signal reflected from ionosphere is always circularly polarized. Thus it can be received by both vertically and horizontally polarized antennas (naturally, with 3 dB attenuation). However I don't trust the source…
Aleksander Alekseev - R2AUK
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6
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How would operating a ham radio affect other wireless devices in my house?

I am interested in getting into ham radio however one of my concerns is could a ham radio affect current wireless communications in my house. I am particularly concerned when it comes to WiFi signals. Where I would likely put a radio, I currently…
Rob Rose
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6
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Pentode vs. Triode in Tuned RF Reflex Receiver

I'm planning on building a multi-band vacuum tube receiver. I've got a circuit diagram in hand for a two triode twin reflex with optional regeneration (P.E. Edelman, Reflex Radio Receivers, 1924, Fig. 35, also discussed here), and expect to use…
Zeiss Ikon
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6
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3 answers

antenna in the rain

What kind of changes can be expected in the behavior (resonance, SWR, etc.) of a mobile vertical HF antenna between dry conditions and wet rainy weather? (assume a coax feed-line and low SWR in dry conditions) Is some form of weatherproofing…
hotpaw2
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6
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How to calculate UMTS bitrates?

Assuming: Radio frame Subdivided in 15 slots Number of chips: 38.400 Duration: 10 ms; each slots = 666.6 μs and has 2.560 chips Example of channels DPDCH (Dedicated Physical Data Channel) (UL) Spreading factor varies between 4 and 256 Data rates…
beginningperl
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6
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FFT showing 2 signals - GNU Radio

I receive OOK signals from a remote control in 433MHz. I'm using a dongle RTL-SDR on GNU Radio. The FFT output signal from the RTL-SDR Source block is represented on the picture: My question is, why i have two signals with similar amplitude?…
Marcos Pinho
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2 answers

Feed-through Capacitors

I'm in the "information gathering" phase of a RF Power Meter project and the design I fancy (W7ZOI Power Meter) calls for a feed-through capacitor at the output port. I understand that a feed-through capacitor is essentially a "trap" or low-pass…
Buck8pe
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