Amateur Radio Stack Exchange
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1500 questions
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2 answers

Weather Imaging with NOAA satellites - legal?

I would like to build an antenna for receiving NOAA weather satellites. They're receivable at around 137.5 Mhz. I'm a total new to amateur radio stuff. I know that it's not legal to communicate as private person on several frequency areas- so I…
leAthlon
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What is the minimum signal strength I need to receive?

Let's say a transmitting station is using a 8W radio with a J pole antenna. The cable connecting the radio to the antenna is RG-58A/U and is 25ft long. At 144.075MHz, the attenuation of the cable is 1.5dB. At 8W, the power from the radio is 9.03dB.…
KM4NTK
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Correct number of elements in 4nec2 antenna simulation

I am designing a 1.25-wavelength dipole antenna with the 4nec2 software. What I noticed is that the input impedance of antenna is changing greatly when I change the number of segments. How many segments should I choose?
Shiva Mudide
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3 answers

How to improve reception with a headphone-cord antenna?

I have a headphone and a cellphone that has built-in FM radio, and the headphone acts as the radio antenna. but my problem is the radio stations I listen to are very far from my place, good thing there are some position where the sound is very…
m0Onfang
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What is Part 97 a part of?

The regulations that govern Amateur Radio in the United States are often described as Part 97. What statute are they a part of? Where can I find other parts of the same law?
Nick ODell - KD0OCR
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What is this large, flat microwave coaxial connector?

I picked up a random piece of RF hardware at a flea market. I'd like to know what these unusual connectors on it are. The jack is flat on its face except for the gold ring. Inside the gold ring appear to be fingers gripping the central pin (which…
Kevin Reid AG6YO
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Can a Yaesu FT-7900R be physically connected to both KPC-9612+ ports?

The Yaesu FT-7900R has a single data port (mini DIN 6-pin) for 1200 and 9600 bps TNCs. Page 10 of the manual states: In accordance with industry standards, the signal levels, impedances, and bandwidths are significantly different on 9600 bps as…
Jacob
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How to stop interference on shortwave radio when connecting to a computer

I have a Tecsun PL-600 and when I can receive clear signals, and they come through just fine on headphones, and through the speaker. If I'm trying to receive RTTY or fax, when I connect the radio to my computer the signal becomes inaudible because a…
smithy212000
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Is there a digital multimeter that is more interesting for a ham than a run-of-the-mill model?

My 22-years old Fluke 79 died on me today... Luckily, it was a quiet dead, but nonetheless it left me a bit emotional... So, I am in urgent need of a replacement digital multimeter. This made me wonder whether there would be a model around that is…
on4aa
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Noise & shielding, SDR Dongle

First, I'm very new to SDR. This may turn out to be really obvious. I just want to verify my thoughts before I spend more dollars. I have a USB dongle with the RT28xx in it. Works great. Side by side I have a 35 year old Azden 2 meter receiver. …
David Hoelzer
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Tuning/trimming a ground plane antenna

I've built a ground plane antenna with a 19.5" vertical and 4 20" radials. Currently, at 147.135 MHz my SWR is 3:1, clearly not ideal (and even bad for the transmitter!). I'm reluctant to start snipping radials because I really don't know if the…
David Hoelzer
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What is the reason/origin of conventional US repeater offsets?

In the US, the common (though not universal) repeater offsets are ±600 kHz in the 2m band and ±5 MHz in the 70cm band. How and why did these offsets come to be standard for amateur repeaters? The minimum simplex channel spacing is much less than…
ESV
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Video transmission between ATV and SSTV

I'd like to experiment with amateur video transmission in a setup halfway between ATV and SSTV. 480 lines of B&W image would be sufficient with 10 FPS, and I'm interested in both digital and analog methods. I'd prefer if I wouldn't have to buy new…
dnet
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Lightning Dissipators

I have heard about many lightning protection strategies in the shack, but nobody mentioned the lightning dissipator. The lightning dissipator consists of many small spikes and prevents a strike by slowly discharging through each little spike.…
Skyler 440
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What does the term 3 kHz deviation relate to in the FM world?

I am confused when someone says "your audio levels are set right and has good deviation at 3 kHz" when talking about wide-band 25 kHz FM signals. First confusion: Why are audio levels measured in kHz? I find it very misleading when you are…
Skyler 440
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