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1500 questions
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1 answer

Antenna for receiving 868MHz rocket telemetry: QFH(QHA), Helical, or?

I'm building a radio communication system for an amateur rocket project. We've decided to use LoRa 868MHz system. My question is, which antenna for the ground station will be the best choice? We're aiming for both vertical and horizontal gain, as we…
leller
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How to make a ferrite bar antenna for RTL-SDR?

I bought a RTL-SDR (blue one with little MCX antenna). I modified its Q branch, and can receive short wave radio with Degen 31MS antenna now. For MW, Degen 31MS antenna has a ferrite bar antenna coupler to work with the internal antenna of the…
jac123
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Impedance Matching between RF Amplifier Stages

I'm in the process of building a RF buffer-amplifier chain for a VFO and I'm experiencing a design issue trying to impedance match between the sections. The issue I'm having is that many (most) of the circuit designs documented are characterized…
Buck8pe
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FCC callsign with incorrect group letter

I just passed my technician exam and received my callsign from the FCC (KC1KHV). I was surprised by the two letter prefix, which seems to come from the class D group. According to the FCC documentation on the topic, a technician license should…
larsks
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4 answers

Efficiency of short dipole receiving antenna

For a transmitting dipole antenna, its length is important. If it is close to half the wavelength, it will be efficient and most of the input power will be radiated. How important is the length of dipole in case of receiving antenna? Will a dipole…
thbnju
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Learning RF electronics

I've been studying and building test circuit for actually several YEARS now, so far with no success. It sounds ridiculous but it's true. So I feel like I have a good understanding or RLC circuits, I can calculate phase shifts and impedances etc., I…
user13171
7
votes
4 answers

Why is the 70cm band commonly referred to as the 432MHz band?

I keep reading and hearing the 70cm band (420-450 MHz depending on local regulation) referred to as the 432 MHz band, particularly by older hams. Why?
Jacob
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What SDR software is available that provides internet control?

I plan to use a SoftRock Ensemble RX II to receive HF transmissions. I'd like to be able to use it wherever I am when I have a few minutes, though, so I'm wondering what software exists that would allow me to control the receiver over the…
Adam Davis
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4 answers

Is there any downside to consolidating on BNC connectors for HF?

I'm new to ham and quickly finding that the new and old equipment I'm accumulating at an alarming rate has an equally alarming array of connectors: UHF PL-259 BNC SMA Type N Is there any downside to consolidating on BNC as my main connector and…
RoboKaren
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Which country’s hams have the longest call signs?

Not including special event callsigns, which group (country/class/etc) of hams have and use the longest callsigns? I know that theoretically the longest would be a (3x4) or 8 character callsign but are these in use? I’m interested in which…
RoboKaren
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2 answers

Morse Code meta-command sequences?

When using Morse Code as an accessibility/disability communication or input method, are there any non-alphanumeric dot-dash sequences that are more common or more suitable for meta-commands, such as “speak the last string”, “send command string to…
hotpaw2
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What is the maximum number of turns in a ferrite core used as a common mode choke?

Is there a way to estimate the maximum number of turns which can be used with a ferrite core used as a common mode choke? It is known that the impedance of such a choke is proportional to the square of the number of turns and so there is a strong…
Chris K8NVH
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How can the design of an RF filter also encompass impedance matching?

I'm installing an antenna which will require a matching network. (A fixed network: the load will not change.) I'm also building some low-pass filters to reduce transmitted harmonics. It would be a simple exercise to design an ordinary 50Ω filter…
Phil Frost - W8II
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Does oxidation of the antenna elements have any impact on the signal quality of the station?

So I'm still QRT; apart from a brown-out on the rig, the support on the inverted-vee toppled over in high winds. Thanks to the topple-over I discovered the conductors (SWG 16 bare copper) had started to turn greenish-black; a sure sign of…
VU2NHW
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DIY lightning arrestor - gap size?

I have an antenna that's well above the treeline, and I've heard I can add some small amount of protection by placing two bolt heads a short distance from each other, one connected to the antenna, the other connected to the ground rod. What distance…
Adam Davis
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