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1500 questions
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2 answers

How is full duplex implemented without swamping the receive circuitry?

I've seen a few references to full duplex SDR radios, and I'm wondering how can one transmit and receive at the same time without overwhelming the receiver, and without heavy filtering such as the cavity filters used in repeaters.
Adam Davis
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GNU Radio sinusoid multiplication does not produce perfect results

I created a simple sketch in GNU Radio that multiples two signals. One is a sine and the other is cosine. I paste a screenshot of it and its results below. I have heard that in DSP, we can do almost perfect signal processing. Hence, I assume…
Denis
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LoRa radio transceiver for PtP mesh?

I am very new to general RF/radio in general other than basic WiFi, but I'm looking at the feasibility and cost of a long range (>200M between nodes, sometimes probably 500+M) in flat terrain, relatively low power (solar + 12V SLA, short term usage)…
Drizzt321
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Is using /AE compulsory?

I'm taking the exam to upgrade my licence to Extra soon, but I'm concerned the ULS might not update in time for Field Day, when I'm supposed to be supervising (and using my call-sign for) my club's GOTA station. If I'm not operating outside the…
RoadieRich AE8RL
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2 answers

RF Transceiver for walkie talkie use

I'm close to my EE. BSc finale and I'm looking to play around a little bit with the stuff I've learned. To be honest, I'm a little bit upset that after 4 years of learning communications theory, I'm not able to choose the hardware I need. My idea is…
Santiago
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1 answer

Is there a legal limit to the bandwidth of a signal used in the amateur bands?

While a normal voice channel is ~10kHz-15kHz in bandwidth, some digital modes can be significantly wider. Are there any legal restrictions on how much bandwidth I could use for amateur radio communications (e.g. video chat over ham radio)?
Stack Tracer
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4 answers

How to tune an FM transmitter to a specific frequency?

I am planning to organise a simple fox hunt, a family event. This includes building a transmitter. I am currently considering the following…
Alexander Churanov
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3 answers

Decibel subtraction in dBm and dB

If i have equations for subtraction of 27dBm-3dBm=27dBm how can this be written as 24 dB. I convert the 27dBm and 3dBm -> 10^2.7-10^0.3.But how can we simply subtract the two dBm Whereas if we have a calculation of 8dBm - (-90dBm)= 98dB this is…
Mayank Mehra
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6 answers

Can I talk 2 Meter VHF across the United States

Can I talk on 2 meters from the east coast to the west coast without using repeaters?
Jim F
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3 answers

How do I send negative numbers or below zero in CW?

Sometimes when operating CW I want to send numbers that are negative. In particular when operating outdoors during the winter and someone asks the temperature, I would like to come back in CW with -5C. For some events like Freeze Your Butt Off,…
Malcolm VE2DDZ
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Is there a difference between AFSK and FSK for AX.25/APRS USE?

APRS uses the AX.25 protocol which assumes the Bell 202 AFSK modulation scheme to generate the actual radio signal. Is there any reason the same signal can't be generated directly with FSK without going through the audio frequencies? My reading…
jgalak
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Can a common-mode current exist on the inside of a coax shield?

People often say common-mode current flows on the outside of the shield, while the current on the inside of the shield is always opposed by an equal but opposite current on the center conductor. This is because skin effect separates the inside and…
Phil Frost - W8II
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2 answers

Do end-fed dipole antennas need choke baluns?

I have a couple of end-fed wire antennas I bought that came with matching baluns. One has a 9:1 unun, and I'm not sure about the other one. In addition to those, should I also put a choke balun on the coax before the matching one?
Pablo Fernandez
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2 answers

Which band will I be authorized the most bandwidth?

Lets say I want to do a bit of experimenting with some high bandwidth uses for transmitting data, high quality voice, etc. Which Amateur band will give me the maximum bandwidth, and what is the maximum width?
Skyler 440
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Is 20m noisy, or do I have a lot of local interference?

I'm making my first ventures into HF with a Yaesu FT-450D and a homebrew 20 Meter inverted-V antenna a local ham helped me set up. I've noticed that the 20 Meterm band seems to have lots of background noise (QRN) everywhere in the band. The S-meter…
Adam KC0DAD
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