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1500 questions
8
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5 answers
Does mounting a ground plane antenna upside down change the takeoff angle?
A typical gain pattern for a quarter wave ground plane antenna is:
Image from a similar question and see watermark.
For a situation where the signals of interest are below the antenna in elevation (e.g. antenna on a hill/mountain), would mounting…
hazzey
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8
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Help understanding path taken by APRS packet
I'm looking at some raw APRS packets over APRS-IS. I'd like to determine which stations heard particular packets, but I'm having trouble understanding how TNC-2 paths work. Here are two examples:
2016-05-19 05:51:46 PDT:…
watkipet
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8
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How can a quarter-wave transmission line transformer be implemented with lumped elements?
Sometimes designs call for quarter-wave sections of transmission lines. There are some situations when using actual transmission lines would not be practical:
The necessary characteristic impedance is something not easily obtained
A quarter…
Phil Frost - W8II
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8
votes
2 answers
How to calculate if low-pass filtering is sufficient?
An answer on this question Suggested method for boosting 0.05 watt transmitter up to 10+ watts? suggests putting a filterless 19dB amplifier between the HackRF (or similar general-purpose SDR) and a larger amplifier — so only the final stage…
natevw - AF7TB
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8
votes
1 answer
Why do USA transceivers limit transmit to 430-450MHz?
The FCC table of frequency allocations clearly states on page 27 that the Amateur allocation for 70cm is 420-450MHz, but I've seen a lot of transceivers that limit transmit to 430-450MHz.
Why is this?
Jacob
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8
votes
4 answers
Why a thousand miles long antenna is not needed to receive LW and MW?
From what I've learnt so far, the longer the wave frequency on which you want to transmit or receive, the longer the antenna needed to do so. However my portable receiver other than SW can also receive LW and MW, and is receiving those using its…
red-o-alf
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8
votes
4 answers
What is the power increase required to double the range of RADAR?
Studying for a Pivate Pilot's Licence (PPL) and I've hit something in the study material that doesn't make sense to me. Typical of the PPL study material, it's quite shallow, so the full explanation may have been omitted.
To double the range of a…
Matt
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8
votes
1 answer
Phased Array Pattern
I'm working on a passively scanned phased array radar project, as a concept and hopefully design.
One of the things that bugs me is that antenna patterning used. The vast majority of radar arrays I've seen employ a hex grid pattern, with a small…
Oliver
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8
votes
2 answers
What chewed my coax
Today I noticed that a piece of RG-58 that's feeding a Beverage antenna for HF was in two pieces. On further inspection it turned out to be cut. On further inspection I think it's actually chewed by some animal.
At the risk of this post being…
captcha
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8
votes
2 answers
Understanding coax radiation and "current on the shield"
I'm having trouble understanding what seems to be the fundamental principle behind baluns (and probably other related topics).
Perhaps some of my confusion comes from an audio background, where one has "balanced" and "unbalanced" cabling in a way…
natevw - AF7TB
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8
votes
3 answers
Why do I only hear broadcasts from 150 kHz to 29.999 MHz?
I am currently studying for my amateur radio license. Until I'm licensed, I'm trying to use a Sony ICF-SW7600GR receiver to listen in on amateur radio "phone" transmissions. No matter what I do, however, I can't seem to locate any amateur radio…
rcampbell
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8
votes
2 answers
Simulating two antennas (transmitter and receiver) using 4nec2 tool
I am trying to find near field mutual coupling affects between two antennas - one being transmitter and other being receiver. The receing antenna is fed with very little voltage (I think, if I don't feed any source, then nec tool inserts default…
Shiva Mudide
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8
votes
5 answers
Is the National Calling Frequency actually used?
I know that the national calling frequency is 146.520. Everywhere I go, it does not give a DUP or TSQ. I am not trying to be or, ask a crazy question but is there or not.
Glenn
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8
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1 answer
Do I need a SWR meter for a basic 2 meter antenna?
I have a 5 watt 2 meter handheld transceiver and want to build a helmet with an antenna, microphone (with VOX enabled) and earpiece for the radio. For the antenna part, I just want to do something simple like a wire at the right length. I'm 15 and…
Skyler 440
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8
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1 answer
What does TX/RX Exchange refer to?
I am using the Aether logging software and it has two fields I do not understand: TX Exchange and RX Exchange. I know TX and RX refer to transmit and receive, but I'm not sure what to populate in these fields. There is already a frequency field so I…
Dan
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