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1500 questions
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What lengths of counterpoise is suitable to support a 58 foot "random wire" antenna?
I am a technician interested in building my first antenna. I want to explore HF bands, 160m - 6m. Quick impedance calculations indicate that a 58 ft "random wire" antenna could work for this. But I am unsure which counterpoise length to select.
I…
mcandre
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5
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2 answers
Understanding Impedance (R+jx)
In a typical antenna (lets say dipole for this discussion), the pattern below is observed in the impedance (R+jx) graph:
I'm trying to wrap my head around this graph.
Why does the resistance spike, and what is the significance of the interval it…
t252
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Can I use speaker wire as a transmission line?
Speaker wire is really cheap and available everywhere, and it doesn't seem that different to 300 ohm twin lead. It seems to me it would make an excellent balanced transmission line.
What would the approximate impedance and loss be? Can I use a balun…
Andrew
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14dB insertion loss for bandpass filter acceptable?
I'm busy with a direct conversion receiver for the 20m band, using a VXO and a 14.060 MHz crystal.
I designed a bandpass filter with the following components, using this design calculator.
Someone gave me a nanoVNA to check the shape of the filter…
Hans Fong
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5
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2 answers
Why do Baofeng radios have such poor reception reliability?
What is the nature of Baofeng radios' poor receiver performance?
This brand of handhelds has somewhat notoriously poor receivers. I hadn't noticed this much when using them for short distance simplex work on hikes and whatnot, but during recent…
natevw - AF7TB
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What kind of soldering iron is best for PL-259 (UHF) connectors?
What do you use to solder connectors onto bulk coax cable?
Soldering the UHF connector to the coax shield on a PL-259 is described as requiring a bit of "experience and skill" in Dave Casler's video.
UHF Connectors 274
The trick is to solder through…
Dax
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Boefeng UV-5RE scanning capability
Since the factory manual is simple and basic, is it possible to use the Baofeng UV-5RE to do these things?
Listen to FM radio, while scanning 2m and 70cm bands in the background (as in hiking)
Set the scan low and high limit, via keypad and/or PC…
EEd
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What's the effect of directly connecting ladder line to coax?
I was watching a video where ladder line (450-ohm) was directly connected to coax (50-ohm) without a matching transformer.
Mating your Coax to Ladder Line
Wouldn't this mismatch make it impossible to achieve a 1:1 ratio back in the shack? What am I…
Dax
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How to calculate coax cable loss for lengths other than 100 feet
Cable loss for coax is mostly given in loss per 100 feet, express in dB. Say I have cable which is 20 dB loss per 100 feet at frequency x. If I use 50 feet (1/2 the length,) would my loss be:
20 dB / 2 = 10 dB
or
2 x the power = 20 dB - 3 dB = 17…
KevinHJ
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2 answers
Is the original satellite dish "ruined" when a slot antenna is cut into it?
A fun vertical antenna can be made by cutting a horizontal slot in a satellite dish, as documented in e.g. http://www.w6nbc.com/articles/2016-3QSTdishslot.pdf and discussed in How does a slot antenna work? and other questions here. But how would…
natevw - AF7TB
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5
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1 answer
Why would a VNA not make a good Spectrum Analyzer? Or an SDR a good VNA?
Happy to be corrected where I'm wrong in any of this but in broad strokes my understanding is:
Spectrum Analyzer
measures input signal strength while sweeping across frequencies, measuring RF emissions
often includes "tracking generator" to output…
natevw - AF7TB
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5
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2 answers
When was the FCC Part 97 requirement for a time-out timer removed from repeaters under automatic control? Or, am I just nuts?
I've been remiss in keeping up with the changes in Part 97, especially in the area of repeater stations. A recent discussion about changing the time-out timer's period had me scurrying to the CFR, and lo, I could not see the requirement in the…
KenTenTen
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5
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6 answers
Does an antenna pick up signals of all frequencies or only its resonant frequency?
I heard that an antenna picks up signals of all frequencies, and then these signals are filtered by a circuit using an inductor and capacitor, and that this is how a radio is tuned.
However, I also heard that an antenna has a resonant frequency, and…
Urthona26
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5
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2 answers
Eliminating RFI from raspberry pi
I am trying to eliminate RFI coming from a raspberry pi 4. The Rtlsdr(enclosed in a metal case) is directly plugged into the pi without any USB extension cable. The frequency of interest is at 1420.40575Mhz, few strong spikes that can be seen in the…
radastro
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5
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3 answers
Which way is a yagi polarized?
I am installing a yagi antenna that will receive signals from multiple omni antennas that are vertically polarized. Which way should the elements of the yagi point to match? Up and down, or horizontal?
I must not be asking the question correctly to…
T3chie - Bitoku Labs
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