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1500 questions
4
votes
3 answers
What is the difference between antenna input impedance and its radiation resistance?
I got to know that the input impedance of the halfwave dipole antenna is given as:
Zin=1/Im* sin(β(H-|Z|))
where Im is the maximum current on the antenna( when excited with a 1 volt supply),
H is the half-length of the antenna,
Z is the position on…
Moulee
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4
votes
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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4
votes
2 answers
VNA basics, antenna coax cable
Recently purchased my first VNA (Nano VNA) and I'm trying to learn the basics.
I have a 150MHz 1/4 wave whip antenna that I need to install on a large metal object so I was hoping to use a VNA to help me understand the performance of the metal…
P_J
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4
votes
1 answer
Phase-tuning Yagi-Uda antennas
Related to my earlier question around the TET-Emtron HB35C antenna. It is advertised as a:
The HB35C is a full size tri-bander, efficiently utilising the DUAL
DRIVE HB9CV system with the revolutionary “PHASE TUNED” VK2AOU multi
band system.
This…
t252
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4
votes
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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4
votes
2 answers
Measuring actual feedpoint impedance for a given frequency
Background
I'm attempting to tune an antenna with my NanoVNAv2.
I calibrated it using the included open/short/(50-ohm)load standards by screwing them directly onto the NanoVNA one by one and running its calibration function.
The antenna itself is a…
Bitbang3r
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4
votes
2 answers
Building Antenna Trap: Highest impedance/lowest capacitance/greatest # of turns?
I made my first multi band antenna this weekend for 20 and 15 meters for an EFHW wire with a 49:1 unun, to be used with 5 W rig. I used a toroid I had on hand, T80-2.
I hang this antenna in my living room as an inverted L. It's far from an ideal…
wbg
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4
votes
4 answers
How can I decode an AFSK 1200 baud audio clip? (ISS)
I'm a new ham. The past few days, I've had a few nearby passes of the International Space Station. As it was going overhead, I managed to record what I believe to be 1200 baud AFSK transmissions from it (AX.25) - from it's 145.825MHz Packet Radio…
Brad
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4
votes
1 answer
Parameters needed to calculate inductor value to achieve proper phase delay?
I'm thinking about trying a coil in my collinear 5/8λ antenna, instead of the 3/8λ phasing delay line between the lower and upper elements pictured below.
I figure that a coil with a certain inductance could give me a current delay of nearly 90° and…
Louis Seaman
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4
votes
4 answers
Why am I hearing FM radio show content on 1.355 MHz? (Using CubicSDR and SDR kit)
I am just beginning to learn about SDR. I purchased a "NooElec NESDR Mini 2 SDR & DVB-T USB Stick (RTL2832 + R820T2) with Antenna and Remote Control"
I plugged it into my Mac, downloaded CubicSDR, and was quickly able to listen to local FM radio…
Jack Amoratis
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4
votes
5 answers
Antenna grounding / bonding in relation to my AC service (with pictures)
I'm trying to figure out how to properly connect new ground rods for an antenna to my main panel. Any advice from those who have done this + have great electrical knowledge would be greatly appreciated.
I plan on hanging a dipole from a tree near…
kr4sh
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4
votes
1 answer
How do businesses develop and test amateur radio products in the US if you cannot be paid for amateur radio use?
Certainly there are companies in the US (like Kenwood) that develop HAM products that transmit. For development and QA they would likely need to test the product outside of a Faraday cage.
How can companies test those products in the HAM bands if…
KJ7LNW
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4
votes
2 answers
Can I use my CB mobile antenna with a 10 meter radio also?
I have a mobile mounted CB antenna that has an SWR of 1.5 on channel 20. Is it possible to use it with a 10 meter radio? I do not have enough room on my car for an additional antenna, so if it is possible to use my CB antenna for 10 meters, that…
diodes123
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4
votes
1 answer
Can a regen receiver be used as a CW transceiver?
I've looked for a while, but I've never found a design like what I imagine: a single-tube (valve) regen CW transceiver (no cheating with a tube/valve that has two or more triodes/tetrodes/pentodes in a single envelope).
The way I imagine this…
Zeiss Ikon
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4
votes
2 answers
Can I ignore the radial elements of a 2m/70cm antenna if it's on a metal roof?
I'm looking for a dual band base station antenna, and find that many of them have short radials around the base.
Due to the specifics of my installation, I need to remove them. However, it is being mounted in a way that the antenna penetrates the…
Adam Davis
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