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1500 questions
5
votes
2 answers
4:1 Balun question
With an OCF dipole, does it matter which leg, short or long, is connected to which side of the 4:1 balun, hot(coax center) or shield? How can you tell which is which, the balun is not marked. Thank you.
John
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5
votes
2 answers
What is a QSL card?
What is a QSL card? Why would I ever receive one? Why would I ever bother to send one? If so, when? Is it rude not to?
Are they postcards sent by physical postal mail, or are they now digital thingys?
hotpaw2
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5
votes
3 answers
What gain and power are required for successful DX contacts on 2m/70cm bands in CW?
I would like to practice in CW on 2m/70cm bands when and if there will be a tropospheric or sporadic-E propagation. However I don't have mush space for the antenna. There is a possibility to install 3+5 el Uda-Yagi antenna on the balcony (the height…
Aleksander Alekseev - R2AUK
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5
votes
1 answer
Do External Signals Affect Antenna S11/SWR Measurement?
Do external signals affect the S11/SWR measurement of an antenna?
For example, if I try measuring the S11/SWR of an HF antenna with a SWR meter or a Vector Network Analyzer in the middle of a field day with many transmitters near the antenna, or try…
比尔盖子
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5
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2 answers
How to properly measure sensitivity of the receiver?
I have Kenwood TH-D72 2m/70cm HT. According to the manufacturer the sensitivity is "Less than 0.18 uV". I would like to check this, since the radio is not new and I'm not it's first owner.
To do this I decided to use the tracking generator of my…
Aleksander Alekseev - R2AUK
- 4,272
- 15
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5
votes
2 answers
Wide band TX capable band-pass filter for VHF and Airband
I want to share the same antenna for VHF (TX/RX 144-148 MHz) and for Airband RX-only (116-136 MHz).
I live on a very congested area where filter is a must, so I'm looking for the best solution for my needs:
Wide bandwidth (~30 MHz)
Transmit capable…
Aldoir
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5
votes
1 answer
Last Morse call for Thomas?
What does this mean:
CQ de KYHP QTC? K
My father-in-law was a radio operator in the merchant marines during WWII — this was his last writing.
rhonda oszczakiewicz
- 51
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5
votes
0 answers
What causes differences in properties of ferrite cores from same material?
Why are the shapes of the impedance curves different for cores made of the same ferrite material?
The impedance (Z) of an inductor wound on a ferrimagnetic core is:
$$Z=j\omega L_s + R_s = j\omega L_0 (\mu_{s}^{'} -j\mu_{s}^{"})$$
where $L_0$ is the…
Brian K1LI
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5
votes
2 answers
Modelling a folded dipole
I am looking at using NEC to model a $0.5\lambda$ rectangular folded dipole, for closely spaced larger sides (choosing a separation of $0.01\lambda$).
In Antenna Theory, Analysis and Design by Balanis, the folded dipole is touched upon, and an…
pymekrolimus
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- 5
5
votes
1 answer
Why is optimal polarization different for fm as to SSB/CW
On the article "7db for 7 bucks", which is an article about building a simple three element 2M yagi, they stated that vertically polarizing the antenna is better for FM work, and horizontally polarizing the antenna is better for SSB and CW…
Skyler 440
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5
votes
2 answers
RF Bridge Problem - K6BEZ Antenna Analyzer
This question regards erroneous SWR measurements of K6BEZ antenna analyzer (links gone from Internet now) design from 2013 using Arduino and AD9850 DDS modules. There have been many variations of it by other people over the years. Good details to…
Peter Buxton
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5
votes
1 answer
How does a Viper Antenna work?
Are any of you guys familiar with a "Viper" antenna? It came up in a recent discussion with club members for higher frequency bands (6m, 4m, 2m). I hadn't heard of it before and internet searches suggest it's a brand as opposed to a type. …
Buck8pe
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5
votes
7 answers
How to match low impedance of NVIS Dipole?
I want to match a 50-ohm coax feed wire to a 40-meter NVIS half-wave dipole. NVIS antenna examples I've found are usually based on a regular dipole (72 ohms in free air). However the impedance drops by a factor of four (to 12 ohms) when it is…
Peter Buxton
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5
votes
1 answer
Counterpoise wire voltages?
One practice which seems common when operating temporary or portable QRP, SOTA, etc., is to throw a counterpoise wire out on the park lawn or shrubbery, mountaintop or hillside or parking lot ground, etc., not buried or wetted, connected to either…
hotpaw2
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5
votes
1 answer
What dot means in JTDX FT8 received messages?
What dot near country means in JTDX? Maybe LOTW?
dsicari
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