Most Popular
1500 questions
6
votes
2 answers
Dummy load construction and heat dissipation
I'm building my own dummy load, consisting of resistors submerged in liquid paraffin (or something similar, not 100% decided).
I had some questions around heat dissipation and how I can calculate and avoid the thing over-heating.
Is there a…
David VK2VXK
- 946
- 5
- 23
6
votes
1 answer
RX antenna and RTL SDR with upconverter ..How to hear something?
I mounted a small RX antenna (mini whip, bought from eBay) (on 10-th floor) and I want to try to listen to something. I bought a RTL-SDR with Upconverter which supports HF. RX antenna's operating range is 100kHz - 30Mhz.
If I want to listen…
kesrut
- 185
- 3
6
votes
3 answers
Will coaxial cable degrade over time?
I have a 40' section of RG-8 that is about 35 years old. One end was terminated with a standard PL-259 and the other was soldered directly to an antenna.
When I removed the connector from the one end, the cable itself appeared pristine. The other…
Lance
- 941
- 1
- 8
- 22
6
votes
2 answers
What are the default repeater offsets on 70cm in different countries?
I am looking for a reference list of the default repeater offsets by frequency and country on the 70cm band, to supply it into a radio control software. Most radios come with a list built-in, but the respective data is hard to collect.
There is an…
Georg DO1GL
- 357
- 4
- 8
6
votes
3 answers
What is the easiest way to print data on qsl cards?
I confirm all QSOs via LOTW and eQSL but some people also request QSL cards via bureau or direct. Of course I don't want to disappoint them and I reply 100%.
But I find it such a burden to print sheets of labels and stick them on the cards. So I…
ON5MF Jurgen
- 803
- 6
- 19
6
votes
3 answers
License upgrade doesn't extend term of license?
I just upgraded my license to Extra about a week and a half ago, so perhaps I'm supposed to know this. The FCC database shows my upgrade to Extra, but the expiration date and callsign haven't changed. I thought that my license would be renewed, at…
Rodney Price
- 355
- 1
- 8
6
votes
3 answers
Does a person still need a ham radio license?
Way back when, if my recollection is correct, the requirement for using ham radio was to have a license and the required skill was some level of Morse code proficiency.
I have heard that Morse code is no longer required — if that's true, does a…
gerryLowry
- 161
- 1
- 4
6
votes
1 answer
What are the most common RF connectors encountered in amateur radio?
SO-239, PL-259, UHF, NMO, SMA male/female, reverse SMA, oh my! Some of these may even refer to the same thing with different names. Can someone list the most common connector types and show a picture of each? Also, please explain common acronyms or…
Dan
- 1,754
- 3
- 16
- 36
6
votes
2 answers
80/160m Shortened Dipole Trap Questions
I seem to have forgotten some things I learned years ago for my amateur radio exams. If I am building a 2 band shortened dipole and want a trap between 80 and 160 do I make the trap resonant on 80 or 160 or elsewhere? I guess I may be mistakenly…
Marcus
- 353
- 2
- 8
6
votes
2 answers
Is it possible for an amateur to transmit ATSC?
Amateur television has long used the NTSC (analog) television standards to transmit video and audio. Several years ago, the digital broadcast television transition made higher-quality television signals possible. Can amateurs acquire and use digital…
JC Hulce
- 901
- 5
- 16
6
votes
2 answers
doppler LEO satellite
I am trying to model Doppler shift of LEO satellite,
From my research so far I have come across the following formula:
\begin{equation}
\frac{f_r}{f_s}=\frac{1-\frac{u}{c}cos\theta}{\sqrt{1-\frac{u^2}{c^2}}}
\end{equation}
that in my understanding…
Rizias
- 161
- 1
- 3
6
votes
2 answers
Filtering for PSK31 demodulation
What's the ideal filter for PSK31 demodulation? That is, something that minimizes ISI, while having a narrow bandwidth to reject adjacent channels, while being reasonably matched?
Most PSK modes use a root raised cosine pulse shape, thus the…
Phil Frost - W8II
- 51,701
- 6
- 88
- 212
6
votes
1 answer
What is spin fading in satellite signals?
Why do signals from satellites experience "spin fading" as the satellite rotates? What are the effects that spin fading has on a radio signal?
From test question: T8B09
JC Hulce
- 901
- 5
- 16
6
votes
2 answers
Mobile phone models that contain 2 way radio functionality
Are there any mobile phone models there that contain 2 way radio functionality?
S-K'
- 163
- 3
6
votes
4 answers
UV-5R 4W BFB297 vs UV-5R 8W BFP3-23 (difference 4W vs 8W)
How big difference will it be between UV-5R 4W & newer UV-5R 8W (difference between 4W & 8W), in real life use 1 on 1 HT.
In SAME conditions, how much different distance / range will we get? (simple example)
So I want to buy two HTs and change stock…
SxOne
- 63
- 1
- 1
- 6