Community Digest

Top new questions this week:

How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...

software-defined-radio theory math mixer modem  
asked by John B 4 votes
answered by Phil Frost - W8II 8 votes

If a sealed, non-airtight pipe is used as antenna element, how big of a problem is condensate trapped inside?

I'm building a vertical antenna. The lowest portion of its element consists of 3/4" type M copper pipe, with end caps that will be soldered on and 3/8-24 screws poking through at both ends (so ...

antenna-construction  
asked by Bitbang3r 3 votes
answered by user10489 2 votes

Installing GNU radio on android

I want to install this miracle program on my smartphone in order to get more mobility. I found such a solution exists: https://github.com/bastibl/gnuradio-android However, I could not do everything as ...

gnuradio mobile  
asked by Антон 2 votes

Does the FCC e-mail when a vanity call sign is approved?

I submitted an application for a vanity call sign a little over 18 days ago, and it's marked "pending". I presume that it will be processed soon, but the FCC's ULS search page is being slow ...

united-states legal callsign  
asked by chrylis -cautiouslyoptimistic- 2 votes
answered by chrylis -cautiouslyoptimistic- 3 votes

What is a 'Call' Channel?

While programming my Icom radio it has MR (memory)channels, VFO (Variable Freq) channels and Call Channels. What are call channels as comparred to memory or vfo channels? What is their use?

icom  
asked by Steve Miller 1 vote
answered by user10489 2 votes

How to model a curved element in 4NEC2

I am in kindergarten with 4NEC2 and trying to model a Gray-Hoverman TV antenna. I have someone else's model and understand most of the file parameters. I have added VHF elements that have S curves at ...

antenna-modeling  
asked by ruggb 1 vote
answered by Brian K1LI 1 vote

Lowest noise MMIC for HF? (160-20M)

I recently learned that these fancy modern ultra-low noise MMIC, while having <1dB noise figure around 1Ghz could be quite bad at low frequencies due to 1/f noise. What is lowest noise MMIC then ...

hf lna  
asked by BarsMonster 1 vote
answered by Phil Frost - W8II 4 votes

Greatest hits from previous weeks:

Why are vacuum tubes still used in amateur radios?

I wonder, even in this modern generation why the outdated vacuum tubes are used. In other electronic circuits they have been replaced by more efficient (and small) transistors years ago. Why they are ...

equipment-design history vacuum-tubes  
asked by Sumithran 13 votes
answered by Scott Earle 15 votes

What is dBm and why is it used rather than watts?

Reading through an RF power amplifier datasheet, I found the sheet only referenced dBm output power, rather than watts. What is dBm? How do I convert it to watts? Why, or when, would you use dBm to ...

rf-power jargon equipment-design amplifier  
asked by Adam Davis 9 votes
answered by Kevin Reid AG6YO 10 votes

Should I chose a vertical or a horizontal HF antenna?

If I only have the budget for one HF antenna, should I chose a vertical or a horizontal antenna?

antenna vertical-antenna hf polarization  
asked by Timtech 17 votes
answered by on4aa 8 votes

Which HF bands are best during the day and which are better at night?

I am rather new to HF operation and have recently purchased my first HF rig. I have read about bands being "open" and "closed" based on various conditions including time of day. As I have been ...

hf propagation  
asked by ghendricks 26 votes
answered by Phil Frost - W8II 24 votes

Why do hams often conclude messages with "73"?

Looking at amateur radio forums and email threads, oftentimes amateur radio operators will use "73" or "73s" where one might otherwise expect to find "Sincerely" or "Regards". Why?

jargon  
asked by Amber 37 votes
answered by Amber 40 votes

Spacing between elements on a Yagi antenna

Does anyone know what the spacing between elements on a beam antenna should be? I built a 146 MHz 3 element beam following instructions, and the spacing was 16" between the driven element and the ...

antenna yagi antenna-theory  
asked by Delta1X 3 votes
answered by Xevious 6 votes

Converting WPM to CPM

I'm using an Anroid app for learning CW. In Germany, it's common to define the speed in CPM ("characters per minute", or German BPM for "Buchstaben pro Minute). However, the Morse trainer I use ...

cw  
asked by Thomas Weller 2 votes
answered by Thomas Weller 4 votes

Can you answer this question?

#APRS error ? (only visible on aprsc status)

I'm playing with Nodered that I'm trying to use to place an aprs object: it works but it does not suit me! No error on findu.com, correct display of frames on aprs.fi or on aprsdirect.com ... but on ...

aprs  
asked by Phil 1 vote
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