# Amateur Radio Stack Exchange Community Digest

## Top new questions this week:

### Importance of Ferrite Size in Coax Choke Balun

The question is quite simple: When making a coax choke balun, does the size of the ferrite matter, and if so, why? I have seen design notes that say to use a single FT240-43 toroid for powers up to ...

rf-power balun transmission-line ferrite choke-balun

### Easy Digi hum with isolated ground

I am creating an Echolink simplex link using a Raspberry Pi 3 B+, a Pluggable USB sound adapter, and an "Easy Digi" sound card interface which has 2 - 600ohm isolation transformers for audio in/out as ...

### Change of Address and Callsign Zone

I'm about to permanently move to another US state, which is in another callsign zone. Will I be forced to get a new callsign in the new zone? Also, when I started, when one was traveling in another ...

united-states legal callsign

### impedance matching with window twinlead

Question from new ham here, regarding ways of matching impedances between a feedline and an antenna. Is it possible to fashion a broadband HF impedance matcher from a length of windowed twinlead, in ...

### Is it legal for an unlicensed person to transmit as long as they are under the direct supervision of a licensed amateur?

Based on another question here, I think it is legal, but I would like it directly from the people who know. Thank you for your time.

united-states legal

### How does this 3 dB splitter/combiner work?

I'm having difficulties to understand how does this circuit work: Apparently T1 is a regular 50 Ohm to 22.2 Ohm autotransformer. Turns ratio 2:3 gives a 0.66**2 impedance converation. Since the ...

ferrite splitter combiner

### Can I have the Hytera PD785G turned on in the charger?

I have a Hytera PD785G. Typically, I charge it overnight, then take it out and use it. Since this is currently my only radio station, I'd like to misuse it as a stationary device. Most of the time, ...

battery-charging hytera
 asked by Thomas Weller 1 vote

## Greatest hits from previous weeks:

### When will propagation on HF improve?

Will the propagation on the High Frequency bands come back up soon?? I am referring to the 3 to 30 MHz range.

hf propagation

### Is free space path loss dependent on frequency?

Free space path loss is calculated as: $$\left( 4 \pi df \over c \right)^2$$ The presence of $f$ in this equation means that losses increase with increasing frequency, so there's an inherent ...

propagation math

### What is the cause of this unusually long period of terrible HF band conditions?

I've been a ham for over 40 years, but never has there been such a prolonged period of such poor propagation. This has been especially the case over the past six months or so, and they continue to ...

hf propagation space-weather ionosphere sunspots

### Why are some 1:1 current baluns twice as complicated as others?

I would like to add a balun/choke to my dipole for the reasons outlined in Using a balun with a resonant dipole. In the spirit of continued kit and/or DIY building for my ham shack, I set out to ...

balun toroid

### How can you calculate the frequencies for each band?

I've just started studying for my HAM license a couple of weeks ago, so please excuse me if this is a remedial question... I have the Canadian Amateur Radio Basic Qualification Study Guide (which I'm ...

frequency band-plan

### Effect of different metals for antenna elements

Other than rust, corrosion, and other reactions with air that would make the use of a metal unfavorable, how do different metals affect the performance? Let's give Yagi an example: Let's say I use 4 ...

antenna antenna-construction physics

### How do I make a RF propagation map for a repeater?

Let's say I have a repeater. Knowing all of the information about antenna height and gain in each direction, as well as power, how can I create a map similar to this map I saw of a repeater in ...

propagation repeater map repeater-coverage