Unanswered Questions
228 questions with no upvoted or accepted answers
9
votes
0
answers
527
views
Beyond Maximum Stable Gain of a transistor
I was plotting constant-gain circles on the Smith chart the other day for a potentially unstable RF transistor.
I recently read on-line that for a potentially unstable transistor the maximum gain ...
- 193
6
votes
1
answer
222
views
How does a Large Loop Antenna work physically?
I am learning about loop antennas at the moment. I read that the response of a small loop Antenna is proportional to the rate of change of magnetic flux through the loop which causes a uniform current ...
CommunityBot
- 1
6
votes
0
answers
2k
views
Simple AM receiver with gnuradio / RTL-SDR
EDIT: I have succeeded in getting the AM receiver to work, by replacing the AM Demod block with a Complex To Mag, and a Band Pass filter (this is noted as an alternative in the AM Demod docs).
...
CommunityBot
- 1
6
votes
0
answers
331
views
How to estimate input and output impedance of an amplifier?
I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in ...
CommunityBot
- 1
6
votes
0
answers
210
views
Choice of PCB coil design for filter inductor at ca 20 to 400 MHz, 5 W
Looking at the diplexer schematic from this nice question,
I realized this can completely be done in PCB-formed elements (minus the connectors). (As a kind of counter-action to the original question'...
- 15.6k
5
votes
0
answers
85
views
Are there any stations other than W1AW that fall under 47 CFR 97.113(a)(3)(iv)?
47 CFR 97.113(a)(3) normally prohibits amateurs from transmitting
[c]ommunications in which the station licensee or control operator has a pecuniary interest, including communications on behalf of an ...
- 15.6k
5
votes
0
answers
742
views
What is an expected IF level of SA612?
I tried to use SA612 as a frequency mixer. Since it's a Gilbert cell, it has a high input impedance. Thus I added a pair of transformers as "Experimental Methods in RF Design" book suggests:
...
- 1
5
votes
0
answers
134
views
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 ...
CommunityBot
- 1
4
votes
0
answers
55
views
Optimizing Half-Duplex Sequencing: Consolidating RF and Power Connections with Bias-T and VOX
I've successfully implemented a half-duplex sequencing mechanism, which I've illustrated below. The outdoor components are represented in green. In my current setup, I utilize a PLC to control both an ...
4
votes
0
answers
62
views
GNU Radio and OsmoSDR AGC for Hack RF
I am trying to construct an automatic gain controller for my HackRF when in receive mode. I am using the gr-osmosdr block in GNU Radio to interface with the HackRF. I am then running my received I and ...
4
votes
0
answers
115
views
Checklist for QRO remote setup
In a few weeks I'm hoping to set up a solid state linear amplifier at a remote shack that I've set up at the house of a friend who lives in a rural area. I've been connecting to this shack remotely ...
- 7,864
4
votes
0
answers
747
views
4NEC2 radials & grounds
Teaching myself 4NEC2 and have most of it under control, which is good.
Regarding radials & grounds, i've been learning the "rules" NEC(2) has, summarised below.
4.1. Free space.
In the ...
- 24.4k
4
votes
0
answers
169
views
Problem with theory of HF detector
I'm currently trying to build my own SWR power Meter. This design is based on the so known HT detector with schottky diode BAS70. For my understanding, and for easy purpose, I'm currently focusing on ...
CommunityBot
- 1
4
votes
0
answers
529
views
The whole neighborhood's internet drops when I transmit on 40M
I recently built a vertical. It's 6M radiator, a coil, and 1.2M more of radiator. It sits on my roof, which is metal, and acts as a ground plane (GND from the feedline is connected to it). There is a ...
- 1,199
3
votes
1
answer
60
views
Statistics on ham operators age, internationally
Are there statistics that cover more than the USA regarding how the age of
licensed amateurs
members of national ham organizations
is distributed? All I get are questionable sources on the internet ...
- 1