Unanswered Questions
42 questions with no upvoted or accepted answers
15
votes
6answers
6k views
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 ...
8
votes
0answers
164 views
How can I do direct digital synthesis of a 630m WSPR signal?
I want to do direct digital synthesis of a 630m band WSPR signal.
Specifically I'd like to use an Atmega 328 chip running at 20 MHz to produce such a signal.
I will use standard phase accumulator ...
6
votes
0answers
69 views
UHF FM power amplifier design without expensive software
I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application ...
5
votes
0answers
89 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 ...
5
votes
0answers
180 views
ISS APRS Digipeater with Kam XL and ICOM IC-910H
I am trying to use the ISS APRS digipeater which transmits at 437.55MHz.
Hardware setup consists of the following
ICOM IC-910H.
The transceiver has been connected to a Windows PC running a HAM ...
5
votes
1answer
558 views
Doppler Shift Compensation in Inter Satellite Communication
I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO).
I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is ±7 GHz. I ...
4
votes
0answers
51 views
Pentode vs. Triode in Tuned RF Reflex Receiver
I'm planning on building a multi-band vacuum tube receiver. I've got a circuit diagram in hand for a two triode twin reflex with optional regeneration (P.E. Edelman, Reflex Radio Receivers, 1924, Fig....
4
votes
1answer
72 views
SNR measurement for a BPSK/QPSK signal
I have created a software (gnuradio) that performs modulation/demodulation and supports a number of modulation schemes and error correcting codes. I'm in the process of evaluating the BER vs SNR for ...
3
votes
0answers
85 views
Kenwood TS-50 and USB to Serial
I paired my old Kenwood TS-50 with serial, by using FTDI TTL-232-5V-AJ USB to serial converter.
I used ideas from here:
http://steeman.be:8080/posts/TS-50%20USB%20Interface/
and here
http://i.imgur....
3
votes
0answers
147 views
What is the external mic/speaker pinout for the Yaesu FT-4XR / FT-65R / FT-25R / SSM-16B?
These newer HTs seem to have a different pinout than the older Yaesu HTs. The older HTs used a single 3.5mm TRRS plug - these use a two-plug connector, with a 2.5mm jack and a 3.5mm jack, similar to ...
3
votes
0answers
601 views
OFDM spectrum, HACKRF, and GNUradio companion
I am trying to analyze the spectrum of wifi spectrum.
I getting a good OFDM spectrum with my HackRF at 2.412 GHz (from my first QTGUI Sink).
But I get nothing out of OFDM Receiver. I was wondering ...
3
votes
0answers
919 views
TS-590 Antenna Tuner Protocol
I'm looking for the protocol used by Kenwood's TS-590S antenna tuner port. I've worked as far as I can with Kenwood's tech support. They know what the pins are labeled, but don't have any information ...
3
votes
0answers
66 views
CML FX919B Forward Error Correcting
I would like to decode de-interleaved demodulated 4FSK symbols that were transmitted using the CML FX919B chip.
The datasheet only gives the following information:
Forward Error Correction In ...
2
votes
0answers
64 views
How to decode 2FSK signal with SDR?
I'm new to radio and SDR but, as a hobby project, I'm trying to decode a 2FSK radio signal received by an RTL-SDR that I sent using an SI4463 transmitter.
The record file contains 3 packets, but I'm ...
2
votes
0answers
242 views
LimeSDR Mini + Raspberry Pi 3 B+ Transmission problem
I am new at this. I would like to transmit an audio signal cleanly using WBFM but I see two signal peaks occur around my fundamental frequency when I start transmitting.
In this case I am using a ...
