112 questions with no upvoted or accepted answers
144 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 ...
152 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 ...
165 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 ...
616 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 ...
116 views

### For a resonant 1/2 wave dipole, does the reflections being in phase with the applied signal cause the zero reactance seen in the feedpoint impedance?

For a resonant 1/2 wave dipole when used for transmitting, does the fact that the reflected waves on the antenna are in phase with the applied signal result in zero reactance at the feed point, or ...
72 views

A single inductive loading coil in a vertical or a pair of loading coils in a dipole are commonly used to match a given total antenna length parameter to a given frequency wavelength (where the ratio ...
66 views

### Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

If I'm building a vacuum tube HF transmitter (say, 40 m band), obviously the simplest mode to build is CW; it's common to key the oscillator input to the final (in order to keep the oscillator running ...
226 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 ...
22 views

### Where to find HF channel models or statistics?

When designing a waveform for packet radio usage, it'd be helpful to know a few things, mainly distribution of coherency bandwidths distribution of coherency times Whilst such statistics are ...
51 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 ...
47 views

### Can the external VFO input in a Heathkit SB-(100, 101, 102) be used to operate on frequencies outside the radio's normal range?

I've got a Heathkit SB-102 that I'm working on making operational (problems with transmit, receiver works just fine). This model radio has a 9-pin Molex connector in the back, intended to connect an ...
49 views

### What dot means in JTDX FT8 received messages?

What dot near country means in JTDX? Maybe LOTW?
37 views

### What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

I am working on space-ground networking for a Cube Satellite, and one of our candidate Layer 2 protocols is AX.25. We haven't settled on a physical layer, but it's likely to be some form of quadrature-...