Archive for category Amateur Radio

On the use of Power Amplifiers in Amateur Radio

As many of you know, I’m a ham operator. I spend a lot of time listening to the HF bands, not a whole lot transmitting, but I do listen. One of the things that tends to irritate me is when I hear some wag putting someone else down because they have a “little signal”, by which they mean 100 watts or so.
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Something for you CW types

You know, I have to confess: CW isn’t my favorite operating mode. It’s ok; sometimes I tune down to the CW portions of the ham bands and copy it for a while just to keep my hand in, but not too often. Consequently, another confession: I’ve not looked really hard into SdrDx’s CW handling until today. When I did, I found there were improvements that could be made, and, because I’m somewhat compulsive, I went ahead and made them, and you’ll find them in the 2.12r OSX beta that’s available for download as of right now. But don’t stop reading yet, please.

My old J-38 straight key

The first thing I did was some work on the high and low adjustment ranges of the CW mode demodulator envelope; CWL now allows from -10 to -1500 Hz, CWU allows from 10 to 1500 Hz. These are sane ranges; previously, it was a little weird, and I apologize for that.

The second thing was change the demodulator envelope adjustment from 100 Hz/step to 50 Hz/step. This allows you to create a properly centered demodulator envelope of an odd width, such as 300 Hz, or to cut the bandwidth all the way down to 50 Hz — a little extreme perhaps, but amazingly usable if the received station is stable.

Lastly, I experimented a bit with the audio notches to see how to best tailor the audio, and I found that with the Q of a notch set to about the third hashmark from the right of the Q scale, the notch was narrow enough to sit right on the upper edge of the demodulator envelope. I’ll give a detailed example:
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New OSX and Windows version of SdrDx – 2.12p

SdrDx 2.12p adds support for the Andrus, FunCube Pro Plus and AFEDRI SDRs; It also provides various features and fixes. See the link to the changes document, below.


  Screen shot: https://www.flickr.com/photos/fyngyrz/8675326983/in/photostream/lightbox/
    Downloads: https://fyngyrz.com/?p=915
Documentation: https://fyngyrz.com/sdrdxdoc/sitemap.html
      Changes: https://fyngyrz.com/sdrdxdoc/changes212.html

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WLO RTTY News Feed Replaced with Weather

Sad news for RTTY SWLs, WLO’s newsfeed at 8473 kHz is gone, replaced with weather broadcasts. The weather broadcasts alternate between RTTY and SITORB, just as the news feed did, but that’s the end of the similarity.

Well, it was nice while it lasted. Sigh.

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New OSX and Windows version of SdrDx – 2.11

SdrDx 2.11 adds visible memory markers, an enhanced internal database, better panning window width by window width, a number of fixes and performance improvements, and additional documentation.


  Screen shot: https://www.flickr.com/photos/fyngyrz/8165852338/in/photostream/lightbox/
    Downloads: https://fyngyrz.com/?p=915
Documentation: https://fyngyrz.com/sdrdxdoc/sitemap.html
      Changes: https://fyngyrz.com/sdrdxdoc/changes211.html

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New OSX and Windows version of SdrDx – 2.10

SdrDx 2.10 adds support for pure audio SDRs such as the Softrock, as well as the ability to demodulate pure audio input from recordings and radios with IQ outputs.

Control of this type of SDR is implemented with an external program that catches TCP messages from SdrDx about frequency changes and forwards them to the audio SDR in whatever format it needs. A sample Python client is supplied that contains everything but the actual mechanism to talk to the specific SDR, which can be implemented as a stand-alond command line program.

2.10 also brings with it an optional new black user interface (BUI), new documentation, and RF waveform fill. The 50 MHz lower limit for the FunCUBE Dongle has been removed in order to accommodate the new FCD Plus, which extends reception into the HF region.


  Screen shot: https://www.flickr.com/photos/fyngyrz/7891402954/
    Downloads: https://fyngyrz.com/?p=915
Documentation: https://fyngyrz.com/sdrdxdoc/sitemap.html
      Changes: https://fyngyrz.com/sdrdxdoc/changes210.html

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New OSX and Windows version of SdrDx – 2.09

SdrDx 2.09 adds the ability to fine-tune the AGC metering to match the sample rate and other varible SDR factors so that the AGC metering is better correlated with the S-meter. DNR metering is now active, but indicates red, when disabled. Auto Noise Floor tracking has been added; this keeps the RF waveform cleanly on the graph even when the noise floor rises significantly. Smooth Noise Floor has been added; this reduces the amplitude of the noise in the RF waveform (does not affect demodulation.) The ability to live-edit the waterfall palette has been added. You can now change colors and adjust the relative distance of one color from another while watching the results on the waterfall. You can save and reload the results, and control which palette is the default waterfall palette. To go along with this, the ranges of the I and C sliders have been extended. An independent high pass filter has been added to complement the low pass filter, and this has been added to the memory system as a memorized setting. The ability to determine the distance of a nearby lightning impulse has been added, along with documentation on how to use the feature. The UI has been changed slightly to accomodate a few new controls.

There have also been significant improvements and additions to the documentation. Some bugs have been squashed, none of them serious.

My sincere thanks to those who helped me test and who took the time to report my errors to me so I could fix them.

Screen shot: https://www.flickr.com/photos/fyngyrz/7852335518/
Downloads: https://fyngyrz.com/?p=915
Documentation: https://fyngyrz.com/sdrdxdoc/sitemap.html
Changes: https://fyngyrz.com/sdrdxdoc/changes209.html

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VFO Suite 1.01 for OSX and Windows

VFO Suite is a TCP client for SdrDx. It works with both the RFSPACE SDRs and the FUNcube. Or both. It provides 26 distinct, radio-style VFOs that track and maintain frequency and display parameters so you can go from band to band (or favorite spot to where-ever) without losing where you were, the adjustments you made for noise levels, and so on. Designed with larger (or multiple) monitors in mind. Enjoy!

Feedback encouraged: If you want features, mods or fixes, please don’t depend on my mind reading abilities. They seem to be somewhat undependable. :)

Screen shot: https://www.flickr.com/photos/fyngyrz/7502244882/
Downloads: https://fyngyrz.com/?p=915
Documentation: https://fyngyrz.com/sdrdxdoc/sitemap.html
Changes: https://fyngyrz.com/sdrdxdoc/vchanges101.html

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