Cerwin Vega AT-15 Xover Schematic

I visually traced out the circuit layed out on the circuit board and then measured with Fluke BK Precision model 886 LCR meter.

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ANL Add-On for Hallicrafters SX-16

Out here in beautiful rural East Texas, the noise levels on the HF bands are not too awful bad – IF you have a decent noise limiter or blanker.

We have some nasty short spike shortwave noise at a 33 mSec rep rate. It may be electric fences? our cable system?, but I have not tracked it down yet since I did not even know it existed due to modern receiver’s good noise blankers. (This explains the picket-fence spectrum of certain frequency ranges on the IF waterfall display).

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Dual-Band X-Frame Shortwave RX Loop

Having a few nice vintage shortwave radios around, I decided it would be nice to actually USE the dang things once in a while 🙂   And given the almost unusably noisy performance of indoor short wire antennas, I made some loop antennas to cover approx 3 – 18 MHz to see if performance could be enhanced.

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Hallicrafters S-53 Ressurection

I really like the classics, the glow of tubes and smell 🙂 of transformers And having a short window of free time decided to pick up a poor ugly semi-rusted Hallicrafters S-53 for cheap. I was interested in it’s somewhat unusual 2.075 MHz IF frequency (used to enhance image rejection). I decided to try out a weird idea in regard to not really restoring, but rather quickly resurrecting an old not-so-valuable boat anchor.

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Small RX Loop Analysis – An Excel Sheet – Fields, Voltages, Noise Levels…

First  cut at an Excel spread sheet to analyze a small RX loop’s noise and frequency response performance.


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Why We Don’t Like Unintended Common-Mode Current Flow On Our Transmission Lines

You may have wondered why some of us keep yammering on regarding “Common Mode Current” on the coax, and why common-mode prone designs (like end-feds and JPoles) are so problematic.  Here’s an example of a 915 MHz antenna for a wideband comm system prototype I am designing. I decided on a wide-band vertical dipole.

In the pix below, we see the dipole front, and the dipole rear in it’s final form (sans heat shrink) – with a single loop binocular type 61 core performing the 1:1 current BalUn / choke function (they are the same thing):

Dipole_Front

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Solar Eclipse Data Showing Propagation Enhancement on the Lower HF Bands

Solar eclipse data shows interesting enhancement of my signals on 160 M (1.8 MHz) during the event. Similar data for another station is shown for 80 M band (3.5 MHz) also.

Eclipse WSPR Data

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Low Gain Ground Mounted Antennas for LEO Satellites

Apparently there are lot’s of differing opinions on antennas – now there’s a shocker   Hopefully, we can put some rough numbers on things to help folks to figure out where opinion ends and basic principle begins.

Turnstile

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Project LOAP (Lipstick On A Pig) – Pixie XCVR Mods with Outboard CW Filter and Audio Amp

The 40 Meter Pixie (available at the time of writing for about $7 assembled on eBay) is an interesting minimalist transceiver design – crystal controlled, 2 transistors and an audio amplifier chip.    And you are on the air with a unit that you can make QSO’s with!  Naturally,  there is much room for improvement, and it can in fact be done for only a few dollars more.  Below I describe a set of additions that I think really enhances the Pixie’s usefulness.

40M LOAP2 Pixie n CW Filter Spkr n T-Tuner Continue reading Project LOAP (Lipstick On A Pig) – Pixie XCVR Mods with Outboard CW Filter and Audio Amp

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80 Meters and Up – Portable Base Matching Unit for 42 to 48 Foot Verticals and Inverted-Ls – Medium Power Version

The unit on the left below is the medium power BMU (Base Matching Unit) intended for 42 foot to 48 foot vertical, sloper, or Inverted-L antennas.  Naturally, these antennas (like all end-fed antennas) require a decent radial system for efficient operation on the lower bands.

BMUs Top View QRP Portable and Med Pwr Continue reading 80 Meters and Up – Portable Base Matching Unit for 42 to 48 Foot Verticals and Inverted-Ls – Medium Power Version

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