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.
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The unit on the right below is the QRP 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.
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As part of renewed interest in portable medium power operations, I wanted a small cheap matcher. The units below are simply standard T-Tuners. Using dirt-cheap construction technique and commonly available parts, these units perform well at a very low cost.
Continue reading Still More Medium Power T-Tuners for Cheap
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As part of project LOAP (Lipstick On A Pig ===> http://vtenn.com/Blog/?p=1348), I wanted a small cheap matching and SWR indication unit for the Pixie-based transceiver system. The T-Tuner and SWR bridge unit on the right, in the picture below, is not vastly different from others, but here it is for your consideration as a good performer at a low cost. Note however, that it has been characterized into real-world impedances with a worst-case loss of less than 0.9 dB.
Continue reading Yet Another QRP Portable T-Tuner and SWR Bridge for Cheap
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In this article we look at the reduction in feedline loss when we use a BMU to mitigate impedance extremes at the base feedpoint of a Vertical or Inverted-L antenna. Naturally, these antennas are worked against a proper counterpoise radial system for decent efficiency, especially on the low bands.
We look at the cases of a 42 ft antenna, and use an average of the measured and modeled feedpoint impedance to calculate feedline losses* for 50 ft of RG8x and for 100 ft LMR400.
The BMU referred to here is:
A 9:1 UNUN for the mid and high bands
A Loading Coil, switched in instead of the UNUN, for the low bands
Continue reading Why we use a Base Matching Unit (BMU) with End/Base-Fed Verticals and Inverted-Ls
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