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Re: Topband: Commercial Antennas

To: "William Shanney" <wshanney@verizon.net>, <topband@contesting.com>
Subject: Re: Topband: Commercial Antennas
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Wed, 30 Dec 2015 20:30:30 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
My Ten Tec 238B L-Network tuner works well at 1500W. Some tuner networks, especially T-networks, can have very high currents through the shunt inductor.


The largest issue with T tuners is capacitor value. Most tuners use generic 230-270 pF maximum capacitance caps, and that makes the network Q way too high on 160 into low Z loads.

The ATR30 has around 500 pF, and that makes quite a difference. It will handle well over 1500 watts on 160 without issues, and several kW on 80 into reasonable impedances. It has a lot of headroom for weird load impedances at 1500W.

All that aside, I don't know why people would want to use a tuner to match a real low impedance anyway. Other than some tweaking to extend useable frequency range, the matching is really best handled at the antenna with the tuner just extending BW a bit.
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