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Re: [TenTec] Tentec Orion & Oscilloscope question

To: eric.sensi@skynet.be, tentec@contesting.com
Subject: Re: [TenTec] Tentec Orion & Oscilloscope question
From: Ken Brown <ken.d.brown@verizon.net>
Reply-to: tentec@contesting.com
Date: Thu, 25 Nov 2004 10:42:48 -1000
List-post: <mailto:tentec@contesting.com>
Eric SENSI wrote:

2. If I can't find this RF bird sampler (the best solution IMO)... then I'll
go for the "T" shaped M/F/F plug on the ANT 1 output... Someone says that
the radio will not see the small impedance bump on HF even with an open
connection on this "T" shaped connector.

It is true that the open circuit stub of a "T" connector will have no noticable or measurable affect on HF (or probably even VHF) frequencies. However if you connect a piece of coax to the "T" then the stub is as long as the coax plus the dimensions of that part of the "T". If you used 10 or 20 feet of coax running to the 1 megohm input of your o'scope this would look like a 10 or 20 foot open (in a 50 ohm system 1 megohm is nearly equal to an open circuit) stub, which would have some significant reactance, possibly acting as a trap at one of the higher HF bands. Therefore if you do use the "T" method you should use a small value capacitor or large value resistor in series right at the T before feeding any cable to run to the o'scope. Then the length of the open stub will appear only about a centimeter or two long, and only matter at 1296 MHz and up, as someone else has pointed out.


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