[TenTec] Tentec Orion & Oscilloscope question

[Ken Brown]

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.

DE N6KB