[Lowfer] Re: PSpice simulation

[Bill Ashlock]

Jim M and all,

>You should specify EITHER NL and F, OR TD, but not both - obviously a 
>conflict will arise in that you are effectively specifying the same thing 
>in two different ways, if you specify both the electrical length and the 
>propagation delay.

Yes, you are correct sir! I received the same reply from 
[pspice_support@cadence.com] yesterday after posting this problem. I 
simulated a number of PA and loop-load combinations, with the coax 
installed, last night, and found some of them cause some real nasty ringing 
and what even appears to be oscillations. I'll have to tabulate these 
results and post them.

>There is also "TLossy", a lossy transmission line model where you specify 
>the length and R,L,G,C, distributed line parameters, and various other 
>lumped transmission line models - refer to a transmission line text book 
>for further explanation!

Just looked at this. Thanks for pointing it out! Will try it out.

>Always bear in mind that you have to give the simulator accurate 
>information to stand any chance of getting a sensible result - this means 
>you must include things like stray inductance, capacitance and resistance 
>if these have a significant effect on the operation of the circuit, as they 
>usually do in a PA for example.

Yes, I've been doing this - typically small series resistors here and there. 
The currents can go out of sight if this isn't done. And of course... an 
actual bench check from time to time is important.

I response to your posting yesterday about the increased loop efficiency at 
higher harmonics, and the need for filtering to reduce these, it's possible, 
that because my loops rest on a group of trees, the efficiency could 
actually fall off as the frequency is increased. I'll have to run a test to 
see what it actually is at a harmonic near 60 meters, where the loop is 1 
wavelength. I have found from previous tests that the AM broadcast band 
radiation is very low. All of this applies to US Lowfer 1W transmissions of 
course (or at 100W when the threat of a forest fire is low <G>).

Thanks a lot for all the input Jim!

Bill A

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