Thomas,
If the coax is buried or lying on the ground, it is probably OK to put the
preamp indoors, since the lossy earth will reduce any noise and signal
pickup on the coax feedline. But if you suspect that the feedline is acting
as an unwanted antenna, it may be useful to put the preamp at the
antenna to boost signals before they enter the feedline.
Note that feedline pickup can also couple energy back into the loop,
which requires a different solution -- proper grounding and common-
mode isolation.
73, Gary
K9AY
> Hello,
>
> I am in the process of constructing a K9AY loop antenna and have some
> questions about shielding for the preamp. My plans call for using the
W7IUV
> preamp circuit and locating it at the antenna. It would be more convenient
> to place it in the shack, but doing so will slightly degrade the system
> noise figure, due to the feedline loss ahead of the preamp. The feedline
is
> RG-58C/U, about 125 feet in length.
>
> A 7-pole Chebyshev high pass filter will be placed in the circuit, before
> the preamp. My question is in regard to the shielding of the preamp. I
have
> an aluminum Bud box, and a painted steel box by Hammond. Either can be
used
> for the enclosure. What is the most effective box material from a
shielding
> standpoint? Does it matter? Or should I just go ahead and place the preamp
> in an enclosure inside the shack?
>
> Regards, Thomas - AC7A (Tucson)
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|