rick darwicki wrote:
> Hi all,
>
> I recently built a sheilded RX loop for 160 per N6RKs Contest Jouranal
> artical. It is diode tuned and covers about 1.5-4 mhz. I am hearing two AM
> radio stations on 1830 khz.
> The anetnna is all sealed up and on the roof. I would like to cure the
> problem without changing to back to back tuning diodes.
First verify that the fault is with the antenna, not the
preamp or radio. BTW, a preamp should not be necessary
with the loop I wrote about, but many people think they
need a preamp ("it can't hurt"). Well, it can hurt
if you are near BCB stations With a nearby BCB station, the loop
has sufficient sensitivity to overload simple
radios like the IC-706 and will also overload even
good preamps. It provides some selectivity against
BCB stations, but it does not replace a filter.
My article in the National Contest Journal mentions that
my Galt QTH is 6 miles from a 50 kW station, and the 20 foot
loop described in the article does not have BCB QRM.
However, a 40 foot circumference loop does have BCB QRM
when built with 2 varactor diodes. The fix for this is
to use 8 varactor diodes in a series parallel push pull
configuration as described in the article. The PC board
does not have to be modified.
Rick N6RK
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
|