Re: [IRCA] More coax experiments

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

> Once that's done, if you needed more isolation, I'd replace the box with
> a metal one. If the sleeve-type choke works well enough, use the plastic
> box you have.

I have been continuing my tests with the CAT5 balanced line.  The BNC
connector, 1.4:1 toroid transformer, and RJ45 were put in a Hammond 1590G
cast aluminum box.  Then I connected the box to the truck radio.  Tuned
through the whole AM band and didn't hear any signal, not even a het with
the R30CC in USB mode.  Nothing.

Next I connected the 150' run of CAT5 to the box and terminated the other
end in a 100 ohm resistor on a RJ45 jack, no shielding.  Very short leads,
however.

In tuning through the band, much of it was below the noise floor of the
R30CC.  Locals were down a significant amount from the whip antenna.
Semi-locals like some Boston stations and all NYC clears were non-existent.
So, the box did help.  Kudos to Rick Kunath for the suggestion.

I need to order some more BNC jacks and some of the Hammond boxes to make up
some more adapter boxes, and cut another length of CAT5.  Next trick is to
put the RPA-1 preamp at the antenna end to further swamp out the remaining
leakage.  I'll just run the preamp off a 12V 7AH lead-acid battery such as
is used in a computer UPS.  That way no wiring needs to go there to supply
the power for the preamp.

Looks like progress!  Once the DX Engineering phaser comes back next month,
I'll try again to phase the two loops.  However, I will set them up away
from any metallic objects.  I think the tower in the yard is warping the
loop patterns.

One other thing I want to try is to roll out some chicken wire over the CAT5
to see if it shields the wire from pickup.  The capacitance to ground, plus
the inherent loss may just help.  Maybe just the 50' closest to the truck.
It will be very easy to do an A/B test.  Set out the CAT5, do a bandscan
with it terminated.  Then roll out 50' of chicken wire over the nearest 50'
and do another bandscan.  Compare notes.  If it helps, then do another 50'.
It may function just as a series of chokes on the wire itself, using the
lossy ground for attenuation.  Chicken wire is cheap, so..

Craig Healy
Providence, RI

_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx