"Dave" wrote in message
...
"Michael Lawson" wrote in message
news
"Dave" wrote in message
...
I recently installed a makeshift antenna on my roof similar to
the
"temporary" one I have been using for a couple of years, but its
performance
is severely degraded (not quite as good as my whip antenna, by
itself). Now
I think I have found the problem, but want to check with those
on
the group
to confirm my suspicions. I used RG59 coax in combination with
300-ohm/50
ohm baluns, but now find a source of information that says RG59
is
75-ohm,
not 52 ohm like the guy at the parts depot told me. Which do I
believe?
The (young) guy who cut the cable for me, or the book on RF
design
that some
people says is full of mistakes? What is the actual impedance
of
RG59 coax?
RG-59/RG-6 is 75 ohm, and RG-58/RG-8x/RG-8 is 52 ohm.
How long of a run do you have from the antenna to the
receiver??
I'd suspect something more than just the coax if you've
got severely degraded performance. What's the radio
and the type of antenna you're using??
--Mike L.
Thanks for the quick response, Mike!
65 feet of coax between the radio (DX-402/ATS-505) and the antenna
(200 feet
of 300 ohm twin-lead hidden along the ridge on the roof of the
house.) And
I don't think I would call it "severely" degraded, only slightly so.
Only a
little less than the old "temporary" antenna (60 feet of four strand
copper
wire thrown over the house.) Also, the new antenna is oriented
primarily E/W
while the "temporary" antenna was oriented primarily N/S, if that
matters.
The orientation does matter if you're not using a vertical,
but the first thing that popped into my mind was overloading
the ATS-505 with 200 feet of antenna wire. The longest
I've ever run into my old DX-440/ATS-803A was about
40-50 feet, and while I never overloaded it, I've never
tried anything close to 200 feet into it.
But yeah, the E/W orientation will work well for stations
that are north or south of you (like tropical band stuff),
but not so good for hearing things east or west of you
(like from Europe or Africa or -depending on where
you're at- relays like Sackville).
If you can get into the attic, try running some of the same
antenna wire north/south and see if you get the same
response.
--Mike L.