From: jbs@rti.rti.org
Newsgroups: rec.radio.cb
Subject: Let's talk about skip (was Re: AM or SSB)
Date: 8 Apr 92 16:15:38 GMT
Distribution: na
Organization: Joe's Bar and Grill

In article <c5eQ02U2c00200@amdahl.uts.amdahl.com> ikluft@uts.amdahl.com (Ian Kluft) writes:
>In article <7APR199213413423@venus.tamu.edu> ami9667@venus.tamu.edu (IACOVIDES, ANDREAS MICHAEL) writes:
>>What's the "max" range you can talk with two AM CB's and what about
>>SSB, when the one will be at the base and the other mobile? What are
>>some good antennas for base and for mobile?
>
>First, in the daytime when the Ionosphere is on causing "skip", the background
>noise level will be high enough that your range between the 2 units will be
>down to a few miles.
>
>At night, the range between 2 mobile CB units with properly matched antennas
>can be up to 6-8 miles without difficulty, assuming a low noise environment.
>(i.e. the San Francisco Bay Area has a lot of RF noise so that cuts range a
>lot.)  Subtract a few miles for cheap or poorly-tuned antennas.  Add a couple
>miles, maybe, if one is a base station (as you asked).

Folks may have noticed that nighttime, at least in the southeastern U.S.
(I'm in N.C.), no longer provides a "low noise environment". Those of us
who monitor channel 9 in the area have been particularly annoyed by the
skip coming in from Venezuela (where, according to a Venezuelan contact
that one of our organization's members has, they use channel 9 much as
channel 19 is used here, and they use channel 11 for their emergency
communications [channel 11 happens to be where the local linear-jockeys
hang out, so I guess Venezuelan operators probably aren't topo happy with
the U.S. right now]).
The skip continues until LATE at night (I mean past 2:00 a.m.), frequently
at levels of 9 pounds, oops, I meant to say 9 S-units, and better.
This has been going on regularly for about two months, and is pretty well
unprecedented in any of our experiences.
Common conjecture is that the cause is ozone depletion; more ionization
than usual is taking place in the F2 layer during the day, and at night
when the UV isn't hitting the "night side" ionosphere anymore, ionization
remains at a high level much later into the night than it used to, and
somehow this is causing the F2 layer to remain active and relatively low
at night rather than receding to a higher altitude and combining with F1
(Have I got the names of my layers right? Probably not).
Anyway, input from more knowledgeable minds will be appreciated. I have
not yet upgraded from Nocode Tech yet, so I haven't been messing about
in the 10-meter band, but I would suspect that they would be experiencing
the same increased nighttime propagation as the CB band.

 
>Elevation can have an affect, too.  I've made crystal-clear mobile-to-mobile CB
>contacts from over 15 miles away when I parked on top of a 2000-foot mountain.
>However, small hills in between two units may make CB contact impossible.

I once talked from my base (1/2 wave ground plane) in Clemmons, N.C. to a
mobile unit atop Grandfather Mountain, N.C., which I would estimate is a
seperation of roughly 90+ miles. Both radios were operating at 5 watts.
Neither of us was using a receive preamp. This was about 6 a.m., and noise
was VERY low at the time. Audio was good, but signal was weak.
I find nighttime mobile-to base range to max out at about 15-20 miles (with
no skip in the way). This is with a Shakespeare 4' continuously loaded (I
believe 5/8 wave electrical length) fiberglas whip mounted on the hood.

  -joe KD4LLV