During the BPL conflagration a number of years ago, most of the concern
seemed to be interference "to" amateur radio operations. I became a bit
concerned that my neighbor would go BPL and my 1200 HF watts would kill
his I'net. Technically and legally his problem, not mine of course, but
I still needed to get along with him.
We had a 69 KV line running through our property tying two hydroelectric
plants together, with a primary 12 KV distribution line underneath which
would have been the BPL feed. At closest approach my antenna and the
lines were about 165 m apart. I modeled them and my sloping-V in EZNEC
and found that the coupling between them was -32 to -35 dB on all bands
except 80 and 160, where it ran about -17 dB on both bands. On 80 and
160, the power lines were in my near-field.
So, I would conclude that Wayne's 30 dB, based on a different model, is
a pretty good estimate. Fortunately, BPL faded into the sunset and I
was never confronted with the problem.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 6/24/2020 12:12 PM, Greg Troxel wrote:
Wayne Burdick <[email protected]> writes:
I set mutual attenuation to 30 dB, a rough estimate of the path loss
using dipoles 500' apart at 7 MHz. This is a pretty wild guess,
though. Loss could be much higher if the antennas were oriented to
avoid coupling, and it'll vary with frequency, terrain, actual
distance, etc. Of course path loss could be lower with gain antennas
at either or both ends, aimed at the other. (A situation generally
avoided at FD.)
I think 30 dB loss is an extremely conservative test and that very few
people will see coupling that strong.
At my club's 2019 Field Day, with help from several, I made measurements
of received signal strength at several of our stations with various
antennas, with a nominal 100W test carrier. Measurements are just
reading a P3 -- and note that none of the P3 owners had paid for the
NIST-traceable calibration certificate.
Setup was CW station with K3newsyn, digital station with IC7300, only
20m separation from one CW antenna to the digital antenna. And SSB
station with K3newsyn, 200m away.
We did not have trouble, but always had at least 50 kHz separation.
Received levels ranged from S9+40 to S9+73, with S9+50 typical.
So received signals were
-33 dBm min, -23 dBm typical, 0dBm max
With +50 dBm transmit, that works out to path loss:
83 dB max, 73 dB typical, 50 dB min
(The 0 dBm received signal was between an OCFD and a G5RV, about 20m apart.)
It is interesting to hear of S9+65 from a neighbor. Even if they are
running 1.5 kW, seems like it must be only a few hundred meters
separation. If it's farther the details of distance, tx power, antenna
types would be interesting.
I realize this is not responsive to Eric's question about the K4, but
thought that additional real-world cosite path loss data points would be
of interest..
73 de n1dam
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