[Top] [All Lists]

[CQ-Contest] path loss per hop

To: CQ Contest <cq-contest@contesting.com>, SECC <secc@contesting.com>
Subject: [CQ-Contest] path loss per hop
From: Rick Dougherty NQ4I <nq4i@contesting.com>
Date: Sat, 2 Jul 2011 11:30:56 -0400
List-post: <cq-contest@contesting.com">mailto:cq-contest@contesting.com>
The following consists of a short study of reverse beacon values
generated during the ARRL CW test on 19 and 20 Feb 2011. The study
compares NR5M and NQ4I
for signal levels(read db or snr numbers) from 3 very active sites in
Europe during the contest. Assumptions are 1500 watts at each station.
And just so some one doesn't say I am using too much power I will
restate my invitation for ANYONE to visit during a contest and bring
your own Bird Wattmeter and measure the output on ANY of my amps! With
that said. The next assumption pertains to antennas...NR5M's station
and description is availabler on his web site and using some
reasonable assumptions. For Instance on 80m NR5M is using phased 4
squares or about 8 db gain...I use a 3 by 3 vertical array with a
theoretical gain of 6.5 db....so using the previous mentioned path
loss figure of 1.4 db then NR5M and NQ4I are equal? The number being
quoted is indeed correct for ionospheric losses, but fails to consider
path losses from ground reflection. The 40 Meter system are fairly
close in Figure of merit and gain. NR5M has a stack of 4 over 4 OWA's
and NQ4I has a 3 over 3 stack of Telrex 3m29's. On 20m NR5M has a 4 Hi
stack of 6 el yagis and NQ4I has a stack of 8 over 5 over 5 that has
approximately same Figure of Merit as NR5M. on 15m NR5M has  4 HI
stack of 6 el yagis and NQ4I has 8 over 8 or 8 stack...advantage to
NQ4I on 15m. 10m is not consider in the study.

Here is how to do it...go to the reverse beacon site and do your own
analysis...it won't change...I have made this same analysis after each
and every contest since the reverse beacon site appeared. My contest
team and I analyze the data to see our strength and weaknesses. And I
especially compare my 160 results!

When you first load up the comparison, the number of spots are very
telling...in every case NQ4I has more spots than NR5M...can only be
one thing! PATH LOSS!!! Or NR5M took some un-necessary time off?

Lets look at the three sites and see what they show in the related
signal strengths between NQ4I and NR5M.

DK9IP 29,011 spots NQ4I spotted 220 times and NR5M spotted 105 times!
Only difference here is Ground related path loss. NR5M's first hops
are most likely over land masses with mountainous terrain which
contributes greatly to spraying or splaying of the signal=greater
loss...had NR5M's hit water on the hops there would have been less

On 80m somewhat equal on this day but NR5M is not able to maintain a
signal level for nearly as long and as strong as NQ4I.
On 40m a very obvious 6-10 db and sometimes more discrepancy between
the two stations. And is you look closely at the early evening you can
see the opening time for both stations. Advantage NQ4I.
On 20m Advantage NQ4I
On 15m Advantage NQ4I

Lets now go to S50ARX with 34,832 spots....NR5M 107 spots and NQ4I 205
spots....advantage NQ4I.

On 80m greater presence at the skimmer site Advantage NQ4I.
On 40m 6-10 db across the board. Advantage NQ4I
On 20m Greater presence and 6 db difference Advantage NQ4I
On 15m Offsetting data. No Advantage.

Next is ES5PC with 27, 849 spots. 132 spots for NQ4I, and 24 spots for
NR5M...Advantage NQ4I.
On 80 m No spots for NR5M. Advantage NQ4I
On 40m Huge presence difference NQ4I Advantage
On 20m Huge presence NQ4I. Advantage NQ4I
On 15m only one spot NR5M. Not enough for comparison. No Advantage.

Now using the same analysis lets compare NQ4I with K3LR (not an east
coast station by one admission) But I intend to provide data that K3LR
is an EAST coast station.

Same date, same 3 sites but throw W3LPL in the mix too.

DK9IP 29,011 spots . K3LR 252 spots W3LPL 232 and NQ4I 220. Advantage K3LR
On 80, 40,and 20m there is 6-10 difference in favor of K3LR and W3LPL.
Could that be the elusive PATH LOSS???  I won't bore you with the
numbers you can go and look them up yourself. They don't lie. They
don't belittle. They don't intimidate. They simply STATE the facts.
Close study of the data in this comapsison shows that K3LR's signals
track W3LPL to the db...I mean it could not be closer in comparison.
Look for your self. K3LR is close enough to New England to benefit
from the Advantage.

Go to the other two reverse beacons and you will see the same
thing...Is a station in W4 or W5 is competitive in this contest? Can
they be? Spend enough money? Work enough hours? Engineer to the max?
None of those will compensate for parh loss and distance involved.

So before you belive some of the numbers being spouted out here. I ask
you to consider who is telling "the rest of the story" and who is
muddling the waters.

I really appreciate the votes of confidence I have received in the
past few days...I took a few days off to let things settle down a
little...and to try to remove myself from the
attacks. In the words of the Terminator ...." I will be back"

CQ-Contest mailing list

<Prev in Thread] Current Thread [Next in Thread>