Comparing a dipole to a yagi is easy to do with any antenna modeling
software and I would trust the results.
Regarding comparing a tribander vs a large monobander, I have tried
comparing various antennas and stacks and I often find the difference very
hard to notice on my transceiver's S meter. I think with QSB 2 or 3 dB is
just hard to see, especially if you're not listening to a steady tone.
John KK9A
To: <towertalk@contesting.com>
Subject: [TowerTalk] Yagi gain vs rotary dipole.
From: "Jim Thomson" <jim.thom@telus.net>
Date: Mon, 24 Nov 2014 08:37:32 -0800
Ok, forget FB and FS for this exercise. Has anybody actually measured the
gain of a yagi vs something like a rotary dipole.... at the same height ?
A lot of yagi vs dipole comparisons are not done right.... since the
dipole is
usually not at right angles to the desired signal. ideally, it would be
nice to have 2 identical height towers..... or at least mount a yagi on 1
tower..and say a full size dipole... made from AL tubing..on another
tower..at
the same height.
And with towers side by side..not behind each other etc. And equal
lengths of
coax.
has anybody done anything remotely like this ? Is your 3 el 20m yagi 5 db
louder than the dipole ? Or another case is a small yagi and a bigger
one...like a 3 el vs 5-6 el. What do u see between
them... 2 to 2.5 db ?? Or do u see a lot bigger differences ?? I
mean....if a 2 el yagi is only 4db gain..that?s only 2/3 of an S unit. Im
looking at this from a sig strength perspective only, NOT F/B or F/S. 2db
with the bigger yagi hardly seems worth it on paper...if it actually is 2db.
Switch in a 2db pad on RX and u will see what I mean.
A buddy back in the 70s had 2 x 100 ft towers up....side by side and 250 ft
apart. equal length feedlines. tribander on tower1 and a hb 6 el 20m yagi
on the other. We could not tell the difference between em, while
switching...listening to EU short path.... night after night. he was not
impressed. F/B and F/S on the monobander was better..and pattern was
narrower,
but that was about it. We tried it on strong and weak signals..and also
with
rf gain backed way off etc.
Jim VE7RF
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