Hi Jim,
To get the same signal strength -4db compared to the 3el yagi on low angles
with your dipole that dipole must be mounted much, much higher then the yagi
and even higher with more elements on the yagi.
Tribanders at the same height as the 6 el monobander certainly will have
identical gain when the effective boom length is identical and enough
elements sitting on it.
I don´t build yagis for getting more gain above dipoles at high lobes, but
for low elevation angles and better receiving.
73
Peter
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson
Sent: Montag, 24. November 2014 17:38
To: towertalk@contesting.com
Subject: [TowerTalk] Yagi gain vs rotary dipole.
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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