Hi John and Lucien,
Overstacking does not degrade gain, it just makes the main lobe
narrower than necessary and also brings up strong sidelobes.
The sidelobes will be close to the main lobe so they are harmless
on EME most of the time. Sometimes they might be advantageous
since the (deep) minimum between the main lobe and a side lobe can be
used to suppress something unwanted.
Conventional stacking on 144 MHz means stacking for a nice pattern
with a gain typically 0.5 dB below maximum. For the same boom
length on 432, maximum gain is at about 75% of this stacking distance.
(maximum gain is with a sidelobe level of about -8 dB) so sidelobes
will not be much below the main lobe. BUT there will not be any loss
of gain or G/T!!! Just a requirement for more frecise moon tracking.
For terrestrial work it might be a good idea to understack on 144
MHz to get a better pattern on 432, but one has to be very careful.
Understacking will cause antennas to couple to eachother and make
the frequency response different. The point of maximum gain would
move downwards in frequency.
All of this can be simulated with good accuracy today. I think
wery good systems with dual band antennas are possible.
Maybe, some day, also as X-pol systems:-)
A ¼ wave on 2m is ¾ wave on 70cm so any ¼ or ½ wave splitter on 2m will
work on 70cm too.. Phasing lines will be long, so higher loss, and stacking
distance will be huge on 70cm though..
73! John PA5MS
[mailto:email@example.com] Namens F1TE
Verzonden: zondag 12 februari 2017 10:38
Onderwerp: Re: [Moon-Net] New dual band antenna and Low band DX HF VHF
Antenna indeed very interesting, but what dual-band solution for coupling 2
or 4 antennas with common connector ?
73, Lucien F1TE
Sent: Sunday, February 12, 2017 10:12 AM
To: Joe Taylor ; moon-net(a)mailman.pe1itr.com
Subject: Re: [Moon-Net] New dual band antenna and Low band DX HF VHF
Antenna itself does not have power limit. No problem to put 1500 W.
But balun have. It is hardly achievable wideband 500 Ohms common mode
impedance. From 140 to 440 MHz. Although on this balun attainable.
On 12.02.2017 00:40, Joe Taylor wrote:
On 2/11/2017 5:09 PM, Dual wrote:
Most beautiful 6m long antenna PA144-432-38-6 with common connector.
Optimization took more than 30 days.
Interesting design. Why the 100/50 W power limit??
-- Joe, K1JT
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