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A 5el rear mounted Slot-Q Yagi beam antenna with exceptional performance. Ideal portable or contesting antenna. New for 2023
What makes the Slot-Q different?
The Slot-Q is based upon the original slot beam design. A driven loop is used as is with LFA Yagis. However, this time the loop is placed horizontally and feed at either the top or bottom. 2 reflectors and 2 directors (per position, top and bottom of ther antenna) effectivley increase the height of the array, a little like a pair of close spaced Yagis with a common feed point. This provides extra gain by suppression of the elevation plane lobe that would otherweise have unwanted pattern both in an upward and downard direction. The suppression of the elevation lobe also reduces down-facing pattern which in return, reduces potential nosie pick-up from below the antenna (neighbours, houses, electrical systems, shack nosie etc.) so this is a win-win scenario!
How high does the Slot-Q stand?
2m band versions of this antenna stand 70cms high. The booms do not need to be large diameter and with the exception of the driven element (which is grounded opposite the feed point) all elements are insulated through the boom.
Why is the driven loop connected to the boom?
The loop is fed by means of a coaxial loop balun, typically at the bottom of the antenna and across the boom. On the opposite side, the loop passes through and is electrically connected to the boom. Theoretically, this is a point of zero current (everything has been radiated) so just voltage at this point. This means, at the design frequency, this electircal connection is not be seen. However, the antenna feedpoint goes very high impedance very quickly either side of the design frequency. This provides a BPF (Band Pass Filter) property to the loop. The final benefit is having the driven element grounded means your receiver is better protected against static discharge related failures.
How much 'extra' gain does it have over other antennas?
It is not just the gain benefit that makes the Slot-Q exceptional, it is the vertical pattern suppression which adds an advantage too. Like Quads, the beneifts in terms of performance decrease with boom length. direct comparions are difficult to acheive as bandwidth and F/B would need to be identical to compare directly. This 5el displaces similar boom length to a much longer 4 elmement Yagi yet delivers similar top-end gain but over the muhc wider 3dB beamwdith of a typical 3 element Yagi. All this with exceptional F/B at the same time.
Lots of gain over a wide 3dB beamwidth
Another benefit of the slot beign short and having high gain is this benefit in performance is spread over a wider beamwdith meaning less rotator tunring is needed. With traditional Yagis, as gain increases, beamwidth decreases. With the slot you achieve the best of both worlds.
Is the slot still 50Ohm direct feed?
during Optimisation, the gain advantages of impedances below 50Ω on smaler examples were exceptional. Therefore the feed impedance is aroudn 25Ω. For single antnennas the twin coaxial loop balun (supplied with the antenna) is used.
Can these slot Yagis be stacked?
Yes they can and with very good effect. infact, they are far easier to stack than with most antennas because there is no need for any splitter nor 'special' impedance coax cable niether. Due to the native 25Ω impedance, a stacked pair of these slots can be connected together by means fo 2 x equal lengths of standard 50Ω coax (not 75Ω, 50Ω). these eaual lengths do need to be odd quarter wavelengths (w/l) long, help with this is provided in the manual. Additionally, any stacked pair would be fed on the loop side closest to one another. For example, top antenna fed at the bottom, bottom antenna fed at the top. This redcued coax lengths needed for any stack and fo course, associated losses too.
No addditional hardware or components (other than extra 50Ω coax) would be needed for the stack on the basis an N-type 'T' is provided with the antennas loop balun. As the loop balun is not needed as a part of a stack, the N-type 'T' used within this arrangement is used to join the coax form each antenna to your feed line. Another win-win!
Front to Back ratio and gain?
Typically, in most directional antennas to acheive higher gain levels, Front to Back ratio has to be given up. Likewise, if you want F/B, you need to give up a little gain. One advantage with the Slot-Q is it tends to deliver exceptional gain and F/B at the same time.
The 3el Slot-Q on test with the provided coaxial 'Loop' Balun
Gain: 9.71dBi free space
3dB Beamwidth: 64.2 degrees
Gain above ground: 15.57dBi @ 10m above average ground
Power Rating: 5kw
SWR: Below 1.4:1 from 144.00MHz to 145.00MHz (for custom versions, 146MHz, 147MHz, 148MHZ or other,
Stacking Distance: 2m
2 Stacked Gain @ 2m spacing: 12.81dBi
2 Stacked F/B: 26dBi
Boom Length: 1m incluidng rear mount section
Distance between booms: 70cms
Weight: 1KG / 2.2LB
Turning Radius: 1.09m
Wind Survival: 184KPH
A single 5el Slot for 144MHz with incredible F/B and gain over 64.2 degrees
5el Slot elevation plot in free space
A single 5el slot placed 10m above average ground
2 x 5el slots stacked @ 2m apart and 10m above average ground
SWR sweep for the single antenna