Скачать или смотреть Spiderbeam Aerial-51 Model 404-UL Antenna Review, Part 1.

This is an off-center-fed dipole By Spiderbeam, the famous antenna mast manufacturer. It does work on the advertised bands, though your SWR will vary depending on location. I would prefer connectors instead of the wires straight into the potted BALUN... It is fairly light and the BALUN works; I only tested it to 50W on 6m. There will always be some residual common-mode RF current on the coax shield though, as with any OCFD antenna. The antenna radiator is made from UL-wire / Liv-2Yz (ultra light aramid synthetic fibre and copper strands, Insulated). The antenna comes including 12m coax which despite the low weight (only 185g) shows only very modest losses (~1dB on 40m, less than 2dB on 10m). Despite the lack of connectors which would make repairs very difficult, with careful handling, the occasional QRP tuner and maybe an extra RF choke, it looks like a decent choice for multi-band operations. I need to test it on other bands and in a different environment... Scroll down for Rick's (DJ0IP) comment on common-mode current with OCF dipoles...
Part 2:    • Spiderbeam Aerial-51 Model 404-UL Antenna ...  
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Rick's (DJ0IP) comment on common-mode current with OCF dipoles:
Once again, you are wrong in saying there will always be some residual CMC on the feedline with OCFD.
WRONG WRONG WRONG.
This is what people wrongly believed until about 7 years ago.
Only when the BALUN is not built properly is there any CMC on the feedline – unless there are some external contributing reflections from near-by metal objects.
I have made over 1500 field measurements on these antennas, and 500 were running 100 Watts into the antenna and measuring the residual CMC with an RF Ammeter. A properly designed BALUN (which is cannot be purchased commercially anywhere that I know of) will eliminate ALL RF on the feedline.
Dozens of engineers have reviewed my measured results; two OM have repeated a few of my tests and confirmed.
It all depends on the balun, and the balun in the 404-UL and 807-HD were both purpose designed to avoid CMC on the feedline.
I have used this antenna in dozens of portable locations running between 50w and 100w; never had any problem. I run 750 watts at home, no problem.
More important, we have 2000 users and so far only ever had complaints about CMC 2 times.
A German magazine tested the 807 for 6 months, making hundreds of QSO on all bands, running a “healthy 750 Watts”. No problems.
ARRL and RSGB tested my antennas. No problems reported with RF on the feedline.
We have a Groups.io user group for OCFD antennas, with about 1400 users. You can ask in that group about CMC on the feedline. They will all think you are crazy. We have known how to eliminate that for about 7 years now, ever since I ran my 2013 CMC field tests.
THE biggest features of my 404-UL is, it is fed so close to the center of the antenna that there is hardly any CMC at all – the Balun eliminates the rest – and it weighs just 400 grams including 12m of coax. This enables hanging it high into the air on a thin fiberglass mast.
Finally, our OCFD antennas are often a few S-Units quieter (less noise) than end-fed antennas.
THESE are features that aren’t apparent in with just a quick installation and a few minutes on the air.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
May the Sunspots be with Us! .
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