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Show all reviews of the Jetstream JTV680 Multiband vertical
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of the Jetstream JTV680 Multiband vertical.
Dec 16, 2012 06:29
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Time owned: 3 to 6 months
It is what it is, and if you really think about it, it is (essentially) a one-half-sized 43' vertical, less the extensive radial field.
First off, the JTV680 is just about the same antenna as the almost twice as expensive CHA-250, only in a longer package (therefore, you're NOT gonna be able to place a disassembled JTV in your trunk like you can the CHA-250 for portable operations.) This is because even when disassembled, the JTV is over 6' long.
Secondly, the antenna DOES indeed work to provide an approximate 50 ohm load to modern transceivers. Therefore, a tuner will not be necessary.
Thirdly, like most antennas, the higher you mount this thing, the better. I started off with it on a 10' pole driven into the ground 4', thereby leaving 6' above ground with which to mount the antenna. However, it didn't work too well so close to the ground (no doubt ground loss / ground absorption.) So, I moved it to 25' above ground, and it plays much better at this height.
Fourthly, I really thought this thing would be an EXCELLENT 17M and/or 30M antenna for PSK-31 operations, however, because it is SO broadbanded, it picks up quite alot of white noise on these frequencies even WITH DSP engaged. It HAS however, become my primary 20 and 40M PSK31 antenna. Band by band results at this QTH follow:
- 6M = Performance is poor. I think due to a combination of transformer loss, coupled with an extremely high angle of radiation, this thing is pretty much a dog on 6M. I am feeding mine with approx. 120' of quality RG-213, so don't think my feedline losses are factor.
- 10M = Performance is poor as compared to a Shakespeare ABS-1600 or an MQ-1 mounted at the same heights. The performance is so poor in fact that there are stations on 10M which are completely uncopiable on the JTV, and yet quite workable on the other antennas.
- 12M = Same as 10M. Performance is quite poor.
- 15M = Down 2-3 S Units (approx. 15 dB) from an MQ-1 (2 element horizontal at same height).
- 17M = Almost useless at this QTH due to white noise. Half (51' long) G5RV at 20' beats it in all directions. Too much white noise on receive for me. Don't think it's locally generated QRN, rather instead, a function of it's broadbandednes, and/or natural resonance? Really dunno, but had expected it to work quite well here.
- 20M = Works better than expected at 25' height. Has become my primary PSK-31 antenna on this band.
- 30M = Same white noise problems here as on 17M, perhaps for the same reasons. Half G5RV kicks it's butt (again) here, (at a tenth the cost!)
- 40M = Surprisingly, works quite well on this band for BOTH local and long-haul DX. This surprised me because I was expecting it to work better on 30M than 40M, but I was wrong. Kicks butt on 40M! No, it is NOT as good as the Half G5RV for local contacts, but holds it's own for DX. Approx. 1 - 2 S Units down from a ground mounted GAP Challenger Vertical on this band, and approx. 2 - 3 S Units down from a full sized (Cushcraft AV-5) trap vertical, ground mounted with extensive radial field. However, for what it is, it performs well on this band. It has become my primary PSK-31 antenna on 40M
- 80M = Well, if you've got nothing else, then use it, but be advised that it is seriously deficient on this band. I've never worked (even PSK-31) a two-way contact on this band. I HAVE however, used it as an effective RX antenna on both 80 and 160M during high atmospheric QRN condx.
- 160M = Although not 'designed' for this band, it does offer an acceptable SWR through the whole range of 1.800 - 2.000 MHz, but no one will hear you due to the extreme lack of radiation efficiency here (probably <1.0%). However, as stated above, it makes a GREAT RX antenna for 160M.
- BCB Receive = A highly effective AM Broadcast band receive antenna for AM DXing (vertical polarization). There are AM Broadcast stations I can hear on this antenna (Wyoming, California, Etc.) which I can't hear on horizontal antennas. Conversely, radio stations in NYC (approx. 60 - 80 miles away), which are booming on my larger horizontal antennas are barely (if at all) heard on the Jetstream
- SWLing = If you stay away from the white noise / natural resonance(s) frequencies of this antenna, it does a auitable and quite effective job for Shortwave listening without the need for a balun, tuner, Q multiplier, preselector, or preamplifier. An added benefit.
- Portable / Temporary / Field-Day Use = This antenna is perhaps the EASIEST antenna I've ever assembled. Went together in (literally) less than 5 minutes. It would make the perfect field day or emergency QRV antenna. Once I determine a suitable replacement for it in it's existing mounting location (perhaps a 6M 5/8 wave vertical), I'm probably gonna use the Jetstream as a portable antenna for when I visit my grandkids out of state. (However, again remember that even when disassembled, it is quite long (6' or so) because it is only in 4 sections.) I may also experiement with it by capacitively (top) loading it to see if I can improve it's performance on the lower frequencies, and/or, eliminate the white noise issues I am experiencing on 17 and 30 meter bands.
That's it (for me) in a nutshell. It is what it is, a highly compromised and yet highly effective antenna that truly performs as designed. It is ingenious in its simplicity, ease of installation, and ease of use. Its effectiveness on the 20 and 40 meter bands (at approx. 1/2 the size of a 43' vertical radiator) have confirmed the effectiveness of a 43' vertical on the 40 and 80 meter bands, and although I don't currently have one, I can now see WHY a 43' vertical can be so appealing to so many people. It also makes me wonder if the white noise I experience on 17 and 30M on the JTV would be white noise on 30 and 60M bands on a 43' vertical. Hmmmmmmmm............
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