Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Apr 12, 2015.
Saw that after I posted ....
Adding to my comments above, my ZS6BKW will work on 80 meters but not on 75 meters. Likewise, it will tune the higher end of 15 meters. It all comes down to what frequency you're talking about. For instance, some folks talk about 80 meters but mean to say they are talking about frequencies in the 75 meter band (3.8 - 4.0 Mhz). For myself, 80 meters starts at 3.5 Mhz and ends at approx. 3.8 Mhz. Beyond 3.8, the tuner starts complaining.
73 from KK4VTC
OCFD, with a good 4 to 1 or 6 to 1 balun
Every time in real world use at 30 feet The Off Center fed with whatever Dimension 80/20 or 70/30 has always worked better for me, by huge margin.
I compared them time to time when operating portable are in my RV I threw the g5rv away.
I didn't want to give it to anybody it performed so poorly in most situations, but I built a lot of off center fed dipoles and gave those to people.
Yeah the guys with g5rvs are making contacts but most of them have not tried an OCFD!! And they will tell you, that they load up good, but so does my dummy load
My 40-10 OCFD has served me pretty well on the bands it can work.
I am using a full size G5RV it's up about 100ft running north west to south east, I can here state side and Australia but there in the noise level of about s5 I can't seem to make any contacts to them.do I need a different antenna to make contact. The noise level is a bit of a pain at times, I live in the country side with no interference from anything so I assume this is normal noise level from the G5
@M7RSD Jon, have you done the standard "turn off the AC master breaker" and "run your receiver from a battery" test?
My experience is that the "noise" can be coming from switching power supplies, wall-warts, computers, LED-lighting, solid-state ballasts in your own house. Killing AC power (make sure that there are no uninterruptible power supplies on your computers), waiting a while, and then listening to the ham bands with the AC off will go a long way to show where it is coming from. If the noise persists with your own AC off, then it is either power line noise or coming from your neighbor's houses. You can do something about the stuff in your own house.
If you find a lot of the noise is coming from your own house, then aggressively choking the coax feedline outside of your house using ferrite core chokes may be the easiest way of cleaning it up.
Does your existing G5RV antenna have a large ferrite balun at the coax to the twin-lead transition? Cheap ones dont; more expensive ones do...
I just realized that this thread is pretty old, but as I had already typed up a response in notepad here's my input.
As has been stated, never trust an antenna manufacturer. I find that their claims are normally a little far-fetched. I think that the only antenna that is versitile enough and works well on more than one band is a log periodic, but these are normally large and expensive.
OCF antennas normally require some kind of matching network in order to match the antenna impedance to something the rig likes to see. An OCF will want to see a feedpoint positioned about 1/4 wavelength from one of the ends to be a decent impedance match on any particular band. Since the wavelength differs significantly for each band, the feedpoint would also differ. In order to make them work on more bands most OCF antennas are designed to have the feedpoint located in a "sweet spot"--a spot on the antenna where most of the impedances for most of the bands 'somewhat' converge (generally about 1/3 wavelength from one end) and are manageable. At this point the impedance will range between about 150 Ohms to around 300 Ohms depending on the band in use. The use of a 4:1 or 6:1 (depending on the antenna design) guanella balun will allow an OCF designed in this manner to be used on many bands, making the antenna system a good compromise overall.
But, just like the G5RV, an OCF dipole is a compromise. Then again, so are ALL antennas. But don't think of the word 'compromise' to mean that these antennas work significantly worse than any other antenna, and that it is a piece of $h!t. This is a trap that many HAMs fall into. Think about it this way: there is not one antenna that will be resonant on all bands, provide excellent bandwidth, is small and simple, and is cheap to set up. Any antenna you set up will be a compromse in one of these areas. The key here is to select an antenna that is a compromise in the area that you can live with. For example, NOT installing a set of stacked resonant beam antennas on an 80+ foot tower may be a performance compromise. You'll not get the same performance from an OCF dipole or a G5RV, but the simplicity and cost of setting these antennas up may far outweigh the cost and complexity of the tower/beam setup. To further muddy the waters, so to speak, an antenna that works well in my environment may not work well at all in yours. So, evaluating one antenna on the basis that it may be "better" than another is a difficult proposition at best, and a futile endeavor at the worst.
In any case, the OCF dipoles and the G5RV's have been used by many HAMs and have been effective in making many, many contacts over the years despite whatever shortcomings Ham Radio Operators attach to them. Pick the one that works best for your particular installation plan and use it to get on the air.
Many antennas work very well on two or more bands. My ZS6BKW works very well without a tuner on 40m, 20m, 17m, 12m, and 10m.
I tend to think that it is possible to build a relatively simple wire antenna that works well on about three or four consecutive bands, i.e. 160/80/60/40m or 80/40/20, 20 to 10m, etc.
I have build/tested several candidates. So far in order of my preference:
1. My 556ft, 50ft high horizontal loop, works really well on 80/60/40/30m (actually all harmonics of 1.825MHz). On 160m it is too low to be a great DX antenna, but gets me on that band out to a distance of ~1000mi. Wont work for most because it is big (I'm on 10 acres)
2. My ZS6BKW. I deploy mine as an inverted-V with a single center 40ft high metal support. The PiNet in a SB220 amplifier will feed it without a tuner in-line on 80/40/20/17m (all I have tried, may work on the others, too).
3. An extremely off-center-fed half wave (like the commercial EFHW-8010). I deploy them in a way that is different to most recommendations you will find on the web. The good news is that one single wire will give you access to several bands.