Well I know that's not the case and I know that my half-size G5RV is a pretty poor antenna even though my ATU can "tune" it on almost any band and give me a 1:1 SWR reading.
The fact that my radio (and ATU) are showing me figures indicating a near perfect match, makes no real difference to the actual resonance of my antenna - the antenna remains as good or as bad as it was before the ATU was installed. My radio 'thinks' it's putting out 10W and none is reflected, but in actual fact, MOST of it might be reflected and I might only be getting 1W out.
That's why I don't expect good results using my G5RV (which also happens to be located in a terrible position and height at my QTH). I use it (and the ATU) because I have no option. I cannot erect anything better, so I have to accept the limitations of the antenna and just do the best I can with it.
Sure, I have managed to get some great QRP results when the conditions have been exceptional. And the G5RV is in all fairness not that bad on 20 & 40 but it's all a compromise and I'm not fooling myself that having a 1.0:1 SWR reading through the tuner is turning my poor antenna into a good one.
The only way to get good and effective results is to use an antenna that is already resonant on the frequency you wish to operate on. For me, that means installing a temporary resonant antenna at weekends such as the SotaBeams 20/40 linked dipole on a telescopic mast in the back garden. The results are great, but at the end of the weekend (or holidays), it has to be dropped back down to avoid objections from the neighbours and landlord and I have to go back to using the G5RV and accept the fact that although I have a 1.0:1 reading, I am in some cases barely getting out!
So, if you're one of those new operators who doesn't quite understand this, take a look at this great video which explains it further.
73
2 comments:
The video is clear enough. A antenna tuner just keeps your radio happy. However....things are a bit different when using a antennatuner at the feedpoint of your antenna. In that case you haven't got the loss over the coax. But this says nothing about the efficiency of the antenna...
Another option is open line feeder. A so called ladder line doesn't have the loss coax has and is a better choice when using a dipole as multiband antenna, in that case you need a good antenna tuner preferable a balanced tuner. I guess you're working with a a so called G5RV junior? In your case to increase efficiency I would forget the G5RV and try a homemade dipole (inverted-V or whatever) configuration and feed it with homemade ladderline. Fed by a good tuner with 1:4 balun or preferable with a balanced tuner or S-match tuner. It will increase your possebilities with our great hobby. (I have used a G5RV for a while, I know...). Good luck! 73, Bas
Okay Bas - I will look into that. My ATU (MFJ 993B) will actually take ladder-line directly. For me, the problem is always how I can make an antenna and feeder invisible to my neighbours and landlord :-)))
Post a Comment