remote vs local antenna 'tuning'
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| Jul 19th 2013, 06:40 | |
AF2UTotal Topics: 0 Total Posts: 0 |
I operate QRP and want to use a single roof-mounted vertical with 32 random-length radials for nearly all the HF bands. For such a design, I'll need a 'tuner'. Which is the most efficient (power transfer wise) to use; a remote 'tuner' tied at the antenna base or a local 'tuner' at the transmitter?? It's my impression that remote is the way to go since the transmitter and coax from it will see 50 Ohms at the 'tuner' near the antenna base. I think my concern is that the coax not be a part of the antenna system that radiates. Can anyone direct me to information regarding making this selection? I understand why a 'tuner' is needed for impedance adjustment, but I'm not certain that having the 'tuner' at the transmitter is the best idea although it is the most common arrangement. tnx, Don |
| Jul 19th 2013, 10:31 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
You are trying to mix two essentially different issues. One is feedline decoupling. The other is an efficient power transfer. It sounds like you are OK for feedline decoupling, with 32 radials, assuming you have a couple that actually work on the band you are using. If you seem to have issues you can fix that by adding more radials to your antenna system. A remote tuner is most efficient--with a matched 50 ohm line, line loss is minimized. I use a remote tuner with my flagpole vertical. The program Trnasmission Lines for Windows--TLW that comes with the Antenna Book can be used to calculate the losses that result from having a high SWR on the line. A concern with some modern rigs is overly aggressive transmitter protection--it might shut down your power with a 2:1 SWR--while someone else with that exact same antenna might radiate a very good signal. My 40M antenna loads up on 6M with a 2:1 SWR--even without a tuner I've worked some nice DX due to favorable band openings--FG5, 9Y4, VO1,and VP2V. Zack W1VT ARRL Senior Lab Engineer |
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