Should I load the Antenna at the base or just put the tuner there? (

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Nat, W8NAT, has quite a dissertation on antenna tuners vs antenna loading? Watch to learn more.
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11 мар 2022

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Комментарии : 17

@battlestarone 2 года назад

it only seems to be radio hams that want to tune an antenna with atu in the shack,,,broadcast and marine services always seem to have tuner at antenna end,,,remote tuners that handle more than 200w are very expensive,,,i favour an L match or Lc match for coupling at antenna end always,,,not do good on pouring rain when ajusting it but works very well,,,seen someone build a remote atu Lc match using little motors to ajust variable capacitors,,worked great and nice project at fraction of the cost .

@Siskiyous6 2 года назад

Good topic and explanation. Sadly capacity hats are a lot bigger to be effective than the relative size in your drawing, that is why they are not more popular, they are fairly large in a place where support is often in short supply. The term screwdriver is from the original models which were battery powered screwdrivers modified for our use.

@alp6475 2 года назад

Just the experiment I planned on doing this weekend! Unfortunately it snowed around here and I it's not safe to work outside :) Will have to wait!

@bentleys5059 2 года назад

Nice video Dave. How do the properties of the antenna change if you lower the capacitance hat closer closer to the mid-way point (as apposed to the top). I'm looking at the capacitance hat for Chameleon MPAS. Thank you for your comments.

@clems6989 2 года назад

Dave, If you havnt already, you might do a video on stacking antennas. The gains and tradeoffs, patterns etc. I think it would be interesting..

@johnyum9021 2 года назад

David I love all of your videos channel You let me know more about radio knowledge from vr2upq HK👍

@timg5tm941 2 года назад

Dave - ATU at base of the vertical - when you say the antenna is "too short" at 20 feet long, I presume you mean 40 and below? 20-10m should be ok (even 40), provided you avoid a halfwave length on a band. Then, even a good ATU might have issues bringing in an impedance of 3000 ohms plus. 73

@kmkessler 2 года назад

The question I hoped would be answered was, if I have a vertical antenna with a loading coil tune to a certain frequency (say something in 40M) and I can take the coil out and tune the same antenna with a tuner to the same frequency with the same SWR, is there any practical difference between the two, in things like efficiency or radiation pattern, etc. I'm building a QRP, loaded antenna with a 102" whip (kind of a Wolf River Coil antenna), and am asking this same question. Is the coil any different than the tuner in this respect?

@davecasler 2 года назад

Use the loading coil. Pattern doesn't change. If high SWR on cable, losses can be high.

@subramanianr7206 2 года назад

Hi, good question. Any vertical antenna of around 1/4 lambda is resonant with sufficient ground radials when mounted on the ground. When it's shorter you need some form of loading to compensate for the short length of the radiator. You can use the spiral loading (common practice) or linear loading (not uncommon but it's going to be different) A Tuner preferably an L match at the base can very well replace the loading coil and bring the radiator into resonance. A high Q loading coil or a tuner of high Q components will not make any difference in principle. But then a tuner of some sort at the base of the radiator would be preferred. In the case of base loaded vertical any residual SWR on the cable from the feed point to the shack may not show up in the meter in the shack; but would be eating the precious RF power by heating up the dielectric material in the cable. The efficiency or the radiation pattern, (provided the power to the radiator is the same) wouldn't change in both cases, for sure. De VU2RZA

@timbookedtwo2375 2 года назад

I had the impression that an "antenna tuner" does not tune an antenna to resonance, like one would tune a guitar string. But rather it is an impedance matching device that matches the antenna's impedance to 50 ohms, more or less. The antenna side of the tuner is still not resonant. The standing waves on thie antenna side would keep bouncing back and forth, like sloshing around in a tub until they dissapate either as RF or as heat. By having a "tuner" at the feedpoint of the antenna, one merely avoids sending the standing waves down the coax and into the shack/radio. Please correct me if I am wrong. I use resonant antennas and avoid the whole "tuner" issue. Just recentl, as a backup antenna (2 i one, one is none) I made a simple dipole antenna for 40 meters using speaker wire and a a simple wire to bnc connector, hung it as an inverted "V" and have full bandwidth coverage with an SWR of less than 1.7:1, in places practically 1.0:1. For my end fed half wave antennas I use a 49:1 or 64:1 transformer.

@criscross6591 2 года назад

Thanks for your great work! My question is, what is the difference between the remote tuner at the base of the antenna and the one in your shack, other than the distance?

@erpece 2 года назад

The tuner will work in both situations, but with the tuner in the shack the coax to the antenna becomes 'part' of the antenna. This results in loss in that length of coax and less power to the antenna. To avoid these losses, place the (remote) tuner at the feedpoint of the antenna.

@subramanianr7206 2 года назад

You need an antenna coupler (commonly known as antenna tuner) at the feed point because the antenna is not resonant. It means it's not having the characteristic impedance of 50 ohm resistive load which your radio wants to look into. That's it is having not just resistance but some reactance too. The reactance has to be annihilated by introducing an inductor in case of a capacitive reactance and vice versa. If you have the remote Tuner at the feed point of the antenna it's going to accomplish this very effectively. If you have the tuner in the shack your radio would see a 50 ohm resistive load but the same high SWR is prevailing in the coaxial cable from the feed point to the shack. This is no good. The dielectric material in the coaxial cable is getting heated up because of the high SWR. The longer the cable more is the loss of precious RF power. I hope this helps. De VU2RZA

@criscross6591 2 года назад

👍👍