Inverted L on 160 as recommended by W1BB
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- เผยแพร่เมื่อ 4 ต.ค. 2024
- Many years ago W1BB sent me info on this antenna. This antenna can not beat a dipole 260 foot high or a full size 130 foot vertical or 4 Square with a decent radial system. However it is, in my opinion, the second best choice if you can not get really high with your antenna. High depends on wavelength. This antenna loses its advantage when dipoles can be installed at a half wavelength or so. Height in wavelengths is easier to obtain as you progressively move from 160 to 80 to 40 and so on.
Great explanation! I wanted to get on 160 for years. After experimenting with a few antennas, I came across this video. I built this antenna and used a fixed doorknob capacitor at the feedpoint. In my case I used 200PF rated at 7.5KV. I adjust the wire length + or - to get a perfect 50 ohm resistive match. I am using 8, 60' long radials. This antenna works GREAT! Significantly better than a dipole at 50 ft. Significantly better than a 1/4 wave vertical because my transmitter likes the match. The vertical height of the wire is about 50 ft running up a tree and through a couple branches. The insulated wire (#10 THHN) running through the branches seems to make no difference. I consistently have a strong signal. The only station that beats me (and not by much) is a guy running a full wave loop at 60 ft running a KW. Thank you and W1AA for this design.
Thanks! You did exactly right! Not sure why a full wave loop at only 60 foot should beat you, except on short skip where it’s high angle dominates his pattern. I have done well with my configuration in contests and it got me 160 DXCC many years ago when it was a bit harder. Have fun! 73, Don N4DJ
Thanks. Looks like you have a good setup!
I do same, except mine is for 7MHz , it is 7MHz half wave end fed in L shape. it works well. I use MFJ 993B auto tuner in water tight plastic box at feed point. it also works as 1/4 wave 3.5 MHz. AG6JU
I have an efhw 80m antenna with the 49:1. Sadly I have nothing but a 30 ft tower. I wondered if I ran the wire up and out if the max current would still be on the horizontal plane.
A local friend has this very antenna you have. He ran 1/4 wave radials everywhere for 160. He has a very large coil at the base and moves the tap point for Cw or phone. He wants to sell me the other coil he had on it prior for 30$. I’m glad to see I can use 165 ish ft and only 3 radials. I’m assuming these coils act as variable capacitors ? Just moving the tap point instead of turning. I would love to have 160m for Cw tests. I’m not sure how well it would do only 30 ft at the Vertical. But it should get me on the air. Thanks bud
About your friends Inverted L....My first thought is that it must be short if he is using a coil to tune it. Coils and capacitors both add reactance. A series coil adds series inductive reactance and a series capacitor adds series capacitive reactance. So you use them for slightly different reasons. First of all you would rather not have the high current point of any antenna near the ground. With a ground mounted vertical that means either installing it upside down ( see my half square video) or making it longer than a quarter wave to move the current peak higher. The inverted L I use is not 130 feet (quarter wave) but 165 plus feet. This makes the input impedance something like Z=50 +j 442 where 50 is the real resistance and 442 is inductive reactance. All you need to do is add a equal amount of capacitive reactance in series and you get 50 +j442 -j442 = 50 ohms of pure resistance left.
I like to avoid coils as they tend to have more loss than capacitors. Remember the current peak is always1/4 wavelength back from the open end of a wire antenna. I can't think of an exception to that rule.
@@dandypoint thank you. Do you know where to find a variable capacitor that handles the limits of we’re doing
@@JayN4GO I have several suggestions, but first how much power do you want to handle?
@@dandypoint 1kw max
@@JayN4GO Sent you an email with info.
How about using a remote trans-match instead of a series capacitor?
Maybe. More parts and wires. The main thing is to have a low loss matching system from 50 ohm coax to whatever the antenna terminals are. Typical load is near 50 +J350 (R=50 and XL =350) you don’t know for sure exactly but that’s ballpark.
If R is near 50 all you need to do is cancel the inductive reactance to get only the real resistance. Anywhere from R=25 to R = 100 will give you a 2:1 SWR. Closer to 50 and the better the SWR and the wider your bandwidth between SWR 2:1 points.
I have used an L network at the base and that works good. I think a good quality series capacitor will be the least loss. But any good matching device should work.
@@dandypoint Awesome. I'm setting up an inverted L for 160. I should be able to get 50 to 75 feet of vertical section....#10 wire.
Jeff W3AAB
@@jwnagy that’s great on the height! A quarter wave will work but I think going longer has some benefits so I went to about 3/8 wave or 165 feet or so. Exact SWR will depend on length of wire and the ground resistance but losses are minimal on 160 due to SWR as long as the transmitter can load it. My Drake L7 is happy with as high as a 2:1 SWR. In a 160 contest I even will go higher in the band than my 2:1 point and it’s still doing fine with the original 1980’s tubes still going!
@@dandypoint I'm shooting for being centralized at 1.9. I just ordered the Mastraint rope from DX engineering, which should arrive mid week. The tree guy is coming out next Saturday to trim my tree and install some pulleys for me. Maybe done by end of March.