Good morning Gentlemen,
Can one roll up the matching ladderline/ribbon stub in a gentle loop to take up the slack of the above antenna when the shack is closer to the feed point as in an apartment ops . And/Or, Can we keep the publicized flat top dimensions and run a shorter stub directly to a balance ATU and retain the characteristics of the ZS6BKW.
Best Wishes and 73, Mark M6AWG
Each part of the ladder-line needs to be a foot away from every other part and no, one cannot shorten a tuned feeder without de-tuning it. Here is one thing that can be done:
Originally Posted by M6AWG
If the feedline spiral needs to come straight down, two messenger lines should be used - one on each side of the spiral.
The ladder line cannot be rolled up it would change the electrical length through capacitive feeding. It should hang straight or as straight as possible. As to hooking to the tuner direct, yes you can do that BUT since it would be through a 4:1 balun in most cases this would change things as far as impedance AT THE TUNER. Another suggestion, don't use the 1:1 balun direct feed the coax (if you use it) to the ladder line. I would use a short piece of coax to help eliminate RF in the shack that ladder line brings in.
GL es 73
But my operating position is only 1/2 the distance of the 11.1 metres of 300 ohm ribbon needed to reach the Tx.. It was my understanding that because the feeder was a tuned stub and presumably didn't radiate that I could form a 1 feet loop of the remaining 16 ft or so?
if not possible, then can I leave the flat top as the classic ZS6BKW with half the feeder length but omitting the coax and running the now shortened feeder directly into the ATU yet retaining all the characteristics of the antenna?
Sorry, that doesn't change the laws of physics. Coiling up ladder-line drastically changes the EM fields surrounding the wires and will cause the ZS6BKW design to malfunction. What you can do is form that extra 16' of ladder-line into a 2.5' diameter spiral with the ends of the spiral about one foot apart. You could hang that spiral from the ceiling or on a wall (assuming wood and sheet-rock).
Originally Posted by M6AWG
Instead of bringing the ladder-line straight to the operating position, can you take an indirect path like back and forth in the form of a curved 'S'? My ZS6BKW feedline is routed that way and works just fine. If you have eaves on your house, you can hang the ladder-line, accordion-style, from the eaves of the house. I've done that and it works just fine.
Yes, Ok Cecil, point taken..
Thank you very much to your good self and Sandor..
Ok..just a new thought.. if the whole antenna is now hoisted above the roof Gaining me 35feet of height and therefore my previous post is now redundant, do I gain substantially seeing that I now have a much higher feedpoint yet a much longer 40 feet rg58 coax section, whereas before it would have been only 6 feet of rg 58 with the lower feedpoint?
What do the professionals feel asuming RG58 is all I have to work with..
Getting the antenna as high as is practicable is the way to go on HF, once it's up the ladder line should fall straight down. If you're operating position is on the second or third floor and you're antenna is above you, let the ladder line droop downward, and toward your operating position. That type of antennas I believe requires a certain amount of coax connected to it. That can be coiled, but not the ladder line.
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Higher is always better. RG58 isn't that bad on HF operation or even VHF. You lose 0.5db on 7MHz and on ten meters you lose 1db. Big deal. What you gain in height and lowered radiation angle more then makes up for that tiny amount of feed line loss. BTW the values I posted are not the difference between a 6 and 40 foot run. It's what a 40 foot run losses would be by itself. Reason, the 6 foot length keeps showing 0.1db everywhere. Apparently the calculator I'm using can't figure the loss of just a 6 foot section. You can do about the right value by calculating for a 60 foot value and divide by 10.
Some RG58 isn't good enough to make the operations that good. As long as you purchased a good quality coax you should be okay.