How to make a ladder feeder survive the wind?

Might S be better as a small plastic pulley? It would let the main system move more freely in wind without adding to the stresses.

Also, I seem to remember seeing an article on building feeder using spacers made from short lengths of clear plastic tubing. Supposed to be more uv resistant or something.

Reply to
mick
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Q. What is Ham Radio?

A. Ham Radio is a technical pursuit for those who are interested in the science of radio wave propagation and who are also interested in the way that their radios function. It has a long-standing tradition of providing a source of engineers who are born naturals.

Ham Radio awakens in its aficionados a whole-life fascination with all things technical and gives an all-abiding curiosity to improve one's scientific knowledge. It's a great swimming pool, please dive in!

This excitement causes a wish to share the experience with ones fellow man, and shows itself in the gentlemanly traditions of Ham Radio.

Radio Hams are in a unique privileged position in that they can construct and operate their own equipment! No-one else has this privilege. Users, such as broadcasters, the po lice and armed farces, CBers and mobile phone users have to purchase ready-made gear. Manufacturers are not licensed to operate their gear. Radio Hams are qualified to design, build and then operate their own pieces of equipment. They do this with gusto, and also repair and modify their own equipment. This is a privilege well worth the effort to gain, and one to be jealously guarded.

The excitement that drives a Radio Ham starts with relatively simple technologies at first, perhaps making his own Wimshurst machine and primary cells. Small pieces of test equipment follow, possibly multimeters and signal generators. Then comes receivers and transmitters. It is with the latter that communication with like-minded technically motivated people takes off. The scope for technical development grows with the years and now encompasses DSP and DDS. There is also a great deal of excitement in the areas of computer programming to be learnt and applied.

The technical excitement motivates Radio Hams to compete with each other to determine who has designed and manufactured the best-quality station. This competitiveness is found in DXing, competitions and fox-hunts.

-----ooooo----

However, beware! A Ham Radio licence is such a desirable thing to have that there are large numbers of people who wish to be thought of as Radio Hams when, in fact, they are nothing of the kind! Usually such people are a variation of the CB Radio hobbyist; they buy their radios off the shelf and send them back to be repaired; they are not interested in technical discussion and sneer at those who are; they have no idea how their radios work inside and have no wish to find out; they are free with rather silly personal insults.

-----ooooo-----

One infallible way to disambiguate the CB Radio Hobbyist from the _REAL_ Radio Ham is to solicit their view of the difference between CB Radio and Ham Radio. A Radio Ham will perceive Ham Radio to be a technical pursuit and will perceive CB Radio to be a social communications facility no different in essence to a land-line telephone or a GSM mobile in the hands of a 6-year-old. Thus a Radio Ham could also use a CB set safe in the knowledge that such use says no more about him than having a land-line telephone, whilst continuing to regard Ham Radio as a separate technical pursuit.

A CB Radio hobbyist, on the other hand, sees no difference between Ham Radio and CB Radio. To him, they are sisters-under-the-skin. Wrongly, the CB Radio Hobbyist then tries to classify himself as the equal of the Radio Ham when, in fact, he is nothing of the kind.

Ham Radio is not CB Radio and has no common ground with it! Ham Radio is _THE_ technical pursuit for gentlemen; CB Radio is the name for the operating hobby for those who buy their rigs and equipment off the shelf.

-----ooooo-----

If you are the sort of person who is motivated by a technical interest in how things work; if you took apart malfunctioning clocks, toasters and the like and put them right despite never having seen them working, then a Ham Radio licence is your traditional route! There has never been a shortage of such people, and those who gravitate towards such an interest have always been welcomed into our shacks and their interests fostered. There is not today, nor has there ever been, a need to go out and encourage and press children, children who have never expressed an interest in Ham Radio, to come into our shacks. Such an activity should cause eyebrows to be raised - what normal well-adjusted adults seek the social acquaintance of children?!

-----ooooo-----

Please remember that this FAQ is a _POSITIVE EXHORTATION_ to you to exert yourselves to join our fraternity!

Reply to
gareth

Ham radio is,

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Reply to
tony sayer

En el artículo , tony sayer escribió:

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Reply to
Mike Tomlinson

Nothing, but what has it got to do with balanced vs. unbalanced feeders?

Reply to
Huge

Don't encourage him. It's bad enough that u.r.a is full of this dross.

Reply to
Huge

If it be your opinion that the maintenance of standards is dross, then your opinion does not cast you in a favourable light.

Reply to
gareth

Well a BALanced to UNbalance device is more often than not used to match differing impedance's together..

Reply to
tony sayer

The need for a balun is the least of your problems. A ladder line fed balanced dipole can be tuned up on a much wider range of frequencies, ideally using a proper balanced output ATU but a broadband 1:2 (1:4z) balun rated for the maximum power on the lowest frequency band of interest (3.5 to 3.8MHz or '80 metres') can be, and usually is, used with an unbalanced output ATU to quite good effect.

Removing the balun away from the feed point of a, typically, short wire dipole at the end of a run of co-axial cable places it at a point where it's sheltered from both the weather and the greater, more unpredictable, extremes of voltage and current standing wave variations to be found at the feedpoints of such antennas.

At least, when it's in the shack, you can see/hear/smell when it's being over-stressed, assuming the tuning capacitors in the ATU aren't already providing their own hint of extreme voltages (and currents elsewhere in the tuning network).

The cost of fabricating the ladder line (open wire feeder) is a damn sight cheaper than the cost of acquiring the necessary high grade Andrews co-axial cable equivalent (and an even beefier and over-specced balun).

Co-ax does have the charm that it isn't sensitive to its immediate surroundings but it does require that the antenna feed point be reasonably well matched to the feeder impedance.

The ladder line (open wire feeder) requires some consideration in regard to its immediate surroundings (brickwork, metalwork, and other structural materials) which may vary in their effect due to precipitation.

The line losses of open wire feeder are considerably lower than that in co-axial cable feeders when operating the line under high VSWR conditions (20:1 or higher) so typical of broadband operation of a short "All Band" dipole antenna setup which is their main appeal to amateur radio operators.

Reply to
Johnny B Good

That seems to be a SWL centric view of the process. More usefully, it's normally considered to be a process that takes the unbalanced transmitter output via short co-axial patch lead into the ATU (Antenna Tuning Unit - which may or may not be automatic) which acts as a tuned impedance matching transformer feeding a pretty beefy 1:2 or 1:4 (1:4 or 1:16 impedance) balun to drive the end of the open wire line feeder. More ideally, in this case, would be a balanced ATU using ganged tuning capacitors and coils fed from a 1:2 input balun of more modest rating, allowing the two outputs of the dual ganged ATU to feed each wire of the open wire feeder directly.

That's pretty well a "No Brainer". The antenna (array) is a single frequency, well matched setup that allows the transmission line to operate very close to 1:1 VSWR. The metal mast often carries more than one antenna array and the immunity of co-axial feeder to other cables and the mast itself simplifies the feeder routing. Co-ax in this usage case is a match made in heaven. Open wire feeder, otoh, simply isn't a practical solution in this case.

Reply to
Johnny B Good

Well something like the Alan Dick Spearhead array can cover most all of Band 2 in one hit as was well as the use of panel aerials in UHF TV transmission, these are rather wideband devices.

Tower space is rather, no very expensive to rent, so combining into a broadband array....

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Isn't it just;!..

It is used in short-wave stations ...

Reply to
tony sayer

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