Back in my TAFE college days we had a campus station running on 1656 khz @ 1 watt (it was more like 10). We needed it to cover the campus which is about half a km radius from the middle. The problem was pushing good signal into places with electrical noise like workshops where arc welders, power tools and fluorescent lights were in use.

First aerial was an inverted "L" between the two ends of the campus' main admin block. The building itself is also an "L" shape. From the ground at one end to it's roof then across to the other side makes an inverted "L". This was matched against a single earth stake into some really rocky ground. It worked ok but not as good as you'd like. This was then moved to the back of the campus. But it wasn't much better either.

I was very green back then and looking back I think it was the lack of a good earth system. The ground was very rocky and we knew (even back then) the TAFE was built on an old quarry site. Not the best place for soil conductivity!

I'm not sure who's idea it was but in the later days we used a helical arrangement. This worked the best and is what I'm going to remodel as Tweaker Stick 1.

There has been a rethink for this model. Putting the loading coil at the top as drawn has been discovered to give poor results. The extra wire for the helical windings themselves adds a lot of loss and weight also. There is another design on the way called Tweaker Stick 4 that is made on PVC pipe and loaded in the same manner like the Tweaker Stick 2.

MF NAS is a small fish scenario. It has potential to earn a dollar if you play your cards right.

MF NAS is not a substitute for a full bells and whistles Commercial AM Service. There are several more non technical reasons for this too!

I'm assuming that the Fordray 50 watt AM TXer is deemed a reasonable low power starting point.

This would be a sensible aerial for 50 watts and won't break the bank or upset the neighbours too much.

This design will get you started! All physically short (or loaded) aerials have issues!

Expected efficiency of this aerial is around 8% at best. Expected power handling is 50 watts max.

50 watts is not going to do any where near the same job as 400 watts into the same aerial. This just doesn't happen!

Proper audio processing is actually VERY important to get the best out of MF NAS. This alone will make your 50 watts sound like 150 watts if done right. This point is ignored too much!

With proper processed audio in place and taking advantage of pos peak mod the expected range of this aerial is approximately 5km radius. Serious punch (or minimum commercial level) will be at about 1/2 km approx. This is assuming 50 watts power - I've not tested this yet!!

Locating this aerial right in the middle of the action is highly recommended.

The Tweaker 1 will be light as possible for roof mounting.

AM is a fairly unforgiving beast. Large amounts of power around various types of Hifi gear or phone systems can get messy. Care must be taken here. If you are putting this on a factory roof and have a choice between the "office block" and a "block of factories" take the block of factories! Chances are there's less likely hood of gear right underneath that will get upset.

I'm taking the old helical idea we did at TAFE years ago and rebuilding it. It's not a perfect solution and it has pitfalls as mentioned above.

The main issue is getting it to handle as much power as possible. This is hindered by the ohmic losses in the wire mostly. Then the inefficiency of the aerial because it is physically short and coil losses. At all times the focus is on power handling and signal push to air.

I'm looking at using round PVC pipe this time. The diameter is likely to be 90/100 mm. The TAFE days were square.

The square stuff used at TAFE was the only UV resistant stuff readily available back then. Plus it needed a lump of wood inside to strengthen it. I'm hoping round pipe is better due to the fact it's not square! Guying the Tweaker Stick 1 at 3m height intervals keeps with the general rules used by TV installers and seems to work. The guys will be non conductive rope & UV resistant too.

There is a plan to make these as light as possible so they can go on tin roofs. This seems to be the way a lot of people like to go. All early prototypes will be made against a ground based set of radials first. Then I'll move it to the roof. There will be no large difference physically. Experience has shown that they are more touchy to tune on the roof though.

I'm proposing to make a simple ATU box that has a lamp in it or an aerial current meter. You tweak this for max glow or max reading. It will get you close and working! For the rest a proper SWR meter would do. Too easy!

Tafe Campus

Tweaker Stick 1

As mentioned the Tafe Admin building is an L shape. The first position was the top one. Then the bottom was last for the inverted "L"

This is what really cranked for us it was on top of the theatre roof. X marks the spot on the admin block roof you see to the left!