best antenna

[Limpost]

Thanks.
This template & computer simulation are design stage of Franklin with thick (5mm dia) rod or pipe.
Prototype is yet to be built & tested.

Hi abcd567,

I regularly visit this column to read up on what is being said about building your own antenna. The Design and Template above is one of the best I have seen anywhere. It is so simple and clear that a primary school student will understand it.

I wonder if an Air Band (118-137 Mhz) antenna could also be built like the above. What would be the dimensions? Thanks.

[peterhr]

Hi abcd567,

I regularly visit this column to read up on what is being said about building your own antenna. The Design and Template above is one of the best I have seen anywhere. It is so simple and clear that a primary school student will understand it.

I wonder if an Air Band (118-137 Mhz) antenna could also be built like the above. What would be the dimensions? Thanks.

That's at about 1/10th the frequency or 10x the wavelength of ADS-B - you would have to multiply dimensions by a factor of almost 10. I guess you could do it but it might be easier to make up using 15 or 22mm standard copper tubing and solder type 'elbow' plumbing fittings (unless you have a pipe bender)

[Limpost]

That's at about 1/10th the frequency or 10x the wavelength of ADS-B - you would have to multiply dimensions by a factor of almost 10. I guess you could do it but it might be easier to make up using 15 or 22mm standard copper tubing and solder type 'elbow' plumbing fittings (unless you have a pipe bender)

Hi Peterhr,

Thanks. Yes, it would end up about 1/2 a metre or more in height. Would need something stiff to keep it upright. Isn't 15 or 22mm tubing too big/thick for this?

[peterhr]

The ads-b version is about half a meter (450mm) , airband the same design would be 0.450 * 1090 / 127 = 3.86m or 12' 8" - I think you'd need something fairly substantial for structural stability.

[Limpost]

The ads-b version is about half a meter (450mm) , airband the same design would be 0.450 * 1090 / 127 = 3.86m or 12' 8" - I think you'd need something fairly substantial for structural stability.

Wow!!!!!!! that would be near to impossible for us amateurs.

[abcd567]

I have been searching for materials for the template/antenna with 5mm wire/tube. I checked most of the stores selling hardware & electrical stuff like wires & cables.

Although Canada has adopted metric system for decades, I was surprised to find that material available is in US measurement system ONLY: dimensions in inches & wire sizes in AWG (american wire guage: inch based).

(1) Wires are available in AWG sizes only. This means not whole mm but odd fractions like
4AWG = 5.19 mm dia
6 AWG = 4.11 mm dia
8 AWG = 3.26 mm dia
10 AWG = 2.59 mm dia
12 AWG = 2.05 mm dia

The 12 AWG (2.05mm) dia wire is available as solid earth wire inside a cable. Higher sizes are stranded.

Bare copper wire is available in 6 & 8 AWG (4.11mm & 3.26mm), but these are stranded.

(2) Bolts are available in inches size only, and largest dia is 1/2 inch. (12.5mm) Metric sizes are not available.

I am trying to find stores which sell material I need.

[abcd567]

Today I purchased:
(1) 3 meters of 6 AWG Bare Copper Wire Stranded @ $1.80/m = $ 5.40
(2) 3 meters of 8 AWG Bare Copper Wire Stranded @ $1.30/m = $ 3.90
Total = $5.40+$3.90+$1.21 tax = $10.51

6 meter wire is sufficient to make 6 antennas.
Cost per antenna = $10.51/6 = $1.75 per antenna ... not bad

BUT.......
1)The wires are not solid. These are stranded. How they will behave during bending? Strands will open apart? kinks? dont know till try.
2)The wires diameters are not exact 3 & 4 mm. These are 3.26 mm (8 AWG) & 4.11 mm (6 AWG)..... Simulation+Dimensions+Template to be modified
3)Could not get 16 mm & 10 mm bolts. Readily available are 1/2" (12.5mm) & 3/8" (9.5mm)..... Simulation+Dimensions+Template to be modified

Too many ifs & buts....
Lets see if I am able to construct it properly & not like ill-fated Brake Line one.
Also lets hope that the trial run of prototype succeeds, and does not end up same way as all of my half-dozen CoCos have ended up - poor performance.

[Teecee]

Hi
If you think the strands are not closely enough woven, you could put one end of the wire in a vice, turn the other with an electric drill. This should 'stiffen' the wire, and increase the copper content per length. You could also run solder between the strands at the bends to hold them together.
Have fun
Terry

[abcd567]

Hi
If you think the strands are not closely enough woven, you could put one end of the wire in a vice, turn the other with an electric drill. This should 'stiffen' the wire, and increase the copper content per length. You could also run solder between the strands at the bends to hold them together.
Have fun
Terry

Thanks for the practical tips.
The wire seems to be woven enough.
When I will bend it in narrow bends required by franklin, I will discover how easy/difficult it is to make a neat & precise bend.

[trigger]

You'll have to get these outside, the heavy mineral based materials (tile / slate) used in out roofs would seriously degrade the signals - other areas use lighter materials and they'd getaway with more than we do.

go to http://www.heywhatsthat.com/ - do a new plot for exactly where you are with your actual antenna height - click 'in the air' (top right of the map and see where 40000 feet ring is. You should reach just beyond that.

Hi peterhr,
How did you combine the plot from heywhatsthat with the range from Virtual Radar? in your sig? I've got my antenna outside with an amplifier and I seem to be getting close to the 40000m ring. I would like to superimpose the 2 plots.

[trigger]

Some results from my "coiled" Franklin. Made from 1.5mm wire stripped from UK 13amp mains cable. Dimensions are further back in this thread (somewhere!) It sits about 15 feet above ground lashed to my sewer vent pipe (note the 2 Red Kites). Range rings are 50nm.

coil.jpg coiled franklin +amp 50nm rings.JPG in the air.jpg coiled franklin.jpg


It has just started raining here and the range has dropped dramatically. Is this to be expected or is it water droplets shorting out the stubs?

[peterhr]

On one of the two I made the background very plain.

Took the two images and resized one to be the same pixel size as the other referencing two land areas (londonderry - the bulging bit of norfolk and the land shape near Edinburgh to isle of wight) (using paint shop pro)

on the simpler one made much of the back ground transparent, copied what remained and pasted it over the other image. because the background was transparent the underlying picture shows through.

I had thought of doing something similar with the FR24 web page - make the background dark and screen shoting the world every - say - 15 mins for a whole day. Then overlay all the images (96 of them) and that would give a a fair coverage map. I'm sure FR24 have something similar themselves but not for sharing.

----

as for range check mine out tomorrow morning about 9 am (should be dry) and Sunday morning at the same time when hurricane bertha is due to arrive - the sheduled flight load across the Atlantic should be similar - see what the weather does to range.

I suspect the droplets on the copper might be affecting the antenna performance - what the big dip to the NE on your chart ... is the due to the pole it's fixed to or a tree, chimney or something.

[abcd567]

Some results from my "coiled" Franklin. Made from 1.5mm wire stripped from UK 13amp mains cable. Dimensions are further back in this thread (somewhere!) It sits about 15 feet above ground lashed to my sewer vent pipe (note the 2 Red Kites). Range rings are 50nm.

[ATTACH=CONFIG]4581[/ATTACH] [ATTACH=CONFIG]4582[/ATTACH] [ATTACH=CONFIG]4583[/ATTACH] [ATTACH=CONFIG]4584[/ATTACH]


It has just started raining here and the range has dropped dramatically. Is this to be expected or is it water droplets shorting out the stubs?

Congratulations you got good results for wrapped stub franklin. Is wrapping dia 22mm?

Later addition:
(1) The "kite" photo shows the wrapping is not a complete circle, but about 3/4 circle (270 degrees) so dia should be about 22 x 4/3 =29mm.

(2) You have made the antenna in a neat & precise manner, which is a big factor in it's success. You are very skilled.

Did you notice a new type antenna lying left of the copper wires photo I recently posted? It is 5/8 wavelength dipole with tuning coil, can fit inside the pipe (coil dia = 10mm).

It is still in trial & tweaking/redesigning stage.

[trigger]

Hi peterhr, thanks for the information, I'll give it a go. I took the antenna down as I haven't waterproofed the amp or the joints and there were rain drops between the stubs. I think the dip to the NE is a Silver Birch tree. I did rotate the piece of dowel to check if the antenna was directional (it isn't). I've also discovered that the antenna cannot be mounted on the vertical elements. It seemed easy to tape the verticals to the dowel but it cut the range a lot.

Hi ab cd, yes I had noticed it . Looking forward to some results. Yes, approx 22mm diameter and the tap is 24mm from the open end of the stub.

Time to get the Raspberry Pi out again.

[abcd567]

........Hi ab cd, yes I had noticed it . Looking forward to some results.

I am experiencing a contradiction in results I get by maths, by simulation, and by trial run of prototype.

Results of maths & simulations agree reasonably close, but when i run prototype, results are much poorer. I dont know why. This happens to Franklins, 5/8, etc.

There is another strange phenomenon with pepsi-can sleeved dipole. Without amp & connected directly by short piece of cable, it gives better results compared to franklin connected to same setup. With amp & long cable, franklin gives better results than pepsi-can sleeved dipole connected to same setup. Very strange.