MF transverter idea

Well, there were two ideas around since I started thinking LF and MF. Transverters are certainly one way to go, although, I built a 600m-exciter by now.
The two ideas are:

1. subharmonic mixing using a 14MHz LO
2. regular mixing using a 10MHz LO

First I thought, subharmonic was the way to go, however, now, I consider the 10MHz option may be the better option.

To be honest with the dear reader, I wanted to have something built by today, however, external events drained my energy once again... So I have to be happy with the few steps I managed to do...

The transverter plan is now to run a 10MHz LO into a 4066 switching converter. Alternatively, a NE612-approach is considered. I hope, I will find my energy soon, time for the 600m experiment is ticking....

600m - Octaplumb online

The tuning/coupling-box attached with just some electrician's tape, the octaplumb does its' job on my roof deck.

600m - Octaplumb update

Eddie was pointing to a source of free ferrite toroids, hence, I took the chance and used one for the Octaplumb. The toroid came as 10:3:3-transformer. To simplify matters, I removed the two low turn count wires and kept the 10 turns winding. So much to coupling....
Resonance is obtained by the typical (see earlier entries) polyvaricon and a parallel capacitance. In this case, 680pF from another slaughtered CFL did the deal getting the loop resonating in the 600m band.
This is what it all looks alike:

600m - Plumbtenna mast

The people in my home improvement store my believe I am totally off. Day by day I drop by and buy some stuff that never will fit together in the conventional way. Example: 8pc 45deg 32mm elbows and a 2m long 40mm pipe, topped with a round furniture slider (for a VFO knob) and some lengths of loudspeaker cable. Hmmmmm ;-)

Oh well, this is what the 2m long 40mm drain pipe is for:

WARNING!

I was not sure how to react on such posts on other blogs, mentioning ME and MY design in a disparaging way like this: http://pa3abk.blogspot.com/2010/02/its-better-to-receive-tha-to-transmit.html

So, is this is what I came up with.

WARNING! 
1) Do NOT build any of my designs, they are all rubbish!
2) If you however still feel obliged to do so, build the stuff the way I designed it - if the designs still don't work, see 1).
3) Do NOT substitute any of the crucial materials, e.g. using cheap alternatives. I am trying to be as cheap as possible (ambiguity here)...

So, this is MY blog, describing MY designs that work for ME! Replace 2.5mm² heavy duty loudspeaker cable by CAT5 UTP (unshielded twisted pair) cable and you did NOT build MY design. Something else is built than. If you feel, with deviating from my design that much, still to blame me on the failure feels like an insult to me. Consequently I consider to share any future development amongst my friends only and removing this blog in its entirety.

Thank you for your understanding.

600m - The Octaplumb in the making

The success of the Plumbtenna made me buying parts for an Octaplumb.
Parts needed as follows:

• 2 × 1m 32mm waste water plumbing pipes
• 8 × 45° 32mm elbows
• 1 × 32mm T-piece

The pipes need to be cut into 8 25cm pieces. One of which will be reduced to fit the T-piece and cut in half.

Due to the 45° elbows, the Octaplumb proved to be much less painfull to fill with wire. Actually, I was able to pay attention as not to twist the twin-lead speaker cable. The octagonal shaped of the aerial increases the antenna surface area. The elbows add some length to the circumference of the loop. All in all, more speaker cable is consumed by the Octaplumb. From the 10m cable, only 25cm on one end and 97cm on the other end are left.

The Plumbtenna proved itself, however, I believe the Octaplumb will take the lead.... Easier to build, neater shape, greater aerial area. With more twin-lead used, more capacitance will be distributed at the loop, less capacitive termination will be needed.

Next step, set up tuning and coupling, apply some glue too, publish the results....

600m - Plumbtenna in use

Plumbtenna as used in the night Februray 17-18 2009

600m - Plumbtenna finished

With the evening passing by, instead of making something that produces r.f. power on 600m, I finished the outdoor frame antenna, the Plumbtenna.
Some mechanics, some basic soldering and some playing with capacitors.
I started at 680pF parallel to the tuning capacitor, resonance was a bit too high. The additional capacitor changed to 820pF resulted in a perfect resonance (503kHz) in the mid-range of the polyvaricon :-) YES!
Here is what the tuning/coupling-box looks like:

 

Funny coincidence, both capacitors I tried, came from the same dead CFL.

Oh, and BTW, I used a 6:1 toroid transformer this time...

600m outdoor loop - The Plumbtenna

Did some cutting and tweaking. This is what is done so far...

The Cutting
Both pipes are cut in half. One of the four pipes is shortened by 4.5cm, this is the approximate width the T-piece will add. Loeki loeki (please ignore the dirty floor, that's my car's room, aka garage):

The Necklace
The sequence of parts is of some importance here. The photo shows the first of the four turns completed. Still lots of slack as one can see. In the process of threading through the rest of the speaker cable, I learned that is helps to stick all pipes into all fittings and just loosen the one I want to thread the wire through. This will result in tighter turns. The cables insulation and the PVC corners create good friction :-( Some petroleum jelly could maybe help here... not willing to have that mess today, I decided to go w/o any lube. Guggsch Du hier:

The Loop
I know, the gray PVC stuff is not the best, electrically - I couldn't find any of the white stuff :-( However, the color makes this thing really look Navy/commercial/military like... OK, maybe the bar-code stickers disturb that impression a bit. Kijk maar:

Conclusions and Future Steps
It is clear that, despite my best efforts, there is still more cable in the pipe than necessary. Well, not much I can do about, should have used petroleum jelly in the first place.
Some measurements:

• one end of cable is about 60cm long
• the other end is about 50cm long
• the minimum inside side length is about 53cm, make that 55cm in average for the individual twin lead

Hence: 55cm × 4 = 2.2m and 2.2m × 4 = 8.8m. With a stretch of 10m cable available, and about 60cm + 50cm = 1.1m outside, just 10cm of cable is distributed wildly about the circumference of the loop. That should not be too bad.

I did not, but the valued reader may, take too much care that the twin-lead is not twisted. Randomly distributed turns and unmotivated twists of the twin-lead will mess with the currents and fields in the loop. Lube may help with one too :-))

Matching and coupling will be done in waterproof box.

600m outdoor loop

Bill of Material

• 10m 2×2.5m² speaker cable (€7.95)
• 2pc 1m 32mm PVC waste water plumbing pipe (€1.85/pc)
• 4pc 32mm PVC plumbing 90deg elbow (€0.75/pc)
• 1pc 32mm PVC plumbing T-piece (€1.65)

The Plan

1. The 1m pipes each will be cut in two, which will provide 4pc 50cm pipes. One of which will later be further split to accommodate the T-piece.
2. Extend the cable to full length and run it successively through the parts, i.e. T-piece - short pipe - elbow - pipe - elbow, etc. An exercise which will be repeated until all parts are dangling on the loose wire loop. Let both ends of the speaker cable some out the angled of the T-piece.
3. Plunge all parts together, carfully pulling the slack out the loop, not fully though! Check everything.
4. When satisfied, apply PVC plumbing glue to the joints and try getting the rest of slack out of the loop.

The should be some excess wire, since the measure just a bit more than 50cm for one side. The total of wire inside the contraption should thus be a little more than 8m.

Alternative Design
I bought 90deg elbows, 45deg ones are available too. Making in octagon-loop will slightly increase the aerial area, which would be a good thing! However, twice the amount of elbows would be required, resulting in severe increase of sawing/gluing work... Well, as I am a lazy dawg, I preferred as much work done as I could... therefore, a square it will be!

Further progress will be posted on the draaggolf, so, stay tuned. The project will be known as the Plumbtenna.