Monday, February 15, 2010

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...

2 comments:

  1. Reading your blog for a while now. And attracted by your high SNR levels earlier this week. I duplicated your first attemp (the 8 windings thing) but I thought to be smart using CAT5 cable. But was a complete faillure. The Q was very low due to the twisted pair wire system. After reading some theory, it's best to separate the winding 1cm from each other, this will give high Q. Most probably due to the loosy windings in your plumber pipes you have an acceptable Q.
    My location is far from ideal for this frequency, but it's a challenge to arrange something and it starts with good listening.
    Best result I have at the moment is with an active antenna (PA0RDT)
    Transmitter I intend to build an upconverter (G4GNT design)from PC soundcard to 500kHz with an IRF540 as PA.
    Ok, Joachim thanks for the inspiration.
    73/Jan pa3abk

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  2. Hoi Jan!
    Bedankt voor je aandacht! Verder in het Engels....
    Actually, I had a total failure on the aerial using 4 pole telephone cable myself. I did not write about it on my blog, however, I am not ashamed of failed experiments either ;-)
    CAT5 seem to be similar to the phone-stuff I failed with.
    As the telephone stuff, CAT5 employs 5 strands only, on a tiny diameter, hence, the losses are vy vy high. My second attempt was using 2.5mm² speaker cable (Hornbach/Gamma/Karwei) which resulted in immediate success.
    Jan, I hope for you, the same will happen! Keep the skeleton of your first frame and wire it up with some heavier gauge cable...
    Oh, and to the proximity of the my frame's wires, those are as close as possible, in the indoor version and in the PVC-type thing, I wanted to have as much capacitance distributed about the wires, so I would need less at the termination point of the aerial.
    Said all this, I would like to stress that this is MY point of view, any alternative ideas are welcome!

    TX: Jan, I could not agree less, the designs are really nice! I built an exciter using 4MHz resonators and a 7493 counter. Thinking of transverters myself (14MHz LO with subharmonic mixers).

    Ik hoop dat wij ooit een kans op een eyeball-qso krijgen!
    73, Joachim

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