2010/5/24 Stefan Schäfer <schaefer@hst.tu-darmstadt.de&= gt;

Hello Roger,

= For your ground electrodes, ground electrodes may be the best "antenna"= in some 10...10m. I'm not sure how to calculate field strengths but i jus= t know about the 1/d^3 dependency, so twice the distance means 8 times the= power for the same signal reception, in the near field. But it is the que= stion what are the electrodes since there is ever a coupling to the mains= earth and all the metallic stuff in regions where people are living so th= is dependency might not be valid in your tests. As mentioned here, you cou= ld benefit from these conductors...

But if you want to reach= more distance with an antenna of the same size (e.g. of your garden)and= the same power, you could try such a TV transformer. Take a wire, as long= as possible and as high as possible, and apply some kV on it by this tran= sformer. It can even be resonated by adjusting the air gap between the bot= h ferrite parts. That results in a maximum output voltage and thus "ERP".= At least this would be a good alternative to your ground electrode tests.= You could easily compare the reachable distances. Here i would use a E fi= eld antenna for reception in the near field.

How far is your= next receiving amateur radio station away? And have you tried to do such= tests outside the village/city, just like Jim does it with his loop anten= na? This could allow you to increase the distance of your reception. Here,= space is not limited and you could try 2x10m, 2x50m, 2x100m and so on and= tell us the difference in the feed point impedance at various frequencies= and your ODX :-) Maybe i will also do some ground electrode tests in summ= er but i am still not sure. The complete receiver of Jim is a really good= idea to check the QRM situation at a given QTH. Probably i will also buit= his loop design for such tests... Would be interesing what is the maximum= distance for a CW reception of my transmitted signal (with the kite anten= na and 6mW ERP) ;-)

I will also do some near field tests in th= is week, to compare the performance of my 2 grabbers. This will be done he= re: http://www.google.de/ma= ps?f=3Dq&source=3Ds_q&hl=3Dde&geocode=3D&q=3Dheiligenberg+= heidelberg&sll=3D47.820666,9.312449&sspn=3D0.106733,0.219383&g= =3Dheiligenberg&ie=3DUTF8&hq=3D&hnear=3DHeiligenberg&ll=3D= 49.419391,8.704101&spn=3D0.001616,0.003428&t=3Dh&z=3D18 in= about 1,8km distance to my grabbers. Power will also be below 100W and th= e antenna wire will be mounted on a tower in abt 15m height. I will transm= it with this TV transformer on a 40m wire.

Roger, what size is= your garden? What is the maximum wire length that you can apply and in wh= ich height? What is your goal (best DX, a reals QSO with the next equipped= station or just do some funny tests?)

So, wish you fun and su= ccess with your experiments!

73, Stefan/DK7FC

PS:= What is your locator / QTH?