Hi Wolf Hence my comment about considerable engineering required! 73 Scott VE7TIL design. Stable caps would be needed and these caps would be very expensive which resulted in my thoughts drifting to
Many thanks Andy. I'll see what the numbers say. Mal, you are right that real two way QSOs may need high power and ERP but surely all forms of experimentation at VLF are valid. I also wonder about th
Just wondering if anyone has done the maths to work out what sort of ERP could be expected at 8.97kHz with, say, 100W to a smallish loop antenna in the garden? It would certainly avoid the need for v
Roger, the antenna reactance about 2.5 Ohm, so the antenna voltage (and thus capacitor voltage) will be less than 100V. I assume that polypropylene caps that work fine on 137 and 500 will also be OK
Hello Scott, the discussion is about a 10 by 10 meter loop and 100W RF power. Using 4 x 1.5mm Cu wire (parallel) the DC resistance of a 10 by 10 meter loop is about 0.1 Ohm. Ignoring other losses and
Roger, as Jim calculated running 100W in a 10 x 10 m loop will give about 0.5uW ERP (is you use 4 x 1.5mm wire in parallel instead of a single 3mm wire in order to avoid skinn effect losses). Using m
Hi Rik I think I missed a message or two. What current level is the consensus for 100W input at 9KHz into a reasonable loop? I missed how this was modeled and wonder if my original assumptions where
I seem to remember from the 73kHz days and article in an early LF Handbook (the blue cover ??) on matching a loop with a pair of capacitors at the feed point and a program to calculate the values. It
Just one caution - particularly for impedance measurements, and probably for operating: Treat the loop as balanced. If you use the capacitor method that Alan suggests to get to 50 Ohms (or whatever),
Hi Scott, design. Stable caps would be needed and these caps would be very expensive which resulted in my thoughts drifting to the concept of a gyrator. Essentially an inductor used to simulate a cap
Hi Rik, Roger, VLF, Good point and good calculation! 1.5 kOhm is very optimistic for such an antenna i think. If we think about the reception of DF6NM using 5 uW by Paul Nicholson, maybe a loop is an
Certainly my own results with WSPR at 136 and 500kHz with just a few watts and quite thin wire and around 80sq m loop area were encouraging. Mind you, 9kHz is very much lower than 136kHz, so the radi
Knowing when to not bother seems logical with small inefficient loops on 9 khz g3kev -- Original Message -- From: [email protected] Andy Talbot To: [email protected] rsgb_lf_group@black
Alan, Yes, you could split the series cap -- assuming that the values were close, the balance would be excellent. Given an audio amp with a bridged output configuration, and the matching network set
Alan G3NYK Handbook feed voltage saturation current from about if I rather conductor. 1.9Ohm/1000ft Ohm [[email protected]] for modeled be Euro antenna in owner-rsgb_lf_group@blacksh
Dear Scott, Roger, LF Group, I'm afraid the gyrator is a non-starter - there are different types of gyrator, but the concept is a feedback circuit that, when you apply a voltage to an input node, dri
Hi Roger The practicality of pumping 35A into a loop is not an easy task! Couple this with the stability of most capacitors creates a real engineering challenge for a loop on 9KHz, notE the BW and Q.
Rik, Roger, Jim, Mal There are soil losses to consider with the loop as well. At 185 kHz (Part 15 lowfer band), I ran a 50' X 50' transmitting loop made from mil spec RG-11 (copper braid) and the soi
Here's an Excel S/S I did in the 73kHz days. Other people have updated versions now, but it serves to get you into a region to design from - or know when to not bother http://www.g4jnt.com/DownLo
Hi Roger The practicality of pumping 35A into a loop is not an easy task! Couple this with the stability of most capacitors creates a real engineering challenge for a loop on 9KHz, notE the BW and
