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K4DTT@... wrote: thanks for the info, defiantly a big help. using hamcalc for 1.9mc I come up with a ~15 turn coil of RG-58 on a 3.5" coil form using ~13' of coax and the 80m loop needs to be

I don't know about the stub but I am sure the trap will cover the band as it seems to be rather low Q. I haven't tried it. 73 Glenn K4DTT *** See what's free at http://www.aol.com.

Rf = free space impedence (small for small loops) Rs = skin effect resistance (depends on bulk resistivity, usable skin area, frequency) Efficiency = Rf / (Rf + Rs) You can see as Rs approaches zero

seems i screwed up my efficiency calculation. but the thought was right... i'll post corrected version in a few minutes. jtm

Thanks Jim, Todd and Dave. Good points. Helps my understanding a lot. Dave G. N2chi actually the that the

Although the cost is high I recommend the use of Cool-Amp _http://cool-amp.com/cool-amp.htm_ (http://cool-amp.com/cool-amp.htm) for use on small loops and RF ground busses. We used this product at the

Don't you need _very_ well matched JFETs to ensure drain current balance in that circuit? Could this be avoided by giving each JFET source an independent primary and 330 ohm resistor, then linking the

[Now a 1:2 transformer] This is like asking us how much string you will need when you won't tell us the size of your parcel ;-) However, assuming you want your transformer as broadband as possible,

In another thread: Loop antenna with coil It really does help make sense of things to keep them in threads, especially for anyone foolhardy enough to visit the Messages archive expecting to find

self resonance is the problem above a particular diameter. you can actually see this as you watch the capacitor needed for a given frequency as you increase the size. efficiency is the ratio of the

wrote: Hi David, Loop efficiency relates to resistive losses in the loop. If there were no losses the efficiency would be 100%. Small loops have very low resistance due to radiation, on the order of

_http://www.pi4cc.nl/link/mkII.htm_ (http://www.pi4cc.nl/link/mkII.htm) Here is a site that describes the trap thing very well. I cannot find the QST article that I was thinking of when I first posted

K4DTT@... wrote: that part I understand, it's what the trap consists of and how to calculate and make it that I'm asking about. -- GB & 73's KA5OAI Sam Morgan

I've been playing with KI6GD's LoopCalc program for small transmitting loops. And I have a couple of questions for those of you who have used it. First, I notice that when the circumference of the

Sam wrote: How about a 1/4 wave (at 160 m) shorted stub of transmission line across the far end of the loop? A balun and a ~30 meter roll of coax could be packaged up pretty small, compared to the

In a message dated 6/18/2007 11:00:49 PM Eastern Standard Time, davidgriffin@... writes: Although, Brian indicates 25% as the max circumference rather than 33%. Does anyone know why either of

Install a 160 meter trap at equal distance from the feed point (half way around the perimeter) of the loop. 73 Glenn K4DTT *** See what's free at http://www.aol.com.

My mistake on that drawing. It should have been a 1:2 transformer, which allows you to twist three pieces of wire together for the best possible coupling coefficient. For HF applications, Fair-Rite

Referring to the schema by Chris Trask http://www.home.earthlink.net/~christrask/New%20Source%20Follower.pdf I ask for help on the 1:3 transformer. What kind of (Amidon) ferrite ring core were

How large a diameter can you comfortably accomodate? Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? /