ok1rr

The 4 rule The reactance of the windings should be at least four times the impedance the winding is designed to look into. where Zi … input impedance Zw … winding impedance thus where Lw … winding inductance Zi … input impedance f … design frequency To find the number […]

This description is taken from the Pete's W2PM posting into Topband reflector.

This antenna is very simple - it's a mini diamond Flag - with a 660 ohm terminating resistor and a 16:1 transformer. It is the exact size of the so-called magnetic loops, - 5 ft per side, 20 ft total wire, and about 7.1 ft wingspan. It has classic Flag cardiodal pattern and, of course, pretty low output (-50 dB from what I recall). F/B is about 30 dB. I use it with a single preamp with good results. This antenna is quite easily rotatable as you can see (altho the standard 15 X 30 ft Flags have been made rotatable too as most of you know).

This has several advantages over the "mag" loop (for those on small lots) - it's broadband 1.8 MHz past 30mhz; cardioid pattern with very nice null to rear, decent low angle take off (abt 32 deg) AND is simple - make it in minutes. I used 2 - 330 ohm resistors a binocular 16:1 transformer. I "potted" the resistors and xfrmr in epoxy.

I've since cleaned mine up - routing the RG-174 coax from the transformer to the center of the crosses, then connect it to a RG-58 run vertically down the mast.

Thanx loads to Earl K6SE for the design.73 Pete, W2PM

by Louis Varney, CEng, MIEE, AIL, G5RV* * (taken from RADIO COMMUNICATIONS, JULY 1984) THE G5RV ANTENNA, with its special feeder arrangement, is a multiband centre-fed antenna capable of very efficient operation on all hf bands from 3.5 to 28 MHz, specifically designed with dimensions which allow it to be […]

Geoff Cottrell, G3XGC, describes his coaxial receiving loop in the March issue of Practical Wireless [1] (download here). This article is widely available over the internet, which is a good point. The less pleasing fact is that this article contains a 'bug' - the primary of the transformer T1 should not be connected to C1 but to the other end of the loop (ie. to the ground).