Perhaps one should re-read and apply what the current ARRL antenna book (22nd edition) says about full length loops and compare it to a multiband dipole of similar height.
Figure 5-18 depicts a pattern of such a 50 ft high (~1.5 Lambda) loop with maximum gain of 5.32 dBd at 15 degrees elevation, which is almost exactly what it shows for a dipole in Figure 3.46J. So no published loop advantage there. What is more limiting about the loop pattern is that its peaks and nulls are at less predictable azimuths then the dipole. Deep nulls (>12 DB) also exist at azimuths all around the loop. Suppose the desired signal impinges at a null, and interference at a peak? How would you resolve it? How would you even know it? Incidentally, I don't find a list of "superior characteristics' compared to a dipole published for the full length loop in your reference. Two orthogonal, multiband dipoles take about the same space as a full length loop but resolve the loop issues and add significant benefits to Flex users. With one multiband dipole feeding RX1 and the other to RX2 you instantly can recognize the preferred antenna. You can also listen in stereo in high angle polarization diversity or use the ESC feature of the Flex. For diverse bands of interest, multiband reception is uncompromised by a miss tuned antenna. All designed bands are always resonant, similar to a LPDA, so you can instantly QSY at QRO power and have no limitations imposed by the characteristics and loss of a tuner. Particularly for wideband Flex 6000 series low band operation, unless you can erect a 160-40 LPDA, a multiband dipole (or better yet orthogonal multiband dipoles), may provide a good choice. Beverages are also a good multiband reception antenna. Why would you incur the cost, RF loss, and inflexibility of a tuner when the answer exists elegantly in wire. Bill AB7AA -----Original Message----- From: Howard Z [mailto:[email protected]] Sent: Thursday, August 02, 2012 10:27 AM To: [email protected] Subject: [FlexEdge] MULTIBAND HF ANTENNA I use a 320 foot long horizontal full one wavelength loop antenna designed for 3.2 MHz. It is fed with approximately 100 feet of 450 ohm ladderline whose exact length is tuned for lowest SWR on its design frequency. Then comes a 9:1 balun from CWS bytemark to a palstar at auto antenna tuner. I have also used this setup with ldg at200pc antenna tuner which is popular for MARS ALE. I have also used it with the flex 5000 internal atu. A 9:1 balun is important when using ATUs with tuning range inferior to the palstar at-auto which is now discontinued. I use this from 160m to 10m and everywhere inbetween. This is a popular MARS antenna hung low for NVIS use. Thus antenna is also popular for MARS ALE use. It sounds to me that those using multiple dipoles are behind the times. You should read about the superior characteristics of a full wavelength horizontal loop in the ARRL antenna book. Regards, Howard Sent from my Verizon Wireless 4G LTE Smartphone _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
