Date: Tue, 1 Mar 94 04:30:14 PST From: Ham-Ant Mailing List and Newsgroup Errors-To: Ham-Ant-Errors@UCSD.Edu Reply-To: Ham-Ant@UCSD.Edu Precedence: Bulk Subject: Ham-Ant Digest V94 #51 To: Ham-Ant Ham-Ant Digest Tue, 1 Mar 94 Volume 94 : Issue 51 Today's Topics: 160 M on G5RV Discone Design Parameters INMARSAT azimuth,angle,antenna Mobile Antenna Tuners New HF Propagation Analysis - Supports MinuiNec/ElNec output Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Ham-Ant Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Sun, 27 Feb 1994 13:59:52 GMT From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!math.ohio-state.edu!darwin.sura.net!perot.mtsu.edu!raider!theporch!jackatak!root@network.ucsd.edu Subject: 160 M on G5RV To: ham-ant@ucsd.edu kg7bk@indirect.com (Cecil Moore) writes: > Ed Engel (eengel@eskimo.com) wrote: > : regular > : Keywords: G5RV > : > : Has anyone figured out how much wire you need to add to a regular > : G5RV to tune it to 160 M? Mine is 102' with the 30' of 450 ohm > : ladder line and I normally run it on 75 and 40 M through a MFJ-949D > : tuner. 73 de Ed Engel N7UQZ > > Antennas West G5RV App note says 204 ft total center-fed with 64 ft > of 450 ohm ladder-line. I suggest 450 ohm ladder-line all the way > to a balanced antenna tuner. Cecil is SPOT-ON here. The *BALANCED* tuner with 450 ohm ladderline from antenna feedpoint to tuner will work all bands 160-10M quite well, and the conjugate match of the system will get a nice signal out. Remember, the original design criteria of the G5RV was a NO-tuner system for several bands... Much of that was acheived through loss in the coaxial feedlines used.... (See Gary Coffman's -- and others -- posts about the fleamarket coax...) If you have a tuner anyway, run ladderline to the tuner and enjoy a good signal. 73, Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^) +--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+ | Jack GF Hill |Voice: (615) 459-2636 - Ham Call: W4PPT | | P. O. Box 1685 |Modem: (615) 377-5980 - Bicycling and SCUBA Diving | | Brentwood, TN 37024|Fax: (615) 459-0038 - Life Member - ARRL | | root@jackatak.raider.net - "Plus ca change, plus c'est la meme chose" | +--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+ ------------------------------ Date: 27 Feb 1994 16:02:58 GMT From: ihnp4.ucsd.edu!swrinde!gatech!concert!balsam!zeno!bennett@network.ucsd.edu Subject: Discone Design Parameters To: ham-ant@ucsd.edu In article francis4@applelink.apple.com (Dexter Wm. Francis) writes: > ... interesting stuff deleted for the sake of brevity ... > >So: Make the included angle of the drooping radials 60 degrees. > The low cutoff wavelength is six times the diameter of the disk. > The radials are 1.428 times the diameter of the disk. > >Enjoy > >-df Many commercial discones incorporate a vertical element designed to increase the 10:1 bandwith to extend from, say 50 - 1300 MHz. Does anyone know how this is done. How long is the element and where does it connect - to the disk or to the cone? Regards -Chuck -- Chuck Bennett bennett@unca.edu Department of Physics (704)251-6442 Univeristy of North Carolina - Asheville Asheville, NC 28804 ------------------------------ Date: 27 Feb 1994 15:28:11 GMT From: ihnp4.ucsd.edu!swrinde!gatech!concert!news.duke.edu!soc4.acpub.duke.edu!hl1@network.ucsd.edu Subject: INMARSAT azimuth,angle,antenna To: ham-ant@ucsd.edu I would like to try to listen to the Armed Forces Radio Television Service (AFRTS) on 1537 MHz on the INMARSAT Atlantic Ocean-West or East. Could someone with a satellite prediction program tell me the azimuth and angle to these satellites from Durham NC? The satellites are geostationary at 15.5 and 55 West longitude. I am tenatively planning to use two 3 wavelength rhombics spaced 1/2 wavelength apart as my antenna. Is this a good choice? Would it be better to mount the rhombics at 90 degrees to each other for cross polarization? What would the 600 ohm rhombic antenna impedance change to at the feedpoint in either case? I plan to use 300 ohm TV twin lead from the antenna to a TV balun to the 50 ohm BNC of my AR-3000 scanner. Will I need to modify the TV balun? Do I need a 1/4 wave matching stub at the antenna? Does any antenna company sell a modestly priced antenna for this service? ------------------------------ Date: Sun, 27 Feb 1994 13:16:52 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!darwin.sura.net!perot.mtsu.edu!raider!theporch!jackatak!root@network.ucsd.edu Subject: Mobile Antenna Tuners To: ham-ant@ucsd.edu Cecil Moore writes: > One wrote me a letter and said, "For best results your HF mobile > antenna must be resonant on your transmitting frequency." > > Maxwell, author of "Reflections" tells us that the radiator of an > antenna system need not be a self-resonant length for maximum resonant > current flow... Correct so far, but there is more than just what Maxwell wrote... > transmission line and the antenna does not prevent the antenna from > absorbing all the power available at the junction. If ten feet of > coax at least the size of RG-8 is used in mobile HF installations, ^^^^ WHOA!!! The *size* of the coax has NOTHING to do with the loss and re-reflection back to the antenna. NOTHING! If you use 2" diameter JUNK feedline with 10% braid coverage, what you say further is simply not going to happen... the physical size is nowhere near as important as the loss characteristic of the feedline, which is NOT directly related to diameter. For example, I am using heliflex (Andrew Cable) in my mobile installation, and have adjusted the antenna for self-resonance at my frequencies of choice...with a matching coil at the base. While I can indeed increase the bandwidth by inserting a tuner, what is happening at the antenna, and let us NOT try looking at 17-10 meters where the physical size of the antenna approaches the unloaded size of a 1/4 wave; instead, let's look at worst (well, penultimate worst ;^) case: 75 meters...where the antenna needs to be 67 feet long to approach a quarter wave, and physically be only about 12 feet tall. This case is far more likely to fall into the statement you first presented: the antenna will perform *best* (emphasis added) when self-resonant. I run a Texas BugCatcher (no relation, just a very satisfied customer, often accused of running a kilowatt from an RV hooked up to a "fixed" antenna) that has been tuned and trimmed to work best at ONE place, with a bandwidth of ~20KHz. I tried a tuner, and while the bandwidth did increase, the performance of the antenna fell off, measureably. Some of that may well have been the nature of the tuner, since it was following more or less the utlimate transmatch design and provided the possibility of imaginary solutions to the three unknowns-two equations algebra of the tuner circuit. Just having the tuner in-line reduced my signal substantially. There is NOTHING wrong with the unit, but the properly tuned mobile system will only gain bandwidth at the expense of signal efficiency, most likely because of the heavily loaded nature of the antenna. Your results on 10-17M would tend to bear that out, although a ham-stick design antenna is a loaded design as well. I suspect that the nature of those bands and the propogation characteristics have as much to do with your observed results as the theory you quote. I, too, have read and studied Maxwell's book. I do not find the material therin to be at conflict with what you say, save the loaded nature of both loads (mine at 75M and yours at 10M) doesn't jibe with what I recall Maxwell saying... I believe he was addressing a non-resonant *and* non-loaded antenna system, not the massive loading one must apply, particularly at the really low frequencies, to make the very short antenna, radiation resistance ~3 ohms, function properly. There are many solutions to the retuning for "resonant" coverage from a mobile, some involving rather ingenious use of cordless screwdriver motors to raise and lower loading coils and whips. These work acceptably (for most people) but for DXCC or WAS on 75 meters from a mobile, a really well-design and properly tuned antenna will perform better than the non-resonant antenna with a tuner for increased bandwidth. I do not like getting out in the rain to swap taps, but when I do, the antenna performs better than with a tuner -- I did A/B tests with a pair of switching relays that allowed the tuner to be in-line or bypassed, just to see...and my signal was reported back to me as noticeably stronger without the tuner in line. I do not see that as conflicting with what you say, but as being explained by the properties of the tuner, the effect of a tuner in line with a tuned system, where the tuner is NOT part of the tuning process, but must be adjusted for minimum impact. I believe, for mobile operations, the statement about self-resonance working best is true. Your system may well work very satisfactorily, but I do not believe the actual radiated energy to be the same as if your antenna system (without the tuner) were tuned to a resonant load. > Once the antenna tuner is adjusted properly, the HF > mobile antenna is FORCED into resonance. I use a 10m Hamstick plus > a mobile antenna tuner to cover all bands from 17m to 10m. The antenna is a shortened, loaded design. And, the characteristics of 10, 12, 15, 17 are such that when the band is open a damp string will radiate and make contacts... When the antenna is foreshortened to ~20% of a 1/4 wave, however, the amount of loading is importaqnt to the antenna's ability to absorb and radiate power. > The antenna expert wrote, "Any instruction book on antenna tuners will > state: The antenna tuner used between the rig and the antenna system is > to achieve maximum performance from the transceiver..." He is WRONG. Maxwell's book quite clearly states that in a properly designed system, the tuner will re-reflect the power back to the antenna load where it is "eventually" absorbed and radiated...the only additional loss being the added feedline loss for each roundtrip along the feedline. This latter statement, that the additional loss, due to SWR alone, is only that loss due to the feedline loss, and is why the charts so clearly show that additional loss due to SWR is so small a fraction of overall feedline loss. > I think the antenna tuner is used between the rig and the antenna system > to achieve MAXIMUM RADIATION FROM THE ANTENNA. I think, if you were to stop right there, you would be correct. The tuner, in your installation, allows the antenna to radiate as much power as possible on the frequencies you are useing the tuner to make the antenna work on... Sheesh! That didn't come out real well... The tuner is permitting you to radiate power on bands the antenna was never design to operate on by providing a conjugate match of the system. However, the fact remains, your antenna will not perform as well, say on 17M as a FULL 1/4 wave antenna would. Materials have an influence, and the resistance of the wire in the ham-stik coils and the Q of the loading are significant factors. > As Maxwell says, "My Transmatch really does tune my antenna". Yep, but a closer to full-sized antenna, with Hi-Q coils will still outperform the ham-stik...tuner or no... 73 ES TNX FER THINKING Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^) +--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+ | Jack GF Hill |Voice: (615) 459-2636 - Ham Call: W4PPT | | P. O. Box 1685 |Modem: (615) 377-5980 - Bicycling and SCUBA Diving | | Brentwood, TN 37024|Fax: (615) 459-0038 - Life Member - ARRL | | root@jackatak.raider.net - "Plus ca change, plus c'est la meme chose" | +--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+ ------------------------------ Date: 27 Feb 1994 15:34:47 -0500 From: ihnp4.ucsd.edu!agate!usenet.ins.cwru.edu!nigel.msen.com!yale.edu!noc.near.net!news.delphi.com!news.delphi.com!not-for-mail@network.ucsd.edu Subject: New HF Propagation Analysis - Supports MinuiNec/ElNec output To: ham-ant@ucsd.edu Skywave Analysis Package CAPMAN -- Computer Assisted Prediction Manager At last, a professional-quality IONCAP package that allows anyone to use the most advanced propagation routine interfacing with the ELNEC and MININEC antenna analysis gain patterns. CAPMAN is the versatile menu/mouse driven IONCAP propagation package developed by Kangaroo Tabor Software and the prime author of IONCAP. CAPMAN delivers IONCAP input file construction and management, two integrated execute functions, the ability to view and manipulate huge output files and display of multicolor output graphs. The package allows you to customize it for your own station -- painlessly. A full-featured location database, indexed on both country name and call prefix, provides access to over 490 prefixes. Each database entry establishes associated information such as prefix, continent, country, city, geographic coordinates, CQ zone, ITU zone, a 900 character note pad, forward and reverse azimuths and distances, and the current local sunrise and sunset times. CAPMAN provides management of "input records" through the use of libraries. Input records may be created, revised, renamed, copied, deleted and combined into "input files" for performing custom predictions. An extensive on-line help system is provided and includes documentation from the IONCAP user's manual. Sunset and sunrise times, for any day, are accessible through the use of a calendar that also displays the current Local Mean, Local Civil and Greenwich Mean times. The predicted Smoothed Sunspot Number may be configured and automatically set for the coming 12 months, providing quick one-step predictions. Many more features are provided in a "friendly" yet powerful "HF Analysis" package. CAPMAN is completely fool-proof for the most advanced or beginning user. Your contacts and friends may be added to the library and run any time with a few keystrokes. A wide choice of antenna routines is available, to be configured for your station, or use the antenna analysis computed using ELNEC or MININEC. Numerous output methods, including a "Long distance" model for the DXer, are easily accessible. The choices of output include MUF, FOT, S/N, Reliability, Service Probability, angles of take-off and arrival at receiver, S-meter units, field strength and modes of propagation -- many more -- using the Es, E, F1 and F2-layers for the HF bands. Graphs of the predicted vertical ionogram, MUF, FOT and LUF are available. This menu driven package features the newest "updated" full commercial version (LU9402) of IONCAP used by over 450 government agencies and commercial communications departments in the USA and more than 100 other countries. This CAPMAN package is a 32 bit version and requires an IBM compatible 80386 or above. For more information on the CAPMAN package contact: LUCAS Radio / Kangaroo Tabor Software 2900 Valmont Road, Suite "H" Boulder, CO 80301 Phone 303-494-4647 / Fax 303-494-0937 ------------------------------ End of Ham-Ant Digest V94 #51 ****************************** ******************************