--------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00035 Date: 12/22/97 From: ROB DENNIS Time: 08:25pm \/To: ALL (Read 0 times) Subj: LPA Antennas Part 5 Original article from: Wayne Sarosi Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). LPA Series - 50-54 MHz USE: Amateur Band 6m Note: See ARRL Antenna Handbook under LPA construction Tau = 0.92 Sigma = 0.17 B = 1.08 COT alpha = 8.5 BAR = 1.42 Bs = 1.534 Lambda max = 19.68-ft Lb = [0.25(1-(1/Bs))COT alpha)Lambda max] = 14.75-ft N = 1 + (log Bs / log (1/Tau)) = 6 The following are in inches, two of each required (L) ------------------------------ L1 = 59.94 d1,2 = 40.97 L2 = 55.22 d2,3 = 37.69 L3 = 50.90 d3,4 = 34.67 L4 = 46.90 d4,5 = 31.90 L5 = 43.20 d5,6 = 29.35 L6 = 39.81 Zt = 29.52 Sigma' = Sigma/sqrt Tau = 0.17723 Ro = 50 Zav = 200.7 using 0.35 dia elements Zo = Ro^2/(8(Sigma'(Zav))) + Ro(Sqrt(Ro/(8(Sigma'(Zav))) + 1) = 63.0 Gain = 8.5 dBi S can be calculated from the ARRL Antenna Handbook. Next is the element attachment. SEE BELOW!!!! ************************************************************* * NOTE: The boom on all these LPAs is 1-inch diameter. * * All elements have a 0.9-in adjustment in the length * * to compensate. Sorry about that. The Freq file will * * have the proper statement put in. * ************************************************************* -WS --- GoldED 2.42.G1219 * Origin: VE3SJN....Moderator....HAM_TECH (1:163/506.4) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00036 Date: 12/22/97 From: ROB DENNIS Time: 08:25pm \/To: ALL (Read 0 times) Subj: LPA Antennas Part 6 Original article from: Wayne Sarosi Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). LPA series element mounting: part 6 As stated before,the element lengths posted in the previous LPA series are 0.9 inches longer for mounting purposes. To mount the elements the boom must be aligned for correct hole placement. There are several ways to align the elements,but they must be inline from one end to the other,180 degrees apart on either side of the boom: | | | | | | | | | | | | | | | ==================================================== | | | | | | | | | | | | Note: elements are not scaled with ascii graphics Build two of these. Element holes are as such: The element side is drilled just large enough to allow the element to be tapped through with a small hammer. The other side is drilled to allow a stainless steel bolt to pass through. On the end of the element, the stainless steel bolt should be slightly arger than the hole in the tubing. Tap the element to the thread size of the bolt. Insert the element into the boom,then insert the bolt into the other ide,and screw in and tighten. *** DO NOT OVER TIGHTEN *** A snug fit is best; screw in and then just a tad bit more. -WS --- GoldED 2.42.G1219 * Origin: VE3SJN....Moderator....HAM_TECH (1:163/506.4) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00037 Date: 12/22/97 From: ROB DENNIS Time: 08:25pm \/To: ALL (Read 0 times) Subj: LPA Antennas Part 7 Original article from: Wayne Sarosi Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). Subject: LPA series part 7 BOOM SPACERS: These items are most important and they must cut in such a fashion as to reflect the log-periodic nature of the element design function. In all the LPAs I have mentioned, each has two booms. These booms must be separate both electrically and physically in the tandard LPA configuration. This means that the spacers must be non-conductive such as plexi-glass, hard rubber, wood, plastic, PVC, etc. Spacers can be attached to the booms in many ways such as the use of nylon screws and nuts, hose clamps, cable ties, etc. Currently I am using the PVC method which provides ease of parts and cost. NOTE: Be advised that at frequencies over 1 GHz,PVC will become increasingly conductive. PVC can be cut to length and the log-periodic spacing can be accomplished with ease. =========================================================== MATCHING: There is no required matching for the LPA. Coax can be directly attached to the LPA. Normally the coax is run in the lower boom from the rear of the LPA or attached to the lower boom. The shield is attached to the lower boom and the inner conductor attached to the upper boom. This attachment is done at the front of the antenna and not the rear as most believe. -WS --- GoldED 2.42.G1219 * Origin: VE3SJN....Moderator....HAM_TECH (1:163/506.4) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00038 Date: 12/22/97 From: ROB DENNIS Time: 08:26pm \/To: ALL (Read 0 times) Subj: LPA Antennas Part 8 Original article from: Wayne Sarosi Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). SUBJECT: Log Periodic Arrays,part 8. Conclusion ANTENNA MOUNTING: There are several ways to mount the LPA to a tower or a rotator. All this depends on what you are looking for in an LPA. The LPA can be mounted at the back-end or in the middle. It can be mounted to a rotator or to the side of a tower. It can be stacked,arm mounted,or all by itself. It can pretty much be treated like a yagi. KINKS: When mounting the LPA (not to be confused with the LPDA) the antenna should* be mounted to a nonconductive support. The antenna is balanced and no part of the LPA is unbalanced. This is not the case in the LPDA where the boom is independent of the ntenna elements. Both booms in the LPA are part of the antenna and are an active art of the antenna. They are the feed elements of the antenna unlike the LPDA. ========================================================== *** DO NOT MAKE A METAL PLATE TO MOUNT THE LPA *** All this will do is short the two booms together and effectively destroy the antenna as an LPA! ========================================================== Mounting the LPA via the end mount way can be accomplish in two ways; first a fixed mount directed to a particular station or area of interest. Also the end mount can be put on a rotator provided that the amateur balance the weight load of the LPA with a counter weight or another antenna 180 egree out from the LPA. You can use U-bolts provided they do not touch or even come close to ouching but use a non-conductive plate like wood or plexiglass. PVC mounting works well and frequencies below 2 GHz. -WS --- GoldED 2.42.G1219 * Origin: VE3SJN....Moderator....HAM_TECH (1:163/506.4) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00039 Date: 12/22/97 From: ROB DENNIS Time: 08:27pm \/To: ALL (Read 0 times) Subj: Mobile Antenna Noise Original article from: Jerry Murphy,K8YUW, (FIDO 1:175/2) Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). =============================== From: JERRY MURPHY Subj: Working via mobile ------------------------------- DB>Larry,this is just a guess,but have you considered the efficiency of your DB>ground plane? Many hams who work mobile put a big effort into making as DB>much of the car as possible part of the ground plane. I read about one guy DB>who welded straps between the body,bumper,and frame in several places. I went to a lot of similar problem solving years ago with a very noisy Olds 88. Every hinge was jumpered,plug wires replaced,wires to and around the distributor shielded,atc,etc. Then I heard the hint that finally solved all f my problems in a very few minutes. I was told to have the receiver on,with my engine running,and listening to the ignition noise. Instead of an antenna,I was to have a long length of coax,one end plugged in the antenna jack. The other end was used as a sniffer,placed in proximity to several points around the car. The hot spots would make the most noise,and be easy to find. Lastly,it was suggested that I start at the exhaust pipe,at the rear of the car. I did all these things and was simply amazed at just how much noise was generated in the exhaust system. It soon dawned on me that the whole system is hung from rubber suspension thingies,and is insulated except at the source. Flowing thru it are hot gases that will cause changes in the electro-mechanical properties of the pipe,thus causing it to become an antenna of sorts. After grounding the tailpipe with a short length of copper braid (former RG8 shield) to the nearby frame,the noise WENT AWAY! This hint works just as well around noisy computer stuff. Sniff,sniff. Of course,you have to use the other well-known and common sense ideas on using large enough power cables,properly installed (direct from the battery, if possible),proper routing,and dozens of other hints. de K8YUW 73,The Jerry Murphy in Lakewood,Ohio * Origin: HelpNet For the Impaired - (216)-356-1872 (1:157/2) --- GoldED 2.42.G1219 * Origin: VE3SJN....Moderator....HAM_TECH (1:163/506.4) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EGS00040 Date: 12/22/97 From: ROB DENNIS Time: 08:28pm \/To: ALL (Read 0 times) Subj: Quad Antennas Original article from: Wayne Sarosi Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo. THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL SALE WITHOUT EXPRESS WRITTEN PERMISSION OF ORIGINAL AUTHOR(S) OF THIS POST. ALL AND ANY COPYRIGHTS RETAINED BY AUTHOR(S). The Quad series: For this series Quads will be discussed in the general sense. This series,construction,dimension formulas,matching,mounting,and such will be covered. Quads are powerful antennas. A three element quad will give a yagi a fit in head to head comparison. On two meters,a ten element quad is hard to beat. Quads can be set up vertical or horizontal. They can be tuned. They can be part of an array. For HF use this series will discuss 2 and 3 element arrays. On VHF/UHF arrays will cover 3 to 10 elements up through 70cm. Just what is a quad? The term is used loosely to discribe a beam antenna ade up of two or more full wave elements, where the elements a parallel to each other and the direction of the radiation pattern is perpendicular (end fire) in nature. There are many terms we are familar with such as Cubical Quad,Quad rray,Loop Array,Moon Raker,PDL-2,Field Gun,etc. All are quads and yes,some are CB antennas listed here (last three). Let me explain why I included these antennas. These antennas are good examples of quad arrays that work and work well. Although designed for 11m,it wouldn't take much in the form of calculations to make a 10m,12m or 15m antenna out of them. Quad means four,which discribes the four quarter wave sides of each element. I refered to a loop array which is sometimes attached to a quad but be aware that there is a circular loop array which packs a bit more punch than a quad. This I'll explain later. The quad elements can come in various shapes from square to diamond. The area that the element encloses will play an very important part in the impedance of the antenna. Quad elements can be combined with yagi elements to form a quagi. Usually the driven element and reflector are quad while the directors are yagi. Polarization is simple to spot on a quad element. It is as such: ------------- ------------- | | | | | | | | | | | |<---- Feed | | | | (Vertical) | | | | ------------- ------------- ^ | Feed (Horizontal) Note 1: Either feed placed on the opposite side will work the same. Note 2: The closer the area of the enclosed quad element approaches a ircle, the closer the impedance approaches 50 ohms. The quad element can be tuned using a tuning bar and dock. --------------- | | | | |==|= * |<--- Feed | | | | --------------- * dock and tuning bar. | | | |_________|__ dock | <---Tuning bar _________|__ | | | | | Close up of dock and tuning bar What this does is provide a way to adjust the length to the element electrically by sliding the tuning bar along the dock. With the tuning bar close to the element side,the length is short or higher in frequency. With the tuning bar at the end of the dock the length is longer or lower in frequency. This tuning method will help with SWR adjustments. A typical dock length is 8 in at 10m. The ratio holds at lower frequencies. In the VHF and UHF ranges this method of tuning may prove impractical. Instead,a shorting arm is used. Also note that in VHF/UHF frequencies,Circular loops are used especially at UHF frequencies. The shorting bar is exactly what is sounds like. It cuts a corner making the length of the circumference shorter. This works for elements longer than what was desired in the design. | | | |\ | \ a | \ c |______\________ b c < a+b VHF/UHF adjustable active element an elements: Above we discussed the use of a dock and the shorting bar for making adjustments in the circumference. Both these methods are limited in their adjustments. The following method allows a greater range of adjustment. This method also has some limitations because it is designed to work with tubular elements and not wire elements. Thus,it's greatest area of use is with VHF/UHF antennas. Within the confines of this modification there are two different applications: One for circular elements and one for square elements. Let's look at the latter first. It is also the easy one to build and adjust. The Square adjustable element is built using two main componets and two mall hose clamps. The adjustable points are located adjascent to the the feed point: ----------========== | ^ | | | | | | |