--------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: E3Z00008 Date: 03/29/97 From: WAYNE SAROSI Time: 08:14pm \/To: ALL (Read 3 times) Subj: VHF/UHF-2 SUBJECT: VHF & UHF Hidden antennas for PUDs/CONDOs/APARTMENTs Part 2 INSTALLATION OUTSIDE continued Next, I'll discuss the 1/4, 3/4 wave ground planes. These antennas have various gains, but all have one thing in common. Each antenna requires no tuning or matching elements. Like the 1/4 wave, 3/4 wave antennas are built in the same manor except the vertical element is 3/4 wave. The Quarter wave 2m antenna can be cut so that it is a 3/4 antenna on the 440-450 MHz band. Thus, a dual band antenna. A 1/4 wave on 222-225 MHz can be cut for a half wave on 440-450 MHz, another dual bander. These dual band antennas will not have the complete range over the secondary band, but will give a piece of it at low SWR. Each antenna will cover the entire primary band it was cut for. I use brass rod for my ground planes. They do not rust and solder easy with a good soldering iron. Hiding these antenna takes a little more foresight. The ground plane shape tends to make the posibilities of a good hiding spot a bit less. But the thin material tends good for trees. They can be hidden as part of the tree with plastic leaves and a blending color paint job. Their size is a good contributing factor. UHF vertical ground planes (VGP) tend to hide hemselves. A UHF 1/4 wave VGP is a mere 9 inches from the base of the ground plane to the tip of the vertical element. I wouldn't leave them out in the open, but little will have to be done to hide one of these UHF VGPs. -+-------------------------------------------------------------------- Discones have been used outside in restricted areas. Hiding one can present a problem because of the dimentions. I would suggest using these antennas indoors and will discuss them later. -+-------------------------------------------------------------------- The Vertical Dipole is an easy antenna to hide. The shape is easy to bend in with surrounding objects and matching can be accomplished by many means as listed in the ARRL antenna handbook. My favorite is the gamma match. I would recommend this for the 2m and 1.25m antennas. At this point, I must say the gamma match works fine, but at UHF frequencies, a Tee match is better. The gamma tend to loose the bandwidth required up on the 440-450 MHz band. It can be hidden in the same manner as the J-Pole. -+-------------------------------------------------------------------- The Full Wave Loop is another favorite. Although this antenna has the best gain of the previously mentioned antennas, it can present a problem in band width and placement. When placed against a building, the SWR goes up. Cutting and tuning a loop to a band may also present some problems. The bandwidth of a loop may not cover all the frequencies desired if operating the repeaters. The circular loop is the best, followed by the square loop. Triangular loops work well also. The area enclosed by the loop is the main facter in approaching the 50 ohm impedance required by amateur radio gear today. Please keep that in mind. Geometric shapes in a natural setting tend to 'stick out' to the human eye. Hiding the antenna will require a crafty plan on the part of the amateur. The bidirectional pattern from the loop my hinder the placement if a specific direction is required. Remember the chimney? Good place to start. -+-------------------------------------------------------------------- Enough for now. Next, I will discuss the VHF/UHF hidden beam antenna. I have not discussed 6m, 33cm, or 23cm antennas, but the same application holds. Here's some info on 1/4, 3/4 wave lengths for the bands 6m, 2m, 1.25m, 70cm, 33cm, & 23cm to give you an idea on the size of the antennas you will be dealing with. The formula use does not always relfect the exact length of the antennas involed, but is to be used for sizing only. 1/4 3/4 f -+---------------------------------------- 6m | 4.73' 14.19' @ 52.0 MHz 2m | 1.68' 5.05' @ 146.0 MHz 1.25m| 1.1' 3.3' @ 223.5 MHz 70cm | 0.55' 1.65' @ 445.0 MHz 33cm | 0.27' 0.806' @ 915.0 MHz 23cm | 0.194' 0.581' @ 1270.0 MHz 73, -WS --- XRS! 4.50+ * Origin: KB4YLY, Moderator (1:374/73.2) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: E3Z00009 Date: 03/29/97 From: GARY SMITH Time: 09:25am \/To: CLAY HARTSOE (Read 3 times) Subj: Re: Shutdown -=> Quoting Clay Hartsoe to Gary Smith <=- CH> Gary, CH> The BBS shut down before I received your latest reply. Please CH> repost on this echo.----Later----Clay Hello Clay, I don't know if I can import the last message into this format for resending. I'll see what I can do. You should have the same message twice waiting for you when your BBS is back up. I sent it once via Juno and once (accidentally) via michiana.org. It's about time to start getting ready to go to the Michigan City ham fest. I'll write more later and catch you up. Ttul, tnx es 73 de Gary -k- --- Michiana Mail Center * Origin: CW Technical Support - South Bend, IN - (219) 272-8129 (1:227/129) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: E3Z00010 Date: 03/30/97 From: CLAY HARTSOE Time: 12:51am \/To: WAYNE SAROSI (Read 3 times) Subj: Re: Shutdown In a message to Clay Hartsoe <03-28-97 20:19> Wayne Sarosi wrote: WS-> CH> The BBS shut down before I WS-> CH> received your latest reply. Please repost WS-> CH> on this echo. ---- Later ---- Clay WS-> Which stuff Clay? Netmail or the old re-runs? Wayne, I sent you two or three messages before the other Board shut down to which I didn't receive a reply. I assume that you received my last message that the other Board will be down until next Saturday, but I will be able to use it once it comes back on line. I tried the antenna on the first four attachment points, but the lowest SWR I got was 3:1. It's acting as if the antenna is too short, but I've got at least eighty feet of wire. I'm going to start over tomorrow and let the Boss adjust the cap while I use the key. Hopefully that will make a difference, I don't want to have to changes in the wire length. Cross your fingers.-----Clay --- GEcho/2 1.20/Pro * Origin: CENTRAL FLORIDA'S HOMEBODY BBS (407)322-3592 (1:363/81) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: E3Z00011 Date: 03/30/97 From: CLAY HARTSOE Time: 12:54am \/To: GARY SMITH (Read 3 times) Subj: No Mail Gary, If things don't speed up we'll have to use snail mail for the next week. I haven't received a message from you since Thursday.---Later---Clay --- GEcho/2 1.20/Pro * Origin: CENTRAL FLORIDA'S HOMEBODY BBS (407)322-3592 (1:363/81) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: E3Z00012 Date: 03/29/97 From: JEFF EDMONSON Time: 03:51pm \/To: STAN BLACK (Read 3 times) Subj: southwext lynx SB> Hi Jeff! Nope! No way to get into it from Abilene...Our link SB> has been down for about 2 years. sorry to hear that. I suppose Armadillo is in place there? ========================================= 73 = Best Regards ka5thb@bigfoot.com -Jeff KA5THB --- * Origin: A point of The Electronic Avenue (1:387/510.1)