--------------- FIDO MESSAGE AREA==> TOPIC: 205 RTTY Ref: BCH00001 Date: 08/10/94 From: REID KELLY Time: 09:47am \/To: ALL (Read 10 times) Subj: Indoor Antennas 2/2 * Originally By: Wayne Sarosi * Originally To: All * Originally Re: [Indoor Antennas - part2] * Original Area: Ham_Tech * Forwarded by : Blue Wave v2.12 SUBJECT: Indoor Antennas for HF & VHF/UHF I thought I would conclude the HF foil antenna here and move on to another subject. Connections from the foil to the coax or BALUN are via the copper tape. There are copper tapes available on the market that are used for EMI applications. These tapes are expensive so if you can get a piece of some of that tape from a buddy, it will work wonders for you. Otherwise, there is a trick with regular copper tape and the aluminum foil that you can do. It's a simple folding technique that insures a good connection and yet requires no soldering except for the coax / BALUN connection. =========================================== Aluminum foil |-----------------------------------|| | ==================================== |------------------------------------------- Copper tape This folding method insures good contact on more than one surface. One warning, do not leave air gaps as it will have a capacitive effect. Solder doesn't stick to Aluminum foil very well. With enough heat, you can solder anything. Too bad the aluminum foil won't hold up at that temperature and neither will the solder. You now can solder leads to the BALUN or solder the coax direct to the copper tape. For an indoor antenna, the foil antenna works rather well. It can out perform a vertical and pull in the weak ones with ease. I think you'll find it one of the most inexpensive antennas you can build yourself. 73, Wayne, KB4YLY -!- ! Origin: KB4YLY (Quick 1:374/73.2) ___ Blue Wave/QWK v2.12 --- Intermail/RA/SX/GE * Origin: The CatWalk BBS Davie, Fl 305-370-3528 USR V.EveryThing (1:369/8) --------------- FIDO MESSAGE AREA==> TOPIC: 205 RTTY Ref: BCJ00000 Date: 08/13/94 From: REID KELLY Time: 06:19am \/To: ALL (Read 9 times) Subj: [Indoor antennas - part 3 * Originally By: Wayne Sarosi * Originally To: All * Originally Re: [Indoor antennas - part 3 * Original Area: Ham_Tech * Forwarded by : Blue Wave v2.12 SUBJECT: Indoor antennas part 3, VHF/UHF Discones The discone antenna is a rather unique antenna for VHF and UHF. The discone has no gain to speak of, yet can provide the user with a range of ten times the design frequnecy for reception and transmitions. This means that a discone designed at 140 MHz will work fine up to 1.4 Ghz. Hiding the discone outside may prove to be quite a feat. Unlike most antennas, the discone has a large skirt and is tall to boot. It's shape can draw attention. If you can place the antenna outside, it will give you excellent coverage over it's range. Inside, the discone works well minus the attenuation caused by the building it's in. There are many Discones available on the market if you choose not to build one. Building one can be fun if you take the time and lay everything out ahead of time. There are a couple items I would like to point out about discones. 1) The gap between the top-hat and the skirt is critical. 2) The area under the skirt is a null to the antenna. Design parameters are easy. o The top-hat diameter is: (0.1778 * (984/f MHz))*12 EX: at 140 MHz --> (0.1778 * (984/140))*12) = 15-in o The diameter of the skirt, at the base, equals the length of the skirt elements. This gives the user the closest impedance to 50-ohms. Thus a skirt element length is: (0.2675 * (984/f MHz))*12) EX: at 140 MHz --> (0.2675 * (984/140))*12) = 22.56-in o The gap is: (0.007114 * (984/f MHz))*12) EX: at 140 MHz --> (0.007114 * (984/140))*12) = 0.6-in A tin funnel works well as a starting base that brass skirt elements can be soldered to. An SO-239 chasis connector can be fit into the cutoff funnel end and the top-hat soldered to the center pin of the SO-239. Insullating spacers can be used to strengthen the gap. I've used a brass screw that was soldered between the center pin and the top-hat, but you can use anything that you can solder. I have a motorized discone in works. The stepping motor will be incorporated to change the gap, to match the frequency, for best SWR. -WS -!- ! Origin: KB4YLY (Quick 1:374/73.2) ___ Blue Wave/QWK v2.12 --- Intermail/RA/SX/GE * Origin: The CatWalk BBS Davie, Fl 305-370-3528 USR V.EveryThing (1:369/8) --------------- FIDO MESSAGE AREA==> TOPIC: 205 RTTY Ref: BCJ00001 Date: 08/13/94 From: REID KELLY Time: 06:19am \/To: ALL (Read 9 times) Subj: [Indoor antennas - part 4 * Originally By: Wayne Sarosi * Originally To: All * Originally Re: [Indoor antennas - part 4 * Original Area: Ham_Tech * Forwarded by : Blue Wave v2.12 SUBJECT: Wire beams, indoor antennas For many of us, the antenna is the biggest problem for most hams. Hams have to contend with neighbors and the XYL in order to pursue their hobby. An interesting HF and VHF idea I've seen used is the wire beam. The wire beam is unrolled and suspended in the direction required for operation. After the operation is complete, the wire beam is rolled up and stored for the next time. This type of beam is excellent for 10m and up to 1.25 m. You may be able to set up a wire beam for frequencies below 10m if you have the space to do so. This antenna is also excellent for suspension in an attic. A simple model is shown below: R DE D -----------||--|-------------|----------|--||----------- || | | | || || | | | || || | | | || -----------||--|-------------|----------|--||----------- || | | | || || | | | || || | | | || -----------||--|-------------|----------|--||----------- Aside from the elements, the rest of the configuration is non- conductive. Wooden dowel supports are outside the ends of the antenna and string/rope can be used to support the elements. The wooden dowels are not required if suspension is taught. You can see that variations of this set-up can be incorporated to accommodate most any frequency from 10 to 1.25 meters. -WS -!- ! Origin: KB4YLY (Quick 1:374/73.2) ___ Blue Wave/QWK v2.12 --- Intermail/RA/SX/GE * Origin: The CatWalk BBS Davie, Fl 305-370-3528 USR V.EveryThing (1:369/8) --------------- FIDO MESSAGE AREA==> TOPIC: 205 RTTY Ref: BCJ00002 Date: 08/13/94 From: REID KELLY Time: 06:19am \/To: ALL (Read 9 times) Subj: [Indoor Antennas -part 5] * Originally By: Wayne Sarosi * Originally To: All * Originally Re: [Indoor Antennas -part 5] * Original Area: Ham_Tech * Forwarded by : Blue Wave v2.12 SUBJECT: Attic VHF/UHF Rotatables In many instances, a ham can mount a VHF or UHF beam in the attic, on a rotor. They can achieve good results depending on their location and height off the ground. Antenna size limitations are soley dependent on the available room in the attic that allows rotation of the beam without hindering it's rotation. To check the attic for the maximum size antenna, the ham must first enter the attic and measure the distances in the area planned for the set-up. Trusses, electrical wiring, air conditioning / heating ducts, and the items that are stored up there, can all play a factor in the actual antenna size. Finding your antenna with a pair of long johns dragging off the front end is not a pretty sight. After measuring the area in the attic, the antenna size and height off the attic cross members can be accomplished. Remember to allow for a base to accommodate the rotor. This too must be calculated into the system. Building a sleek system, to rotate two or three small beams, can be dashed, when the system will not turn because of an oversight in the measured values of the attic area in question. Turning radius is the important factor. Each antenna forms a rectangle ABCD where the maximum distance is AD or BC. A------------------------------------B | | | | ----|----------------------------------|---- BOOM | | | | C------------------------------------D For horizontal antennas, the turning radius is from the mounting point to the tip (either side) of the longest element. Multiple this figure by two for the turning diameter of the antenna. For vertical antennas, the truss angle places the biggest problem as the height from the boom to the tip of the refector (B or A). In essence, this will shorten your boom length or require a lower rotor mounting. These tips will help the Amateur avoid any problem before getting the system in the attic. -WS -!- ! Origin: KB4YLY (Quick 1:374/73.2) ___ Blue Wave/QWK v2.12 --- Intermail/RA/SX/GE * Origin: The CatWalk BBS Davie, Fl 305-370-3528 USR V.EveryThing (1:369/8) --------------- FIDO MESSAGE AREA==> TOPIC: 205 RTTY Ref: BCJ00003 Date: 08/13/94 From: REID KELLY Time: 06:19am \/To: ALL (Read 8 times) Subj: [Indoor Antennas -part 6] * Originally By: Wayne Sarosi * Originally To: All * Originally Re: [Indoor Antennas -part 6] * Original Area: Ham_Tech * Forwarded by : Blue Wave v2.12 SUBJECT: Indoor telescoping beams One problem I have encountered from Hams living in apartments is the space to place a VHF/UHF antenna. This concerns operation of the beam from a bedroom or porch. In these cases, the Ham can not keep the antenna up and must remove the antenna after he or she finishes. Using telescoping elements can solve the problem. Adding a two or more section boom can further the portablilty for the antenna making it idea for field day, camping, or travel also. Dimensions for beams have been discussed earlier, so I won't rehash them here. The best portable and quickest for set-up is the four element VHF antenna. A two section quick clamp boom with mounting flange for a camera tripod provides the base. Each element contains two telescoping units and a snap on fitting for attachment to the boom. The driven element has shorter telescoping units to preserve the gamma match section as one piece. The antenna described here can be stored in a briefcase save the camera tripod. A VHF four element antenna can provide 9dBi of gain for the apartment dweller. -WS -!- ! Origin: KB4YLY (Quick 1:374/73.2) ___ Blue Wave/QWK v2.12 --- Intermail/RA/SX/GE * Origin: The CatWalk BBS Davie, Fl 305-370-3528 USR V.EveryThing (1:369/8)