These two simple wire antennas are designed to operate in the 1.9 MHz amateur band . They are connected to a coaxial cable with a characteristic impedance of 50 or 75 ohms. Total length of the wire antenna should be: for the first figure of 38 meters, the second slightly longer than 43 meters . Of both figures show that the wire antenna for 1.9 MHz band as it split into two sections - the antenna itself and reduced to connect the matching device and coaxial cable. Here it should be noted that the ratio of these areas antenna wires can be anything, the main thing here is the total length of the antenna wire and the length of these sections can be arbitrary. Inductance for the first wire antenna is 13 micro Henry , she performed on a frame of 50 mm diameter , has 20 turns of copper wire with a diameter of 0.8-1.0 mm. Winding length of 50 mm. In this design, the wire antenna for 1.9 MHz is much more difficult to make (or find) the variable capacitor ( in terms of its dielectric strength ) , to transmit power to 10 watts , you can use a regular capacitor . Setting a first embodiment of a wire antenna for a range of 1.9 MHz start with the settings in the resonance of the capacitor at the operating frequency , on the selection of the number of coil turns achieve minimum SWR. Antenna in the second picture has an active component of the input resistance of about 50 ohms. Please compensate capacitor C reactive component of the input resistance (it has an inductive character ) , and then pick the length of the antenna SWR , each time adjusting the capacitor C. Because of the high input impedance of this antenna is more efficient than the first wire antenna pattern but the latter is easier to setting , as it requires careful selection of the overall length of the antenna. For these two wire antennas for a range of 1.9 MHz required good " grounding system " , in the simplest case, a system of " earth " should be supplemented by at least one counterweight to the maximum possible length ( but not less than 5 m) .
Friday, January 17, 2014
On this page of their site, I want to tell you that I found this description of the Russian Internet wire antenna , which I was very interested . This wire antenna for observers (SWL). What I'm interested in this dish: the first - is its simplicity , the second - that I have the opportunity to set it up , and the third - this antenna anti noise , well, that this fourth antenna operates in the long and medium waves . About the last ( fourth ) will say that I particularly recently started exactly like the medium wave and long wave bands and radio stations operating amplitude modulation. Real romance for radio amateur observer why I ceased to please ssb I do not know , but it seems just tired of these unnatural narrowband signals. And maybe that's why I decided to turn its attention to the low-frequency ranges . Of course these bands in Russia is very much noise but may be due to its two digital radio WinRadio and SDR-IQ that will work with this wire antenna I get to grips with this problem. This summer I will try to install this antenna . And so I will not steal someone else's article and pictures here and just giving this < link > to it . And to describe briefly what there are articles and pictures I think you will understand even though they are in Russian, everything is clear . For a full translation of an article on this wire antenna , you can use < translator google>. It states that the use of an antenna that receives the magnetic component of the electromagnetic field to reduce the noise level is almost 100 times ! Wire antenna in question in the article is very close to the ground , you can even put it in general . Admission to this antenna is carried out with the direction perpendicular to the plane of the frame antenna , ie reception of the station most distant from the point of finding antenna (similar vertical emitter ) . Due to the fact that the wire antenna is very low to the ground resonance it is missing, it is obtained as a shunt to ground. Dimensions of this antenna is to be performed for the highest frequency band ( wire antenna dimensions for a range of communication and there are doors ) . There's also said that raising it too high , too, do not need , it will lead to a drop in antenna gain . The antenna connected to two coaxial cables , and there are drawings of how to connect these cables to the symmetric and symmetric receiver input . The author writes that he took the radio communication range and doors to all on a very short antenna , but with a short wire antenna becomes difficult to receive distant stations . Generally, if it is not clear that you will be from the translation please contact me by e-mail envelope is below , we will try together to understand this wire antenna for SWL.
(here the translation of the text in the picture)
(here the translation of the text in the picture)
at 10:25 PM
Thursday, January 16, 2014
Building A Homebrewed Off-Center Fed Dipole Scanner Antenna.
Aluminum/copper tubing construction:
You will need to check the fit of the tubing with the T connector and the caps while you are at the store. One combination that fits nicely is 3/4" copper pipe with 3/4" CPVC fittings (not to be confused with 3/4" PVC fittings which will be too large). The tubing/connector is held in place with 2 stainless steel sheet metal screws for connecting the balun to each element.
Find a "U" bolt to fit your mast. Drill two holes in the support pipe to fit the U bolt.The support pipe is 18" from the "T" to the mast.
Remember, bandwidth increases as diameter of the elements increases. I think, if I remember correctly, at the hardware store, that a few CPVC fittings will fit copper tubing perfectly!
Some say that the 18" element on top mounted works best,Some like the 48" element on top.It does'nt matter,it works the same. If you use the copper tubing,be sure to paint it with some good,non-conductive paint.I used to paint mine light grey. -Have fun! (Teraycoda)
For an alternate/temporary mounting option, drill a hole in one of the end caps and put in an eye bolt with a nut on the underside of the cap to secure. Be sure to secure this end cap to the copper tubing somehow, perhaps with an additional small stainless sheet metal screw. Be sure that the eye bolt itself doesn't make electrical contact with the tubing. Also, drill a small weep hole in the bottom end cap to allow any moisture to escape that may accumulate inside. Use the eye bolt and some rope to pulley the antenna up high in a tree, or use a hook to hang it somewhere. Give careful consideration to safety and grounding depending on your particular usage scenario. (Qdude)
Variation for Off-Center Fed Dipole Using Simple Wire and 75 to 300 ohm TV Balun Transformer
Electrically, this version is the same as the one using copper tubing (above) but can be assembled quickly and is quite portable. While not as broadbanded as an OCFD using copper tubing or other metal with a larger diameter, the OCFD made from simple wire turns in great receive performance in all the commonly scanned bands, as reported here on RR in multiple message threads.
The legs/ends of the dipole are simple bell wire and shown here coiled up. Uncoil them and hang them vertically; doesn't matter if the long or short leg is at the top... works the same either way. The wire terminal lugs shown at the end of the legs of the dipole antenna should NOT be connected electrically to the wires - just crimp them on over the wire insulation. They are used as convenient hangers for the antenna, and not meant for electrical connection. Obviously, the lugs at the TV transformer/balun ends of the wire should be stripped before crimping on the terminal lugs to ensure contact with the antenna wires when you attach the TV transformer. Ensure the 75 ohm coax feedline that you connect from the balun/transformer runs away from the antenna at as near a 90 degree angle as possible.
at 10:45 AM
Friday, January 10, 2014
Compared with the antenna for the transmitter antenna to the receiver is not too difficult , even for a band as 1.9 MHz . Typically, such wire antenna is a frame that consists of one or several coils . Wire loop antennas have two distinct minimum when the signal directed perpendicular to its plane . Suppression of radio signals and interference are the side of the loop antenna can reach about 30 dB ( five points on the scale S!). An embodiment of the wire loop antenna shown in Fig . The antenna has three turns ( a square with sides 1.5 meters ) , forming a frame, and one round of communication . Any wire diameter , the usual equipment wire. The frame is placed in the electrostatic shield , open at the top. The screen can be made of braided coaxial cable , fixed to the frame cross member of the dielectric. Framed wire antenna is tuned to the operating frequency of the capacitor C1 , which must be protected moisture. To frame the receiver is connected via coaxial cable with a characteristic impedance of 50 ohms.
at 9:56 PM
Friday, January 3, 2014
Range of 1.9 MHz or 160 meters when it was very popular among novice hams former USSR. Today, apart from interference on it you will hear nothing . One of the problems of falling interest to a range of 1.9 MHz was of course the complexity of the antenna . To work effectively in this range, the length of the antenna wire should be 40 meters, depth of the antenna should be almost the same at a lower altitude aerial suspension ceases to work effectively in medium and long routes . The most effective range of the antennas to 1.9 MHz (160 meters) are the dipole and loop antenna , the length of which is commensurate to the wavelength. But to establish a dipole wire antenna type is also problematic , such an antenna length should be about 80 meters. In order to reduce the physical length of the antenna can be applied lengthening doghouse as in antenna w3dzz, the antenna can be used to work in a range of 1.9 MHz as shown in the figure below . Unlike in this embodiment w3dzz no capacitors and it can also perform as the " inverter V". The length of the wire antenna is reduced in two (in comparison with the dipole ) , to reduce the loss extending spools must have their own small losses and high Q (of order 150) are also protected from moisture. Connect the antenna 50 ohm coaxial cable , when the size of said inductance coils L1 and L2 should be 70 mH. Setting wire antenna produce change in the length of external conductors ( Figure they have a length of 14 meters) . Having measuring instruments MFJ or other firm I think setting this wire antenna will not cause difficulties . Antennas operate as " inverter V" on the mast height of 15 meters.
at 10:52 PM