Amateur Radio Stack Exchange is a question and answer site for amateur radio enthusiasts. It only takes a minute to sign up. This entire setup lives indoors as I'm not able to put anything up on the roof right now. My understanding of a discone antenna is that the downward diagonal elements are supposed to act as an arbitrary, floating ground plane against which the vertical elements resonate.
This setup works as it is but I'm getting problems with pickup on the metal case of the SDR. What was a relatively quiet waterfall becomes a bright red mess as soon as I lay my hand on the case. That said, I cannot hear any difference in the demodulated signal 2 Meter band, AM for instance.
It seems in my mind like this pickup should be prevented because of the connection to a real earth ground via the PC's mains power supply. There is good connductivity between the diagonal elements of the Discone and earth ground less than 2 Ohms at DC, according to my multimeter. The USB is about 2 metres long, the Coax is about 3 metres. All connectors are soundly fastened and have good conductivity.
Is this detrimental to the use of a discone antenna? Is it bad to have a metal case on an SDR? Is there anything I can do to improve this setup?
The symptoms described are consistent with common mode currents. These are undesired currents flowing on the outside of the shield of the coax desired currents flow on the inside of the shield and the center conductor. The result is that the exterior shield of the coax acts as part of the antenna. By touching the coax or the electrically connected SDR enclosure, your body becomes part of the antenna system altering its performance for better or worse.
Common mode currents can be suppressed by installing a choking balun on the coax as it exits the discone. Ferrite type baluns are usually the best but you can experiment with simply winding 6 to 8 turns of coax in a 6 to 8 inch diameter bundle. This is a compromise balun that works best over the range of a few ham bands. Experiment with the number of turns and the diameter to optimize your results. These types of baluns can be effective up to 30 MHz or so.
With higher frequencies, other methods must be deployed. Unfortunately, the higher frequency solutions are usually effective for a single band and its odd multiples. This tends to present a high impedance to the common mode currents. But because the length of the coax must be adjusted according to the frequency, it is only practical for a small range of frequencies.
Another example of this type of frequency dependent solution is a sleeve balun. One side effect of reducing common mode currents is that your antenna may not perform as well as it had.Your question may be answered by sellers, manufacturers, or customers who purchased this item, who are all part of the Amazon community.
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There was a problem filtering reviews right now. Please try again later. Priced very low. Verified Purchase. This is not the first time I have bought this antenna and the price for this one is the lowest I have seen.A discone antenna is a version of a biconical antenna in which one of the cones is replaced by a disc.
It is usually mounted vertically, with the disc at the top and the cone beneath. Omnidirectionalvertically polarized and with gain similar to a dipoleit is exceptionally widebandoffering a frequency range ratio of up to approximately The radiation pattern in the vertical plane is quite narrow, making its sensitivity highest in the direction of the horizon and rather less for signals coming from relatively close by.
On February 6,Armig G.
Homemade Discone for RTL-SDR Use.
Kandoian of New York City was awarded U. Excerpt from the Kandoian patent: . In keeping with progress made during the last few years in the development of ultra-high frequency radio technique, and applications thereof to aircraft communication, direction findingand so forth, it has become necessary to develop special antennas and antenna systems suitable for installation on such aircraft.
Flying conditions are such that these antennas must necessarily be small and rigid in their construction and also offer a minimum of wind resistancein order that the flying efficiency of the aircraft will be unimpaired.
In accordance with my invention I have provided a small rigid antenna suitable for mounting on the surface of the fuselage or other component of the airplane structure and in certain embodiments I have also provided a streamlined protecting shield or housing covering or so cooperating with the construction of the antenna system as to greatly reduce wind resistance.
The discone antenna has a useful frequency range of at least 10 to 1. SWR standing wave ratio is typically 1. A discone may be made from solid metal sheet often copperwhich is practical for small indoor UHF antennas, such as for Wi-Fi. At lower frequencies a sufficient number of metal wires or rods in a spoke configuration is often used to approximate a solid surface. This simplifies construction and reduces wind loading.
The spokes may be made of stiff wire, brazing rods or even coat hanger wire.
Thinking Of Installing A Discone For My SDR Receivers
The discone's wideband coverage makes it attractive in commercial, military, amateur radio and radio scanner applications. The discone's inherently wideband nature permits it to broadcast undesirable spurious emissions from faulty or improperly filtered transmitters.
A vertical whip may be affixed to the center of the disc in order to extend the low frequency response, but this may compromise efficiency at higher frequencies. In this configuration, at lower frequencies the discone may more closely resemble a ground plane antenna or a coaxial dipole. From Wikipedia, the free encyclopedia. This article includes a list of referencesbut its sources remain unclear because it has insufficient inline citations.
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CQ Communications, Inc. Electronic Communication Systems 4th ed. American Radio Relay League. Antenna types. Isotropic radiator. Categories : Radio frequency antenna types Antennas radio. Hidden categories: Use American English from March All Wikipedia articles written in American English Articles with short description Articles lacking in-text citations from April All articles lacking in-text citations Commons category link is on Wikidata.
Excellent for testing various transmitters or to be used with any wide band SDR receiver. Includes SO connector, 50 feet coax with PL installed, stainless steel elements and mounting hardware.
If you are new to the hobby this is very good starting antenna. VA2PVFeb 8, Cool video and antenna, Pascalbut the first thing I would do if I bought one of those would be to ditch the 50 feet of RG58 that it comes with! The RG59 can be used for HF which is what it's a lot more suited to.
NH7ROFeb 8, And, so sorry Pascal but, considering the continuing level of very poor customer service and dismal product reliability, I wouldn't consider anything from Mississippi State since my last and final conundrum with them.
Last edited: Feb 9, NU4RFeb 9, SO connectors for UHF???? Come on now! Broadband antennas are notorious for having peaks and "valleys" in their coverage. The valleys usually are right over what you want to monitor. And transmitting into one of those discones? BTW, these broadband discones aren't anything new. N9LCDFeb 9, KC0BIN likes this.
I heartily second the idea of the discone NH7ROFeb 9, VA2PVFeb 10, You can find that discone from several sources.QRZ Forums. SDR receiver antenna? I guess this could be considered a "beverage" type antenna?
I have a pretty good length of just "random wire" that's maybe around 80' long. I'm considering routing it outside, up a corner of my house behind the vinyl siding and then across the length of my house as far as it will go.
Maybe adding some more wire to it and wrapping it on around? I like this idea as it would be hidden. There's also a barbed wire fence next door that runs around an adjacent lot. How would connecting my long wire to this fence work out? It's non electrified, btw. I can only imagine in a receiving scenario that getting "as much" wire up and out as I can is going to be best - just unsure of what implementation would give me the best performance.
KV4JWOct 18, I use two antennas on my SDR radios. One I built for HF, and one I bought for everything else. A Loop on Ground antenna works good up to 20 meters and will shock you on Commercial AM, ,80, and 40 meters.
Just requires 60 feet or wire and voltage Balun. I bought a Discone antenna and it works great up to 1 Ghz. K3RW likes this. Try looking into active antennas. It seems that the small wire antennas can receive quite a good signal--but due to poor matching, can't drive any sort of transmission line. But if you go into a high impedance buffer, a small antenna can receive quite a bit. But what the heck, if you have wire already, go for it. It's an RX antenna, not a TX antenna that could cause problems.
Worst case, you don't like the results and have to move it. AA7QQOct 18, I have the wires laid out and staked down in the yard. Just waiting on some bits to assemble a transformer now. Really pumped! KV4JWOct 22, You must log in or sign up to reply here. Show Ignored Content. Share This Page. Your name or email address: Password: Forgot your password?
Register for a free QRZ account.I needed to build an antenna for it and a discone antenna seemed to fit the bill. The discone antenna basically has a disc connected to the conductor on the coax, and a cone as the ground. Discone antennas are great for receiving, they have a very wide bandwidth around bandwidth range so a single discone can do almost the whole range of the SDR sticks bandwidth!
They are not too good for transmitting. The disc diameter should be a 0. This means a disc diameter of around 45cm and cone rod length of 65cm.
I drew up the antenna in SolidWorks and figured out a structure I liked:. The antenna consists of two 8mm thick aluminum discs with threads for 8 rods each. The rods are made from 6mm diameter aluminum tubing, with M5 threads in the ends. I did this by making a jig to hold the disc, then at an angle I milled flats at the correct angle to the disc with my drilling machine which did not fare too well with the 6mm end mill!
Maybe I should try replacing the bearings at some point… and then drilled the actual holes after that. This worked better than I expected. Subscribe to RSS feed.
DGK Electronics. Home About me Electronics projects. I drew up the antenna in SolidWorks and figured out a structure I liked: Discone antenna drawing. Rendered discone antenna. Discone antenna exploded view. Discone antenna, not yet finished. Close-up up the discone antenna. Discone antenna finished. Share this:. Email Print Digg. Geraldo says:. Lucas Fonseca says:. Leave a Reply Click here to cancel reply. Sorry, your blog cannot share posts by email.Forums New posts Search forums.
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MFJ-1868 - Discone Antenna for Broadband SDR receivers
Over the last few years I have been putting my time, attention and especially money into photography and astronomy equipment. I have decided to take a brief rest from that to boost up my radio reception equipment. I have had an Ettus B SDR for a few years but didn't use it hardly at all because I have no outside antenna, I bought several small screw on antennas for it but I was only ever able to receive the strongest FM radio stations.
I got bored with that and put it away for the last several years. My problem is at the moment I want to be able to receive everything because I don't know what I want to listen to yet.
I would like to listen to civilian aircraft, military aircraft if any are aroundpolice, fire, ect. I've done some reading about discone antennas and it seems I may have to put up two or three antennas to cover the majority of frequencies since the published frequency range of the discones don't really cover what they say they do. A few years ago I bookmarked a post I read here made by prcguyI was impressed with his description he gave of his discone antennas he frequently uses.
His setup sounds like it would cover what I would like to listen to. I have no experience with using all of the various antennas available so I have no idea what antennas would and would not work with what I want to do.
I will probably need at least 2 if not 3 antennas to perform decently in the large range of frequencies I want to explore, then trying to use them all on one SDR receiver is another challenge. At one point I was thinking of a discone with multiple vertical elements tuned for the various frequencies instead of one long whip on top.