Discone Scanner Antenna For SWL?

[ridgescan]

Yup.
Diamond d130j For Shortwave - YouTube

Diamond D-130J Used For Shortwave - YouTube

I better go get my shield

 

[zl2taw]

nice videos' Ridgy
very impressed, sort of make me thinks anything from 10MHz will be ok on the discone IMO

 

[ridgescan]

Thanks I showed this back in '09 too. I wish I'd kept those videos so I could put them up again. Anyways, I think the first video clearly shows that until I connect that coax jacket to the antenna switch thereby grounding it, the discone AND the coax shield are acting together as the antenna-soon as the coax is fully connected therefore grounding the shield, only the discone is acting as the antenna. The signal strength goes down and noise goes away.

 

[LtDoc]

anything can be used as a receiving antenna if it's an electrical conductor. That doesn't say anything about how -well- it will work, but it will 'work'. You aren't the first (or the last) one to do something like this, using a non-resonant antenna to listen to things. I don't think you need to worry about finding your 'shield' yet...
- 'Doc

 

[n8zcc]

Climb up and disconnect the feed line from the discone and see if there is a difference. My guess is the delta will be unnoticeable. Your feed line is the antenna.

 

[prcguy]

Using a VHF/UHF Discone for HF is a viable alternative if you don't mind some reduction in signal level compared to a larger antenna. The Discone top disc is definitely the antenna element and in this case it becomes an E field probe, which operates under a different set of rules compared to an antenna element that is a larger with respect to wavelength.

There are lots of effective very short whip (1m or less) HF/VLF receive antennas that have either a high ratio matching transformer or transistor circuit to perform impedance matching. The impedance of a 1m or less whip at HF is a couple of thousand ohms and a VHF/UHF Discone disc would be similar. If you could put a 100:1 transformer between the Discone disc and coax center conductor the HF signal levels would improve drastically.
prcguy

Climb up and disconnect the feed line from the discone and see if there is a difference. My guess is the delta will be unnoticeable. Your feed line is the antenna.

 

[ridgescan]

Climb up and disconnect the feed line from the discone and see if there is a difference. My guess is the delta will be unnoticeable. Your feed line is the antenna.

Been there done that-nothing but line buzz. No different than running it ungrounded.

 

[ridgescan]

Using a VHF/UHF Discone for HF is a viable alternative if you don't mind some reduction in signal level compared to a larger antenna. The Discone top disc is definitely the antenna element and in this case it becomes an E field probe, which operates under a different set of rules compared to an antenna element that is a larger with respect to wavelength.

There are lots of effective very short whip (1m or less) HF/VLF receive antennas that have either a high ratio matching transformer or transistor circuit to perform impedance matching. The impedance of a 1m or less whip at HF is a couple of thousand ohms and a VHF/UHF Discone disc would be similar. If you could put a 100:1 transformer between the Discone disc and coax center conductor the HF signal levels would improve drastically.
prcguy

Thanks for explaining what's going on here prcguy always great info!

 

[ve3fnd]

I think alot of what your seeing is the fact that you going to a vertical antenna. I switch from a long wire and g5rv to a antron 99 and see that my s-units drop but the noise level drops so low that its better on the antron

 

[vagrant]

I've used a discone and a ST2 in a pinch as a RX antenna for handheld receivers. In fact any antenna I have outdoors is better than one indoors, as anyone who's ventured outdoors knows. As to prcguy's comment about the transformer, I agree. I use a Winradio WR-LWA-0130 long wire adapter and the difference is significant with and without it, even indoors with some random length of wire. Connect a proper connector for your coax and enjoy it with a discone, slinky, wire, or whatever fits your needs.

I've watched your videos and you're working with a limited area, but have pretty good results. You are definitely fortunate to have roof access.

 

[prcguy]

Using a Discone for HF also depends on the sensitivity of the receiver and I find my AOR AR8200MKIII, Yupiteru 7100 and Yaesu VR-5000 get very decent signal levels from a Radio Shack Discone since they are tailored for short whip antennas. These same receivers are useless on a large wire antenna because they overload easily.
prcguy

 

[vagrant]

It is good you pointed that out for anyone who stumbles on to this thread. The handheld receivers I referenced above are a Grundig G5, Yaesu VR-500 and a Kenwood TH-F6A. All of which are happy to overload on a long wire. I have to employ a PAR AM BCB filter at my location as well for those radios. I've got it bad from two different AM stations close by and these smaller radios somehow do not perform as well as my more expensive HF radios when filtering. Funny that.

Using a Discone for HF also depends on the sensitivity of the receiver and I find my AOR AR8200MKIII, Yupiteru 7100 and Yaesu VR-5000 get very decent signal levels from a Radio Shack Discone since they are tailored for short whip antennas. These same receivers are useless on a large wire antenna because they overload easily.
prcguy

 

[ridgescan]

I've used a discone and a ST2 in a pinch as a RX antenna for handheld receivers. In fact any antenna I have outdoors is better than one indoors, as anyone who's ventured outdoors knows. As to prcguy's comment about the transformer, I agree. I use a Winradio WR-LWA-0130 long wire adapter and the difference is significant with and without it, even indoors with some random length of wire. Connect a proper connector for your coax and enjoy it with a discone, slinky, wire, or whatever fits your needs.

I've watched your videos and you're working with a limited area, but have pretty good results. You are definitely fortunate to have roof access.

Thanks to the previous 3 for your responses. Vagrant, I hear ya brother on having roof access, and I am very thankful to be able to keep 'em up there all these years. Luckily, I made the antennas as unobtrusive as possible and it worked thanks for checking the videos too.

 

[jdobbs2001]

I am using a discone with my FDM-S2 and I am surprised at how effective it is.

 

[ridgescan]

I am using a discone with my FDM-S2 and I am surprised at how effective it is.

It surely will do in a pinch, at least. I started "SWL with a rooftop antenna" in this shack with my d130j back in '08 because sometimes a guy just has no room for a proper SWL antenna. I didn't at that time, and this did ok for what it is good to know for those who own a discone for scanners and may want to give SW a shot.

 

[SCPD]

I am using a discone with my FDM-S2 and I am surprised at how effective it is.

You're probably getting most of the signal via the coax shield and not the actual antenna. Just about anything will work for a receive antenna. Metal gutters, metal roofs, fences, etc.

 

[ridgescan]

You're probably getting most of the signal via the coax shield and not the actual antenna. Just about anything will work for a receive antenna. Metal gutters, metal roofs, fences, etc.

Yeah nevermind what that dumb old ridgscan said in post #3-he don't know nuthin