desktop discone... a joke?

[JELAIR]

For use indoor in an apartment buried deep within a city-complex, with no access to any kind of height or, as they phrased it in "Logan's Run"; outside...

...is this antenna an option worth considering?

https://www.wimo.com/download/18065_neu.pdf

Or is it just basically a mean joke?

I have a 'bunny-ear' TV-antenna set up currently (which includes a loop between the bunny-ears) and it's receiving from the CB-band to the 7cm band (It's tuned for the civil airband)

I'm just wondering if I could squeeze out a few dB extra with that odd looking contraption sold by the German Wimo website (which is otherwise a great place to shop, great people, not scammers, which is the only reason I'm even considering this 'desktop discone' as it does look to me like something a chinese ebay-scammer would try to sell)

 

[ko6jw_2]

It only receives transmissions in German.

Seriously, it is a bizarre design. Basic discones do not need whips above the "disc." These are typically added to provide coverage below the discones frequency band. In this case the antenna functions like a ground plane.

The description claims coverage from 25Mhz to 2Ghz. This is probably false. Discones typically have a 10:1 coverage ratio.

As for extra dB, a properly designed discone has unity ( 0 dB gain ). So even if their claims were real, there would still be no gain.

Diamond does make a small discone that was intended for mobile operation. You could use it indoors with some sort of base (mag mount??). It has a UHF connector.

We could give you more advice if you gave some details about the bands you want to listen to, distances etc.

 

[mancow]

Short answer, yea a joke.

 

[mmckenna]

Dimensions seem awful small for the frequencies suggested.

However, keep in mind that even a paper clip will pick up a strong enough signal on any frequency.

I agree, it's a joke. Snake oil antenna sales, they prey on amateurs and scanner hobbyists. Unfortunately there are enough fools that buy this stuff to keep the market alive.

 

[JELAIR]

It only receives transmissions in German.

Seriously, it is a bizarre design.

LOL I get enough of those already

Yes I had a feeling it was an oddball, but thanks for the confirmation.

I use this (15 US$) antenna currently (it's a danish website, but there's a picture of it): https://www.biltema.dk/kontor---tek...endorsantenne-analogdigital-dvbtt2-2000033100

I tuned the 'ears' of it to the civil airband, but it still happily picks up receptions (at fair levels*) from as low as CB to as high as just under 500 MHz.

*If I tune it to other frequencies I can boost the SNR for those frequencies a bit, but even when tuned to the airband, my main interest, it doesn't really lose much hearing between 27 to 500 MHz.

I have experimented with building dipoles and loops, and various other types of antennae, but this TV-antenna has out-performed them all.
So either it is just very good, or I am a poor builder (Which is why I am looking for a pro-built alternative to see which one it is )

Basically I just want to get the best possible broad-band reception (as wide as possible) from a single antenna, since I am using it with an SDR-scanner.
Or, alternatively, the best SNR, and farthest reach along the ground, in the civil and military airbands (so from 118 to 400 MHz)
Basically all the things that usually require an outside setup placed high (both of which are currently impossible to do)

Thanks for your reply

 

[JELAIR]

Short answer, yea a joke.

+

Dimensions seem awful small for the frequencies suggested.

However, keep in mind that even a paper clip will pick up a strong enough signal on any frequency.

I agree, it's a joke. Snake oil antenna sales, they prey on amateurs and scanner hobbyists. Unfortunately there are enough fools that buy this stuff to keep the market alive.

Thanks.
Yes, I was afraid of that.

I am still fairly new at the antenna-side science of the radio-hobby, so I am not quite there yet where I can easily tell a dud from a gem.
But it's good to know I am at least on the proper track to better understanding, since my suspicions about this desktop-antenna was confirmed.

Thanks

 

[buddrousa]

And from most of us here welcome to RR and the hobby.

 

[dlwtrunked]

It only receives transmissions in German.

Seriously, it is a bizarre design. Basic discones do not need whips above the "disc." These are typically added to provide coverage below the discones frequency band. In this case the antenna functions like a ground plane.
...

Diamond does make a small discone that was intended for mobile operation. You could use it indoors with some sort of base (mag mount??). It has a UHF connector.

We could give you more advice if you gave some details about the bands you want to listen to, distances etc.

Putting whips atop a discone to extend the frequency coverage into other bands is a standard technique. One of the best discones that I owned was made by ICOM and had a whip on top to go down to 6m (that model is no longer current). The Diamond discone has a whip with two loading coils in it and I use it here in the house for short range stuff. I mounted mine on a mike stand with of hardware made to connect and NMO to a pole-mount and an NMO to SO-239 adapter. Earlier I used one on my car roof. It worked well but got too many comments and once when pulling into a government parking lot, they debated whether they should let me in.

My guess it that the advertised antenna does work better than a back of the set antenna and probably about as good as anything on a desktop (which is far from being a good location). Seeing no loading coils will likely not do well below about 100 MHz but that is typical. Whips on the top are to improve specific bands as posted above and sometimes the 800 MHz band as discone performance their depends largely on the space between the disk and cone and is often larger than desired.

Note: *Many" want the greatest range they can get over a wide range of frequencies (and that is required and not arguable for them). That means usually a discone or similar. Yes, a single band directional antenna will do better on a band but that is not what they need.

That being said, one should always go for a high antenna if one wants to extend range and the discone link posted has less than the optimal number of elements in the disk and larger discone or may be the Diamond would do better. But on top a desk, testing the one posted against the Diamond would be an interesting test.

 

[TailGator911]

I have two Diamond discones and swear by them. A full-sized one on my antenna mast on the house, and the small Diamond discone mentioned by ko6w_2 that I put on top of my RV. They both have the long whips up top and they both perform as advertised. I have experimented with several antennas with the RV and the small Diamond works the best. I am currently jury-rigging a mount for it with a CB antenna mirror mount affixed to the railing on the roof of my RV so that I can use it while mobile. Have yet to road test it, but soon. I used the same antenna mirror mount for my Dish satellite and it works great up there.

JD
kf4anc

 

[mmckenna]

I am still fairly new at the antenna-side science of the radio-hobby, so I am not quite there yet where I can easily tell a dud from a gem.
But it's good to know I am at least on the proper track to better understanding, since my suspicions about this desktop-antenna was confirmed.

Thanks

You are on the right track.

There is no magic involved in antenna design, it's all physics. The laws of physics can't be cheated by any antenna manufacturer, although there are plenty that want you to think they can.
Comparing like for like when looking at decibel number is important. Make sure you are comparing dBi to dBi or dBd to dBd.

When in doubt, compare to the known name brand commercial antennas. Unfortunately there are a lot of amateur and hobby vendors that will cloud the truth.
If any of these "magic" antennas actually really worked, you'd see them in use for public safety applications.

In other words, it's good to be skeptical if it seems to good to be true.

Also, the proven commercial brands are always going to be a good guidepost. I gave up on the amateur/hobby grade antennas after the first one I tried. I stick with the name brand public safety/commercial brands and have never been disappointed.
I have 30 year old Larsen antennas I'm still using. On the other hand, the last amateur/hobby antenna I bought has long since ended up in the trash.

 

[Ubbe]

I use this (15 US$) antenna currently (it's a danish website, but there's a picture of it): https://www.biltema.dk/kontor---tek...endorsantenne-analogdigital-dvbtt2-2000033100

I tuned the 'ears' of it to the civil airband, but it still happily picks up receptions (at fair levels*) from as low as CB to as high as just under 500 MHz.

I looked inside it and run an SWR analyze on it. The left telescope are only the groundplane and are connected to the coax braid and circuit board ground. If you angle the two telescopes straight out to the sides and have it vertically it will work as a dipole antenna. But there's a couple of filters inside it that makes the right telescope only work for the low frequencies up to 200Mhz for the FM broadcast band.

The loop are designed to, and the filters makes it work especially well on, 230MHz DAB frequency and a bit less well in the 470-700Mhz range for television. It seems to have a bandstop filter designed to attenuate 350MHz.

The filters makes it unsuitable for the 300-400MHz range. Are you actually receiving anything in the mil-air range?

The signal level potentiometer is a joke. It is a 10k pot, probabaly selected to be used in an active amplified model. For this application it should be 100-500 ohm as it sits directly connected to the coax. As soon as you touch it from its max setting the signal goes dead.

If you would like the loop to also work in the 300Mhz range you could remove either of the components marked C2 or L1. If you want the right telescope to also work up in the 400Mhz range you have to bridge the L3 component, solder a wire across it. The telescope also seem to have a 230Mhz bandstop filter and if you wish to exclude that, it probably also attenuate considerable in the 300MHz range, you should bridge the L2 or C4 component.

/Ubbe

 

[CQ]

Looks like this one.

https://www.amazon.co.uk/INDOOR-DESKTOP-DISCONE-SCANNER-ANTENNA/dp/B0078ZKJ1A

 

[RFI-EMI-GUY]

Reception on the inside of any structure is increasingly problematic. The noise floor is constantly increasing in power and frequency as higher speed LAN's and processors proliferate. Get it outside, on the roof. A common wideband discone is better.

 

[JELAIR]

And from most of us here welcome to RR and the hobby.

Thank you

The Diamond discone has a whip with two loading coils in it and I use it here in the house for short range stuff. I mounted mine on a mike stand

+

I have two Diamond discones and swear by them. A full-sized one on my antenna mast on the house, and the small Diamond discone

+

You are on the right track.

There is no magic involved in antenna design, it's all physics. The laws of physics can't be cheated by any antenna manufacturer, although there are plenty that want you to think they can.
Comparing like for like when looking at decibel number is important. Make sure you are comparing dBi to dBi or dBd to dBd.

So this has led me to focus on these 3 options:

A 'small' discone:
https://www.diamondantenna.net/d220.html
I don't know if it would be much different from their larger version, but since my aim is to use it indoors the larger one may be a bit much to handle (unless I could perhaps disguise it as a Christmas-tree and put it out on the balcony, where antennae are prohibited)

Or one of these 2 by DPDprod (DPDprod seems to be praised by several users on this forum)

A dedicated civ/mil airband antenna:
https://dpdproductions.com/collecti...tennas/products/air-omni-uhf-vhf-base-antenna

Or a similar, but with wider coverage, scanner-version, which seems to cover the civ/mil airband about the same:
https://dpdproductions.com/collecti...-antennas/products/omnix-scanner-base-antenna

I think the DPDprod antennae would be easier to set up indoors, since they mostly take up space in 2 dimensions, where the discone takes up space in 3 dimensions.
But I'm not sure if I'm missing something.

I looked inside it and run an SWR analyze on it.

( . . . )

The filters makes it unsuitable for the 300-400MHz range. Are you actually receiving anything in the mil-air range?

I saved your tech-directions so I can perhaps buy an extra one to take apart and experiment with

I am receiving the military control-center at around 309 MHz. It comes in at about the same strength as the civil control-center at around 123 MHz.

I don't know where either transmitter is located though, so I can't really evaluate if I should be able to receive it stronger than I do.

When I experimented with home-made dipoles (I even tried using a T-connector with 2 antennae, 1 tuned for civ, the other for mil), both centers were also received (comparably similar to what I get with the TV-'bunny', but with less power)

I have no real clue as to why the 'bunny' performs so well for me, but perhaps the filters built into it help in some non-trivial way with local radio-interference (which there is TONS of here Computers, TVs, pulsating lights and all kinds of wifi and short-range-devices etc)

Get it outside, on the roof.

I can only dream of that in this place
I am at the bottom of a high-rise, surrounded by other high-rises.
There's a tiny balcony, but house-rules that no antenna may be put on it (and it's placed so low that people outside can literally just reach up an grab things on it. So I can't really disguise an antenna on it. On the higher floors I could probably have gotten away with putting one up, since up there it wouldn't be very visible from below)

 

[mmckenna]

So this has led me to focus on these 3 options:

A 'small' discone:
https://www.diamondantenna.net/d220.html
I don't know if it would be much different from their larger version, but since my aim is to use it indoors the larger one may be a bit much to handle (unless I could perhaps disguise it as a Christmas-tree and put it out on the balcony, where antennae are prohibited)

Or one of these 2 by DPDprod (DPDprod seems to be praised by several users on this forum)

A dedicated civ/mil airband antenna:
https://dpdproductions.com/collecti...tennas/products/air-omni-uhf-vhf-base-antenna

Or a similar, but with wider coverage, scanner-version, which seems to cover the civ/mil airband about the same:
https://dpdproductions.com/collecti...-antennas/products/omnix-scanner-base-antenna

I think the DPDprod antennae would be easier to set up indoors, since they mostly take up space in 2 dimensions, where the discone takes up space in 3 dimensions.
But I'm not sure if I'm missing something.

Issue is, antennas work best when they are resonate at the frequency you are trying to use. For VHF, you need something 19 inches or longer. For UHF, 6 inches or longer. For 800MHz, 3 inches or longer.
When you try to shrink the antenna down, it's difficult to make it work correctly.
Any "compact" antenna is going to be a poor performer.

And, as stated above, indoors is going to be an issue. Noise floor is a big part of it. Too many consumer electronics spewing forth lots of noise will create issues.
And then, there's the construction of the building. The following materials are going to create issues:
Steel reinforced concrete.
Foil backed insulation/vapor barrier.
Metal siding.
Steel lath behind stucco or plaster.
Metal plumbing pipes.
120 volt wiring.
Phone wiring.
Heating/air conditioning ducts.
Ventilation ducts in bathrooms, kitchens, water heaters, vents, etc.
"Low-E" energy efficient glass.
Metal window screens.
Metal doors
Metal window frames.

All those things are going to block RF.
Getting the antenna outside really is important.

Putting a basic scanner antenna outside on your balcony/patio is going to improve performance.
Restrictions by the owners are an issue, but they can be overcome.

Antennas can be disguised as flagpoles. Place a tall potted plant/bush/tree on the balcony and stick the antenna inside. Use a magnet mount on the railing and remove it when not in use.
There are a bunch of solutions, you just have to get creative.

 

[allend]

I have tested all sorts of antennas and the Antenna Craft ST-2 was the best even though they do not make them anymore. The antenna had a lot of metal and when mounted high in the sky that antenna pulled in the signals.

So far for the money the Diamond D3000 N Discone antenna is the best out there. Its right under or around 100 bucks. I have tried all the other brands that tend to say they have more gain or have all of these spider designs and claim to be better and I have been really dis-appointed.

I bought this one below to replace the Diamond and I ripped it down and took it to the dump and put my Diamond back up

Your main goal is to not use indoor antenna's. Run feed line to an antenna and put it as high as the sky in the air outside.

HAM Radio Base Station Antenna 25MHz

 

[Ubbe]

Modify the one you have and it's easy enough to modify it back, or then get a new one.

As it stands unmodifed it has about 2-3 times worse reception in the 400MHz range and 3-4 times at 320MHz compared to the standard Uniden rubber antenna for their portable scanners.
The 122MHz airband has about half the signal compared to the rubber antenna.

Just by removing L1 or C2 (they are connected in series) you get about the same signal strength or a little better in the 400MHz band as the rubber antenna and twice the signal level in the 300Mhz band. A good increase in signal strenght in the milair range. The loop are connected with a balun so it seems to have gotten the most attention in the design. Telescope elements have no significant effect at 320Mhz and above.

Whatever I do I cannot make the telescope work any better than half the signal strenght in the airband compared to the Uniden antenna. It's probably the dual antenna connection that reduces the signal to half.

/Ubbe

Thank you

Originally Posted by Ubbe View Post
I looked inside it and run an SWR analyze on it.
( . . . )

The filters makes it unsuitable for the 300-400MHz range. Are you actually receiving anything in the mil-air range?

I saved your tech-directions so I can perhaps buy an extra one to take apart and experiment with

I am receiving the military control-center at around 309 MHz. It comes in at about the same strength as the civil control-center at around 123 MHz.

 

[Peerlessk]

Honestly it’ll receive. If your not transmitting it’ll do well other than 800-900

 

[mrkelso]

https://www.diamondantenna.net/d220.html

I own 2 mounted above the rain gutter and two indoors and they work real well for me and that includes 700 and 800 MHZ

My QTH is approx 66 feet above sea level and i am hearing all over the State of NJ and NY

 

[JELAIR]

Thank you all

I will see if I can find some 'thing' I can put on the balcony that can hold an antenna without looking like one

Seems like that's the better alternative to investing more in an indoor-solution.