Thanks for the detailed analysis, I'm having second thoughts about purchasing one of these now. Not sure what an alternative "scanner" antenna is now....
Actually, I suspect all discones probably perform similarly. For scanning, it probably doesn't matter as much, although if the SWR is all over the map across the spectrum, it means it won't be as sensitive on certain frequencies. I will say the quality of the Comet 150 build is excellent, so it may last a long time.
Thank you for explaining the principle of a discone. Never knew that. My question though; Does a bad vswr also influence the receiving capacity? I thought the vswr was only important for transmitting
Generally speaking, a high VSWR will degrade reception. High VSWR indicates that the antenna's impedance differs from that of the transmission line, which inhibits efficient transfer of signal energy. For low VSWR, however, the mismatch may not have a noticeable effect on reception.
I know this is an old video but considering that this antenna is not the correct size to transmit below 50 megahertz It is not surprising that the analyzer showed it to be bad that those frequencies. I've looked at the literature on the manufacturer does not claim that it is suitable for transmitting at those frequencies rather that it is suitable for 6 m, 2 m, 70 cm, 33 cm, 23 cm. The only claim for lower frequencies is for receive, which is white band from approximately 25 MHz up to approximately 1300 MHz. Biconicals and the variant the discone are extremely wide band antennas and can be suitable for transmitting over very wide frequency ranges. Unfortunately most of the commercial offerings have insufficient elements to make them very efficient with a solid cone and disc being the optimal design.
If I put up a wideband discone, would I need a diplexer or duplexer if my radio has VHF and HF antenna ports to scan the who range? And isn't swr mostly used for how well a transceiver will transmit on an antenna?
It depends on the discone. There are some that claim to cover the HF band, but I am doubtful that they would do well on both HF and VHF simultaneously. There may be some frequencies where they work as well as a resonant dipole, but will be horrible at others. No discone is completely flat in response. If, however, you do find a good one, you probably could use a diplexer, as long as it covers both HF and VHF. I don't honestly know if they exist. I think you would be better off with two separate antennas dedicated to each band, though. SWR is definitely important when transmitting, because damage to the finals could occur with excessive SWR. But an antenna that is resonant at a particular frequency (ie. low SWR), without the use of an antenna tuner, will work better for both transmit and receive because it's more efficient. An antenna tuner may seem to improve the receive response, but its purpose is primarily to make a badly mismatched, inefficient antenna look like 50 Ohms to protect the transmitter finals.
Good video….I’m looking at purchasing an antenna for just listening purposes on the fm broadcast, 2 meter and 70 cm bands. I already have a comet gp6 that I will be using as a transmit antenna. I will be using this disc cone with a sdr on my laptop for relaying information from weather nets and so forth. I have heard that these disc cones are great for “listening”. What is your opinion? Or are there better options out there?
Per the measurements on the VNA, I would find it difficult to recommend a discone like this for reliable wideband listening. However, it does appear that Comet has tried to optimize it for 2m and 70cm. As well, it looks good on the aircraft band. By extension, I would assume it should be ok for FM, but not optimal. The best antenna is always one that is cut for a particular frequency, but in a pinch, for broadband listening, the discone is a good 'compromise'.
You certainly can remove it. It may have a slight effect on the V/UHF bands, but I have not measured that condition yet. My guess is the effect would be minor.
Realistically there's nothing on 6 meters and there's nothing in between 6 meters and fm broadcast where the discone offers extra coverage, anyone with a scanner or an sdr dongle would be better off with a vhf based ground plane antenna or dipole
What a terrific video. Excellent work with the NanoVNA too. Your voice makes it easy to listen to.
Thank you. I had much the same results on a no brand discone.
Thanks for the detailed analysis, I'm having second thoughts about purchasing one of these now. Not sure what an alternative "scanner" antenna is now....
Actually, I suspect all discones probably perform similarly. For scanning, it probably doesn't matter as much, although if the SWR is all over the map across the spectrum, it means it won't be as sensitive on certain frequencies. I will say the quality of the Comet 150 build is excellent, so it may last a long time.
diamond discone d3000n
Thanks for this video, I found it really interesting and useful.
Thank you for explaining the principle of a discone. Never knew that. My question though; Does a bad vswr also influence the receiving capacity? I thought the vswr was only important for transmitting
Generally speaking, a high VSWR will degrade reception. High VSWR indicates that the antenna's impedance differs from that of the transmission line, which inhibits efficient transfer of signal energy. For low VSWR, however, the mismatch may not have a noticeable effect on reception.
Thanks!@@radiotopics1874
So the whip on the top of the discone has meaning only for 6meters band. If you put it lower / cutting a little can you center berter the middle band?
I know this is an old video but considering that this antenna is not the correct size to transmit below 50 megahertz It is not surprising that the analyzer showed it to be bad that those frequencies. I've looked at the literature on the manufacturer does not claim that it is suitable for transmitting at those frequencies rather that it is suitable for 6 m, 2 m, 70 cm, 33 cm, 23 cm. The only claim for lower frequencies is for receive, which is white band from approximately 25 MHz up to approximately 1300 MHz. Biconicals and the variant the discone are extremely wide band antennas and can be suitable for transmitting over very wide frequency ranges. Unfortunately most of the commercial offerings have insufficient elements to make them very efficient with a solid cone and disc being the optimal design.
If I put up a wideband discone, would I need a diplexer or duplexer if my radio has VHF and HF antenna ports to scan the who range? And isn't swr mostly used for how well a transceiver will transmit on an antenna?
It depends on the discone. There are some that claim to cover the HF band, but I am doubtful that they would do well on both HF and VHF simultaneously. There may be some frequencies where they work as well as a resonant dipole, but will be horrible at others. No discone is completely flat in response. If, however, you do find a good one, you probably could use a diplexer, as long as it covers both HF and VHF. I don't honestly know if they exist. I think you would be better off with two separate antennas dedicated to each band, though.
SWR is definitely important when transmitting, because damage to the finals could occur with excessive SWR. But an antenna that is resonant at a particular frequency (ie. low SWR), without the use of an antenna tuner, will work better for both transmit and receive because it's more efficient. An antenna tuner may seem to improve the receive response, but its purpose is primarily to make a badly mismatched, inefficient antenna look like 50 Ohms to protect the transmitter finals.
Good video….I’m looking at purchasing an antenna for just listening purposes on the fm broadcast, 2 meter and 70 cm bands. I already have a comet gp6 that I will be using as a transmit antenna. I will be using this disc cone with a sdr on my laptop for relaying information from weather nets and so forth. I have heard that these disc cones are great for “listening”. What is your opinion? Or are there better options out there?
Per the measurements on the VNA, I would find it difficult to recommend a discone like this for reliable wideband listening. However, it does appear that Comet has tried to optimize it for 2m and 70cm. As well, it looks good on the aircraft band. By extension, I would assume it should be ok for FM, but not optimal. The best antenna is always one that is cut for a particular frequency, but in a pinch, for broadband listening, the discone is a good 'compromise'.
Antenna D-130
Does this model allow for removing the lowband whip for optional operation? I'd be curious what the Smith chart would look like then on VHF and UHF.
You certainly can remove it. It may have a slight effect on the V/UHF bands, but I have not measured that condition yet. My guess is the effect would be minor.
dangit you skipped the gmrs band. ):
Realistically there's nothing on 6 meters and there's nothing in between 6 meters and fm broadcast where the discone offers extra coverage, anyone with a scanner or an sdr dongle would be better off with a vhf based ground plane antenna or dipole
I like to hear in places where there is nothing on it.. I don't know why!