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Discone antennas and gain


WSAK691

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Well before I got a GMRS license I was a radio hobbiest in a more general sense, and my sort of "workhorse" antenna for VHF and UHF is a Taurus D-1000 discone antenna which lives atop a 21ft mast from ground level. It's marketed as a "scanner antennas" but does state that it's capable of transmitting up to 200 watts as well. I've connected it to a NanoVNA analyzer, and sure enough it has some nice dips at VHF and UHF. About 1.3 at 467ish.

Ive gone online to try to find any spec literature on this antenna but come up empty. So,.. since this is sort of a widebanded antenna with transmitting being secondary in importance marketing wise, should I assume that while you CAN transmit on this antenna, it's unity gain? Also, what's the radioation pattern/take off angle like? Am I just shooting a sphere with tons of RF going up to space?

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20 minutes ago, kidphc said:

You can transmit on discones. Especially, if the swr is acceptable in the transmit range.

They are really optimized for recieve. So mileage would vary. The transmit radiation pattern are often not very good because of this.

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Yes, the antanna can take the RF input and has perfectly adequate SWR, but my question is what that radiation pattern is like.. If the radiation take off angle is such that an equal about of it is radiating at 1 o'clock upwards as it is 3 o'clock, that's not very good. 

my question is if that's the case? Unity gain?

 

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Yes, the antanna can take the RF input and has perfectly adequate SWR, but my question is what that radiation pattern is like.. If the radiation take off angle is such that an equal about of it is radiating at 1 o'clock upwards as it is 3 o'clock, that's not very good. 
my question is if that's the case? Unity gain?
 
From what I get.

The pattern is close to omni directional radiation pattern like. They will be varying lobe gain values, small fingers.

They harder thing to figure out is gain values for a particular frequency. Reading it is between 1.2-2.3 dbi or so.

The gain problem is only a problem if you are a ham might cause some pain doing the rf exposure studies, that we are required to do now. Which i know really affects hf users more than vhf/uhf/shf/ehf.


Also for these frequencies I not sure take of angle is going to matter especially with an omni directional pattern.




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It matters a good bit on VHF and UHF but you desire a more shallow angle. Every bit of RF that is radiated into a wasted direction is inefficiency towards your "fars capability". Good 9db gain omni verticals will squash the radiation donut into a thinner pattern in vertical diameter. My suspicion is that the radiation pattern from this discone is apple-shaped.

For HF, that's fine to shoot your RF up at a high angle for ionospheric reflection. But as we know, UHF is just going out never to return.

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It matters a good bit on VHF and UHF but you desire a more shallow angle. Every bit of RF that is radiated into a wasted direction is inefficiency towards your "fars capability". Good 9db gain omni verticals will squash the radiation donut into a thinner pattern in vertical diameter. My suspicion is that the radiation pattern from this discone is apple-shaped.
For HF, that's fine to shoot your RF up at a high angle for ionospheric reflection. But as we know, UHF is just going out never to return.
I get it. Other designs have similar issues. But let's be truthful here, we aren't going to be talking skip zones often with uhf. For me almost the same guys on 2m or 70cm ssb. Well minus some tropo.

Yagis are another example.. Sadly, they have a crap ton take off angle. Tons of the energy is lost up high and into the ground So much so I was trying to design a workable cubic or quad-cubic antenna, by design they are flatter and tighter in radiation angles.

But since a discone, is considered an omni-directional antenna, it is basically a sphere. So yes, 1/3 of the radiation is up top, is in an undesirable angle. So is up to the lower 1/3.

Basically, don't sweat it too much :)

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2 minutes ago, kidphc said:

I get it. Other designs have similar issues. But let's be truthful here, we aren't going to be talking skip zones often with uhf. For me almost the same guys on 2m or 70cm ssb. Well minus some tropo.

Yagis are another example.. Sadly, they have a crap ton take off angle. Tons of the energy is lost up high and into the ground So much so I was trying to design a workable cubic or quad-cubic antenna, by design they are flatter and tighter in radiation angles.

But since a discone, is considered an omni-directional antenna, it is basically a sphere. So yes, 1/3 of the radiation is up top, is in an undesirable angle. So is up to the lower 1/3.

Basically, don't sweat it too much :)

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That's essentially all that I am trying to sort out. I have both this discone as well as a yagi with a perfect 1.0 dip RIGHT at 467.55. I use a repeater about 20 miles out and I can hit it with both types of antenna. The discone comes in a bit fuzzy and the occasional drop out. The yagi hits the repeater full quieting. It's just that I have to physically go out to my mast to rotate the yagi in the various directions that I'm aiming to target. I have a repeater that's actually excellent in my area that I'm fortunate enough to be 2 miles away from, which is where I stick around on mostly and for that my discone hits that rock solid and full quiet..

Additionally, the discone sits atop my mast about 21ft high, and the yagi is further down the same pole only about 12 feet up, and it still gets out 30+ miles fully quiet with about 7.5 watts.

I'm just doing some anecdotal testing of the antennas I have access to. Seeing first hand how antenna design, decibel rating, and lobe patterns really do translate into empirical results. I didn't know much about this end of radio stuff beyond a year ago despite having been involved with it since a young age. Just sort of going down a rabbit hold of antenna gain and the capabilities that can be achieved on the antenna side of things even with low power by paying attention to how things radiate. 

I think a lot of people get hung up on sheer wattage power, when your radiation efficiency is a far bigger factor.

 

 

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That's essentially all that I am trying to sort out. I have both this discone as well as a yagi with a perfect 1.0 dip RIGHT at 467.55. I use a repeater about 20 miles out and I can hit it with both types of antenna. The discone comes in a bit fuzzy and the occasional drop out. The yagi hits the repeater full quieting. It's just that I have to physically go out to my mast to rotate the yagi in the various directions that I'm aiming to target. I have a repeater that's actually excellent in my area that I'm fortunate enough to be 2 miles away from, which is where I stick around on mostly and for that my discone hits that rock solid and full quiet..
Additionally, the discone sits atop my mast about 21ft high, and the yagi is further down the same pole only about 12 feet up, and it still gets out 30+ miles fully quiet with about 7.5 watts.
I'm just doing some anecdotal testing of the antennas I have access to. Seeing first hand how antenna design, decibel rating, and lobe patterns really do translate into empirical results. I didn't know much about this end of radio stuff beyond a year ago despite having been involved with it since a young age. Just sort of going down a rabbit hold of antenna gain and the capabilities that can be achieved on the antenna side of things even with low power by paying attention to how things radiate. 
I think a lot of people get hung up on sheer wattage power, when your radiation efficiency is a far bigger factor.
 
 
What you say is empirical. Unfortunately, a lot of factors come into play.

The theory is just a start. Antenna theory isn't magical, it's physics. So no super bending the laws to get magical more "farz" from similar designs. We give up some here for more there. Unfortunately, advertising from the companies selling us stuff obfuscates a lot of the truth, and the internet adds more.

Same thing with the gear we use. X vs y company. How much it cost vs quality. Does it make a difference? Yes/no. Hard to explain or quantify even in person.

Glad you are testing with things and coming up with your own answers. Knowledge is king.

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On 2/4/2024 at 10:33 AM, WSAK691 said:

That's essentially all that I am trying to sort out. I have both this discone as well as a yagi with a perfect 1.0 dip RIGHT at 467.55. I use a repeater about 20 miles out and I can hit it with both types of antenna. The discone comes in a bit fuzzy and the occasional drop out. The yagi hits the repeater full quieting. It's just that I have to physically go out to my mast to rotate the yagi in the various directions that I'm aiming to target. I have a repeater that's actually excellent in my area that I'm fortunate enough to be 2 miles away from, which is where I stick around on mostly and for that my discone hits that rock solid and full quiet..

Additionally, the discone sits atop my mast about 21ft high, and the yagi is further down the same pole only about 12 feet up, and it still gets out 30+ miles fully quiet with about 7.5 watts.

I'm just doing some anecdotal testing of the antennas I have access to. Seeing first hand how antenna design, decibel rating, and lobe patterns really do translate into empirical results. I didn't know much about this end of radio stuff beyond a year ago despite having been involved with it since a young age. Just sort of going down a rabbit hold of antenna gain and the capabilities that can be achieved on the antenna side of things even with low power by paying attention to how things radiate. 

I think a lot of people get hung up on sheer wattage power, when your radiation efficiency is a far bigger factor.

 

 

When I was still doing ham radio, had same basic setup (Diamond discone up top working as a scanner receiver, Yagi down a bit from there for 2M/440. I put a rotator on the whole mast.  The Discone didn't notice that it was rotating :) Moving the Yagi to point the right way for a particular repeater was the only way to do nets and stuff on the far-far away 2M repeaters. This was back when there was any activity on 2M. 

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