When Dave says "center of gravity," that's also called "center of radiation." Even though the antenna may radiate along it's entire length, that can be modeled as radiating from a single point.
Thanks for the info. On a large scale, you can model the antenna as a single point, but to capture the effects of additional elements, etc., modeling usually is done on a multiple points per element basis.
I have my GP9N mounted about 60' up and use 75' of LMR-400, which has an attenuation of 1.5db/100ft at 146MHz. There's a ridge west of my house that's around 50' above my property, so this pokes my antenna up above that. So it's good to know the theory but also your particular situation. In general, though, height is going to have diminishing returns while coax has accumulating losses. From tests I've seen online there seems to be some pretty big gains to be had by going up 20' - 30', but after that the improvement seems to drop off (the testing I saw was with the same length of coax, so it was just testing the height only, not the effect of height plus the longer length of coax you'd need to reach that height).
I had D130 discone antenna, and F23H ( 5/8 wave x 3 ) similar characteristic to GP9 on 144MHz band. D130 antenna feed point height 24 FT, F23H base height was 16 FT. I always heard better on D130 at 24 FT. so I took down F23H. F23H was replaced with 1/4 wave antenna at 24 FT, which hear better. I guess height matter more than gain. AG6JU
I wonder if Ham radio will get to the place that cellular is where the actual transmitter will be mast/tower mounted direct to the antenna, or with a very short jumper and a control cable that runs down to the shack. A fiber optic control cable would reduce the chance of lightning/ESD into the shack.
With a Wifi-equipped radio (eg I have an IC-705) you could have that in a weather-proof box with any other needed equipment up at the top of your mast and have the antenna come straight out of the radio. With Icom's RS-BA1 software you could then control everything via the WiFi connection, including winlink, FT8, etc. from your computer in your home. Add a remote antenna switch for whatever antennas you're using plus a dummy load. You'd just need to run a power cable up there, making sure the voltage drop isn't too much. Or have solar panels and a battery up there and then there'd be no wires at all.
@@truhartwood3170 Indeed. You'd need a mast strong enough to hold that in heavy winds. Tower probably. I wonder if anyone has done that. Do you know of anyone?
@@davecasler I don't know of anyone, just answering off the top of my head! Definitely need a tower, yes, especially with any solar panels, though if they were horizontal that would theoretically not have too much wind resistance. Overall, the project would be more of a "can we make it work?" rather than being super useful or worth I would think. I can't think of a use-case off the top of my head that this would be good for as far as amateurs go. Maybe if you had a huge rural property where your house was in a bit of a valley or gully, but there was a peak on your property quite far from your house where you wanted your tower to be?
Many commercial wifi access points use a controller that contains all the smarts and the access point is just a rx/tx with an IP converter to send the data to the controller for processing. This would allow for a truely software defined radio that could run as either a simplex or duplex. This would both revolutionize the HAM market while almost overnight, destroying most of the radio manufacturers. The second is probably why no manufacturer is even looking at this.
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Height does not matter (much) if you are working tropo, meteor scatter, or EME. Gain and noise figure are the key in these cases.
When Dave says "center of gravity," that's also called "center of radiation." Even though the antenna may radiate along it's entire length, that can be modeled as radiating from a single point.
Thanks for the info. On a large scale, you can model the antenna as a single point, but to capture the effects of additional elements, etc., modeling usually is done on a multiple points per element basis.
I have my GP9N mounted about 60' up and use 75' of LMR-400, which has an attenuation of 1.5db/100ft at 146MHz. There's a ridge west of my house that's around 50' above my property, so this pokes my antenna up above that. So it's good to know the theory but also your particular situation. In general, though, height is going to have diminishing returns while coax has accumulating losses. From tests I've seen online there seems to be some pretty big gains to be had by going up 20' - 30', but after that the improvement seems to drop off (the testing I saw was with the same length of coax, so it was just testing the height only, not the effect of height plus the longer length of coax you'd need to reach that height).
Thanks for the info, and glad you can get over that ridge!
I had D130 discone antenna, and F23H ( 5/8 wave x 3 ) similar characteristic to GP9 on 144MHz band. D130 antenna feed point height 24 FT, F23H base height was 16 FT. I always heard better on D130 at 24 FT. so I took down F23H. F23H was replaced with 1/4 wave antenna at 24 FT, which hear better. I guess height matter more than gain. AG6JU
Thanks for telling me about your station.
I wonder if Ham radio will get to the place that cellular is where the actual transmitter will be mast/tower mounted direct to the antenna, or with a very short jumper and a control cable that runs down to the shack. A fiber optic control cable would reduce the chance of lightning/ESD into the shack.
There's no technical barrier to doing this, but this path just hasn't been explored in ham radio.
With a Wifi-equipped radio (eg I have an IC-705) you could have that in a weather-proof box with any other needed equipment up at the top of your mast and have the antenna come straight out of the radio. With Icom's RS-BA1 software you could then control everything via the WiFi connection, including winlink, FT8, etc. from your computer in your home. Add a remote antenna switch for whatever antennas you're using plus a dummy load. You'd just need to run a power cable up there, making sure the voltage drop isn't too much. Or have solar panels and a battery up there and then there'd be no wires at all.
@@truhartwood3170 Indeed. You'd need a mast strong enough to hold that in heavy winds. Tower probably. I wonder if anyone has done that. Do you know of anyone?
@@davecasler I don't know of anyone, just answering off the top of my head! Definitely need a tower, yes, especially with any solar panels, though if they were horizontal that would theoretically not have too much wind resistance. Overall, the project would be more of a "can we make it work?" rather than being super useful or worth I would think. I can't think of a use-case off the top of my head that this would be good for as far as amateurs go. Maybe if you had a huge rural property where your house was in a bit of a valley or gully, but there was a peak on your property quite far from your house where you wanted your tower to be?
Many commercial wifi access points use a controller that contains all the smarts and the access point is just a rx/tx with an IP converter to send the data to the controller for processing. This would allow for a truely software defined radio that could run as either a simplex or duplex. This would both revolutionize the HAM market while almost overnight, destroying most of the radio manufacturers. The second is probably why no manufacturer is even looking at this.
Thanks. N0QFT