by G0DJA » Fri Jan 03, 2020 5:27 pm
Those multiband "White stick" antennas are a bit of a compromise. Ignore the claimed gain figures, they are often optimistic and are often quoted in meaningless units like "XdB gain", compared to what, a piece of wet string? When you dig deeper, you often find that they quote the gain over an isotropic radiator (in dBi) which is a theoretical radiator that transmits a signal over a uniform spherical pattern. That gives them 2.15dB more gain to claim than from something compared to a dipole (dBd).
Your mates 3 element Yagi will have a gain of about 7.5 dBd. Your white stick is throwing the RF in all directions and, on looking the specification up I see that they have, indeed, used dBi for their gain claims. So, your V2000 has a real world gain of about 4.05 dBd on 144MHz, if you believe the claims of the manufacturer. That's the same as your mate using a V2000 as well, but doubling his power output. (7.5dBd - 4.05dBd = 3.42dB and every 3dB extra is the same as doubling the power output).
I wouldn't trust a rigs "S-meter" reading either, they often don't keep to the "6dB per S point" standard and especially when the needle goes past the 'S9' reading. One manufacturer often sets their S-meter readings to a different value to another. The ARRL used to test new radios and the discrepancies where sometimes quite large.
Again, I assume your mate is using his Yagi in vertical polarization? If not, then you can take another 1dBd or so off your gain figure for the vertical, although there's some debate about whether this actually happens when signals are being reflected and bent by propagation effects.
At 1st I thought you were saying that your mate could hear you, but you couldn't hear him, but you mention a station on the Isle of White. If we are talking about your mate hearing the guy on the IoW and you can't then that just adds another level of complexity. How far away are you from each other? Propagation can be very good in one spot, I've heard of people working Spain on 144MHz FM using handhelds from Cornwall when people at home, a few miles away, hear nothing even though they have, technically, a better set up. It can be really frustrating to see DX Cluster spots from a neighbour, only a few miles away, working long distances but you can't hear a thing but, one day, the boot is on the other foot and you are working long distance stuff and your neighbour is hearing nothing this time. It gets 'worse' the higher you go in frequency. The guys near the coast, using 23cm and above, often hear and work DX that we poor people further inland don't hear due to sea paths. Then, another day, a good duct throws signals down in the middle of the country, going over the heads of the guys on the coast...
Those multiband "White stick" antennas are a bit of a compromise. Ignore the claimed gain figures, they are often optimistic and are often quoted in meaningless units like "XdB gain", compared to what, a piece of wet string? When you dig deeper, you often find that they quote the gain over an isotropic radiator (in dBi) which is a theoretical radiator that transmits a signal over a uniform spherical pattern. That gives them 2.15dB more gain to claim than from something compared to a dipole (dBd).
Your mates 3 element Yagi will have a gain of about 7.5 dBd. Your white stick is throwing the RF in all directions and, on looking the specification up I see that they have, indeed, used dBi for their gain claims. So, your V2000 has a real world gain of about 4.05 dBd on 144MHz, if you believe the claims of the manufacturer. That's the same as your mate using a V2000 as well, but doubling his power output. (7.5dBd - 4.05dBd = 3.42dB and every 3dB extra is the same as doubling the power output).
I wouldn't trust a rigs "S-meter" reading either, they often don't keep to the "6dB per S point" standard and especially when the needle goes past the 'S9' reading. One manufacturer often sets their S-meter readings to a different value to another. The ARRL used to test new radios and the discrepancies where sometimes quite large.
Again, I assume your mate is using his Yagi in vertical polarization? If not, then you can take another 1dBd or so off your gain figure for the vertical, although there's some debate about whether this actually happens when signals are being reflected and bent by propagation effects.
At 1st I thought you were saying that your mate could hear you, but you couldn't hear him, but you mention a station on the Isle of White. If we are talking about your mate hearing the guy on the IoW and you can't then that just adds another level of complexity. How far away are you from each other? Propagation can be very good in one spot, I've heard of people working Spain on 144MHz FM using handhelds from Cornwall when people at home, a few miles away, hear nothing even though they have, technically, a better set up. It can be really frustrating to see DX Cluster spots from a neighbour, only a few miles away, working long distances but you can't hear a thing but, one day, the boot is on the other foot and you are working long distance stuff and your neighbour is hearing nothing this time. It gets 'worse' the higher you go in frequency. The guys near the coast, using 23cm and above, often hear and work DX that we poor people further inland don't hear due to sea paths. Then, another day, a good duct throws signals down in the middle of the country, going over the heads of the guys on the coast...