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Homemade Sigma 4 11 meter base antenna

Sirio's recommendations for antenna mounting

I just got a email reply from Sirio about whether to electrically isolate the Vector 4000 from it's mounting support or not. Here's their reply.
"From the electrical point of view, there is no difference. You can use a metal mast and avoid mechanical problems..".
 
Last edited:
Lil'Yeshua said:
I just got a email reply from Sirio about whether to electrically isolate the Vector 4000 from it's mounting support or not. Here's their reply.
"From the electrical point of view, there is no difference. You can use a metal mast and avoid mechanical problems..".
Click to expand...

That is the brief answer to the question and the result is the same. Mount it directly to the mast. I had the opportunity to elaborate with one of Sirio's engineers regarding the Vector, CST model, and CMC on the mast. Since the radials of this antenna are connected to the same point as the mast and the radials are in phase with the radiation currents, and currents on the mast will also be in phase along the first 1/2 wavelength of mast.

The engineer concluded by saying the currents on the mast would be less than what is on the cone but never the less, the phase was desirable and contributed to gain. This is not the case with many other end fed antennas. Isolating the Sigma from the mast will not improve performance while you may not see the small loss in gain.
 
Shockwave said:
That is the brief answer to the question and the result is the same. Mount it directly to the mast. I had the opportunity to elaborate with one of Sirio's engineers regarding the Vector, CST model, and CMC on the mast. Since the radials of this antenna are connected to the same point as the mast and the radials are in phase with the radiation currents, and currents on the mast will also be in phase along the first 1/2 wavelength of mast.

The engineer concluded by saying the currents on the mast would be less than what is on the cone but never the less, the phase was desirable and contributed to gain. This is not the case with many other end fed antennas. Isolating the Sigma from the mast will not improve performance while you may not see the small loss in gain.
Click to expand...

Thanks. That's what I had concluded
 
Shockwave said:
That is the brief answer to the question and the result is the same. Mount it directly to the mast. I had the opportunity to elaborate with one of Sirio's engineers regarding the Vector, CST model, and CMC on the mast. Since the radials of this antenna are connected to the same point as the mast and the radials are in phase with the radiation currents, and currents on the mast will also be in phase along the first 1/2 wavelength of mast.

The engineer concluded by saying the currents on the mast would be less than what is on the cone but never the less, the phase was desirable and contributed to gain. This is not the case with many other end fed antennas. Isolating the Sigma from the mast will not improve performance while you may not see the small loss in gain.
Click to expand...

so on a short 18-20 ft of mast a .82 vector actually has almost 50 ft of in phase radiation ?
 
BOOTY MONSTER said:
so on a short 18-20 ft of mast a .82 vector actually has almost 50 ft of in phase radiation ?
Click to expand...

Well, in theory this is true but it's important to realize the current on the mast will be very small. Almost as small as the J-Pole camp thinks the currents on the cone are. Especially if the antenna is tuned properly since the majority of this energy will be radiated from the tuned cone.

We shouldn't think of the mast as having the ability to add another 1/2 wave of effective radiation as much as we should feel confident that adding a mast will not deteriorate the performance as W8JI has suggested. This is because what the mast adds is much less than the cone. That can actually be seen in the CST model since it does contain about a foot of mast.
 
Shockwave said:
Well, in theory this is true but it's important to realize the current on the mast will be very small. Almost as small as the J-Pole camp thinks the currents on the cone are. Especially if the antenna is tuned properly since the majority of this energy will be radiated from the tuned cone.

We shouldn't think of the mast as having the ability to add another 1/2 wave of effective radiation as much as we should feel confident that adding a mast will not deteriorate the performance as W8JI has suggested. This is because what the mast adds is much less than the cone. That can actually be seen in the CST model since it does contain about a foot of mast.
Click to expand...

thanks .

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can you link to where that info came from Lil'Yeshua ? i like the E1/2WL idea myself . even though it doesn't change anything TX or RX wise .
 

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