Sirio 5000...two questions

[The DB]

if you want to replace the original coax, why not use a halfwave multiple like sirio do, ever wonder why they give you exactly 3.6m on an mag145pl?

if it didn't do anything why would a company like sirio go to the bother of exact cutting and not just stick random lengths on?

Not arguing against your statement on the 18 foot myth, however, I seem to remember someone on this forum emailing Sirio and getting a response that they use the length that they think it takes to get form the antenna to the radio... Although it may have been some other company...

I'll have to look for the post it I guess...


The DB

Here is at least one of the posts in question...
link

 

[Lil'Yeshua]

Email from Sirio

"Good morning

Thank to choose our product

The 4m is a length it was choosed only for to have lenght for the connection at the transceiver and not for the necessity of a specific fraction of wave length. In fact if the magnetic mount has a correct surface, is the roof to work as ground plane and not the cable

Best regards

D'Aleo Mercurio / Electronic engineer
SIRIO Antenne Srl
via Liguria 15
46049 Volta Mantovana, MN - ITALY

Ph. +39-0376-801515; Fax +39-0376-801254
m.daleo@sirioantenne.it
Sirio Antenne - High Performance Antenna

----- Original Message ----- From: "Stefania Grazioli" <info@sirioantenne.it>
To: "Xxxxxxxxxxxxxxxxxxxxxxxxxxx"
Sent: Saturday, March 16, 2013 3:25 AM
Subject: Re: Performer pl5000 & 145 mag mount


Dear Sir
Our technical people will answer you back on Monday
Regards
Sirio antenne"

"Il giorno 15/mar/2013, alle ore 18:09, xxxxxxxxxxxxxxcccx
<xxxxxxxxxxxxxxxxxxxx> ha scritto:

Hello
I purchased a Sirio PL5000 antenna and the Sirio 145 mag mount. I was
thinking about changing the coax cable for a rg8x type cable. Is there any
reason why the coax on my mag mount is 4 meters? Is that the half
wavelength of the rg58u coax that is presently installed in it? Thanks for
any help you can give me"

 

[Robb]

Not arguing against your statement on the 18 foot myth, however, I seem to remember someone on this forum emailing Sirio and getting a response that they use the length that they think it takes to get form the antenna to the radio... Although it may have been some other company...

I'll have to look for the post it I guess...


The DB

Here is at least one of the posts in question...
link

One needs to first understand why the 18ft myth started. It is obvious to most that the perception that 1/2 wavelength of 11m (~36ft) is of course 18ft. But their misconception is that the velocity factor of the coax isn't brought into the calculation, as Jazzy George brought up.

If they can see that different kinds of coax have different velocity factors, and then use that factor as a multiplier, they can see that it is often shorter than the measured length of a piece of coax.

Velocity Factor in Cables

In theory, electrical signals move at the speed of light. Cables only slow them down. The ratio of actual speed to the speed of light is known as the velocity factor, or Velocity of Propagation (VOP), expressed as a percentage of the speed of light in free space.

This slowing effect is almost entirely caused by the dielectric material; in coaxial cables, the insulation between the shield and the center conductor. For a closed-cell foam dielectric, for example, the VOP may approach 90%, meaning that a signal will travel at 90% of the speed of light. For solid Teflon®, the VOP is typically about 70%.

(These figures can differ according to specific formulation of the material. They are also subject to variation depending on the construction of the cable.)

What effect does the VOP have? After all, 70% of the speed of light is still pretty fast! Fact is, in some avionic and other electronic applications, speed and delay are critical factors and need to be measured with precision.

The delay from one end of a cable to the other is inversely proportional to the VOP: the lower the VOP %, the longer the delay.

This can be important in relative signal timing, for navigation systems, for example. Delay is independent of frequency. In effect, it is the defining factor of the electrical length of a wire or cable.

Cable Velocity Factor | Velocity of Propagation | Coaxial Cable

 

[222DBFL]

I thought that 17ft 4in was the right length for rg8x, but have been told as well that cable length is what is needed to reach point a to point b, in mobile setup. Please correct me if I am wrong as I am asking here. You see so many different things on the good old internet lol.

 

[Mudfoot]

Point A to point B is correct.

 

[W5LZ]

I think it would be fairly safe to take Mr. Mercurio's explanation. The coax isn't used for any sort of timing/phasing or impedance matching, it's just to get the signal to the antenna. One possibility about that 4 meter length, or 17' 4" length is that European cars are shorter than in the USA? Or that a meter stick happens to be what they were measuring the feed line's length with?
Using the length that reaches comfortably from here to there is the correct length for almost all installations. The exceptions to that don't apply here.
- 'Doc

 

[The DB]

"Good morning

Thank to choose our product

The 4m is a length it was choosed only for to have lenght for the connection at the transceiver and not for the necessity of a specific fraction of wave length. In fact if the magnetic mount has a correct surface, is the roof to work as ground plane and not the cable

Best regards

D'Aleo Mercurio / Electronic engineer
SIRIO Antenne Srl
via Liguria 15
46049 Volta Mantovana, MN - ITALY

Ph. +39-0376-801515; Fax +39-0376-801254
m.daleo@sirioantenne.it
Sirio Antenne - High Performance Antenna

----- Original Message ----- From: "Stefania Grazioli" <info@sirioantenne.it>
To: "Xxxxxxxxxxxxxxxxxxxxxxxxxxx"
Sent: Saturday, March 16, 2013 3:25 AM
Subject: Re: Performer pl5000 & 145 mag mount


Dear Sir
Our technical people will answer you back on Monday
Regards
Sirio antenne"

"Il giorno 15/mar/2013, alle ore 18:09, xxxxxxxxxxxxxxcccx
<xxxxxxxxxxxxxxxxxxxx> ha scritto:

Hello
I purchased a Sirio PL5000 antenna and the Sirio 145 mag mount. I was
thinking about changing the coax cable for a rg8x type cable. Is there any
reason why the coax on my mag mount is 4 meters? Is that the half
wavelength of the rg58u coax that is presently installed in it? Thanks for
any help you can give me"

This is what I was looking for, was looking for the original post it was in but this works to...


The DB

 

[The DB]

I thought that 17ft 4in was the right length for rg8x, but have been told as well that cable length is what is needed to reach point a to point b, in mobile setup. Please correct me if I am wrong as I am asking here. You see so many different things on the good old internet lol.

Half wavelengths accounting for common coax velocity factors for 27.185 MHz...

.66 velocity factor is a hair under 12 feet
.85 velocity factor is about 15 feet 3 inches

These lines account for the lower and upper ends of the coax velocity factor scale... If you use some 450 ohm windowline (not the old 300 ohm tv twinlead stuff) you can get in the range of 17 feet 2 inches, however, that type of feedline, while useful in its own right, is rarely if ever used for CB operation, especially by those that perpetuate the 18 foot myth... If your a real stickler you can custom make some open wire feedline that has even higher velocity factors, in the range of .97 and higher.

However all of this information is useless to you unless you are either phasing antennas, using a quarter wavelength feedline transformer of another impedance, or you have a tool more advanced than an SWR meter...

If you want to confuse those who perpetuate this myth even more mention to them that the 1/2 wavelength of the standing wave on the coax is 1/4 electrical wavelengths long, just to get their reaction...


The DB

Edited for accuracy.

 

[Lil'Yeshua]

You got it. I may have mentioned it more than one time in different posts. I kept Sirio's email reply for future reference. At the time I was wondering if Sirio made the 145's coax length one quarter wavelength long taking into account for it's velocity factor. I wanted to know that in case if I changed the coax out for different one.

 

[Lil'Yeshua]

Everybody around my neck of the woods still measure their coax either by 9 or 18 feet. Be ready to educate someone who's willing to leave tradition behind for the truth.

 

[M0GVZ]

But their misconception is that the velocity factor of the coax isn't brought into the calculation, as Jazzy George brought up.

Please don't listen to that blithering idiot. He only regurgitates the bullshit he's read elsewhere.

 

[jazzsinger]

Not arguing against your statement on the 18 foot myth, however, I seem to remember someone on this forum emailing Sirio and getting a response that they use the length that they think it takes to get form the antenna to the radio... Although it may have been some other company...

I'll have to look for the post it I guess...


The DB

Here is at least one of the posts in question...
link

I Think if you look in the sirio catalogue dv leads etc are 4m, but the ml145pl is deffo 3.6m, i've repaired enough of them, also straight out the box as the factory couldn't even put them on the correct screw thread and people were coming to me with 3:1 swr's they couldn't budge, once i tested with an avo meter i noticed the only thread with continuity wasn't the one thats normally a different shape to the rest which the shield had been connected too, as soon as i put the shield contact on the one with continuity rectified the swr issues, i've had 3 out the box in glasgow to do, possibly a faulty batch.Same fix sorted them all,

others i've had the centre pin coax inner fall right off with factory soldering, the solution for that was to file the inner pin and tin pin and coax before soldering, I can only say what i see

the sirio catalogues make a lot of claims about dbi gain on mobiles, they have some very clever design engineers but i fear their workforce ain't as clever.

 

[Robb]

Please don't listen to that blithering idiot. He only regurgitates the bullshit he's read elsewhere.

George was right about bringing up the Velocity Factor.

 

[jazzsinger]

Everybody around my neck of the woods still measure their coax either by 9 or 18 feet. Be ready to educate someone who's willing to leave tradition behind for the truth.

The truth can be a bitter pill to swallow, but an open mind is the key to finding it

 

[jazzsinger]

Please don't listen to that blithering idiot. He only regurgitates the bullshit he's read elsewhere.

excellent, you stalking me, or just want to hang about with me in the hope i drop some knowledge and you can source an enigma machine to decipher it for you?