Predator 10k vs shaft length

[sp5it]

Hi. Before I will order one I would like to know.
What is advantage to have 27" shaft over 17"?

Antenna will be mounted on the roof of my car. i want best performance i can get.
So... which one to get? 22 or 17... or maybe different antenna?
I already have 1.8m bottom loaded antenna.
Mike

 

[todt061458]

IMHO their is no advantage. yes the antenna will be taller. but will hit low objects hanging over the road more often. it will be a pain to garage it or use public parking garages.I use a 17" shaft for my pickup truck and my Kenworth. on the pickup it can be too high on country roads. the trees reach out and rip it off my roof. good luck with your choice what ever height you choose. Great antenna. Have you thought about a base load antenna?like a wilson 5000 or a K40> just a thought.

 

[sp5it]

I already have good performing base load antenna. Want try something different.
Mike

 

[DXman]

Here is what I had to do.

I first started with the 10K on a 17" shaft. But the antenna was not performing good, even the readings on the MFJ 259b were not good.
So I contacted the builder and he suggested that I go with the 22" shaft. So after installing the 22" and checking with the 259 again, the readings were great. It was now preforming lots better, was able to talk 25 miles fairly easy with just 25 watts.

With 275 watts I have been able to work lots of European countries on 11 meters, Netherlands, France, Norway, Sweden, Denmark, Italy, Spain etc. Also; Russia, Japan, Taiwan, Micronesia, Indonesia, North Cook Islands, etc etc. One thing to note - I have used just 25 watts and worked many of the European stations also.

I had mine mounted in the center of the roof on the Ford F-150.

 

[MrSuburban]

Here is what I had to do.

I first started with the 10K on a 17" shaft. But the antenna was not performing good, even the readings on the MFJ 259b were not good.
So I contacted the builder and he suggested that I go with the 22" shaft. So after installing the 22" and checking with the 259 again, the readings were great. It was now preforming lots better, was able to talk 25 miles fairly easy with just 25 watts.

With 275 watts I have been able to work lots of European countries on 11 meters, Netherlands, France, Norway, Sweden, Denmark, Italy, Spain etc. Also; Russia, Japan, Taiwan, Micronesia, Indonesia, North Cook Islands, etc etc. One thing to note - I have used just 25 watts and worked many of the European stations also.

I had mine mounted in the center of the roof on the Ford F-150.

What frequency are you making all these contacts on? I have been on air since 1976 havent heard that many countrys in total in 35 years.

 

[sp5it]

27555 probably

 

[BOOTY MONSTER]

http://www.worldwidedx.com/predator-10k-antennas/26388-biggest-best.html

 

[AudioShockwav]

What frequency are you making all these contacts on? I have been on air since 1976 havent heard that many countrys in total in 35 years.

385/395/555, I have had QSO`s with Larry Hundreds of times, and he was always running up at the top of the contact list when we used to do the DX contest`s.....That Man got Skill`s when it comes to working that RCI technology, on the flat side of his beam.

He was the first half of the West Coast Tag Team.

73
Jeff

 

[W5LZ]

Bottom shaft length, plus the top whip's length, plus the inductive reactance furnished by the coil equals resonance. Shorten that bottom part and you have to lengthen the top part if the coil stays the same. Lengthen the bottom part and you have to shorten the top part if the coil stays the same. Both will result in resonance, which is the whole point of it. That's the "X" part being zero on that analyzer reading (or as close to zero as you can get it). That does NOT mean that the "R" part will end up 50 ohms. The important part is the resonance, the "X" = 0.

This part applies to all antenna, not just the "Predator 10k", or just mobile antennas in general. It applies to using an antenna analyzer.
If the "R" = 50, and the "X" = 0, you have resonance and an SWR of 1:1, and that's as good as it get's. Those "R"s and "X"s combined equal the input impedance seen by an SWR meter. There are a lot of combinations of "R"s and "X"s that can make an SWR meter think it sees a 1:1 when the "X" does not equal zero, which means there is no resonance. (The "R" can be almost anything.)
All impedances are composed of "R"s and "X"s. How well an antenna works depends on resonance. So, if that "X" isn't zero or very close to it, the antenna isn't going to work as well as it should/could. If that "X" isn't zero then the antenna will not radiate all of the power getting to it, some of that power isn't radiated, which means a weaker signal. May not be 'much' weaker, but it's still weaker.
An SWR meter can't tell anything about resonance, it wouldn't know an "X" is it bit it, it can only read the -combination- of "R" and "X".
- 'Doc

 

[sp5it]

Thanks BM for the link.
Thanks Doc for explanation. I have VNA, so any measurment can be done here.
Center loaded antenna is performing better, than bottom loaded. How high should be the coil over the roof to get this?
Mike

 

[W5LZ]

The idea would be to get the roof out of the coils field. That would mean you will have to compromise a bit, there will be some interaction no matter what you do. So, as far above/away from that roof/metal as is practical. How much is that? How would I know, your the one doing the mounting and will have to live with it.
As for the bottom, center, or top loading, yes it will make some difference. That 'difference' is not going to be very much, not 'daylight' and 'dark'. A base loaded antenna is a hell'ov'a lot easier to live with than a top loaded one, the center loaded one is just a compromise between the other two. That's just being practical, and why you don't see many top loaded antennas.
- 'Doc

 

[DXman]

What frequency are you making all these contacts on? I have been on air since 1976 havent heard that many countrys in total in 35 years.

How about the good old 11 meter band.......

As far as not hearing that many country's in 35 yrs, then all I can say would be - get a better antenna and you will hear them!

Audioshockwav and I have always been competing against each other in them past CDX contest....it was fun wasn't it Jeff.

 

[BOOTY MONSTER]

what's your antenna setup for 27MHz. MrSuburban ?

 

[MrSuburban]

How about the good old 11 meter band.......

As far as not hearing that many country's in 35 yrs, then all I can say would be - get a better antenna and you will hear them!

Audioshockwav and I have always been competing against each other in them past CDX contest....it was fun wasn't it Jeff.

I dont go up on the freeband, and i dont consider that the 11 meter band actually so I would assume I am missing who ever talks there, but I have access to and can go from 1.8 Mhz to 30 Mhz on HF. I have had beams and omni's and wire antennas, I have friends with 7 ele beams 80' in the air with low loss hardline. What amazes me is your doing this while the sunspot cycle is at a low.

 

[MrSuburban]

what's your antenna setup for 27MHz. MrSuburban ?

Depends on the day of the week or year

right now .... a vector, 1/4 wave gp, dipole, 2 element flat side