Son of a Gunn

[Robb]

I suggest that you both familiarize yourselves with the regulations regarding antennas. Several years ago a law was passed that prevented omnidirectional CB antennas from being made of metal. There are only allowed to be made of a non-conductive material like fiberglass. It seems someone thought too many CB'ers were killing themselves by contacting power lines while erecting their antennas. The Jo Gunn antenna in this thread is made of aluminum therefore is not allowed to be erected for CB purposes. I know, stupid law but nevertheless that is the reason why it is stated as not for use on 11m. BTW lets not get into a CBer versus ham stupidy thread regarding antenna erection. The government passed the stupid law and had nothing to do with hams. Just thought I would drop that little note as this has been brought up several times before and almost always evolved into a "hams are smarter than CB'ers so they are still allowed metal antennas" thread. We do not want that to happen.

2004 CFR Title 16, Volume 2

Sooo . . . the Maco V-58 (all aluminum) CB antenna is OUTLAWED!?!?
What will they think of next!

Hey Booty - yer an O U T L A W !

I appreciate the tip. Just had to add some sarcasm about the 'politics' because that was obviously the reason for it anyway.

 

[AudioShockwav]

not intended for 11meter use

X2 What Eddie Said, I think that is the reason as well.

73
Jeff

 

[bob85]

the tabular currents are no good to me eddie, i don't understand them, i use EZBOB,
i don't think the hoop is needed if the radials are set at the right length,

the pattern looks much better with the extended radials,

does your model show that altering the radial length alters the phase relationship between upper 1/2wave and lower 1/4wave sleeve effecting radiation angle?.

 

[Captain Kilowatt]

Sooo . . . the Maco V-58 (all aluminum) CB antenna is OUTLAWED!?!?
What will they think of next!

Hey Booty - yer an O U T L A W !

I appreciate the tip. Just had to add some sarcasm about the 'politics' because that was obviously the reason for it anyway.

I guess you missed the part where I said hams had nothing to do with the law being written or passed.

I do have to ask what was so obvious to you that this was not the case. Maybe it was just a personal uninformed opinion instead?

On second thought, don't answer that. It may lead to that other part in my post that I said we didn't want to happen.

 

[Marconi]

X2 What Eddie Said, I think that is the reason as well.

73
Jeff

That's right Jeff, my momma read me the wisdom of the Good Lord's word first, in order to secure my salvation, and then she read to me the tales of Uncle Remus, so I'd knows' the difference.

 

[Mudfoot]

I always knew...

The reason for encapsulating antennas in fiberglass, but didn't recall the guvment made it a law.

It is a good thing as it does help some.

I was first certified as a Paramedic in 1978 and retired a few years ago after 30 years. Eight of them years were military as a secondary MOS/AFSC. I have encountered several poor souls being killed installing antennas. One kid lifted his magnet mount up off his truck and touched his service drop. The last was in 1997 while a father and son were putting up an Antron that fell on the service drop. The son was locked on and the dad was fried trying to pull his son away. It was a sad day, but the fiberglass did not help one bit cause it had been raining earlier and was all wet. Depends on weather, humidity and near field currents that can stray and jump.

Have also seen where utility workers were zapped by high voltage lines that were a foot or less away without touching. I am always on the look out for lines and stay as far away as I can. High voltage lines just freak me out and make me sweat.

Anyways, The instructions on the Jo Gunn is the only CB antenna I recall having that warning printed.

These dudes were all CB'ers...The only HAM I recall running on was a fat dude that fell off his tower with no safety gear. Fell about 40' and busted both clavicles and his sternum. The dude still climbs, but owns a decent harness.

 

[Marconi]

the tabular currents are no good to me eddie, i don't understand them, i use EZBOB,
i don't think the hoop is needed if the radials are set at the right length,

the pattern looks much better with the extended radials,

does your model show that altering the radial length alters the phase relationship between upper 1/2wave and lower 1/4wave sleeve effecting radiation angle?.

Yes the extended radials did fix the phase issue. The full radiator length for the S4 is now in phase with the bottom radiator, the radials, and the top of the mast. No cancellation noted on the Sigma4, but the angle is about 10* degrees and that was set by the diameter for the hoop, not by me.

When I modeled this part of the antenna, I had to set the hoop first, to the spec's diameter. Then I extend the radials between the base bracket I built and out to the proper segment junction on the hoop. It is not an easy process or I would fix the S4 model to show the radials at 30* degrees...like you suggested and see what happens.

Thus, you're right, the S4 model appears to work about the same without the hoop, but you have to extend the radials. The radial angle looks to work out to 8.8888' feet to bring the model back to a similar pattern for the hoop model, and this task was just trial and error tweaking. I wish I could model the gamma match, and then maybe I could really check this all out by comparing match and resonance.

The no hoop model does show 4.38 vs. 4.61 gain for the S4 with a hoop, so I can only guess there is a little less current flowing in the radiator for the no hoop model, but the phase for each is very close to the same.

I don't think Jgar will likely be successful with such a modification unless he does some serious fabricating to the radials if he were to go up in angle. I don't think 30 degrees above the horizon will get it.

Added note: I did go back and compare the currents and the "no hoop" model has slightly less current in all parts of the radiator, and more in the radials and mast.

 

[bob85]

in my experience the trick in making these work is getting sleeve and monopole lengths optimised, hundreds of settings tune ok but some work better than others,

you could have less current due to the different detuning effect of the two radial setups moving resonant frequency, antenna mode current in the monopole is highest @3/4wave and lowest @1/2wave,
you could try changing the monopole length a little to see if you can increase current.

 

[Mudfoot]

I think I'd rather romance a fat girl than try to tune one of these antennas.

 

[W5LZ]

Hey, what's wrong with fat girls? They seem to be more appreciative, you know?

 

[Marconi]

in my experience the trick in making these work is getting sleeve and monopole lengths optimised, hundreds of settings tune ok but some work better than others,

you could have less current due to the different detuning effect of the two radial setups moving resonant frequency, antenna mode current in the monopole is highest @3/4wave and lowest @1/2wave,
you could try changing the monopole length a little to see if you can increase current.

Well Bob, the model did not work as you suggested. I think I found this before. My S4 model is set at 28.7' feet and that was where I stopped, but I don't remember why I stopped there. I do remember you suggesting I go longer before, and again I noticed the same thing then as now...the gain went down a bit when I went longer than 28.7' feet, so maybe that is why I stopped there.

I went the other way, down to 26.4' feet for radiator length and the gain improved. I did not change the segment counts for the wires involved as I made them longer and shorter, so I saw the current in the radiator increases, which might be expected. However the currents in the radials, and mast decreased without changes to their lengths and I would consider that good. BTW, the pattern started getting a high angle lobe as I went shorter. So, even while the gain shows some improvement the pattern is not. If I tweaked the segment count as I made such changes, the model may not show the same however. That is just too much to try and keep up with. Boy, I don't know how in the world you could have determined this without testing using very fine detail. I could never see such changes using real world adjustments and using my radio. EzBob is a real optimizing wizard worker to detect such small changes. I changed the antenna length 1" at a time, up to a point, then I started moving the radiator shorter 5" at a time near the end.

If an inch makes this much difference while adjusting the radiator length, then imagine how small adjustment might have to be adjusting a gamma match. But I've said this before.

Here are my notes if you can read them on these post-its.

The three columns to the right are for:

Radiator tip height in inches
Gain
Angle

View attachment Notes making S4 longer and shorter..pdf

 

[bob85]

going longer worked for me with the gamma fed setup close to ground,
antenna mode current in the monopole will drop either side of 3/4wave for direct fed setups like your model,
with the gamma you are not tied to 3/4wave,

im reasonably happy with ezbob, its free, much simpler than nec and more accurate than precision guesswork

we don't have any problem seeing changes in signal between antennas or installs when conditions are stable.