Zero Five 11 meters

[222DBFL]

Feedpoint is the best spot!! I was just curious!! Continue on man. Hope you get it dialed in!!

 

[The DB]

I took it out of tune getting to impatient, but I did notice something really weird, I went ahead and transmitted on it with 40 watts, now a guy about 10 miles from me compared the Maco v5000 and the Zero5, on the Zero5 I hit with a 9s solid, then I switched to the v5000 and gave an 7s, the receive on my end didn't change as both was the same except maybe a little more static with the v5000 but not much...not sure how the transmit signals were night and day but maybe someone could explain

There are any number of things that could explain this.

First off, the big flaw in this test is the measuring equipment. A receiver's S meter could simply be that inaccurate, I've seen s-meters give different readings for the same signal from the same antenna on different key ups a few seconds apart from each other. Especially on the CB side of things, and even with most higher end CB radios, s-meters are inaccurate pieces of crap, plain and simple. They are also affected by other circuits in the radio, like an ALC circuit, which does nothing but make them even less reliable for said comparison tests, which is all they were really useful for anyway, and they don't even do that very well... The fact that your readings were very close and his were not is just more evidence of what I am talking about here.

If you are using an s-meter for things like this you really need multiple different reports from multiple different directions and multiple different distances. One contact simply does not tell you very much. The more you can get from as many different locations, the better... Further, you should trust what you see on the receive meter more than any reports from anyone else, just make sure you are not letting what you want to see, or expect to see, affect what you actually see.


The DB

 

[Marconi]

Yeah I contacted yesterday.He said he'll help me out.The antenna comes marked so all you do is put it together, but yeah no instructions on what you need to do to to get it fined tuned, 3 things you can tune on it. 1 the length of antenna 2 wire tap and 3 the capacitor..and I'm lost with what to tackle first

Good. you may have to change the tip length to re-tune for another band, but for the CB band I think the capacitor will tune it across the entire band.

The moves in making the capacitor/radiator shorter will probably be very small, less than the width of the mark provided...like I suggested earlier.

The tap point may be right where it belongs. Was it also marked?

1st id tackle the overall lenth if this is marked then shoul be fairly easy

Good point hotrod.

Are you taking these readings directly at the feed point of the antenna? Didn't see where or if that was posted anywhere? Or are you using a very short jumper, like 1ft or less?

I agree with 222.

yeah doing at the feedpoint, what jumper length is ok to use?

The shorter the better...you could even use a dual female connector to connect the analyzer directly to the antenna.

 

[bob85]

Thanks for sharing your measurements DB, so about 3 - 4.5pf or 1.3-2kohm in parallel with the coil,
That's much less than i get with the av190, i would imagine the BIG-MAC is similar to the MaCo.

 

[Marconi]

Thanks for sharing your measurements DB, so about 3 - 4.5pf or 1.3-2kohm in parallel with the coil,
That's much less than i get with the av190, i would imagine the BIG-MAC is similar to the MaCo.

Bob or DB, how do you make this measurement?

 

[The DB]

Bob or DB, how do you make this measure?

???

I didn't make a direct measurement, and didn't claim to have done so.

I took the diameter of the outer surface of the inside tube, calculated its circumference, then multiplied by the length of overlap to get the area I used. I then used the capacitance formula using my calculated area with the teflon dielectric and thickness (as well as for PVC) to calculate the numbers I posted. It will be a little off as the calculator assumes two flat sheets, which a curved tube won't have, but it will still be close, and if anything my numbers should be a little low as I calculated the area of the smaller of the tubes... I chose the conservative estimate due to the nature of the conversation that led up to me doing these calculations.

Everything needed to get my numbers (and for that matter the calculation that Bob has done as well) is available online, except the dimensions from the antenna itself, which I measured myself. The outside of the inner tube is 1 inch in diameter, and the length of overlap is four inches. I forget the diameter of the teflon insulation, think it was 1/8 of an inch (I rounded some here as the calculator I used wanted millimeters), and it has a dielectric constant of 2.1. If you want to calculate for PVC use the same figures except a dielectric constant of 3. Feel free to check my work.


The DB

 

[bob85]

Eddie,
I used my capacitance meter to measure the av190 between the bolts that fasten the hoop,
There will be some error as I did not remove the base section of the radiator,
I did remove the so239 & mounting tube and elevated the antenna a few feet off the ground.

 

[Marconi]

Bob or anybody, do you think this capacitor on the Z5 is adjustable? I see a hose clamp, but what moves if it is loosened?

I think maybe I was wrong earlier when I said it was adjustable, and adjusted the radiator length.

 

[bob85]

If he has not glued the tubes its adjustable just like a tube in tube style gamma match capacitor but doing a different job,

It won't alter the radiator length, it will adjust the capacitance in parallel with the hoop.

 

[314]

ok been about a week the weather has been good the last 2 days. I got it tuned about 1.1-1.2 swr up until about the high end of the band which is 1.4....I'm ok with that might need to adjust the length lower, but on the readings of the mfj 259...My R=70-80, and X=0 thru the whole band...like I said good SWR, I did notice that the wire tap connector is bulky as hell and think its not getting a good solid connection around the ring. so with those readings and SWR went ahead raised it fully up to 40ft, Didn't notice anything on the recieve end compared to a Macov5000, but my TX came up a little for everyone to notice..Just wondering why my resistance (R= ) is 70-80..If anyone can chime in, and would that sort of number hinder the performance

 

[314]

ok guys I think those readings on the Mfj259 are good, reading alot of info on how it works and seems I got it where it should be. I think one could read to much into these analyzers( Like Myself) and go completely nuts..

 

[Marconi]

314, I thought you had a better match earlier.

I don't believe you should expect the value of X=0 ohms to cover the entire CB bandwidth, if you took your readings at the feed point...even if you had a perfect match.

You might however see a very low SWR reading across some larger portion of the CB band...if you took your readings at the radio end of the feed line.

Good luck and keep us posted.

 

[314]

ok going back to the Maco v5000, wasted over $300 for this antenna, just cant get it tuned where it needs to be

 

[222DBFL]

What is the issue 314? Did you ever get the adjustments reset to the factory positions? Or were some things like the matching section area not marked?? Just curious man as I hate to see someone just throw away money. These antennas should work well given you take your time tuning it. Yes it won't be easy if you messed with things. But don't get discouraged as this is a good learning process. It was and still is for me!! Had similar issues with an antenna setup so this is why I am saying all this. Step back and reckeck all your measurements. From top to bottom. You should be able to get back where you were before. Tuned at 27.205. The Maco 5000 isn't going to be a put it together and put it up antenna either, it will take some tuning to get it right if that is what you choose. Not sure what you are after. But to get these type antennas right you have to take your time and it will take some time to get it right! But once done you'll be happy you did it!! Like I said, don't give up so soon. The antenna was obviously tuned at some point, so you should be able to replicate it. Just step back and take a breath and just take your time! Even if it takes you a couple of days!! Don't give up yet!! JMHO.

 

[bob85]

314, since you already have the antenna and it looks much better quality than the MaCo I would try again to tune it,

give this a go,

mount the antenna at a height that you can connect the analyser straight to the feedpoint or just with a few inches of coax, as high and far away from conductive things as is practical while still been able to read the analyser and adjust the antenna,

set the capacitor so the inner tube is level with the bottom of the Teflon insulator as seen in the pics on their website,
adjust the antenna length so that x is as close to zero on the centre of the frequencies you want to use it on, if you can't get x=0 tweak the capacitor a fraction,

if that works then adjust the tapping point so that r=50ohms or close to it,
x will probably move so tweak the cap and or length for x=0 again,

work back and forth until you get as close to r=50ohms x=0 as you can.,


r=70-80 is around 1.5:1 vswr if measured at the antenna, you say vswr is 1.2:1 so the antenna feedpoint is not r=70-80,

whenever the feedpoint does not match the characteristic impedance of your coax you will get transformation of the true feedpoint impedance depending on the electrical length of the coax @ the frequency you are measuring the antenna on,

common mode current can also cause issues skewing the feedpoint impedance, try a coax choke or balun at the feedpoint to minimise any possible common mode currents,

i have no idea how you are measuring x=0 over the whole band.