.64λ Homebrew

[HomerBB]

I worked on this thing some more today trying to prove to myself it could be done.
Here is what I did and the results.

First using this coil:

2.0 R= 28 X= 21 --------- 28.713
1.5 R= 56 X= 21 --------- 28.108
1.2 R= 61 X= 7 ----------- 27.804 (lowest)
1.2 R= 53 X= 9 ----------- T5
1.2 R= 50 X= 11 ---------- 27.405
1.3 R= 52 X= 14 ---------- 27.185
1.5 R= 61 X= 22 ---------- 26.869
2.0 R= 110 X= 0 ---------- 26.244


Second using this coil:

2.0 R= 28 X= 20 ---------- 28.769
1.5 R= 53 X= 23 ---------- 23.243
1.1 R= 51 X= 5 ---------- 27.706 (lowest)
1.1 R= 52 X= 8 ---------- T5
1.2 R= 49 X= 10 ---------- 27.405
1.3 R= 51 X= 14 ---------- 27.185
1.5 R= 59 X= 22 ---------- 26.884
2.0 R= 110 X= 0 ---------- 26.249


Third using second coil and adding 10" to length to compensate for the portion of the vertical beneath the radials:

2.0 R= 27 X= 19 ---------- 28.814
1.5 R= 51 X= 23 ---------- 28.293
1.1 R= 60 X= 0 ---------- 27.754 (lowest)
1.1 R= 51 X= 6 ---------- T5
1.2 R= 48 X= 9 ---------- 27.405
1.3 R= 50 X= 13 ---------- 27.185
1.5 R= 59 X= 21 ---------- 26.859
2.0 R= 108 X= 0 ---------- 26.225


AT THE SHACK END OF THE FEEDLINE:

 

[Marconi]

I worked on this thing some more today trying to prove to myself it could be done.
Here is what I did and the results.

First using this coil:



2.0 R= 28 X= 21 --------- 28.713
1.5 R= 56 X= 21 --------- 28.108
1.2 R= 61 X= 7 ----------- 27.804 (lowest)
1.2 R= 53 X= 9 ----------- T5
1.2 R= 50 X= 11 ---------- 27.405
1.3 R= 52 X= 14 ---------- 27.185
1.5 R= 61 X= 22 ---------- 26.869
2.0 R= 110 X= 0 ---------- 26.244


Second using this coil:



2.0 R= 28 X= 20 ---------- 28.769
1.5 R= 53 X= 23 ---------- 23.243
1.1 R= 51 X= 5 ---------- 27.706 (lowest)
1.1 R= 52 X= 8 ---------- T5
1.2 R= 49 X= 10 ---------- 27.405
1.3 R= 51 X= 14 ---------- 27.185
1.5 R= 59 X= 22 ---------- 26.884
2.0 R= 110 X= 0 ---------- 26.249


Third using second coil and adding 10" to length to compensate for the portion of the vertical beneath the radials:



2.0 R= 27 X= 19 ---------- 28.814
1.5 R= 51 X= 23 ---------- 28.293
1.1 R= 60 X= 0 ---------- 27.754 (lowest)
1.1 R= 51 X= 6 ---------- T5
1.2 R= 48 X= 9 ---------- 27.405
1.3 R= 50 X= 13 ---------- 27.185
1.5 R= 59 X= 21 ---------- 26.859
2.0 R= 108 X= 0 ---------- 26.225


AT THE SHACK END OF THE FEEDLINE:

Homer are the results noted above: "AT THE SHACK END OF THE FEEDLINE," using your 1/2 wave x 6 working feed line and a report from the antenna with the #3 coil?

What does T5 designate?

 

[HomerBB]

Only the blue box is at the shack.
T5 = 27.555
BTW, these readings are in the main mode.
Additionally, in the last two readings i had compressed the spacing together more on the bigger coil.

 

[Marconi]

Homer are the results noted above: "AT THE SHACK END OF THE FEEDLINE," using your 1/2 wave x 6 working feed line and a report from the antenna with the #3 coil?

What does T5 designate?

Only the blue box is at the shack.
T5 = 27.555
BTW, these readings are in the main mode.
Additionally, in the last two readings i had compressed the spacing together more on the bigger coil.

Regarding your last comment, is it your opinion then that compressing the big coil makes the resonance go higher and thus the antenna is shorter?

My question was, did you use your electrical 1/2 wave x6 as the feed line when testing antenna #3?

T5 = 27.555, so what is the reason for writing it that way? Is that another feature I need to try and understand regarding the use of the 259B?

 

[HomerBB]

I used the 1/4 x 6 on those above the blue box. The blue box is using an additional 89' of coax to get onto the shack.

I don't know what effect compressing the coils closer had. I also lengthened the antenna physically at that time. I thought the portion of the vertical beneath the radials in the mounting bracket area may not have been in play due to decoupling by the radials, so I tried to compensate. I have aways kept the vertical entirely above the radial systems on my GP antennas.
Maybe someone has a thought on this?

 

[W5LZ]

Compressing those coils increases the inductance of the coil. Lengthening the antenna also increases the inductance (inductive reactance) of the antenna. Depending on just where those coils were compressed (in relation to the 'tap' on that coil) you effectively increased the length of the antenna more than just the change in physical length.
(The coil above the tap is a loading coil, making it bigger means lengthening the antenna (increasing the load). If that 'compression' happens 'below' that tap, the the matching coil is changed. No telling how that would affect things. Also no telling how 'proportional' that compression was, so you have tp figure that by how the antenna reacts to it.)
- 'Doc

 

[HomerBB]

Thanks, Doc.
Trying to build an antenna with an analyzer is new territory for me, and things taken for granted using only a SWR meter don't add up with this tool. After all my SWR meter likes the antenna no matter what . . .

I wonder if I can trade the 259B in for a guitar . . . I can't play it either.

 

[AudioShockwav]

I also tried the analyzer directly into the antenna with no feedline, but that did not work. I think it was too close to the radiating antenna.

Question:
I do not know if you still have the choke wound below the feed point,( looking at old pictures) so did you just try using a double connector to put the MFJ right on the PL 259 and bypass the choke?
When you say it would not work, can you tell us how/what did not work?
I am just asking out of curiosity.
A very short jumper 4/6 inches should make very little difference in you readings.

Man I wish it was easy to have my antenna up at height and still have easy access to the feed point.

Thanks for doing all the work, and sharing the results with everyone here.

73
Jeff

 

[Marconi]

I used the 1/4 x 6 on those above the blue box. The blue box is using an additional 89' of coax to get onto the shack.

I don't know what effect compressing the coils closer had. I also lengthened the antenna physically at that time. I thought the portion of the vertical beneath the radials in the mounting bracket area may not have been in play due to decoupling by the radials, so I tried to compensate. I have aways kept the vertical entirely above the radial systems on my GP antennas.
Maybe someone has a thought on this?

Well I figured you were probably using your 1/4 wave electrical jumper to test the antennas above the blue box, I guess I was wrong again.

So, you used two 89' foot feed lines to get to the shack, and a similar single length of 89' feet of coax to test the other antennas above, right?

Based on my thinking to you a while back...that the length of feed line connected to a reactive load will produce variable results on an SWR meter, and your analyzer as well...relative to their location on the line, so I ask my questions.

You indicated earlier, as I understood you to say, that when you tested you used a signal 1/4 wave length electrical jumper vs. that same jumper length x 6 multiples, and that you saw exactly the same analyzer results from both lengths. If I'm right, I would argue that could only happen if the load and frequency were considered purely resistive, with no reactance, and the system was showing 1.00:1 SWR, using such a 1/2 wave electrical feed line jumper at the specific frequency cut. Since your antenna is close to on the money, your results are also close also, but I think I still see a difference that should be noted. If, for example, your antenna was off further than noted here, then you would likely see more difference. That is my only point to consider.

This is why I suggest careful consideration when using any length of feed line attached between your analyzer with a load of unknown values for R,X,SWR, and for sure when using a very long feed line, relative to the wavelength. If so, this is to say one can expect the results to be somewhat less revealing and variable...unless a true resistive match is present and very low SWR is present at the feed point.

I contend, that otherwise your results can be variable and misleading, even when using what is considered to be a 1/2 wavelength electrical jumper for a specific frequency.

Homer, this is not to be critical of your results, I think you are remarkably close for a home made antenna. This is just for consideration only.

 

[BOOTY MONSTER]

just wanted to thank homer and everyone contributing to this thread .
lots to think about .

 

[Marconi]

Question:
I do not know if you still have the choke wound below the feed point,( looking at old pictures) so did you just try using a double connector to put the MFJ right on the PL 259 and bypass the choke?
When you say it would not work, can you tell us how/what did not work?
I am just asking out of curiosity.
A very short jumper 4/6 inches should make very little difference in you readings.

Man I wish it was easy to have my antenna up at height and still have easy access to the feed point.

Thanks for doing all the work, and sharing the results with everyone here.

73
Jeff

Jeff that is what I do when testing at the feed point. Homer said his meter would not work when hooked directly to his feed point, but that is not my experience either.

These meters put out very little RF, so I doubt RF is the issue that caused Homer's meter not to work. However, on the other hand, your body or hands can sometimes produce enough interference or create enough capacitance in the antenna, and that for sure might ill-affect the meter's operation.

A while back I made a video testing the frequency of my meter against my new Galaxy 2547, and when my meter was on the frequency that the radio was set at, and I touched the back of the meter, the frequency squeal of being on frequency changed, so I know my meter could be affected in some ways by my own body. Maybe that is what Homer noticed.

Marconi demonstrates the use of his VA1 analyzer on a dummy load. - YouTube

I have often tested my A99 directly connected to the feed point, and the meter seems to respond just fine, or at least as I might expect. I often see notable difference at the same height however, when I add a moderately long feed line, whether it is considered an electrical 1/2 wave or not. IMO, this happens because the A99 load is not purely resistive showing a 1.01:1 SWR, even though it is low to the Earth in such test.

Somehow I threw away all of my old Antenna Reports showing analyzer bandwidth curves for my A99, or I would show such results testing directly at the feed point from back in 2009 when I tested my using tuned jumpers to match my A99 without radials.

One thing I think I learned in that experience was that the antenna match responded within the range and numbers that I expected, even though the antenna did not have a feed line attached. I did not have the antenna isolated from the mast, so I concluded that the antenna may be using the mast as many report. So, if I ever get able to do more work I will surely test such and idea with the A99 isolated and without the feed line to see if doing so ill-affects the matching results.

Over time I have asked others to test such ideas, including adding of radials if the match went bad due to isolation...as I think might happen.

So far no takers.

 

[HomerBB]

Question:
I do not know if you still have the choke wound below the feed point,( looking at old pictures) so did you just try using a double connector to put the MFJ right on the PL 259 and bypass the choke?
When you say it would not work, can you tell us how/what did not work?
I am just asking out of curiosity.
A very short jumper 4/6 inches should make very little difference in you readings.

Man I wish it was easy to have my antenna up at height and still have easy access to the feed point.

Thanks for doing all the work, and sharing the results with everyone here.

73
Jeff

The choke is still there, however, when I had the analyzer directly under the antenna it as you said, a coupling connector with no coax jumper.

Why/how it didn't work was I had readings that I didn't record which were all over the place. Changing location on the band, or even changing bands did not result in any real changes to off the chart readings. I concluded I was tucked too close into the RF field of the antenna.

 

[HomerBB]

Well I figured you were probably using your 1/4 wave electrical jumper to test the antennas above the blue box, I guess I was wrong again.

You are correct. I was using the longer line so that I could use the same when I got my antenna higher in the air than the single 1/4 wave jumper could reach.

So, you used two 89' foot feed lines to get to the shack, and a similar single length of 89' feet of coax to test the other antennas above, right?

correct

Based on my thinking to you a while back...that the length of feed line connected to a reactive load will produce variable results on an SWR meter, and your analyzer as well...relative to their location on the line, so I ask my questions.

No doubt. So I have been trying to work with a line useful for varying heights and then perhaps it will be useful with those lengths in line.

You indicated earlier, as I understood you to say, that when you tested you used a signal 1/4 wave length electrical jumper vs. that same jumper length x 6 multiples, and that you saw exactly the same analyzer results from both lengths. If I'm right, I would argue that could only happen if the load and frequency were considered purely resistive, with no reactance, and the system was showing 1.00:1 SWR, using such a 1/2 wave electrical feed line jumper at the specific frequency cut. Since your antenna is close to on the money, your results are also close also, but I think I still see a difference that should be noted. If, for example, your antenna was off further than noted here, then you would likely see more difference. That is my only point to consider.

This is why I suggest careful consideration when using any length of feed line attached between your analyzer with a load of unknown values for R,X,SWR, and for sure when using a very long feed line, relative to the wavelength. If so, this is to say one can expect the results to be somewhat less revealing and variable...unless a true resistive match is present and very low SWR is present at the feed point.

Perhaps I should have run comparisons on all the test changes between the two line lengths instead of one. I made the mistake of assumption so will likely have to revisit it again.

I contend, that otherwise your results can be variable and misleading, even when using what is considered to be a 1/2 wavelength electrical jumper for a specific frequency.

Homer, this is not to be critical of your results, I think you are remarkable close for a home made antenna. This is just for consideration only.

I hear ya. And I'm listening.

 

[HomerBB]

I have the antenna 42' in the air, and it changed again. I'll get numbers later when I can. The SWR meter still likes it, but the analyzer is as demanding as an mistress about it all. Seems she has me scratching for more . . .

I'm working today and it's raining. . .

I will say the internal SWR readings from the 2950 like it, too.

 

[HomerBB]

In the shack, antenna at 42' height:

28.265 ------------ 2.0 R=61 X=34
27.979 ------------ 1.5 R=49 X=22
27.571 ------------ 1.0 R=45 X=1
27.555 ------------ 1.0 R=46 X=1
27.405 ------------ 1.2 R=49 X=9
27.185 ------------ 1.5 R=55 X=21
26.965 ------------ 1.8 R=74 X=27
26.549 ------------ 2.0 R=108 X=0

It is much narrower banded, and friendly higher up the band.

What the SWR meter in the shack says:

28.485 ------------ 2.0
28.305 ------------ 1.5
27.555 ------------ 1.0
27.405 ------------ 1.0
27.185 ------------ 1.05
26.965 ------------ 1.25
26.800 ------------ 1.45
26.600 ------------ 1.0

Seems the SWR meter has a different point of view on the whole thing.