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Old July 3rd 15, 07:34 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

In message , John S
writes
On 7/3/2015 10:17 AM, Ian Jackson wrote:
In message , John S
writes
On 6/29/2015 10:48 AM, Wayne wrote:
As a lead in, I use a 16 ft vertical on 20-10 meters, mounted on a flat
metal roof. The antenna is fed with about 25 feet of RG-8, and there is
a tuner at the transmit end.

While I'm pretty happy with the antenna, I'd like to simplify the
matching.

Thus, the question: what is the purpose of a 1:4 unun on a 43 foot
vertical? ( I assume the "4" side is on the antenna side.)

I'd expect a better coax to antenna match when the antenna feedpoint is
a high Z (example, at 30 meters), but I'd also expect a worse coax to
antenna match when the feedpoint is a low Z (example, at 10 meters).

Is that the way it works, or is there other magic involved?

I think we strayed off the path to answering your original question.

The short answer is that you are correct and there is no magic
involved. A bit longer answer is:

A 43ft vertical will present a feed impedance of 1010 + J 269.2 ohms
at 30 meters. Using a 1:4 transformer at the feed point will reduce
that to 253 + J 67 ohms. That is a bit closer to your 50 ohm line.


A fixed-tuned TX will still need a matcher.



That was not part of the original question(s).



At 10 meters, the antenna will present a 147 + J 133 ohms impedance. A
1:4 transformer will reduce that to 37 + J 33 ohms.


A fixed-tuned TX will probably be reasonably happy with a direct
connection - although maybe even happier with a series capacitor of -J22
ohms.


That was not part of the original question(s).

There are several disclaimers I could include, but I think you
understand that the answers cannot be exact with the info presented.

I hope this helps.


The question is really whether the losses with the 4:1 transformer, plus
those of any matcher at the TX end, exceed those when there is no
transformer (but with higher loss on the coax), plus a matcher. Put
another way, for short feeder lengths, is it better to use the transformer?


That was not the question he asked. Please re-read the OP. I was trying
to address his original question(s) as best as I could. In addition I
also said that there were "several disclaimers I could include" which
may involve your personal concerns. I did not want to muddy the waters.

I think I answered Wayne's question(s), but I will wait to hear from
him to see if that is so.


You have certainly answered "Thus, the question: what is the purpose of
a 1:4 unun on a 43 foot vertical?" (ie to reduce the horrendous
mismatch). However, don't you think there's any virtue in wondering
whether, in the circumstances described (with the relatively short
feeder), it will be any better than a direct connection to the antenna,
and to do all the matching at the TX end? Also, would you use a
transformer if there was hardly any feeder at all, or (in an extreme
case) if the antenna was fed directly from the TX? I'm not advocating
anything - only wondering.
--
Ian
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Old July 3rd 15, 08:27 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical



"rickman" wrote in message ...

On 7/2/2015 8:53 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/2/2015 3:52 PM, Wayne wrote:

Why will the reflections not have losses?

Because the assumption I posed was for a lossless line. In that case,
with a conjugate match on both ends, wouldn't there be maximum power
transmission regardless of the SWR?


You aren't grasping the issue. Losses are *not* only in the transmission
line. When a reflected wave returns to the transmitter output, it is not
reflected 100%. If the output and transmission line are matched exactly,
50% of the reflected wave reaching the output will be reflected and 50%
will be dissipated in the output stage.


I don't think I've ever heard that anywhere before. Could you elaborate?


Are you suggesting that the conjugate match will reflect back to the
antenna 100% of the original reflected wave from the antenna?


Well, yes. Minus losses in matching networks and transmission lines.

In examples with lossless lines and lossless matching networks, wouldn't it
be 100%.

  #73   Report Post  
Old July 4th 15, 06:22 AM posted to rec.radio.amateur.antenna
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Posts: 550
Default An antenna question--43 ft vertical

On 7/3/2015 1:34 PM, Ian Jackson wrote:
In message , John S
writes
On 7/3/2015 10:17 AM, Ian Jackson wrote:
In message , John S
writes
On 6/29/2015 10:48 AM, Wayne wrote:
As a lead in, I use a 16 ft vertical on 20-10 meters, mounted on a
flat
metal roof. The antenna is fed with about 25 feet of RG-8, and
there is
a tuner at the transmit end.

While I'm pretty happy with the antenna, I'd like to simplify the
matching.

Thus, the question: what is the purpose of a 1:4 unun on a 43 foot
vertical? ( I assume the "4" side is on the antenna side.)

I'd expect a better coax to antenna match when the antenna
feedpoint is
a high Z (example, at 30 meters), but I'd also expect a worse coax to
antenna match when the feedpoint is a low Z (example, at 10 meters).

Is that the way it works, or is there other magic involved?

I think we strayed off the path to answering your original question.

The short answer is that you are correct and there is no magic
involved. A bit longer answer is:

A 43ft vertical will present a feed impedance of 1010 + J 269.2 ohms
at 30 meters. Using a 1:4 transformer at the feed point will reduce
that to 253 + J 67 ohms. That is a bit closer to your 50 ohm line.

A fixed-tuned TX will still need a matcher.



That was not part of the original question(s).



At 10 meters, the antenna will present a 147 + J 133 ohms impedance. A
1:4 transformer will reduce that to 37 + J 33 ohms.

A fixed-tuned TX will probably be reasonably happy with a direct
connection - although maybe even happier with a series capacitor of -J22
ohms.


That was not part of the original question(s).

There are several disclaimers I could include, but I think you
understand that the answers cannot be exact with the info presented.

I hope this helps.

The question is really whether the losses with the 4:1 transformer, plus
those of any matcher at the TX end, exceed those when there is no
transformer (but with higher loss on the coax), plus a matcher. Put
another way, for short feeder lengths, is it better to use the
transformer?


That was not the question he asked. Please re-read the OP. I was
trying to address his original question(s) as best as I could. In
addition I also said that there were "several disclaimers I could
include" which may involve your personal concerns. I did not want to
muddy the waters.

I think I answered Wayne's question(s), but I will wait to hear from
him to see if that is so.


You have certainly answered "Thus, the question: what is the purpose of
a 1:4 unun on a 43 foot vertical?" (ie to reduce the horrendous
mismatch). However, don't you think there's any virtue in wondering
whether, in the circumstances described (with the relatively short
feeder), it will be any better than a direct connection to the antenna,
and to do all the matching at the TX end? Also, would you use a
transformer if there was hardly any feeder at all, or (in an extreme
case) if the antenna was fed directly from the TX? I'm not advocating
anything - only wondering.


Yes, I agree that there is virtue in fully examining all the
possibilities. I may or may not use a transformer with a direct
connection to the antenna. It depends on my source's capabilities. Of
course, anything added to improve a match also causes a bit of loss.
It's all tradeoffs, as you well know.
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Old July 4th 15, 07:34 AM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

Okay. This data set is for a 43' carbon steel antenna on a perfect
ground fed with 25' of RG8A/U. No transformer.

Freq R X SWR

4.000 2.52 -12.74 21.140
5.000 20.16 20.82 2.977
6.000 28.78 -30.81 2.586
7.000 8.04 -5.76 6.307
8.000 5.68 12.25 9.337
9.000 6.08 30.66 11.344
10.000 8.95 56.02 12.703
11.000 20.21 104.84 13.685
12.000 137.06 277.80 14.297
13.000 126.21 -267.32 14.174
14.000 19.15 -95.40 12.417
15.000 11.09 -43.81 8.067
16.000 17.90 -11.07 2.949
17.000 56.99 -15.98 1.384
18.000 20.29 -31.49 3.568
19.000 9.29 -12.21 5.711
20.000 6.95 3.56 7.236
21.000 6.99 19.13 8.217
22.000 9.03 38.15 8.829
23.000 15.83 67.71 9.161
24.000 48.70 132.94 9.150
25.000 418.45 49.46 8.488
26.000 60.45 -119.25 6.589
27.000 28.69 -45.41 3.465
28.000 46.51 -9.99 1.245
29.000 62.03 -48.79 2.397
30.000 21.38 -41.26 4.116


This data set is the same except with a 1:4 transformer at the antenna.

Freq R X SWR
4.000 4.07 19.59 14.187
5.000 25.57 74.28 6.633
6.000 153.39 -83.56 4.058
7.000 25.51 -38.52 3.333
8.000 15.35 -6.11 3.312
9.000 16.11 18.43 3.567
10.000 26.59 49.05 3.970
11.000 87.00 102.27 4.497
12.000 180.75 -114.05 5.136
13.000 28.87 -72.84 5.814
14.000 11.18 -31.02 6.256
15.000 8.52 -4.23 5.914
16.000 13.30 23.05 4.607
17.000 50.10 61.48 3.196
18.000 107.24 -32.07 2.383
19.000 36.37 -30.20 2.135
20.000 22.85 -5.54 2.222
21.000 22.77 16.08 2.474
22.000 33.85 41.69 2.827
23.000 85.10 73.92 3.268
24.000 165.89 -60.03 3.790
25.000 39.38 -70.12 4.323
26.000 15.47 -31.46 4.605
27.000 12.03 -4.86 4.197
28.000 18.81 20.71 3.175
29.000 54.98 43.57 2.257
30.000 85.50 -14.78 1.786

Is this of any help?
  #75   Report Post  
Old July 4th 15, 03:10 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

On 7/4/2015 1:34 AM, John S wrote:
Okay. This data set is for a 43' carbon steel antenna on a perfect
ground fed with 25' of RG8A/U. No transformer.


I made a mistake. I used 3" copper pipe. I will re-do with 3" carbon
steel pipe.

No transformer:
Freq R X SWR
4.000 2.61 -12.68 20.382
5.000 20.92 20.65 2.867
6.000 28.18 -30.18 2.600
7.000 8.03 -5.57 6.304
8.000 5.70 12.35 9.317
9.000 6.11 30.75 11.314
10.000 9.00 56.13 12.662
11.000 20.37 105.05 13.626
12.000 139.02 278.20 14.204
13.000 125.69 -265.07 14.021
14.000 19.40 -94.97 12.182
15.000 11.41 -43.56 7.809
16.000 18.65 -11.02 2.830
17.000 56.19 -17.88 1.426
18.000 19.92 -31.06 3.599
19.000 9.26 -12.02 5.720
20.000 6.96 3.68 7.228
21.000 7.02 19.23 8.195
22.000 9.09 38.27 8.792
23.000 15.99 67.89 9.102
24.000 49.53 133.22 9.057
25.000 412.93 41.45 8.343
26.000 60.97 -117.33 6.399
27.000 29.70 -44.72 3.324
28.000 48.31 -10.74 1.247
29.000 60.26 -49.68 2.445
30.000 21.05 -40.86 4.142

1:4 transformer:
Freq R X SWR
4.000 4.21 19.69 13.745
5.000 26.48 74.45 6.450
6.000 149.09 -82.20 3.972
7.000 25.55 -37.90 3.288
8.000 15.45 -5.81 3.285
9.000 16.25 18.68 3.549
10.000 26.91 49.36 3.954
11.000 88.45 102.31 4.478
12.000 177.47 -114.21 5.105
13.000 28.81 -72.20 5.756
14.000 11.31 -30.71 6.152
15.000 8.73 -3.99 5.767
16.000 13.78 23.29 4.469
17.000 51.75 60.81 3.109
18.000 104.23 -32.25 2.336
19.000 36.12 -29.39 2.111
20.000 22.93 -5.09 2.210
21.000 22.96 16.44 2.467
22.000 34.32 42.05 2.819
23.000 86.65 73.65 3.255
24.000 162.78 -61.65 3.764
25.000 39.08 -69.10 4.270
26.000 15.65 -30.95 4.510
27.000 12.38 -4.51 4.075
28.000 19.52 20.93 3.075
29.000 56.33 42.38 2.197
30.000 83.40 -15.44 1.755



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Old July 4th 15, 04:55 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical



"John S" wrote in message ...

On 7/4/2015 1:34 AM, John S wrote:
Okay. This data set is for a 43' carbon steel antenna on a perfect
ground fed with 25' of RG8A/U. No transformer.


I made a mistake. I used 3" copper pipe. I will re-do with 3" carbon
steel pipe.


No transformer:
Freq R X SWR
4.000 2.61 -12.68 20.382
5.000 20.92 20.65 2.867
6.000 28.18 -30.18 2.600
7.000 8.03 -5.57 6.304
8.000 5.70 12.35 9.317
9.000 6.11 30.75 11.314
10.000 9.00 56.13 12.662
11.000 20.37 105.05 13.626
12.000 139.02 278.20 14.204
13.000 125.69 -265.07 14.021
14.000 19.40 -94.97 12.182
15.000 11.41 -43.56 7.809
16.000 18.65 -11.02 2.830
17.000 56.19 -17.88 1.426
18.000 19.92 -31.06 3.599
19.000 9.26 -12.02 5.720
20.000 6.96 3.68 7.228
21.000 7.02 19.23 8.195
22.000 9.09 38.27 8.792
23.000 15.99 67.89 9.102
24.000 49.53 133.22 9.057
25.000 412.93 41.45 8.343
26.000 60.97 -117.33 6.399
27.000 29.70 -44.72 3.324
28.000 48.31 -10.74 1.247
29.000 60.26 -49.68 2.445
30.000 21.05 -40.86 4.142


1:4 transformer:
Freq R X SWR
4.000 4.21 19.69 13.745
5.000 26.48 74.45 6.450
6.000 149.09 -82.20 3.972
7.000 25.55 -37.90 3.288
8.000 15.45 -5.81 3.285
9.000 16.25 18.68 3.549
10.000 26.91 49.36 3.954
11.000 88.45 102.31 4.478
12.000 177.47 -114.21 5.105
13.000 28.81 -72.20 5.756
14.000 11.31 -30.71 6.152
15.000 8.73 -3.99 5.767
16.000 13.78 23.29 4.469
17.000 51.75 60.81 3.109
18.000 104.23 -32.25 2.336
19.000 36.12 -29.39 2.111
20.000 22.93 -5.09 2.210
21.000 22.96 16.44 2.467
22.000 34.32 42.05 2.819
23.000 86.65 73.65 3.255
24.000 162.78 -61.65 3.764
25.000 39.08 -69.10 4.270
26.000 15.65 -30.95 4.510
27.000 12.38 -4.51 4.075
28.000 19.52 20.93 3.075
29.000 56.33 42.38 2.197
30.000 83.40 -15.44 1.755


Yes, very interesting. Throw in 75 feet of cable, and things get "better".

The lowest SWR is about 2:1 at 19 MHz.
It is about 6:1 on 20 meters.


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Old July 4th 15, 05:34 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

On 7/4/2015 10:55 AM, Wayne wrote:


Yes, very interesting. Throw in 75 feet of cable, and things get "better".

The lowest SWR is about 2:1 at 19 MHz.
It is about 6:1 on 20 meters.



Of course. More loss in the cable makes it "better" (but, you know that).
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Old July 4th 15, 06:05 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

On 7/4/2015 10:55 AM, Wayne wrote:


By the way, Wayne...

Are you aware of a companion Excel application for EZNEC called AutoEZ?
You can run many test cases in a few seconds using it. You can find it
on the EZNEC site.

It is how I generated the data I posted.

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Old July 4th 15, 06:32 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical



"John S" wrote in message ...

On 7/4/2015 10:55 AM, Wayne wrote:


By the way, Wayne...


Are you aware of a companion Excel application for EZNEC called AutoEZ?
You can run many test cases in a few seconds using it. You can find it
on the EZNEC site.


It is how I generated the data I posted.


Thanks, I'll look for that. I run the old wood burning version 3.0.

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Old July 4th 15, 09:07 PM posted to rec.radio.amateur.antenna
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Default An antenna question--43 ft vertical

On 7/3/2015 3:27 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/2/2015 8:53 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/2/2015 3:52 PM, Wayne wrote:

Why will the reflections not have losses?

Because the assumption I posed was for a lossless line. In that case,
with a conjugate match on both ends, wouldn't there be maximum power
transmission regardless of the SWR?


You aren't grasping the issue. Losses are *not* only in the
transmission line. When a reflected wave returns to the transmitter
output, it is not reflected 100%. If the output and transmission line
are matched exactly, 50% of the reflected wave reaching the output
will be reflected and 50% will be dissipated in the output stage.


I don't think I've ever heard that anywhere before. Could you elaborate?


I'm not so sure now. I think I mentioned before that I learned about
transmission lines in the digital context where source and loads are
largely resistive. Resistance dissipates power. So when matched the
source dissipates as much power as delivered to the load (or
transmission line). Likewise, matched impedance will not reflect power,
but rather it is all absorbed. That is what happens at the antenna for
sure. But I'm not clear about what this conjugate network is really.
If it is purely reactive, then it will not have losses other than the
parasitics.

I have to admit I am not fluent in the complex math of networks. So off
hand an impedance of 1063 -j0 says to me resistive. The imaginary part
implies phase shifting, no? With that term being 0 doesn't that say the
capacitive and inductive parts cancel out leaving only resistance? If
you can, please explain how I am wrong.


Are you suggesting that the conjugate match will reflect back to the
antenna 100% of the original reflected wave from the antenna?


Well, yes. Minus losses in matching networks and transmission lines.

In examples with lossless lines and lossless matching networks, wouldn't
it be 100%.


I don't get how the matching network will reflect the wave from the
antenna 100%. Is that something you can explain?

--

Rick
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