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.

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.

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?
--
Ian

In message , Ian Jackson
writes


although maybe even happier with a series capacitor of -J22 ohms.

Sorry - somebody obviously swapped the '2' and '3' keys.


--
Ian

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.

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

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.

"John S" wrote in message ...

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.

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.

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.

Thanks John.
Yes, we have strayed from the original question, but I have found the
discussion stimulating.
Perhaps a new thread should be started to address those subjects.

If I use EZNEC to model the 43 footer over perfect ground with a 3 inch
diameter radiator, I get impedances in the same ball park as you list.

If I change the "alt SWR Z0" to 200 ohms (presumably what the antenna would
see as a feedline, if a 4:1 unun had 50 ohm coax on the other side), the SWR
plot becomes interesting.

The plot has SWRs of about 2.5:1 to 5:1 over most of the range, with SWR
getting below 2.5:1 around 29 MHz.

Is that a valid approach?

On 7/3/2015 10:37 AM, Wayne wrote:


"John S" wrote in message ...

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.

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.

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.

Thanks John.
Yes, we have strayed from the original question, but I have found the
discussion stimulating.
Perhaps a new thread should be started to address those subjects.

If I use EZNEC to model the 43 footer over perfect ground with a 3 inch
diameter radiator, I get impedances in the same ball park as you list.

If I change the "alt SWR Z0" to 200 ohms (presumably what the antenna
would see as a feedline, if a 4:1 unun had 50 ohm coax on the other
side), the SWR plot becomes interesting.

The plot has SWRs of about 2.5:1 to 5:1 over most of the range, with SWR
getting below 2.5:1 around 29 MHz.

Is that a valid approach?

I have not done what you have done, but it sounds correct. I'll try to
verify what you have done when time permits.

I really think you know what you are doing. Don't forget that EZNEC can
use transmission lines, transformers, inductors, capacitors, resistors
and other stuff to help in your analysis. Although the true answers come
from the physical implementation, it is very helpful to use EZNEC to
gain insight into the situation. And, I think you know that as well.

On 7/3/2015 10:37 AM, Wayne wrote:


"John S" wrote in message ...

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.

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.

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.

Thanks John.
Yes, we have strayed from the original question, but I have found the
discussion stimulating.


Indeed! So have I.


Perhaps a new thread should be started to address those subjects.


Please start one if you feel compelled.


If I use EZNEC to model the 43 footer over perfect ground with a 3 inch
diameter radiator, I get impedances in the same ball park as you list.


Ha! I used 1.5 inches. I will re-do.


If I change the "alt SWR Z0" to 200 ohms (presumably what the antenna
would see as a feedline, if a 4:1 unun had 50 ohm coax on the other
side), the SWR plot becomes interesting.


I've never done that. I will explore this set-up.


The plot has SWRs of about 2.5:1 to 5:1 over most of the range, with SWR
getting below 2.5:1 around 29 MHz.

Are we still considering a 10MHz to 30Mhz frequency sweep?

Is that a valid approach?

You might be ahead of me on this.

"John S" wrote in message ...

On 7/3/2015 10:37 AM, Wayne wrote:


"John S" wrote in message ...

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.

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.

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.

Thanks John.
Yes, we have strayed from the original question, but I have found the
discussion stimulating.


Indeed! So have I.


Perhaps a new thread should be started to address those subjects.


Please start one if you feel compelled.


If I use EZNEC to model the 43 footer over perfect ground with a 3 inch
diameter radiator, I get impedances in the same ball park as you list.


Ha! I used 1.5 inches. I will re-do.


If I change the "alt SWR Z0" to 200 ohms (presumably what the antenna
would see as a feedline, if a 4:1 unun had 50 ohm coax on the other
side), the SWR plot becomes interesting.


I've never done that. I will explore this set-up.


The plot has SWRs of about 2.5:1 to 5:1 over most of the range, with SWR
getting below 2.5:1 around 29 MHz.

Are we still considering a 10MHz to 30Mhz frequency sweep?

Well, I have been running the SWR across 4 to 30 MHz, but mainly looking at
10 MHz and above.

As for EZNEC and transmission lines, I have never done that, but plan to
when I can. I don't follow how to do it. In the few cases I wanted the
info for a single frequency, I just used a Smith chart.

This thread has given me a lot to consider in improving my whip setup, but
details of the possibilities would run the thread off in the weeds

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?