On Tuesday, June 30, 2015 at 2:36:51 PM UTC-4, rickman wrote:
On 6/30/2015 12:40 PM, Tom W3TDH wrote:

I know that what I am about to say is provocative to some but I still
think it is worth saying. If you look at the way that commercial and
military radios are matched to antennas you will notice that most of
the matching is done as close to the feed point as practical.

Since only the power that actually reaches the antenna can be
radiated I have a hard time seeing the point of matching the
transmitter to the feed line. Matching at the feed line connection
point will prevent damage to the transmitter but if that were the
main objective a dummy load would accomplish that.

When you couple the antenna to the load at the feed point you can
have extremely low losses in the feed line. When you do the matching
at the feed point you will transfer the most energy possible to the
antenna and will get the highest available effective radiated power.
Since the objective is the transfer of the highest practical amount
of power to the antenna the place to do that is at the feed point
were possible.

I do realize that it is often simpler and easier to match at the feed
line connection but I felt obliged to point out that is is not the
most effective place to do the job.

Has it occurred to you that it might be important to match impedance
both at the transmitter and at the antenna? When the feed line is not
impedance matched to the transmitter output the maximum power is not
transferred into the feed line. Then you have already lost power that
can't be recovered by the matching at the antenna even if it is perfect.

Your statements are not really provocative, they are just incomplete
and/or wrong.

--

Rick

Rick

OK I'll buy incomplete and therefore wrong.

Now given a Fifty Ohm feed line connected to a transmitter that is designed for that impedance at the antenna connector does not the actual mismatch occur at the antenna feed point? Certainly that can be compensated for at the transmitter but isn't there a likelihood or at least a risk that you will loose significant effective radiated power in spite of adjusting the apparent feed line impedance to the transmitter? If I do the matching at the feed point will I not maximize the effective radiated power of the antenna by installing the tuner at the feed point.

I have already conceded that it is not as convenient to do the matching at the feed point. I do not allege that doing the matching at the transmitter end of the feed line is inherently ineffective only that there is a greater likelihood of loosing ERP needlessly and invisibly if the matching is done at transmitter end of the feed line. By this I mean to ask if I may well deceive the power meeter into showing more power out then I am actually getting. If any power lost is very likely to be insignificant at a practical level than help me to understand why that would be true and I will sell off my Icon AH-4, together with the control converter that allows my Yaesu FT-857D to control it, and my SGC SG-235 and go back to using the Yaesu FC-30 tuner with my FT-857D and the built in tuner on my Yaesu FT-1000.

This is especially important for me to get right with my FT-857D since it is the transceiver that I use for my personal go kit. If putting the Icon AH-4 on the mast and running the control line in addition to the coaxial cable is a waste of time I would really appreciate knowing that.

Thank you for helping with my education on this issue.

--
Tom Horne W3TDH

In message ,
writes
On Tuesday, June 30, 2015 at 2:36:51 PM UTC-4, rickman wrote:
On 6/30/2015 12:40 PM, Tom W3TDH wrote:

I know that what I am about to say is provocative to some but I still
think it is worth saying. If you look at the way that commercial and
military radios are matched to antennas you will notice that most of
the matching is done as close to the feed point as practical.

Since only the power that actually reaches the antenna can be
radiated I have a hard time seeing the point of matching the
transmitter to the feed line. Matching at the feed line connection
point will prevent damage to the transmitter but if that were the
main objective a dummy load would accomplish that.

When you couple the antenna to the load at the feed point you can
have extremely low losses in the feed line. When you do the matching
at the feed point you will transfer the most energy possible to the
antenna and will get the highest available effective radiated power.
Since the objective is the transfer of the highest practical amount
of power to the antenna the place to do that is at the feed point
were possible.

I do realize that it is often simpler and easier to match at the feed
line connection but I felt obliged to point out that is is not the
most effective place to do the job.

Has it occurred to you that it might be important to match impedance
both at the transmitter and at the antenna? When the feed line is not
impedance matched to the transmitter output the maximum power is not
transferred into the feed line. Then you have already lost power that
can't be recovered by the matching at the antenna even if it is perfect.

Your statements are not really provocative, they are just incomplete
and/or wrong.

--

Rick

Rick

OK I'll buy incomplete and therefore wrong.

Now given a Fifty Ohm feed line connected to a transmitter that is
designed for that impedance at the antenna connector does not the
actual mismatch occur at the antenna feed point? Certainly that can be
compensated for at the transmitter but isn't there a likelihood or at
least a risk that you will loose significant effective radiated power
in spite of adjusting the apparent feed line impedance to the
transmitter? If I do the matching at the feed point will I not
maximize the effective radiated power of the antenna by installing the
tuner at the feed point.

I have already conceded that it is not as convenient to do the matching
at the feed point. I do not allege that doing the matching at the
transmitter end of the feed line is inherently ineffective only that
there is a greater likelihood of loosing ERP needlessly and invisibly
if the matching is done at transmitter end of the feed line. By this I
mean to ask if I may well deceive the power meeter into showing more
power out then I am actually getting. If any power lost is very likely
to be insignificant at a practical level than help me to understand why
that would be true and I will sell off my Icon AH-4, together with the
control converter that allows my Yaesu FT-857D to control it, and my
SGC SG-235 and go back to using the Yaesu FC-30 tuner with my FT-857D
and the built in tuner on my Yaesu FT-1000.

This is especially important for me to get right with my FT-857D since
it is the transceiver that I use for my personal go kit. If putting
the Icon AH-4 on the mast and running the control line in addition to
the coaxial cable is a waste of time I would really appreciate knowing
that.

Thank you for helping with my education on this issue.

It's indeed surprising how well things still work if you use the lowest
loss coax you can beg, steal or borrow, and do all the matching back in
the comfort of the shack.
--
Ian

On 6/29/2015 3:47 PM, 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.

You use a 16ft vertical as a lead-in? For what and how is that done?

Grammatically, the description of the vertical is a lead in for the
question, not an actual antenna lead.


What are the dimensions of the metal roof?

Somewhat irrelevant to my question. But it's about 20 by 35 feet.
I'm not looking for an analysis of the existing antenna.


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

To what matching do you refer? You don't want to use the tuner, or is
there some other stuff you have not mentioned?

I want the tuner matching to be less awkward on some bands.
I'm willing to live with the existing high SWRs on the upper bands.


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.)

You wrote that you were interested in a 16ft vertical. Now it is a
43ft vertical?

Please disregard all about the 16 ft vertical. I'm asking about a 43 ft
vertical 1:4 unun.


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?

All this depends on your answers to the above questions.

So, lets begin again, with no distractions.

What is the purpose (or benefit) of using a 1:4 unun on a 43 ft vertical.

Ok. Well, 43ft is a half wavelength at about 12MHz. The vertical will be
very high impedance at that frequency and a 1:4 unun will theoretically
bring that impedance down closer to the feed line impedance.

Does this help?

In message , John S
writes
On 6/29/2015 3:47 PM, 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.

You use a 16ft vertical as a lead-in? For what and how is that done?

Grammatically, the description of the vertical is a lead in for the
question, not an actual antenna lead.


What are the dimensions of the metal roof?

Somewhat irrelevant to my question. But it's about 20 by 35 feet.
I'm not looking for an analysis of the existing antenna.


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

To what matching do you refer? You don't want to use the tuner, or is
there some other stuff you have not mentioned?

I want the tuner matching to be less awkward on some bands.
I'm willing to live with the existing high SWRs on the upper bands.


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.)

You wrote that you were interested in a 16ft vertical. Now it is a
43ft vertical?

Please disregard all about the 16 ft vertical. I'm asking about a 43 ft
vertical 1:4 unun.


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?

All this depends on your answers to the above questions.

So, lets begin again, with no distractions.

What is the purpose (or benefit) of using a 1:4 unun on a 43 ft vertical.

Ok. Well, 43ft is a half wavelength at about 12MHz. The vertical will
be very high impedance at that frequency and a 1:4 unun will
theoretically bring that impedance down closer to the feed line
impedance.

Does this help?

It was been pointed out to me that the figures for feeder loss with an
imperfect SWR are only correct when the length is fairly long (at least
an electrical wavelength?). How much loss does 25' of RG-8 really have
at 12MHz, when there's a halfwave hanging on the far end?
--
Ian

On Tue, 30 Jun 2015 15:13:55 -0400, Jerry Stuckle
wrote:

Yes, it's most effective to match the feedline to the antenna at the
antenna connection. But it's also important to match the transmitter to
the feedline.

This latter piece is often ignored because people will use a feedline
who's characteristic impedance matches the transmitter already (i.e. 50
ohm line for a 50 ohm transmitter).

However, there are exceptions. For instance, if you're feeding a 75 ohm
antenna (i.e. a dipole) with 75 ohm coax, a 1:1 balun at the antenna
will provide a good match (ideally, 1:1). But there will be a 1.5:1
mismatch to a 50 ohm transmitter. In this case it would be better to
have the matching network at the transmitter.

We may have had this discussion before. Matching a 75 ohm load to a
50 ohm source might be academically interesting, but the actual loss
is almost negligible. for a VSWR of 1.5, the return loss is 14dB and
the load mismatch attenuation is 0.177dB. That's about what I would
expect to lose in two coax connector pairs.

You could also feed the antenna with 50 ohm feedline and place the
matching network at the antenna. The effect would still be a 1:1 SWR,
but the lower impedance of the coax would create higher i^2R losses; not
important if you're talking a short line, but a longer one would lower
output at the antenna.

True, but for roughly equivalent sizes of coax cables, the 75 ohm
cable has less loss and the equivalent 50 ohm cable. If you want to
handle high power, use 50 ohms. If you want low loss, use 75 ohms:
http://www.belden.com/blog/broadcastav/50-Ohms-The-Forgotten-Impedance.cfm
Note that these are for air dielectric cables.

Things are not so neat if we consider the dielectric. See the bottom
paragraph and graphs:
http://www.microwaves101.com/encyclopedias/why-fifty-ohms
Dielectric Dielectric const Minimum loss impedance
solid PTFE 2.2 50 ohms
foam PTFE 1.43 60
air 1.0 75
RG-6/u CATV 75 ohm foam coax still has slightly less loss than the
equivalent 50 ohm cable, but not as much as I've previously claimed.

This is cute:
http://cablesondemandblog.com/wordpress1/2014/03/06/whats-the-difference-between-50-ohm-and-75-ohm-coaxial-cable/
"A good rule of thumb is that if the device being connected
via coaxial cable is a receiver of some kind, 75 Ohm Coax is ideal."


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 7/1/2015 10:20 AM, wrote:
On Tuesday, June 30, 2015 at 2:36:51 PM UTC-4, rickman wrote:
On 6/30/2015 12:40 PM, Tom W3TDH wrote:

I know that what I am about to say is provocative to some but I
still think it is worth saying. If you look at the way that
commercial and military radios are matched to antennas you will
notice that most of the matching is done as close to the feed
point as practical.

Since only the power that actually reaches the antenna can be
radiated I have a hard time seeing the point of matching the
transmitter to the feed line. Matching at the feed line
connection point will prevent damage to the transmitter but if
that were the main objective a dummy load would accomplish that.

When you couple the antenna to the load at the feed point you
can have extremely low losses in the feed line. When you do the
matching at the feed point you will transfer the most energy
possible to the antenna and will get the highest available
effective radiated power. Since the objective is the transfer of
the highest practical amount of power to the antenna the place to
do that is at the feed point were possible.

I do realize that it is often simpler and easier to match at the
feed line connection but I felt obliged to point out that is is
not the most effective place to do the job.

Has it occurred to you that it might be important to match
impedance both at the transmitter and at the antenna? When the
feed line is not impedance matched to the transmitter output the
maximum power is not transferred into the feed line. Then you have
already lost power that can't be recovered by the matching at the
antenna even if it is perfect.

Your statements are not really provocative, they are just
incomplete and/or wrong.

--

Rick

Rick

OK I'll buy incomplete and therefore wrong.

Now given a Fifty Ohm feed line connected to a transmitter that is
designed for that impedance at the antenna connector does not the
actual mismatch occur at the antenna feed point? Certainly that can
be compensated for at the transmitter but isn't there a likelihood or
at least a risk that you will loose significant effective radiated
power in spite of adjusting the apparent feed line impedance to the
transmitter? If I do the matching at the feed point will I not
maximize the effective radiated power of the antenna by installing
the tuner at the feed point.

I have to plead ignorance. How can you deal with impedance mismatch of
the antenna and feed line by a network at the transmitter?

If you assume the transmitter is matched to the feed line, then yes, you
should only need matching at the antenna if that is mismatched. This
seems like a bit of a silly strawman, but maybe I am just not informed
and this is the typical scenario.


I have already conceded that it is not as convenient to do the
matching at the feed point. I do not allege that doing the matching
at the transmitter end of the feed line is inherently ineffective
only that there is a greater likelihood of loosing ERP needlessly and
invisibly if the matching is done at transmitter end of the feed
line. By this I mean to ask if I may well deceive the power meeter
into showing more power out then I am actually getting. If any power
lost is very likely to be insignificant at a practical level than
help me to understand why that would be true and I will sell off my
Icon AH-4, together with the control converter that allows my Yaesu
FT-857D to control it, and my SGC SG-235 and go back to using the
Yaesu FC-30 tuner with my FT-857D and the built in tuner on my Yaesu
FT-1000.

This is especially important for me to get right with my FT-857D
since it is the transceiver that I use for my personal go kit. If
putting the Icon AH-4 on the mast and running the control line in
addition to the coaxial cable is a waste of time I would really
appreciate knowing that.

Thank you for helping with my education on this issue.



--

Rick

"rickman" wrote in message ...

On 7/1/2015 10:20 AM, wrote:
On Tuesday, June 30, 2015 at 2:36:51 PM UTC-4, rickman wrote:
On 6/30/2015 12:40 PM, Tom W3TDH wrote:

I know that what I am about to say is provocative to some but I
still think it is worth saying. If you look at the way that
commercial and military radios are matched to antennas you will
notice that most of the matching is done as close to the feed
point as practical.

Since only the power that actually reaches the antenna can be
radiated I have a hard time seeing the point of matching the
transmitter to the feed line. Matching at the feed line
connection point will prevent damage to the transmitter but if
that were the main objective a dummy load would accomplish that.

When you couple the antenna to the load at the feed point you
can have extremely low losses in the feed line. When you do the
matching at the feed point you will transfer the most energy
possible to the antenna and will get the highest available
effective radiated power. Since the objective is the transfer of
the highest practical amount of power to the antenna the place to
do that is at the feed point were possible.

I do realize that it is often simpler and easier to match at the
feed line connection but I felt obliged to point out that is is
not the most effective place to do the job.

Has it occurred to you that it might be important to match
impedance both at the transmitter and at the antenna? When the
feed line is not impedance matched to the transmitter output the
maximum power is not transferred into the feed line. Then you have
already lost power that can't be recovered by the matching at the
antenna even if it is perfect.

Your statements are not really provocative, they are just
incomplete and/or wrong.

--

Rick

Rick

OK I'll buy incomplete and therefore wrong.

Now given a Fifty Ohm feed line connected to a transmitter that is
designed for that impedance at the antenna connector does not the
actual mismatch occur at the antenna feed point? Certainly that can
be compensated for at the transmitter but isn't there a likelihood or
at least a risk that you will loose significant effective radiated
power in spite of adjusting the apparent feed line impedance to the
transmitter? If I do the matching at the feed point will I not
maximize the effective radiated power of the antenna by installing
the tuner at the feed point.

# I have to plead ignorance. How can you deal with impedance mismatch of
# the antenna and feed line by a network at the transmitter?

If there is a mismatch at the antenna (and there is no matching at the
antenna), then maximum power transfer will occur when the conjugate match is
applied at the transmitter end of the feedline.

Loss in the feedline will include the normal loss of a matched line, and
additionally the loss caused by a SWR other than 1:1.

With low loss feedline, and SWRs under perhaps 5:1, the additional loss is
small and often quite acceptable.

Why do it that way? You can have control in the shack, and you throw less
money at the problem.

In my own particular case, an automatic remotely tuned ATU would be a pain
to install/maintain.

"Dave Platt" wrote in message ...

In article ,
Wayne wrote:

On the 43 foot vertical it could be that the 4:1 unun provides a lower
amount of SWR induced additional feedline loss on high Z feedpoints. Of
course, the unun might increase the SWR induced additional feedline loss
for
smaller Z.

From the charts, that kinda does appear to be the case.

Add into consideration the fact that losses go up with the square of
the current.

Another issue is the other aspect of SWR - voltage. If you're trying
to run "legal limit" or close to it, high SWR on the feedline coax
could exceed the voltage rating of the coax dielectric, and you'd get
arcing in the coax (or arcing at the connector between your feedline
and shack tuner).

Installing a hefty 4:1 unun right at the antenna would reduce the
worse-case voltage on the feedline, and inside the shack tuner
considerably. Depending on feedline length, that might be even more
of a consideration than the increase in peak feedline current and the
associated I^2*R losses.

Good points. I'm running low powers at the moment, but there was a time
where I burned up a lot of stuff running a KW

On 7/1/2015 1:01 PM, Wayne wrote:


"rickman" wrote in message ...

On 7/1/2015 10:20 AM, wrote:
On Tuesday, June 30, 2015 at 2:36:51 PM UTC-4, rickman wrote:
On 6/30/2015 12:40 PM, Tom W3TDH wrote:

I know that what I am about to say is provocative to some but I
still think it is worth saying. If you look at the way that
commercial and military radios are matched to antennas you will
notice that most of the matching is done as close to the feed
point as practical.

Since only the power that actually reaches the antenna can be
radiated I have a hard time seeing the point of matching the
transmitter to the feed line. Matching at the feed line
connection point will prevent damage to the transmitter but if
that were the main objective a dummy load would accomplish that.

When you couple the antenna to the load at the feed point you
can have extremely low losses in the feed line. When you do the
matching at the feed point you will transfer the most energy
possible to the antenna and will get the highest available
effective radiated power. Since the objective is the transfer of
the highest practical amount of power to the antenna the place to
do that is at the feed point were possible.

I do realize that it is often simpler and easier to match at the
feed line connection but I felt obliged to point out that is is
not the most effective place to do the job.

Has it occurred to you that it might be important to match
impedance both at the transmitter and at the antenna? When the
feed line is not impedance matched to the transmitter output the
maximum power is not transferred into the feed line. Then you have
already lost power that can't be recovered by the matching at the
antenna even if it is perfect.

Your statements are not really provocative, they are just
incomplete and/or wrong.

--

Rick

Rick

OK I'll buy incomplete and therefore wrong.

Now given a Fifty Ohm feed line connected to a transmitter that is
designed for that impedance at the antenna connector does not the
actual mismatch occur at the antenna feed point? Certainly that can
be compensated for at the transmitter but isn't there a likelihood or
at least a risk that you will loose significant effective radiated
power in spite of adjusting the apparent feed line impedance to the
transmitter? If I do the matching at the feed point will I not
maximize the effective radiated power of the antenna by installing
the tuner at the feed point.

# I have to plead ignorance. How can you deal with impedance mismatch of
# the antenna and feed line by a network at the transmitter?

If there is a mismatch at the antenna (and there is no matching at the
antenna), then maximum power transfer will occur when the conjugate
match is applied at the transmitter end of the feedline.

Loss in the feedline will include the normal loss of a matched line, and
additionally the loss caused by a SWR other than 1:1.

With low loss feedline, and SWRs under perhaps 5:1, the additional loss
is small and often quite acceptable.

Why do it that way? You can have control in the shack, and you throw
less money at the problem.

In my own particular case, an automatic remotely tuned ATU would be a
pain to install/maintain.

When you say you have control in the shack, why do you need to do
anything other than install it? Would this matching network change with
use at different bands?

Also, why is this a lower cost solution?

--

Rick

"Jeff" wrote in message ...


If there is a mismatch at the antenna (and there is no matching at the
antenna), then maximum power transfer will occur when the conjugate
match is applied at the transmitter end of the feedline.

Surely a conjugate match will only match the load if the coax length is 1/2
wavelength or multiple thereof, and the feeder is also lossless.

Any other coax length will introduce a phase shift that will require a
different match.

Yes, I'm assuming that the antenna tuner conjugate match is for the end of
the feedline, not for the antenna itself.

Wayne
W5GIE
exiled to W6