Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Internal tuner vs external tuner efficiency  (Read 2529 times)
KD2CJJ
Member

Posts: 368




Ignore
« on: May 12, 2013, 04:56:50 AM »

which is more efficient, a good external tuner or the internal rig tuner?
Logged

73

Mike
KD2CJJ
KB3HG
Member

Posts: 404




Ignore
« Reply #1 on: May 12, 2013, 06:01:24 AM »

Mike,
Efficiency, a nefarious term. The Losses involved in the turner are small compared to the coax line losses. Start at the antenna is the SWR low across the band? Did you plot SWR in different beam headings? What is the bandwidth of the antenna vs the bandwidth of antenna tuner regardless of interior or exterior. If you don't have an antenna analyzer beg borrow one. Measure close to the antenna with a known good piece of coax. Rotate your beam check again. I read the other post. Personally I use a manual external tuner. If the antenna is stable suspect cables move down the line. 
Getting back to inefficiency a receiving station won't know the difference. your jumps in swr are more than likely a mechanical problem. and where your antenna is mounted you have good access to it to check it out.
I saw you state it was not the antenna on the other postings, are you sure? He sure gave you sound advice.

Tom Kb3hg
Logged
WB6BYU
Member

Posts: 12986




Ignore
« Reply #2 on: May 12, 2013, 10:00:26 AM »

It depends on the tuner designs, the frequency and the load impedance to be matched.

There is no inherent reason that internal tuners need to have higher loss, though  in some
cases the smaller size of the components may make a difference.  But for the same amount
of power lost in the tuner, a larger external tune may dissipate the heat more efficiently,
while a smaller internal tuner may overheat.  Of course, some external auto-tuners may not
be any larger than an internal tuner.

Auto-tuners that use relay switching often have less capability to match high impedances
because the relays have a limited voltage rating, while for low impedances the manual tuner
may suffer from limited capacitance, while a relay-switched tuner can be designed to have
much more capacitance.

Then of course there is a lot of variation among external tuners due to how they are
assembled, include the effects of stray reactances, poor connections, and poorly planned
RF paths that have been known to make even large expensive units have poor efficiency.
Logged
KE3WD
Member

Posts: 5694




Ignore
« Reply #3 on: May 12, 2013, 11:21:41 AM »

There are other considerations besides just whether the tuner is internal or external. 

The design of the internal tuner is of importance.  For example, an internal tuner that uses relays to switch fixed capacitance and inductance in and out won't likely be able to keep up with an internal tuner that uses motor driven variable capacitance and possibly variable L as well. 

But that isn't the whole story either, there are different tuner designs that must be considered as well. 

Avoid the commonplace mistake of approaching a multiple-input problem by considering only one of the possible inputs. 

All possible inputs must be evaluated in each scenario. 

Whether or not the tuner is internal or external to the rig is likely one of the inputs that does not yield much in the way of the definitive. 

73
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #4 on: May 12, 2013, 11:22:23 AM »

which is more efficient, a good external tuner or the internal rig tuner?

For most cases, I don't think it matters.   The radios now auto-tune and get the signal out.  With an Amp - missing 50W isn't going to make a difference with 600W+

Yes, all the other factors are more important.

I was using my Kenwood auto-tuner but bought the Palstar AT2K (great product for $$) because of 80 and 160M dipole.   I also wanted to find out exactly where I stood.

If you want to see exactly what's going on and don't mind moving the dials to pre-recorded numbers you put on a cheat sheet.. it works.   Otherwise the radios tuner will work fine and an external meter like the Diawa CN-801HP will guide you.

I was playing with the RTTY Volva contest last night and I was down at 14.0850 where I'm usually not.   I could auto-tune but I have the AT2K now and moved the output dial just a little and the Reflected needle lays flat with maximum power and I can see it on both meters.   No doubt etc.

So I would say.. not necessary for most but a tool.
Logged
KD2CJJ
Member

Posts: 368




Ignore
« Reply #5 on: May 12, 2013, 11:28:05 AM »

Tom

Unfortunately I'm fighting my environment.. Eventually I will raise the antenna to get it away from the aluminum flashing and aluminum ridge vent.

The issues are at specific headings thus why I can't believe it's anything else.  I will be borrowing an analyzer to confirm this.  Even with this small swr shift the antenna performs better in comparison to my end fed up 40 feet and my wire fan dipole... It's limited bandwidth is really the only crutch... With that said it does need a tuner when I go outside the resonant range which is about 100khz and why a tuner is absolutely needed with this Antenna...  And thus why I have been inquiring about tuners....
 


Mike,
Efficiency, a nefarious term. The Losses involved in the turner are small compared to the coax line losses. Start at the antenna is the SWR low across the band? Did you plot SWR in different beam headings? What is the bandwidth of the antenna vs the bandwidth of antenna tuner regardless of interior or exterior. If you don't have an antenna analyzer beg borrow one. Measure close to the antenna with a known good piece of coax. Rotate your beam check again. I read the other post. Personally I use a manual external tuner. If the antenna is stable suspect cables move down the line. 
Getting back to inefficiency a receiving station won't know the difference. your jumps in swr are more than likely a mechanical problem. and where your antenna is mounted you have good access to it to check it out.
I saw you state it was not the antenna on the other postings, are you sure? He sure gave you sound advice.

Tom Kb3hg
Logged

73

Mike
KD2CJJ
W5DXP
Member

Posts: 3532


WWW

Ignore
« Reply #6 on: May 12, 2013, 11:39:08 AM »

which is more efficient, a good external tuner or the internal rig tuner?

Mostly a moot point with those maximum SWR=3:1 internal tuners. If an internal tuner can match the impedance, it's not a big mismatch and therefore probably efficient. The biggest advantage that an external tuner has is the much wider range of impedances that it will match. So which is better, an inefficient external tuner or an internal tuner that cannot achieve a match? Smiley
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K0JEG
Member

Posts: 627




Ignore
« Reply #7 on: May 12, 2013, 11:39:48 AM »

Would an exception be a tuner at the antenna instead of at the radio? Just thinking that with good quality coax (consistent impedance) the signal will lose less in the coax due to strange/less than idea mismatches.
Logged
W5DXP
Member

Posts: 3532


WWW

Ignore
« Reply #8 on: May 13, 2013, 05:14:26 AM »

Would an exception be a tuner at the antenna instead of at the radio?

More like a third option - 1. internal vs 2. external vs 3. remote. A good remote tuner indeed does alleviate the coax line losses due to SWR. Here is such an antenna:

http://www.w5dxp.com/vert4010.htm

Technically, a remote tuner is also external, but most hams would assume the context of an "external tuner" being located in the shack between the transmitter and the transmission line.
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KD2CJJ
Member

Posts: 368




Ignore
« Reply #9 on: May 13, 2013, 08:29:12 AM »

Interesting discussion.... 

If we assume that the line is not resistive and is capacitive thus having a high SWR, can anyone explain to me the theory behind why there are "losses" in the feedline WHEN there IS a tuner inline, the SWRs are 1:1 AND the transceiver is putting out full power (since there is no fold back due to high SWR)?

AND

If we assume the above, does this have an affect on receive?
Logged

73

Mike
KD2CJJ
WB6BYU
Member

Posts: 12986




Ignore
« Reply #10 on: May 13, 2013, 08:58:37 AM »

Quote from: KD2CJJ

If we assume that the line is not resistive and is capacitive thus having a high SWR...




First we have to get the terms right:  the line isn't capacitive, though the load
impedance attached to it might be.

Transmission lines have a characteristic impedance:  when terminated in this
impedance, the current and voltage are the same all along the line.  When terminated
in a different load impedance, the impedance (the ratio of the voltage to the current)
will vary along the line.  The effect is that the voltage and/or current (at different points)
are higher then the matched condition:  most of the feedline loss is due to increased
current flowing through the same resistance.

Transmission lines are sometimes seen as capacitive at very low frequencies, such as the
AM BC band, where the total length is much less than half a wavelength.  In that case
you can analyze short pieces of coax as being capacitive if the load impedance is higher
than the characteristic impedance.  But that's just an approximation, and it falls apart
as the coax length gets longer with respect to the operating wavelength.  It is rarely
a practical means of analysis for HF antennas.



Quote

can anyone explain to me the theory behind why there are "losses" in the feedline WHEN there IS a tuner inline, the SWRs are 1:1 AND the transceiver is putting out full power (since there is no fold back due to high SWR)?



Quite simple:  if the tuner is at the shack, the SWR on the coax from the tuner to the
antenna is still operating at a high SWR, regardless of the tuner adjustments and transmitter
output power.  The tuner just reduces the SWR on the coax between the tuner and the rig,
presenting a favorable impedance for the transmitter to deliver power into.

There are two main sources of loss in a transmission line:  the inherent loss of the matched
line due mostly to the RF resistance of the conductors (which varies with frequency), and the
additional loss in the line due to high SWR, due to the higher currents required to transfer
the same amount of power.

Even when the far (antenna) end of the coax is open or shorted, there will still be some
finite impedance at the shack end of the coax due to losses:  for example, with 100 feet
of shorted RG-213 on 20m, the impedance at the shack is about 14+j73 ohms.  This is well
within the matching range of many tuners.  So you can adjust the tuner and your rig will see
a perfect 1 : 1 SWR and deliver full power output.  Since there is no load connected on the
far end of the coax, all that power will be dissipated as heat either in the tuner or in the
feedline.  Obviously the losses in the feedline are very high, even though the rig sees a
good match.

That's why you can't use the ability to match your antenna with a tuner as any indication
of how well your antenna is working.



Quote

If we assume the above, does this have an affect on receive?



The receive case is slightly different since the load that the feedline sees is the input
impedance of the receiver transformed by the tuner settings.  But when the receiver
input is close to 50 ohms, conditions will generally be similar for transmit and receive.

That's why we often preset our tuners for best receive signal before keying the
transmitter - it allows us to find approximate tuner settings.
Logged
W5DXP
Member

Posts: 3532


WWW

Ignore
« Reply #11 on: May 13, 2013, 11:15:36 AM »

... the SWRs are 1:1 ...

That is the SWR on the three feet of coax between the transmitter and the tuner input and has nothing to do with the actual SWR between the tuner output and the antenna. If one wants to know the actual SWR on the 50 ohm coax between the tuner and the antenna, one needs to install an SWR meter between the tuner and the antenna. One way to do that is to set the transmitter and tuner to a low power level, put the tuner in bypass mode, and measure the actual SWR at the tuner output.

I have an IC-756PRO with a built-in autotuner. I also have an Autek WM-1 SWR meter on my transceiver output so I will always know what SWR the autotuner is having to deal with.
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KD2CJJ
Member

Posts: 368




Ignore
« Reply #12 on: May 13, 2013, 11:44:27 AM »

WB6BYU
Wow.... I had an Ahhhhah moment! I have to say this is by far one of the best responses I have ever had to a question - and I ask a ton (some a little far fetched I might add)!  

I am studying for my Extra and in parallel  studying Antenna System theory and this cleared up a few misunderstandings I had - which in turn has brought some clarity on other related topics/areas.

 

Much appreciated!

W5DXP
Thanks and I actually did that after submitting this thread and another tuner thread.  I used my internal tuner and internal SWR meter to contrast what was the SWR on my external feed line system... and clearly the SWRs were different after a tune (before the tune they were the same).  The SWR meter read the true SWR and the internal SWR meter, after the tune showed a 1:1.


I read your article: http://www.eham.net/articles/29821 Could you bring some clarity what you were saying in this article as it to my understanding, which may be wrong, is contradictory to the above.

PS - great article!

Quote from: KD2CJJ

If we assume that the line is not resistive and is capacitive thus having a high SWR...




First we have to get the terms right:  the line isn't capacitive, though the load
impedance attached to it might be.

Transmission lines have a characteristic impedance:  when terminated in this
impedance, the current and voltage are the same all along the line.  When terminated
in a different load impedance, the impedance (the ratio of the voltage to the current)
will vary along the line.  The effect is that the voltage and/or current (at different points)
are higher then the matched condition:  most of the feedline loss is due to increased
current flowing through the same resistance.

Transmission lines are sometimes seen as capacitive at very low frequencies, such as the
AM BC band, where the total length is much less than half a wavelength.  In that case
you can analyze short pieces of coax as being capacitive if the load impedance is higher
than the characteristic impedance.  But that's just an approximation, and it falls apart
as the coax length gets longer with respect to the operating wavelength.  It is rarely
a practical means of analysis for HF antennas.



Quote

can anyone explain to me the theory behind why there are "losses" in the feedline WHEN there IS a tuner inline, the SWRs are 1:1 AND the transceiver is putting out full power (since there is no fold back due to high SWR)?



Quite simple:  if the tuner is at the shack, the SWR on the coax from the tuner to the
antenna is still operating at a high SWR, regardless of the tuner adjustments and transmitter
output power.  The tuner just reduces the SWR on the coax between the tuner and the rig,
presenting a favorable impedance for the transmitter to deliver power into.

There are two main sources of loss in a transmission line:  the inherent loss of the matched
line due mostly to the RF resistance of the conductors (which varies with frequency), and the
additional loss in the line due to high SWR, due to the higher currents required to transfer
the same amount of power.

Even when the far (antenna) end of the coax is open or shorted, there will still be some
finite impedance at the shack end of the coax due to losses:  for example, with 100 feet
of shorted RG-213 on 20m, the impedance at the shack is about 14+j73 ohms.  This is well
within the matching range of many tuners.  So you can adjust the tuner and your rig will see
a perfect 1 : 1 SWR and deliver full power output.  Since there is no load connected on the
far end of the coax, all that power will be dissipated as heat either in the tuner or in the
feedline.  Obviously the losses in the feedline are very high, even though the rig sees a
good match.

That's why you can't use the ability to match your antenna with a tuner as any indication
of how well your antenna is working.



Quote

If we assume the above, does this have an affect on receive?



The receive case is slightly different since the load that the feedline sees is the input
impedance of the receiver transformed by the tuner settings.  But when the receiver
input is close to 50 ohms, conditions will generally be similar for transmit and receive.

That's why we often preset our tuners for best receive signal before keying the
transmitter - it allows us to find approximate tuner settings.
« Last Edit: May 13, 2013, 11:54:47 AM by KD2CJJ » Logged

73

Mike
KD2CJJ
NR4C
Member

Posts: 306




Ignore
« Reply #13 on: May 13, 2013, 12:59:23 PM »

It depends on the radio and the antenna and a lot of other things.

In the past it was easier.  Most older radios with internal ATUs were limited inthe range of impedances that could be matched.  But more recent models such as the Elecraft K3 and KX3, Ten-Tec Eagle and the Kenwood TS-590 and TS-990 have internal ATUs that are equal or exceed the range of external ATUs.  Note that this list may be outdated but the point is, check the specs on the ATU in question (interfnal or external) and make your choice.

...bill nr4c
Logged
W5DXP
Member

Posts: 3532


WWW

Ignore
« Reply #14 on: May 14, 2013, 07:06:49 AM »

I read your article: http://www.eham.net/articles/29821 Could you bring some clarity what you were saying in this article as it to my understanding, which may be wrong, is contradictory to the above.

That article has been revised and posted on my web page at:

http://www.w5dxp.com/OWT1.htm

The confusion seems to be between two types of matches, an impedance match and a conjugate match, and they are not the same when reactance is present.

If we are dealing purely with resistance values, an impedance match and a conjugate match are the same thing because the reactance is zero.

If we are dealing with reactive loads, an impedance match and a conjugate match are essentially the opposite of each other.

An impedance match implies an SWR of 1:1 but does not result in maximum power transfer when the reactance is not zero.

A conjugate match implies maximum power transfer but does not result in an SWR of 1:1 when the reactance is not zero.

Here's the tricky part. When we adjust our antenna tuners for a 50 ohm match to the transmitter, we have adjusted the conditions between the transmitter output and the tuner input to a resistance-only condition and thus have achieved both an impedance match and a conjugate match between the transmitter output the tuner input. The impedance looking into the tuner input is 50+j0 ohms and the impedance looking back into the transceiver (during receive) is 50-j0 ohms. That is both a conjugate match and an impedance match so maximum power transfer is occurring.

Let's say the impedance looking into the transmission line at the antenna output terminal is 100+j200 ohms which is clearly an impedance mismatch for 50 ohm coax. The SWR on the coax is 10.4:1. But that 50 ohm Z0-match at the tuner has an amazing effect. If the tuner is lossless and we measure the impedance looking back into the tuner output terminals (during receive) we will measure 100-j200 ohms. Thus, even when the SWR is 10.4:1, we have achieved maximum power transfer because the tuner is providing a conjugate match. This happens automatically when the tuner is adjusted for a 100+j200 ohm to 50 ohm impedance transformation.

Note that in the real world when losses are present, we are only achieving a near-conjugate match. As a rule-of-thumb, I consider anything withing 10% of an ideal conjugate match to be a near-conjugate match. That only occurs in low-loss systems.

We are always striving for a conjugate match at the tuner output. The only time we settle for an impedance match at the tuner output is when the reactance is zero in which case (and only in that particular case) an impedance match and a conjugate match reduce to the same thing.

Also note that in an ideal lossless system, a conjugate match at any single point in the system implies a conjugate match at every single point in the system. In the real world, we can only come close to that ideal condition because of system losses but we can achieve a conjugate match at a single point in the system which is usually at the tuner input when we adjust for the 50 ohm Z0-match. The fact that same 50 ohms is also an impedance match seems to be the confusing part.
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!