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[Articles Home]  [Add Article]  

Get Rid Of That Lossy (Lousy) T-Match

Dale (W6TZI) on August 16, 2014
View comments about this article!

L-match vs T-match, when properly designed they have about the same insertion loss but the antenna handbook says the L-match is harder to make due to unwieldy capacitance values.

I have read that what you get out of a T-match will be ( -1.5 db ) 23% less than what you put into it, OR WORSE. The " or worse " scenario is when the two series capacitors have low values, meaning the radio is lightly coupled to the antenna. The radio sees a good match, but much of the power is wasted in the tuner instead of being coupled to the antenna.

Tuning a G5RV type antenna with a MFJ type universal T-match would not be considered a properly designed matching network, specifically on any band where smaller values of series capacitance are needed to acquire a match. This also applies to the majority of all internal and external automatic tuners, as with rare exception, THEY ARE ALL T-MATCHES.

I recently built a 1/4 wave ground mounted vertical for 80 meters and wanted to incorporate a remote tuner at the base of the antenna to resonate the antenna on 40 and 30 meters. This antenna resonates on 80 meters with no tuner on the design frequency of 3.576 mHz with a SWR of 1:1 and a 1.5:1 bandwidth of around 150 kHz.

Not wanting the losses associated with a T-match, I decided to build a remotely tuned L-match for 40 and 30. After some trial and error I came up with a simple matching network that could get a 1:1 match anywhere on 7 - 7.3 mHz and 10.1 - 10.15 mHz using one variable capacitor ( the shunt element ) and band-switching the coil ( the series element ) by using one relay for each band. To remotely rotate the capacitor I used a 3 RPM gear-reduced motor and two relays for FWD and REV control of the DC motor.

Tuned the antenna on 7.076 mHz to a 1:1 match using the remotely controlled capacitor, and then switched the tuner to 30 meters and found that the SWR on 10.138 mHz was already a 1:1 match with no further tuning needed. Needless to say I was very happy about that! Essentially get 80-40-30 meters with no tuning ( only band switching ) on the design frequencies of 3.576, 7.076, and 10.138 MHz.

I was so happy that I bought a MFJ-948 antenna tuner for the purpose of converting it to a L-match to see how well it worked with my 80 meter ladder line-fed dipole. Well it worked amazingly well, resonating my dipole from 80 - 10 meters without having to modify any of the taps on the coil or the tap switch. The two capacitors were wired in parallel for the extra capacitance needed for 40 and 80 meters. I get 1.3:1 SWR or better on all bands with my G5RV type antenna, but what is truly amazing is that since the antenna is resonated with NO SERIES CAPACITORS I could hear what a GREAT RECEIVE antenna it really is. Yeah, for the FIRST TIME I could hear everything my antenna was receiving without the 23% OR WORSE loss of the T-match I used to use. Loss is a double-edged sword folks, cutting both TX AND RX.

I have a 20 meter 1/4 wave ground plane antenna that has a 1.2:1 match at 14.076 kHz, but it would be nice to work this antenna on 10,12,15, and 17 meters also, wouldn't it? Soooo I bought ANOTHER MFJ-948 and converted it to a L-match. Replaced its overly large coil with a smaller one and only needed one of the tuning capacitors to get the range needed for a good match on these higher bands. Could also get this antenna to tune well on 40 and 30 meters, but I have a better vertical antenna for those bands!

To recap, the L-match is simple to make and has no air gaps, just solid wire from the radio to the antenna. Great for ladder line-fed dipoles (G5RV) or any other coax-fed antenna that requires a tuner.

73 de W6TZI

Member Comments:
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Get Rid Of That Lossy (Lousy) T-Match  
by KF4CQR on August 16, 2014 Mail this to a friend!
My C-L-C tuner that I made has virtually no loss on 80 meters (my estimate is .1 -.3 db). I use big caps (900 pf each).
 
Any photos of your setup?  
by K3VAT on August 16, 2014 Mail this to a friend!
Thanks for the article. Do you have any photos or schematics of these L-C networks that you've built? Perhaps ones including the internal mountings of the various components?

Now that would be helpful (at least to me).
73, Rich, K3VAT
 
Get Rid Of That Lossy (Lousy) T-Match  
by W1ITT on August 16, 2014 Mail this to a friend!
I'm curious as to how you know that your T tuner is "lossy". Is some component heating? Do you see arcing across insulators? Energy has to go somewhere, and losses are often expressed as heat.
I have built and operated a few different T-match tuners at full legal limit, as well as broadcast stations at high powers, but I have yet to experience coil heating or heating at connections with properly sized components. There is plenty of folklore regarding tuners. Playing with words, there is no such thing as "loss" of energy. If a tuner is "lossy", then show me the heat.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by NO9E on August 16, 2014 Mail this to a friend!
T tuners are lossy matching low impedance loads. Biggest problem on lower bands where the capacitance is low. T tuner even has a loss at 50 Ohm load as there is a transformation up and down. Up generates high voltage.

T tuners are simple to tune.

L Tuners have no components switched at 50 Ohms and can match any load. But manual tuning takes longer time and one may run of capacitance.

L design is utilized in automatic tuners. Their biggest problem seems to be low Q of some toroids at higher frequencies.

I used T MFJ962C and L TT235. The first one tuned very fast but also heated up (changed SWR) at higher power and longer transmission. Never a problem with the second one at any power but tuning took much longer.

To find out more, see W8JI site, section on tuners. Also see losses and matching range in QST reviews. In these reviews, losses at high Z may be inflated IMHO.

In practice, if T works, let it be. If it heats up, then L. If you homebrew it for one antenna, L. One component less and lower V/A.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by NO9E on August 16, 2014 Mail this to a friend!
T tuners are lossy matching low impedance loads. Biggest problem on lower bands where the capacitance is low. T tuner even has a loss at 50 Ohm load as there is a transformation up and down. Up generates high voltage.

T tuners are simple to tune.

L Tuners have no components switched at 50 Ohms and can match any load. But manual tuning takes longer time and one may run of capacitance.

L design is utilized in automatic tuners. Their biggest problem seems to be low Q of some toroids at higher frequencies.

I used T MFJ962C and L TT235. The first one tuned very fast but also heated up (changed SWR) at higher power and longer transmission. Never a problem with the second one at any power but tuning took much longer.

To find out more, see W8JI site, section on tuners. Also see losses and matching range in QST reviews. In these reviews, losses at high Z may be inflated IMHO.

In practice, if T works, let it be. If it heats up, then L. If you homebrew it for one antenna, L. One component less and lower V/A.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W4OP on August 16, 2014 Mail this to a friend!
"I recently built a 1/4 wave ground mounted vertical for 80 meters and wanted to incorporate a remote tuner at the base of the antenna to resonate the antenna on 40 and 30 meters."

I don't see the relationship between VSWR and resonance.
An end fed half wave is resonant but the VSWR is around 80:1. Few classes of antennas display a low VSWR at resonance. Most need a matching network to achieve a low VSWR.

Dale W4OP
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by G3RZP on August 16, 2014 Mail this to a friend!
I agree with Dale about resonance and SWR.

A T match is fine for a 'match almost anything tuner with varying efficiency'. An L match has losses depending on the impedance transformation ratio: in some cases, the old fashioned link coupled tuner can do better. For my folded unipole vertical, I now have a an L match using a roller coaster from a WW2 RCA ET4336 tx, a 500 pF 7500 volt vacuum variable and a switched in 250pF 10kV, 25kVA ceramic padder for 160. The top loading was such that previously, I only needed one coil with a tap for 80 and one variable cap, with a padder added for 160 in the L network.. Then I changed the top loading from a Hy-Gain 205BA 5element 20 metre monobander at 62 feet and a Cue-Dee 4element 15 metre beam interlaced with a 4 element 10 metre beam at 68 feet to a 4 element SteppIR. Even with the directors and reflector bonded to the boom and the elements fully extended, I still need variable L and variable C to cover all of 160 and 80m. Both L and C are remotely tuned. If using remote tuning, build in provision for local control so you can be with the tuner and drive it for checking purposes.

You can get a good idea of what is needed by measuring the antenna impedance, but remember that antenna analysers (and VNAs!) lose accuracy (and some times, resolution) at high SWRs. But the L match may need two variables, depending on your impedance and their values may not be very practical.
 
Get Rid Of That Lossy (Lousy) T-Match  
by KB4QAA on August 16, 2014 Mail this to a friend!
25% losses in T matches, which most hams use? BALDERDASH!!!

Where is that heat? Could you keep your hand on a 25W light bulb? No tuner I've ever used gets that hot.

Test your claim. Put a power meter between the radio and tuner, measure then move it to the tuner output. The difference is losses.

http://www.w8ji.com/antenna_tuners.htm

Tom W8JI discusses T, L and EF Johnson Matchboxes and compares losses between T and L. They are almost all below -0.5db and generally around -0.1 or less.

However, the L tuner cannot cover as wide a range as a T match.

Bottom Line: Don't fret about losses in T matches. They are minimal.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by WB6BYU on August 16, 2014 Mail this to a friend!
The T match has a wider matching range: it is a better choice for a "match anything" circuit.

A given L network tuner can only match half the Smith Chart: that's why autotuners that use an L network have to switch the shunt element (which can be either a coil or a capacitor) between the input and the output to cover as wide a range of impedances.

The L network is a good choice if you know the impedance you have to match is greater than 50 ohms (preferably > 100 ohms), as is often the case with a long wire antenna that is longer than about 1/4 wavelength. But shorter lengths would require the step-down L network. (Yes, you can build a tuner so that you can swap the connectors to reverse the circuit, but that doesn't work if the box also includes an SWR meter.)


Also, having series capacitors has absolutely nothing to do with the loss in a tuner or any other circuit. Actually [i]coils[/i] are usually responsible for more loss in a tuner than the capacitors. An L network can just as well be built with a series capacitor and a shunt inductor - sometimes the values are more convenient that way. (It is easier to use a small switched coil than a large variable capacitor when you need a small reactance.)
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by WB6BYU on August 16, 2014 Mail this to a friend!
[quote author=KB4QAA]

Bottom Line: Don't fret about losses in T matches. They are minimal.

[/QUOTE]


Not always! I've seen coils get so hot the plastic support rods melt and they unsolder themselves from the circuit, and that was at well below the rated power.

But the problem is mostly at low impedances on 80m and especially 160m where the capacitors aren't large enough. (Bigger capacitors improve the efficiency in those cases, but make it harder to adjust on the higher frequency bands.)

Most often this happens when matching a high SWR in on coax with a feedline length that puts the tuner at a low impedance point in the circuit. Changing the length of the feedline will vary the impedance that the tuner has to match, and make a significant difference in the tuner loss.

Note that the losses can be significant for an L network in the same situation: it will likely require the shunt element on the rig side rather than on the antenna side, and the capacitor might need to be 2000pF to get a match. (That's an example where you might want to use a coil instead - a 1 uH coil has the same reactance as a 2000pf capacitor on 80m.)

You can evaluate the expected loss of a T-match using W9CF's convenient tune simulator applet here:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html

 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by G3RZP on August 17, 2014 Mail this to a friend!
A L network with the capacitor switched between ends has trouble at the boundary between the parts of the Smith chart where you switch ends because of the component values needed. Where you have a single antenna that you want to match, the best approach is to measure its feed impedance on the bands you are going to use it on, and then choose an appropriate network. A network such as T or whatever meant for an 'almost any impedance all bands' can well end up as a compromise needing a lot of experimentation with the variables to avoid the situation of large circulating currents in the tuner.
 
Get Rid Of That Lossy (Lousy) T-Match  
by N6JSX on August 17, 2014 Mail this to a friend!
Your article is sound but I'm confident you have lost most of the readers that are not familiar with these matches. They will have a hard time visualizing your concepts. Plus you have no measurable data over specific band spectrum just estimates.

Here is where eHAM should be proof reading and advise prior to posting on how to make an article reach out to eHAM's demographics. eHAM should work with the writer if they want to improve their hit counter views!

You need pictures/diagrams/drawings to give context. Or at a minimum reference web links or page numbers to ARRL Handbook, ARRL Antenna book or RSGB Antenna books.
 
Get Rid Of That Lossy (Lousy) T-Match  
by K1ZJH on August 17, 2014 Mail this to a friend!
All of the high power Ten Tec tuners that I have seen are L Match tuners. They seem to work fine.

I've a Dentron MT-3000A with damaged switch contacts (overheated) and a damaged coil when it was used to match an antenna with an extremely low impedance at 800 watts.

All tuners can be lossy and have design limits.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on August 17, 2014 Mail this to a friend!
I think the person above who mentioned that the "amount" of L and C settings overrides the type network itself is spot-on.

If a person (probably most of us) uses a T network, he'd be well advised to optimize his L/C combo settings. It will make a big difference in either case of the actual network design used.

 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by N4LQ on August 17, 2014 Mail this to a friend!
Hold the key down at 1000 watts for about 5 minutes and you'll find the heat. Lots of it.
Transmitting at a low duty cycle with SSB or CW won't heat anything.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by N4LQ on August 17, 2014 Mail this to a friend!
All automatic antenna tuners are L type. They have less loss than the T type. There was a QST review that verified this.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K0ZN on August 17, 2014 Mail this to a friend!
Agree with N4LQ. Put a brick on your key with a legal limit amplifier for a minute or two.....then CAREFULLY feel the components, especially the coil! Obviously, as stated, the LOAD that the tuner is seeing has a lot to do with heat and losses. With "reasonable" loads presented to a tuner, the losses are also reasonable. If you try to load a 20M dipole on 80M, expect to melt your tuner! Common sense (and a little technical knowledge) goes a long way in this game.

I also have seen tuner components get quite hot and also have seen them operate "cool" at high power levels.
"It is all relative....."

73, K0ZN
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K0ZN on August 17, 2014 Mail this to a friend!

This falls into the "DUH" Dept. but I guess I really should add this.....sadly, there are people out there......

DO NOT ATTEMPT to touch or feel any Tuner components while transmitting !!! Even with 100 W you can get a nasty RF burn. At legal limit you WILL get a trip to the ER for treatment of serious burns.

73, K0ZN
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W5WSS on August 17, 2014 Mail this to a friend!
K0ZN W5WSS likes your reply funny.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W5WSS on August 17, 2014 Mail this to a friend!
To WB6BYU assertion spot on. Knowing what the impedance excursion ranges are prior to applying a tuner type helps allot.

Use a T-match with an integral 1:1 current balun for the higher ranges of impedance, and in most cases the multi band doublets benefit the T-match tuners.

Do not assume measure first.

73
 
Get Rid Of That Lossy (Lousy) T-Match  
by K1DA on August 17, 2014 Mail this to a friend!
This is counting angels on the head of a pin.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by N4LQ on August 17, 2014 Mail this to a friend!
A HOT pin.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by N4LQ on August 17, 2014 Mail this to a friend!
Ahhhh....A balun! Another nice gadget to heat up.
 
Get Rid Of That Lossy (Lousy) T-Match  
by JOHNZ on August 17, 2014 Mail this to a friend!
T versus L and L versus T, an endless discussion as to which is better. Fact is each has advantages and disadvantages. Actual loss differences are insignificant.

OK, maybe the L has a little less loss, plus it "self-protects." It will not match a bad load impedance and usually will not match loads that greatly increase heating. L will match known load impedances on a single band but are not good for wide range general matching, unless you want to spend some time and money.

If you get frustrated with the L match, go back to the cheaper T match, because it will easily match more things.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by N4LQ on August 17, 2014 Mail this to a friend!
Ok....T match and a fan.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K3VAT on August 18, 2014 Mail this to a friend!
to N4LQ: Quote "... all automatic tuners are L ..."

Not so. Check out this top-of-the-line auto tuner from Germany: http://arraysolutions.com/Products/Remote_Tuners.htm

Of course, if one considers a Pi arrangement just two back-to-back Ls, then the quote may be considered correct.

73, Rich, K3VAT
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by AI4WC on August 18, 2014 Mail this to a friend!
In the real world, when we don't get a match, we begin usually begin by adjusting our antenna, or try our other tuner (surely, we all have more than one?). At least, that's been my experience. Heck, I don't even know which kind of tuner my MFJ 945E, my LDG AT200 or my Kenwood AT-130 is; I would be even more pressed to verbalize the problem in terms of tuner type(s). As with most articles like this, if I get something out of it; fine. If not, I move on to the next article. Life is too short to argue such things. Next!!
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K1DA on August 18, 2014 Mail this to a friend!
You could take the cover off and looki nside. It's allowed.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W6GX on August 18, 2014 Mail this to a friend!
Tuner losses at 6.25ohms 8:1 SWR on 160m. Source: ARRL

Palstar AT-Auto 42%
Palstar HF-Auto 41%
Ameritron ATR-30 20%
MFJ-986 47%
Vectronics HFT-1500 45%
Ten-Tec 238A (L tuner) <10%

Tuner losses at 6.25ohms 8:1 SWR on 80m. Source: ARRL

Palstar AT-Auto 24%
Palstar HF-Auto 19%
Ameritron ATR-30 12%
MFJ-986 31%
Vectronics HFT-1500 42%
Ten-Tec 238A (L tuner) <10%
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by WB6BYU on August 19, 2014 Mail this to a friend!
And what are the corresponding losses at 400 ohms?


The Ten-Tec 238 is commonly thought of as an L-match tuner, but looking at the circuit that is only for the higher impedance positions. In the others it is a PI network with shunt capacitors at both the input and the output (though not very large ones.) It also allows terminals for adding external capacitance (nominally 1000pf) when needed for a match - a feature that would improve the efficiency of the T network tuners significantly at low impedances.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KB4QAA on August 19, 2014 Mail this to a friend!
Sooooo... the lesson is, If you are trying to load up things that don't remotely resemble an antenna, the L-match is more efficient! :)
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W6GX on August 19, 2014 Mail this to a friend!
Quote from KB4QAA "Sooooo... the lesson is, If you are trying to load up things that don't remotely resemble an antenna, the L-match is more efficient! :) "

On the lowbands very few antennas look like a proper antenna. On 160m who can hang a dipole at 1/2 WL AGL (260') or put up a 1/4 wave vertical that is 132' tall ;-)
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KB4QAA on August 19, 2014 Mail this to a friend!
So what? You can always set up an antenna improperly or choose an extreme impedance/swr as an example. :)
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KB4QAA on August 19, 2014 Mail this to a friend!
So what? You can always set up an antenna improperly or choose an extreme impedance/swr as an example. :)
 
Get Rid Of That Lossy (Lousy) T-Match  
by K7PHX on August 20, 2014 Mail this to a friend!
A T-Match may or may not be the simplest network for your setup. But a network is not "lossy" unless there is power being dissipated as heat. The usual suspect would be resistive losses in the inductor, but that is not the fault of the network design.
 
Get Rid Of That Lossy (Lousy) T-Match  
by W1FBV on August 21, 2014 Mail this to a friend!
Help me here. My TS-590 is set and rated at 100 watts out. The power output per the meter on my MFJ-962D tuner shows 100 watts, I assume to the antenna feed. Where is the 47% loss?
 
Get Rid Of That Lossy (Lousy) T-Match  
by K8NS on August 21, 2014 Mail this to a friend!
How about the pi-network? Food for thought.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by W6GX on August 21, 2014 Mail this to a friend!
W1FBV- the SWR and power meter in a tuner are positioned on the input side of the tuner. Power measurements taken on the output side of the tuner (i.e. antenna jack) won't be accurate due to the non-50ohms load. The SWR reading has to be on the input side of the tuner because that's what your radio/amplifier sees. Assuming the tuner is working as expected the SWR should be 1:1. So no you wouldn't see any losses since there's no power measurement at the antenna end with your current setup. Measuring losses of a tuner is a complex process. There's an article on this topic published by QST. I hope this helps.
73,
Jonathan W6GX
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on August 22, 2014 Mail this to a friend!
>>>>by JOHNZ on August 17, 2014
OK, maybe the L has a little less loss, plus it "self-protects." It will not match a bad load impedance and usually will not match loads that greatly increase heating. L will match known load impedances on a single band but are not good for wide range general matching, unless you want to spend some time and money.<<<<


Yeah, and I get a little suspicious about grand claims such as the thread author have made in comparing the two types. As with anything, especially in electronics/ham radio, there's no super-duper anything. If the L network is trying to match something by using lots of L, the coil efficiency will become a huge factor, so much to the point that it may even look resistive to the transmitter. That means joule heating.

I don't know, maybe he's got a smaller point than he's asserting, but this is classic back-to-basics stuff....big, long well-designed antennas are everything.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on August 22, 2014 Mail this to a friend!
>>>>by AI4WC on August 18, 2014..... Heck, I don't even know which kind of tuner my MFJ 945E, my LDG AT200 or my Kenwood AT-130 is; I would be even more pressed to verbalize the problem in terms of tuner type(s....<<<<

Whoa, seriously? Well, I guess the learning never ends, even for someone with an extra class license. Good grief.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KL7CW on August 23, 2014 Mail this to a friend!
An L tuner will often suppress harmonics of the TX frequency better. A T tuner will often be better suppressing energy below the TX frequency. For someone located near a high power AM Broadcast station a T tuner might just reject enough BCB energy to improve receive. However a BCB rejection filter on the RX would offer much better attenuation. Likewise an L tuner might offer better attenuation of close by high power FM stations, although self resonances due to lead length and component selection probably would compromise attenuation of VHF and UHF frequencies. A good LPF in the TX or RX path would do a better job of
FM rejection. Both L and T tuners can be effective matching tools in different situations.
Rick KL7CW Palmer, Alaska
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K0BG on August 25, 2014 Mail this to a friend!
Interesting comments.

I don't know about the harmonic suppression attribute, as the LC match in all of the units I'm aware of, is highpass.

LC tuners don't match line Z very well either, and if you plot one on a Smith Chart, you'll know why.

Someone mentioned T match doesn't do too well at low Zs, and that's true. But they don't do high Z (&#8776;>2.5K&#937;) very well either.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on September 2, 2014 Mail this to a friend!
>>>>by W1FBV on August 21, 2014 Help me here. My TS-590 is set and rated at 100 watts out. The power output per the meter on my MFJ-962D tuner shows 100 watts, I assume to the antenna feed. Where is the 47% loss?<<<<


It's not happening. Those "terrible" loss figures that W6GX and others are claiming are at the very edges and extremes of feed impedances and antenna matcher capabilities. By intended omission, they're misleading people grossly into thinking it's the case for all scenarios....but it's most definitely NOT the case at all.

 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on September 2, 2014 Mail this to a friend!
This whole thing is crazy. Pi, L, T (which is simply a double L)....they're all going to perform poorly if you're loading up a coat hanger. Why these discussions get so much play is beyond me, but never is their any mention of the idiocy of purchasing Isotron antennas, etc. They're alive and well, even after all of these years....there's obviously a (very misguided) market for them, and your friendly AES salesman will hook you right up with one. L vs. T losses are "junior varsity" compared to snake oil like that.

Again.....big, conventional, well-designed antennas that don't show a gross impedance to an antenna matcher will make topics like this as moot as they are ridiculous.

 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KI4WCA on September 6, 2014 Mail this to a friend!
To K9MHZ...it is difficult on a small city lot to erect a decent full size antenna for 80 or 160.In extreme cases like this the L tuner has some advantage.Look me up on qrz and laugh at my homebrew L/pi tuner.I get out pretty well with my very compromised antenna. The L tuner is better....but the size of the capacitors makes it expensive to match a large range.Mine is configured as a low pass network as well.

Very low impedance on 160 here.No problem with my ugly tuner.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by K9MHZ on September 8, 2014 Mail this to a friend!
It's all a matter of degree, OM. The boilerplate matter is big compromise and inefficiency. Using an L versus a T is just a Bandaid. When you compare them in feeding good systems, the differences fade substantially.

Hey, whatever works for you....that's great. I'm just very leery of those (the OP) who discover something they think is magical, when they're just showing how much they really don't know. Hey, I'm anything but an expert, but this hobby sees so much ignorant hype that it gets tiresome.

Have fun, those low bands are great. 73.
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KI4WCA on September 8, 2014 Mail this to a friend!
I hear you.The other thing the L has over the T is the L tunes up in only 1 possibility...it either tunes or it doesn't.A T tuner can be tuned to a number of incorrect and inefficient positions.And this can lead to problems!!True, experienced users shouldn't make this error but it happens.I agree wholeheartedly that a better antenna system makes the differences fade....but real world applications often use very sub optimal elements.
This is why I don't have a Rhombic or Sterba curtain or a lazy H or a phased tower array. So I minimize loss where I can.A Wullenweber would be cool too....

Or a very high Yagi for 80m 5 elements would be nice.

But yes, I understand your frustration.

 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by NJ0IP on September 11, 2014 Mail this to a friend!
Gentlemen,
There is an awful lot of generalization here. Most of the answers I read can be right and can be wrong - depending on the circumstances.

The circumstances include the frequency, the impedance, and the dimensions of the components of the particular matchbox.

A properly dimensioned and properly tuned T-Match will come so close to the efficiency of the L, that there is no noticeable difference. The problem is, most people have no clue how to properly tune it.

Making a statement like "get rid of that lossy tuner" is kind of silly without saying which tuner is lossy. Not all T-Network tuners are lossy, at least not at all frequencies and all impedances.

The ARRL has tested an abundance of tuners in the past 15 years and published specs on efficiency. However finding all the articles in one place is difficult.

To help compare tuners, I have created a "Matchbox Shootout" which is an Excel spreadsheet showing efficiency by frequency and impedance for each matchbox, as tested by the ARRL. I have not changed anything, but I have added background colors (green, blue, yellow, orange, red) as indicators of the efficiency (i.e. Green = <10% loss). This makes it easy to find a matchbox which will be efficient for your needs (if you understand your needs).

You can download the Shootout at the bottom of the page and see for yourself, here: http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ .

BTW, the German matchbox referred to earlier is not a fully automatic matchbox; it is semi-automatic - manual tuning but memories for automatic returning to the settings. There is even a separate, similar box called the Christian Coupler.

73
Rick, DJ0IP
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by NJ0IP on September 11, 2014 Mail this to a friend!
Gentlemen,
There is an awful lot of generalization here. Most of the answers I read can be right and can be wrong - depending on the circumstances.

The circumstances include the frequency, the impedance, and the dimensions of the components of the particular matchbox.

A properly dimensioned and properly tuned T-Match will come so close to the efficiency of the L, that there is no noticeable difference. The problem is, most people have no clue how to properly tune it.

Making a statement like "get rid of that lossy tuner" is kind of silly without saying which tuner is lossy. Not all T-Network tuners are lossy, at least not at all frequencies and all impedances.

The ARRL has tested an abundance of tuners in the past 15 years and published specs on efficiency. However finding all the articles in one place is difficult.

To help compare tuners, I have created a "Matchbox Shootout" which is an Excel spreadsheet showing efficiency by frequency and impedance for each matchbox, as tested by the ARRL. I have not changed anything, but I have added background colors (green, blue, yellow, orange, red) as indicators of the efficiency (i.e. Green = <10% loss). This makes it easy to find a matchbox which will be efficient for your needs (if you understand your needs).

You can download the Shootout at the bottom of the page and see for yourself, here: http://www.dj0ip.de/antenna-matchboxes/matchbox-shoot-out/ .

BTW, the German matchbox referred to earlier is not a fully automatic matchbox; it is semi-automatic - manual tuning but memories for automatic returning to the settings. There is even a separate, similar box called the Christian Coupler.

73
Rick, DJ0IP
 
RE: Get Rid Of That Lossy (Lousy) T-Match  
by KM3F on September 23, 2014 Mail this to a friend!
Out of curiosity I did some testing with my old Heathkit SA2060 both at Cin/Cout at zero and matched flat with the L, and at Cin/Cout at 100 matched flat with less L.
I could see a perceptible different on the watt meter for I presume a loss of about 10 watts out of 400 watts from my AL80B at 7.255 with 25 watts of drive to the amplifier.
The power meter used is an Autek WM1 set on average.
The setting of zero Cin/Cout with the higher L won the test by that small amount on this T type tuner.
I would assume this indicates the high C (lower loss impedance power pass through) with higher impedance L to ground is the better lower loss setup even though it's not an L circuit.
10 watts loss out of 400 is not that much but maybe at 1500 watts the same percentage might be a consideration in some tuner designs.
Good luck.
 
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