Print

[W9IQ]

simple solution:  use a resonant antenna and eliminate the tuner

Resonance does not necessarily negate the need for a tuner. Resonance simply means no reactance. It says nothing about the real part of the impedance.
nor its match to the Z_O nor the match of the input impedance to the rated output impedance of transmitter.

- Glenn W9IQ

[W1VT]

My 80M top loaded vertical has a 2:1 SWR of about 200kHz.  I can change the top loading wires to set it for either phone, data, or CW.
It is more practical to use the in shack tuner and accept the decrease in efficiency when the weather turns bad.
Especially when it is 13 degrees and my back yard has a large sheet of ice directly under the 80M feedpoint. 
Falling on ice is a big danger when you live in New England.

[W6MK]

An inexpensive IR cooking thermometer can be used to measure temperature rise in different parts of the the antenna system.
Zak W1VT

Or it can be used to measure any comparative temperature rise in each tuner's inductor when the system is tuned.

[KH6AQ]

I am wondering how much difference in loss there is between the two tuners if the mismatch is the same?

Here is one way to answer your question. You will need another receiver located from 1 wavelength to a few miles away. An ionospheric path such as the RBN or another station is not suitable to discern the (probably) small difference between antenna tuners. 

Method 1
Set up a RX (mobile, another ham's house, etc.) some distance away.
Tune tuner A at 100W and record the remote S-meter reading.
Tube tuner B at 100W and record the remote S-meter reading.
Repeat tuner A, B, A, B to account for short term measurement variations.

Method 2
Set up a TX (mobile, another ham's house, etc.) some distance away. It can be a 1 mW.
Tune tuner A at 100W and record the S-meter reading of the remote TX.
Tube tuner B at 100W and record the S-meter reading of the remote TX.
Repeat tuner A, B, A, B to account for short term measurement variations.

Note that while an IARU S-unit is 6 dB, some Japanese S-meters are 3 dB/S-unit. The Elecraft K3 is 6 dB/S-unit. A QST review might show many dB/S-unit your remote receiver is. Or, use a 1 dB/step attenuator to determine it. If you have such an attenuator it can be used to adjust each tuner test for the same S-meter reading.

This method can discern a 2 dB difference and I would not be surprised if you find no discernable difference between tuner A and tuner B.

[WA3SKN]

Like others, I would be less concerned about the loss differences in the tuners and more concerned about the coax losses with the mismatch.  But the coax length and loss has never been addressed.  A 5:1:5 SWR dummy load could easily be made either/or 5 ohms and 250 ohms and measurements be made.
As far as the 80m bandwidth issue, consider making a 3 or 4 wire folded dipole and feed it with open wire line and your tuner for a low loss high bandwidth solution.
Losses are easily measured.  What test eqpt do you have available?

-Mike.

[KT0DD]

simple solution:  use a resonant antenna and eliminate the tuner

As I previously stated, I rent and don't have the real estate for a resonant antenna for each band or resonant antenna on every section of each band. Many hams like me have to compromise. I have 2 antennas to make 75-10m and that's all I can have.

Todd - KT0DD

[KT0DD]

Hi,

I'd keep the Ten-Tec as it's a very good tuner.  Not much to go wrong with the metering circuit.  If the lower power ones work, the only things it could be on the 2kW circuit is the calibrating trimmer pot or switch.  I could just be that the trim pot contact is dirty.  Those can lose contact after sitting in one place for ages.  Mark the location and put a bit of Faderlube on it.

73

I got into the tuner today and after some probing around, you were right. It was the VR that controls the meter setting in the 2000-watt range. With some working it back and forth and spraying a tiny amount of DeOxit on it, the 2000 range is reading fine. I set it to match the readout on my AL80B amplifier power meter as it's the only reference I have. I'm sure it's close enough. I'll probably keep the 238C for now and use the Palstar on my backup station. Thanks for the advice on where to look. 73.

Todd - KT0DD
 

[KT0DD]

Thanks to all who furnished constructive replies. I fixed the faulty power meter and installed the Ten Tec 238C in my main operating position. It takes a little more adjusting at first vs the Palstar, but I'll make a tuning chart for the settings like I have on my AL80B amp. The Palstar AT2KD will go on my backup station FT101EE, AL811H and the AT2KD.

The 02/2003 ARRL review of the Ten Tec 238C L-Network shows it to have the lowest insertion loss of all the tuners (except for on 10 meters) tested at that time. I hadn't read that review until now.

I'll be keeping both tuners for now. 73.

Todd - KT0DD

[N2SR]

simple solution:  use a resonant antenna and eliminate the tuner

As I previously stated, I rent and don't have the real estate for a resonant antenna for each band or resonant antenna on every section of each band. Many hams like me have to compromise. I have 2 antennas to make 75-10m and that's all I can have.

Todd - KT0DD

two words:  fan dipole

[KT0DD]

two words:  fan dipole

Possibly. PITA to trim to resonance on every band if I build my own and no guarantee the commercial ones won't need trimming, but I'll look around. Still may need a tuner for band edges. Already have something in the air, and really don't want to change as my health has taken a downturn. Maybe this late spring I'll re-visit it. 238C is tuning everything for now.

[N7EKU]

Good news Todd,

I'm glad it was a simple fix!

Hope your Holidays are great and have a happy new year :-)

73,  Mark

Hi,

I'd keep the Ten-Tec as it's a very good tuner.  Not much to go wrong with the metering circuit.  If the lower power ones work, the only things it could be on the 2kW circuit is the calibrating trimmer pot or switch.  I could just be that the trim pot contact is dirty.  Those can lose contact after sitting in one place for ages.  Mark the location and put a bit of Faderlube on it.

73

I got into the tuner today and after some probing around, you were right. It was the VR that controls the meter setting in the 2000-watt range. With some working it back and forth and spraying a tiny amount of DeOxit on it, the 2000 range is reading fine. I set it to match the readout on my AL80B amplifier power meter as it's the only reference I have. I'm sure it's close enough. I'll probably keep the 238C for now and use the Palstar on my backup station. Thanks for the advice on where to look. 73.

Todd - KT0DD