- Dentron Super Tuner Plus Manual
- Dentron Super Tuner Plus Schematic
- Dentron Super Tuner Plus Manual Free
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Modifying the Dentron Super Tuner
Modify your amateur radio to get better performance, or more functions. This site is for HAMs there want all the best from his radioamateur equipment. Visit you will not be disappointed. Dentron 160 - 10 Super Tuner Schematic Operating. DENTRON SUPER TUNER PLUS-ANTENNA TUNER For SaleThis is the Dentron Suoer tuner plus which we repaired here and had on another site and this is working perfectly and is a very nice piece.its a 1 KW rated tuner of superior design and well made.it has a monitoring circuit and relative output met free classifed ads used surplus electronics. A heavy duty 2 core balun is included for open wire or single long wire operations. A selector switch on the front panel allows selection of an alternate antenna (or dummy load), bypass, coax, single, and balanced. Power handling capability of the Super Tuner Plus is 1 KW CW and 1200 Watts PEP SSB (both measured in DC input to the final amplifier).
Antenna Tuner
I’ve owned quite a number of antenna tuners, both commercial and home-brew throughout my 50 plus years of ham radio.One of the most practical and useful tuners I ever owned was the one made by the Dentron Company back in the 1970s and early 80s.The one they called the “Super Tuner” is small but will match a wide range of loads.It was 10 1/4” wide, 5 1/2” high and 9 3/4” deep and had a nice black finish.
The tuner was the popular circuit with two variable capacitors in series with the input and output coaxial sockets and a tapped inductor between the junction of the two variables and ground.
I’ve seen various power ratings assigned to this unit but I think it was typically advertised as a KW tuner.I would not hesitate to run a 1200 watt amplifier to it and perhaps even higher if the tuner was not required to deal with an extreme SWR.The box sold for $99.99 back during its day and I’ve seen them sell for up around the $150 range on ebay, even in this day and age.
When I owned my ham store in Broken Arrow, Derrick Electronics, I sold many of these tuners and everyone always seemed happy with their purchases.The tuner has insulators in the rear apron to attach a single wire, a coax output, or a balanced feedline via the internal 4:1 balun.
To use these various outputs, one must disconnect the others, i.e., to use the coax output, the feedline to the balanced line must be disconnected or to load up a single wire antenna, the coax must be removed from the output coax socket. |
I use my Super Tuner when camping in my trailer and I’m never sure which type of antenna or feedline I might be using so I use them all, however, I thought it would be much easier to use a switch, accessible from the front panel, to switch the tuner circuit to the desired output appendage and remove the connection to the other, unused ones.While I was at it, I decided to add an SWR Bridge, a low and high scale wattmeter, and a dummy load.That prompted a desire for an additional feature of a hang-time peak-reading on the wattmeter.
This is the revised schematic for my Dentron Super Tuner 160-10. | |
The switch I used is a 3 wafer ceramic 6 position switch but I’m only using 5 of the 6 positions.This allowed me to select the 5 positions of: 1 – Wire antenna 2 – Balanced antenna (using 450 ohm ladder-line, etc.) 3 – Tuner to output to coaxial Antenna socket 4 – Bypass tuner – Input connects directly to Output 5 – Dummy load | |
The dummy load I used is the same non-inductive resistor used in the original Heathkit HM-31 Cantenna.As a matter of fact, I bought this one sometime in the 1970s from Heath Company as a replacement part for the Cantenna.Dentron also used the same resistor in their MT-3000A tuner as a built-in dummy load.Obviously, these sources are no longer available but you could add an additional SO-239 coax socket to the back apron and wire it as shown in the schematic.If you have a Heath Cantenna, a Dentron “Big Dummy,” an MFJ Dummy Load or any other good 50 ohm non-inductive load, you could plug it, via a piece of coax, into this added socket and accomplish the same thing. |
I also added an SWR / Wattmeter circuit to allow easier tune-ups without have additional external pieces and extra coax jumpers.The wattmeter has two ranges:0-100 watts and 0-1000 watts.The front panel also has a switch to allow for peak reading of the power.Since the meter movement cannot respond as quickly as the human voice, the peak reading feature lets you see a bit more accurately how high your output power is peaking.
The SWR bridge even has an extra RCA phono socket on the back to allow the user to plug in an additional meter to read reflected power while the panel meter is reading the forward power.I always intended to replace the front panel meter with a dual-needle meter so I could watch both forward and reflected power simultaneously but I just never quite got around to changing out the meters.The extra plug-in reflected meter accomplishes the same goal. |
The small meter used on the front panel comes from one of the cheap CB SWR bridges sold for many years.The pick-up circuit I use is more accurate than the one used in the cheaper CB bridge but the meter comes already printed with a calibrated SWR and wattmeter meter scale so that gave it a nicer appearance.I picked up my cheap CB bridge at a garage sale some years ago for, I believe, a dollar.
The original tuner unit is well built on a plated steel chassis.The built-in 4:1 balun is heavy duty and is the same one Dentron used in their MT-3000A tuner that was rated at 2000 watts.The pictures below show the Dentron Super Tuner as it was originally, prior to my modifications. |
Here’s what my modified Super Tuner looks like, looking at the front panel, the insides, and the rear part.
Dentron Super Tuner Plus Manual
The basic schematic for the Wattmeter/SWR Bridge is shown below:
The new schematic for the tuner is shown above when the additional pieces are added, the complete schematic for the wattmeter and tuner looks like this:
If you prefer to wire your tuner with the dual-needle meter you can use this schematic but it only shows it wired as an SWR bridge without the wattmeter calibration components:
The wattmeter is made using an Amidon T-68-2 core.This is defined as .68 inch OD and the –2 designates the frequency range for this core.The –2 core will be painted red.I wound 45 turns of #20 enameled wire around the core and it is center-tapped.The best way to do this task is to get a long piece of the wire in hand, find the center and scrape off the enamel for an inch or so.Twist that into a loop and wind the turns on the core.I would have used a bit smaller gauge wire if it had been available. |
The diodes used were silicon 1N914, which are just general-purpose units from my junk box.If I were buying new parts, and particularly if I expected to be using lower power transmitters, I would try to find a matched pair of germanium diode units like 1N34s.The germanium diodes have only a .2 volt junction drop whereas the silicon units have a .7 volt drop. |
The potentiometer that sets the forward and reverse SET position can be other values but should always be a dual-pot where both pots are the same value and move together. Since the Low/High calibrations are in series, adjust the Low power pot first, then the pot for High power. |
The capacitor used for the peak-reading feature is a tantalum type capacitor.There is a lesser possibility of the capacitor changing its value over time with this type.I used a 33 mfd/10 volt cap because I had that in my junk box and that value seemed to give me about the right hold time on peaks.I just noticed that my schematic shows this as a 33 pfd but that is incorrect and should be mfd. |
The switch used to direct the tuner to the various outputs was also a junk-box special and is held in place by the screws which hold the wafers together.Originally the switch had 4 wafers so the screws are too long after one wafer was removed.The extra length of the screws is noticeable in the rear view of my tuner as they stick out for an extra inch or so.I always planned to trim them down to something neater and, perhaps, some day I will. | If you were buying a new switch you would want a 3 pole-5 position non-shorting type and I prefer ceramic wafers since it’s carrying RF voltages.Many switches like this are actually 12 position for full rotation and if you want it to turn fewer positions, you can place a mechanical stop to limit the rotation to 5 or whatever you desire. |
Created January 13, 2009
Last updated04/07/2009 12:22:25 PM
Of all the transmatches I own, this is my favorite. It consistently gets a 5 rating on eham reviews. It does not attempt to add 'features' like a power or SWR meter or antenna selector, which I prefer to add separately. I am very picky about those items, and prefer to choose them separately. I have never found it lacking in performance. It matches any antenna I have ever connected to it. It handles all the power from my Heathkit SB200, about 700 Watts output with no signs of arcing or heating. I recently upgraded to a legal limit ALS-1300, and it works fine with that, for coax fed antennas. All the internal components are super heavy duty compared to commonly available new units. This transmatch comes in a variety of flavors. The early Dentron Super Tuner is rated at 1 KW; I have run it at 100 Watts AM (equivalent to 400 Watts or more PEP) with no problems. A smaller 160-10AT looks like it will be OK for a 100 Watt CW or SSB signal; I have another page for that tuner, with a mod which works better on 160 and 80 meters. A big brother is the 3000 Watt model, which is the exact same components as the MT-2000A, except it includes a SWR/Power meter. In the photos below, you can see the MT-2000A chassis is punched for the extra accessories included in the MT-3000. These all typically go for $90 to $300 depending on the power rating at swapmeets or better web sites. The authoritative clunk of the switch speaks of the quality and dependability of this well built unit. I quickly became dissatisfied with the match range and reliability of the Ten Tec 238 transmatch reviewed elsewhere on this page. These Dentrons are definite keepers. 5 out of 5.
Have you ever seen a manufacturer dare to state the insertion loss in dB? Read the specs included later to see. QST often finds even 2 or 3 dB on recent transmatch product reviews.
See the interior photos to understand the detaiiled notes below.
The only problem I encountered was the breakage of the lucite plastic insulators beneath the tuning capacitors. Some glue corrected this easily. Everything else is built like a tank. This unit weighs 18 pounds due to the substantial cabinet.
The lightning protect switch was stuck in place when I bought it used after a long period in storage. I applied some WD40 and let it soak in several times. I removed the knob and used vise grips to carefully rock the switch shaft till it became operable. Since I have external grounding type antenna switches, this feature is not used at my station. I always disconnect the antennas outside at a grounding rod when not in use during lightning season. If you find one at a swap meet with this switch frozen in the lightning protect position, just disconnect the wire to the right hand capacitor.
The capacitor tuning shafts have plastic extensions. If these ever break, I plan to use a ceramic shaft coupler and add surplus vernier reductions to the stock knobs. At higher frequencies, the tuning is a bit touchy, but not to the point that you cannot use it in stock form.
Building a transmatch that covers 160 through 10 Meters is a challenge. The capacitors have to have a maximum capacitance sufficient to function at 160 Meters. This makes it difficult to achieve minimum capacitance values to work at 10 Meters. You may find that the small vertical coil in the front of the cabinet can be adjusted by spreading its top two turns. This may allow better match on 10, 12, 15, AND 17 Meters. Be very careful you do not stress the switch while making this adjustment. Support the connecting wire to the switch with pliers to remove the stress from the ceramic switch.
The long piece of buss wire attaching the rear of the capacitors might benefit from replacement with wide copper strap or heavier guage wire. I plan to experiment with this later when appropriate.
The coax wires inside the transmatch could be replaced by RG8 mini.
EXTRACT OF SALIENT SPECIFICATIONS AND INSTRUCTIONS FROM MANUAL:Note - Full manual available at http://www.radiomanual.info/schemi/ACC_matching/Dentron_MT-2000A_user_WA0KKE.pdfSPECIFICATIONS:
NOT INCLUDED:
SUPPLEMENTARY TUNING INSTRUCTIONS:
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HOW TO ADD VERNIER TUNING TO THE DENTRON MT-2000A TUNER
The capacitor tuning can be jumpy and critical as you approach SWR minimum, as I noted above. If you really want to adjust SWR for exactly 1:1, a gear reduction to the capacitor tuning is a big help. The parts employed for this improvement are available from Ameritron, because they use the same technique to get smooth tuning of their amplifier plate tuning controls. The Jackson ball bearing drive and the red pointer (the smaller one) are what you need to buy. Also, this photo essay shows replacement of the plastic insulator rails which mount beneath the tuning capacitors. These fail when the unit is shipped or handled roughly. The plastic appears to be a brittle lucite, which is a good insulator, but not robust mechanically. I used some scraps of nylon from a project I did at work years ago. I learned from my grandfather (who went through the depression) to never throw out good pieces of a 2 X 4, because you never knew when you would need a piece of wood to fix something.
You may find that the leads on the balun are too short to reinstall it about an inch and a half to the left of the original position. You may either leave the balun out or extend the wires. This is a voltage balun; you should probably be using a modern current balun, if you need one. In that case, it needs to be mounted externally anyway. As baluns of this vintage go, this is a large robust one, and you may find it meets your needs just fine. It is potted in insulating material, so its arc resistance is better than you will find elsewhere. Teflon wire is used, for better heat resistance than standard insulation. Dentron gives extra attention this type of detail all through their product. I plan to do some tests on the balun that did not reinstall easily, and post data here later.
I chose to remove the 'lightning protect' switch permanently and replace it with a junk rotary switch, to preserve the appearance of the tuner. This feature can cause problems if you inadvertently leave it in the wrong position. The manual warns you about this, and rather than risk that outcome, I chose to disable the switch altogether. It also does not afford much true protection in the case of a lightning strike. I disconnect the coax antenna wires outside the house when the station is not in use. In any event, it does not need to be taken out to do these mods.
Dentron Super Tuner Plus Schematic
The coax used in the Dentron MT-2000 is RG-58/U. You could replace that with RG-8/U for better power handling capacity. This might be important if you use an end fed wire, since that coax section on the output is at higher voltages than might be expected for a coax fed antenna. Alternatively, heavy solid buss wire or copper strap could be used; in that case, some small SWR will result on 15 and 10 meters when you operate the tuner in bypass mode. I chose to leave it alone, since I had no problems at this time. Have whatever parts you need for this work on hand before beginning.
Dentron Super Tuner Plus Manual Free
You will also need to order the following parts from MFJ-Ameritron before you begin this project. Ameritron is kind to amateur radio homebrewers by selling parts used in their products, but PLEASE do your homework before calling and wasting their time. Small orders like this are not profitable for them; think about ordering something else to make it worth their while. An MFJ-212 antenna tuner adjustment noise bridge works nicely with any tuner. Or a new station clock from MFJ.
- 729-0142 planetary reduction (vernier) drive - TWO EACH
- 726-0230R small pointer - TWO EACH
- Note that this is the SHORTER length pointer style, not the 726-0227R.
- You COULD order the vernier elsewhere. You could make the pointer yourself.
You will also need two 2-56 screws 1/8 long, to fasten the pointer to the vernier drive, from your LOWE'S hardware store. Also obtain some 4-40 X 1/4 screws, nuts, and internal tooth lockwashers to mount the vernier drive to the front panel. I also used some longer 6-32 screws to mount the insulating rail to the chassis for my replacement rails. If your rails are in good shape, re-use the original Dentron hardware.
LETS GET TO WORK:
- First, you need to pretty much strip out everything except the coax connectors, Tuner/Bypass switch and wiring, and main inductor and tap selector wiring. Be sure to remove the balun and ceramic insulators, since the balun needs to be relocated or removed to clear the back of the right hand capacitor. If the wires of the balun reach, drill a new mounting hole about 1 to 1 1/2 inch to the left, as viewed from the front. Also drill a hole for the ground lug. It is easier to remove the ceramic insulators as wired to the balun, so you do not have to solder to reinstall them. Also, it eliminates the hazard of breaking the ceramic insulators when installing the new capacitor assemblies.
- Fabricate new plastic capacitor mounting rails, if needed. Be sure they are the same height of the original. Note there are small shim washers under the tuning capacitors. Also, I use mounting holes OUTSIDE the footprint of the capacitor, to eliminate the need of countersinking the mounting holes to secure the insulator rail to the chassis. You WILL have to countersink the holes for mounting the capacitor to the rail. I also use a drop of hot glue from a gun to ensure insulation from the chassis, once the final mounting position is determined. This prevents potential arcs to the chassis when using high impedance antennas. Another approach would be to drill a fairly large half inch diameter hole in the chassis under the spot where the capacitor mounting screws nearly meet the chassis.
- Punch new holes using a Greenlee punch to clear the front of the Jackson ball drive planetary gear reduction unit. Punch the front panel and the chassis separately. This new large front panel hole is shown as (1) on the photos below. The thickness is too much for the punch to handle both at the same time. This requires careful alignment of the punch to avoid the final holes not aligning properly between the chassis and panel. NOTE: The new Jackson planetary gear drive mounts to the INSIDE surface of the front panel and chassis.
- Mount the Jackson ball drive to the tuning capacitor. Do not lose the set screw, which is inside the plastic bag used to ship the unit. Only one set screw is furnished, and I did not need a second set screw to prevent dial slippage.
- Be careful when handling the capacitors to not break the plastic insulating shaft, which prevents electric shock. If you break the plastic, you will have to install an insulated shaft coupling to provide insulation, since the frame of the capacitor is hot, above ground potential. Due to the short shaft insulator, it will be difficult to find a suitable shaft coupling if you mess this up.
- Assemble the capacitor to its insulator rail and temporarily install the capacitor assembly in the chassis.
- Mark the mounting holes (2 in the photos below) for the planetary gear ears on the inside of the cabinet, using an automatic center punch. This punch, which does not require a hammer, is available at Harbor Freight. When you push the punch top part, it clicks and makes a mark to start a small drill. Assemble the front panel to the chassis, using the coil and tuner/bypass switches, being careful to align the capacitor access holes. Drill two very small pilot holes from the inside of the chassis, one for each ear of the planetary drive. Finish the drilling for clearance for a 4-40 screw. Keep these holes out on the ears of the drive, so that there is room for the nut.
- Complete the assembly of the capacitor, insulator rail, planetary drive, and screws holding it all together. The assembled unit mounts to the INSIDE of the front panel, as shown by the (3) arrow in the photos below. If you are going to use some hot glue to insulate the counter sunk capacitor mounting screws, this is the time to do it. Another approach would be to drill a fairly large half inch diameter hole in the chassis under the spot where the capacitor mounting screws nearly meet the chassis.
- You may need to 'adjust' the hole in the red pointer to align the hole in it with the Jackson planetary drive with a small modeler's file. Use a 2-56 screw to mount the pointer to the Jackson planetary drive. Install the capacitor tuning knob.
- Repeat the process with the right hand capacitor.
- Reinstall all wiring.
- Building a transmatch that covers 160 through 10 Meters is a challenge. The capacitors have to have a maximum capacitance sufficient to function at 160 Meters. This makes it difficult to achieve minimum capacitance values to work at 10 Meters. You may find that the small vertical coil in the front of the cabinet can be adjusted by spreading its top two turns. This may allow better match on 10, 12, 15, AND 17 Meters. Be very careful you do not stress the switch while making this adjustment. Support the connecting wire to the switch with pliers to remove the stress from the ceramic switch.
- Reinstall the balun. If the wires do not reach, you may be able to extend them with bare wire, or simply leave the balun out.
- Using an ohm meter, test the bypass function. Also test for shorts to ground.
- OPTIONAL: I observed that the coax used to wire the Dentron MT-2000A tuner is only RG-58/U. When running higher power, this could be a problem, especially on the output side with a high impedance antenna like an end fed wire. I did not replace it with RG-8/U, because I do not use it that way, and never have had any problems with it. I also did not wish to risk possible damage to the bypass switch during the modifications. You might want to upgrade to better coax while you are in there.
- NOTE: The coax connectors will melt if you use excessive heat. You can remove the nut and take the coax connector out, assemble the new coax to the connector, and reinstall it as an assembly, with the coax all stripped, tinned, and ready to solder to the tuner/bypass switch. You may find that premium grade RG-8/M will do the job for you, and is easier to work with than RG-8/U. Do not cut corners, if you are doing an upgrade. If you do this, it will be a lot easier to do it while the chassis is stripped, before you reinstall the balun and tuning capacitors.