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Author Topic: HomeBrew Tuner Parts Recommendations  (Read 16146 times)
K7ZRZ
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Posts: 279




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« on: June 09, 2010, 07:27:31 PM »

While this isn't specifically an amplifier topic, perhaps it's close enough.

I'm in the process of gathering parts and components for a motorzied remote tuner building project - just like the one that can be seen at the AB2CD QRZ.com page.  Looking down the page a ways, you will find pictures of the fine construction of his tuner.

I'm not experienced at all with small motors, pulleys, and belts. I'm hoping I can get some advice here as to what to look for in that department. I'd like to identify what motor is in those pictures... and where to look for little pulleys and belts like those shown. The motor is only identified as a dc motor, and the net is overloaded with small motors of all types. I'm hoping for some direction on this. I have already ordered a new roller inductor and variable capacitor.

I've communicated with Jim AB2CD in the past about his unit, but I'm unable to get a response from an email to him now that I'm ready to actually progress on this.

Thanks if you can help.
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Brian K7ZRZ
« Last Edit: June 09, 2010, 07:30:37 PM by Brian J. Ingoldsby » Logged

Brian K7ZRZ
K8AC
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« Reply #1 on: June 10, 2010, 04:32:11 AM »

You're looking for a "gear motor".  They may be found at www.jameco.com or www.allelectronics.com or a host of other sites.  Usually, the ones you see for sale are new surplus and an exact make/model is unlikely to be found.  But, Jameco sells a line of Chinese gear motors that are reasonably priced and seem to hold up pretty well.  The things to look for are: voltage, output RPM at rated voltage, output shaft diameter.   Most of the surplus motors seem to be 12VDC models, but many are 24 V.  The 24 V models will run fine on 12V, but at reduced speed.  You'll have to do some thinking about the RPM output you want and in a more conventional tuner design, you'd want a higher RPM output for a rotary inductor than for an air capacitor (the inductor might turn 22 times to cover it's range, the capacitor 1/2 turn).  Stick with 1/4" output shafts.

The cogs and pulleys can be purchased from Small Parts Inc. (www.smallparts.com).  Cogs are available with and without skirts and I usually mate a cog with skirts on both sides with one having a skirt on only one side.  That allows you to slip the belt off for service without removing a cog.  Small Parts has a good selection of cog sizes, so you can easily gear up or down if required using the appropriate belts.  For example, on my tuner I drive 10 turn sensor pots and so I have to match a 10 turn pot to a 20+ turn inductor and to a 25 turn vacuum capacitor. 

Here's a link to my website (www.k8ac.net) where you'll find a link to some photos of my tuner which makes extensive use of the cogs and belts from Small Parts.  This tuner was a prototype and no attempt was made to optimize the space used and there's no housing as it resides in a garden shed.  It's been in operation for 7 years now and over that time I've lost one gear motor to lightning.  It's a good idea to buy a spare duplicate motor as a replacement otherwise might have an entirely different mounting requirement.  The cogs from Small Parts are made of Delrin and will likely last a lifetime in this application.  The belts are under no tension and are likely to last forever.
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K7ZRZ
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« Reply #2 on: June 10, 2010, 08:21:33 AM »

Thank you, Floyd.  I'm sure your assistance in this is going to be most helpful.

My situation is that I'm retired and living in a motorhome fulltime, spending generally a month or two at a time in an Oregon State Park campground or day-use park, as volunteer host or caretaker. At the beginning of an assignment, I usually pick a couple of trees in convenient locations and setup an inverted L style end-fed wire antenna of 150 - 200 feet. I feed the antenna with coax, transforming to the wire with a 4:1 unun, and match the whole thing with a big ol' Dentron MT3000A tuner inside. http://www.qrz.com/db/k7zrz That works well enough, but I'm intregued by the possibility of being able to match at the antenna feedpoint, and know I can do it much better that way.  And, as you can see in the picture at the QRZ.com site, I'm using high-power, so it needs to be something of my own making. (Actually, the QRZ.com callsign managment interface is not functioning properly just now, and the image of the station with my Clipperton L, which I'm using currently, won't upload and change.)

The concept (you didn't seem to catch this part) is that of the one motor driving both coil and capacitor simultaneously. The Capacitor rotates fully and continuously - one turn for each single coil winding advancement of the roller. In which case, every possible combination of coil/capacitor setting is made through the entire travel of the roller inductor. (Hope I'm not wrongfully presuming you didn't see that part on the AB2CD site.)  It's quite ingeneous.

So I need a REVERSABLE gear motor, with a .25" shaft - long enough to mount a pulley (cog?).  I don't have a concept of speed requirements, nor do I have an understanding of current draw (as expressed with motors on the Jameco site).  Another bit of confusion is that the motors on the Allelectronics site seems to list their shaft sizes in metric (I can determine with 1/4" is in mm, but it threw me when I looked briefly).

If you can get me started with a suggested baseline of specifications on this motor, (or just pick one for me as an example of something close to what I need) I'd really appreciate it.  I suspect I'll have to fashion a mounting plate of some kind, but that shouldn't be too difficult.

The position pot is going to be another matter for devisement, but I'll work that part out in another stage.

Once again, thank you very much for taking the time to help me with this. I deeply appreciate it.

Brian K7ZRZ
« Last Edit: June 10, 2010, 08:35:56 AM by Brian J. Ingoldsby » Logged

Brian K7ZRZ
K8AC
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Posts: 1884




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« Reply #3 on: June 10, 2010, 09:07:14 AM »

Sounds like an interesting way to spend the summer.  When traveling, I use a 40 meter center fed dipole (inverted vee configuration), fed with 450 ohm open wire line.  The line drops straight down to the ground where I use a balun and automatic tuner (MFJ in this case) and I use the antenna generally on 40, 20, 17 and 15 meters.  That limits me to 100W, but that's fine for my travel setup.  I did catch the part about one motor driving both capacitor and inductor.  I read that article when it came out and thought it was pretty clever, but rejected it for use here.  I use a vacuum cap on my tuner and of course they are not continuous rotation - mine is 25 turns stop to stop. 

I don't recall how that fellow sensed the component positions (if he did) and retuned to the proper positions when changing bands.  I also recall questioning how the air variable bearing surfaces would hold up with the many rotations the cap would go through while traversing the rotary inductor range. 

ALL DC gear motors are reversible - all you need to do is to reverse the DC voltage fed to them and you can easily do that with a DPDT switch if controlling the motor manually.  I wouldn't be concerned about the shaft length and the pulleys.  I don't recall ever seeing one of the motors with a shaft so short it wouldn't handle the pulley.  I suspect the Small Parts site has info somewhere about what the minimum shaft length is.  Most of these motors mount to a flat plate (with shaft extending through a hole in the plate) with three screws.  If you look at my photos, you'll see that all of the metal mounting brackets are off-the-shelf pieces from Home Depot or Lowes.  They're thin galvanized steel used to join lumber together.  A power hand drill is all you'll need to get the proper holes drilled.  I checked the gear motors in my junk box and the shaft diameters range from .210 to .250.  The pulleys will fit OK on any of those with only a tiny bit of out-of-round motion on the smaller shafts.

The speed you want depends upon how many turns are on your inductor and how long you want it to take to go from one end of the inductor to the other.  If the inductor has 20 turns and you get a 20 RPM output motor, it will take a minute to get from one end to the other.  I usually try to find one that takes a minute or two to make the distance.  Since you'll be turning the capacitor with the same motor, you'll want to stay with the lower RPM units or it will be very difficult to stop the capacitor  at the proper place when tuning.  Jameco has these units: P/N 155839 (runs at 20 RPM) and P/N 155821 (runs at 4.5 RPM).  One of those might do the job for you.  If you guess wrong at the speed, you  can always change that later by changing the pulley ratio.  On the other hand, it might be cheaper just to buy another motor!  Don't be concerned about the current draw of the motor - most of these are quite low (less than half an amp). 

One other thing - as you can see in my photos, I use homemade shaft couplings made from heavy plastic tubing from Home Depot and a couple of steel expansion clamps.  This provides a very stiff coupling that can accommodate shafts that are a bit out of line.  I've found that these couplings can take a lot of torque without slipping. 

73, Floyd - K8AC

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K7ZRZ
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Posts: 279




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« Reply #4 on: June 10, 2010, 10:15:45 AM »

Floyd,

This is developing very nicely... and I thank you again.  The Smallparts.com site was very revealing. I'll look at the motor you specified.  I can't tell from the pictures of the cogs on the smallparts site where exactly the set screw is located, but I suspect it's on the collar behind the cog section.

I agree on the wear of the variable capacitor bushings with the rotational requirements. I don't actually do a lot of wandering across the bands, so I suspect that my unit will likely be spending most of its time parked on one section of 75 meters. But I do go elsewhere occasionally.  I have ordered the indivitual components from Palstar - http://www.palstar.com/c500.php  and  http://www.palstar.com/ri28.php  The shafts look a little short, but those components will be arriving here in a few days, and I will be able to determine those things (shaft diameter, also) then.

I envision the position indicating circuit to just be a simple pot, geared from one of the components and read with a meter... just like you've done.  And I have oodles of 12 volts to work with, of course. Because of my need for simplicity and lightweight, I'm sure I'll build the thing on a base panel of some kind and enclose it in a simple light weight plastic container.

I'm out here doing this park hosting thing full time, and it is indeed a great way to spend time. I'm single, and it gives me the opportunity to interact with others on a daily basis. Also, the Oregon state parks are all full of great trees, and I have never been denied the permission to string up the wires and spread the radials for my antenna. I'm in my third year with this.

Ok on all for now. I'm very encouraged... and thanks again.

Brian
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Brian K7ZRZ
K7ZRZ
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Posts: 279




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« Reply #5 on: June 10, 2010, 04:56:41 PM »

Floyd,

How about one of these?? http://www.anaheimautomation.com/products/brush/dc-gearmotor-item.php?sID=245&pt=i&tID=103&cID=46

The shaft is about 1/4" and .6 depth to mount the cog.. plus a number of gear reductions available, based on the full 12V motor speed of 4000 rpm.

Brian K7ZRZ
« Last Edit: June 11, 2010, 07:04:49 AM by Brian J. Ingoldsby » Logged

Brian K7ZRZ
K7ZRZ
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Posts: 279




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« Reply #6 on: June 11, 2010, 05:41:58 PM »

I've come to find out that the beautiful motor, or anything close, from the Anaheim Automation place is not available and won't be for an unspecified time.  So I ordered a couple of motors from a place called Skycraft Parts & Surplus... and a selection of cogs (pulleys) from another place. (Belts to be determined a bit farther into the layout phase.)  The project parts are beginning to come together. I'll keep a record here once in a while about how it goes.  It's a very worthy project. Too bad someone hasn't taken this device on as a marketable piece. I know there's a lot of hams out there running high power that would benefit from a remote tuner that can take it.

Brian
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Brian K7ZRZ
K7ZRZ
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Posts: 279




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« Reply #7 on: June 14, 2010, 08:56:56 AM »

For the purpose of remotely bypassing the tuner or switching a lump of capacitance into the tuner circuit (for 160 M), is there some reason why I couldn't use a relay(s) like this in some configuration?  http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/16A_Latching_Octal_Relays/755-2CD-24D

Or there's these (the latching one) http://www.surplussales.com/relays/REVacRel-3.html  -  but at only SPST, it sure would take a flock of the expensive little critters to do the same thing as a single DPDT relay.

Brian K7ZRZ
« Last Edit: June 14, 2010, 09:23:33 AM by Brian J. Ingoldsby » Logged

Brian K7ZRZ
W9AC
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Posts: 115




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« Reply #8 on: June 14, 2010, 09:57:49 AM »

While this isn't specifically an amplifier topic, perhaps it's close enough.

I'm in the process of gathering parts and components for a motorzied remote tuner building project - just like the one that can be seen at the AB2CD QRZ.com page.  Looking down the page a ways, you will find pictures of the fine construction of his tuner.
__________________
Brian K7ZRZ

Brian,

Floyd, K8AC and myself have nearly identical ATUs (in addition to nearly identical call signs!).  You can see photos of my variation of the balanced AG6K style tuner on the QRZ.com website.

After spending quite a bit of time with this tuner, I'll offer up the following comments:

1) The tuner you referenced appears to be a reversible "L" network.  If you're going to use only balanced transmission lines, then you'll want to consider another inductor in series with the line as Floyd and I have done; 

2) Unless you’re using short wire antennas with a low Z present at the TX end of the feed-line, I wouldn’t bother with the reversible C in back of the two roller inductors.  I think far too much attention is given to tuners that attempt to match the proverbial “wet noodle.”  These are antennas I don’t want in the first place.  I only want to work with wire antennas that are at least 80% of a physical half-wave on the lowest operating frequency for all-band operation.  These antennas should almost always present a Z of at least 40 ohms at the end of the line, regardless of line length and line-to-load mismatch.  For that reason, I would only add the reversing C circuitry if you’re going to run physically short antennas;

3) Floyd’s suggestion of using Small Parts is an excellent choice for cogged belt and coupling hardware;

4) As W8JI has shown, the choking reactance needed on an input balun when used with a truly balanced ATU is less than is otherwise needed when a balun is placed on the input of a “floating” unbalanced tuner (e.g., “T” and “L” types that do not use an ground point) – or on the output of these same tuners with a ground reference..  The W2DU slip-on ferrite bead type balun should be fine for 160m-10m operation, even at high power where other configurations fail;

5) If you’re locating the tuner outdoors, consider building into a NEMA-grade enclosure.  Since I’m in Florida, I use about 2 lbs of compressed nitrogen to keep positive cabinet pressure – this prevents moisture ingress if the cabinet is subjected to the hot sun and becomes quickly cooled during an afternoon thunderstorm;

6) The DC motors that Floyd and I are using work great – although mine spin a bit too fast for the gear reduction used.  I just purchased a pair of inexpensive pulse-width-modulation (PWM) circuit boards that allow for precision motor movement without stalling the motors.  Temptation to series limit a DC motor will result in high current draw through the series limiting resistor and getting slow resolution will almost always stall the motor.  Not so with a cheap PWM circuit.  Of course, that circuit is also an RFI generator but since it’s only powered during the tune-up procedure when the rig is in TX, RFI probably does not matter as much.  Still, my power and control leads have multiple turns wrapped on #31 ferrite cores right next to the PWM board;

7) Another alternative to using a DC motor is a Stepper motor.  I have no experience with these, but my understanding is that one can attain PWD-like speed control since the motors require their own electronic control circuitry;

8  Some folks have had good success with common buss-wire roller inductors.  I have tended to gravitate to edge-wound roller inductors – or in the case of my variation of the AG6K tuner, the use of old surplus Collins ribbon inductors.  There are no contact points with this form of variable inductor.  Silver tape is spooled off a conductive drum onto a ceramic form;

9) With a big enough enclosure, you can always start with a basic set of RF components, then upgrade to better components as time and money permits.  You'll also want to add some of your own ideas.  For example, I recently added amplifier lock-out (ALO) for tuner protection at high power, as well as a peak reading kit to my Bird Thru-Line meters on the control panel;

11) Floyd’s latest iteration of his tuner is superb.  I think it’s interesting how he evolved the tuning system from moving-coil meters for indexing, to digital meters, then finally to a PIC-based memory controller written in Assembler.  I have started writing my own code, although I’m probably several months from completion based on other pressing home projects.

Paul, W9AC
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K7ZRZ
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« Reply #9 on: June 14, 2010, 10:48:48 AM »

Paul,

Very nice writeup and I appreciate it greatly.

I have already purchased the variable cap and roller inductor - units obtained from Palstar. I realize that they are intermediate in quality for a project such as this, but sufficient for my "development and experimentation" process. I have also ordered a variety of cogs (pulleys) from SmallParts, (belts yet to be determined) and two motors from Skycraftsurplus.com - one of these: http://www.skycraftsurplus.com/6-24vdcgearheadmotor.aspx  and one of these:  http://www.skycraftsurplus.com/12vdcgearheaddcmotor136rpm.aspx  One of them (or perhaps even both) should work right for me.

I apprecate the suggestion about the PWM circuit for slow motor control. The more I think about trying to tune with a switch handle, the more I realize that it's going to be tricky if the motor is running too fast, even with a "flick/bump"

My antennas are never going to be shorter than the 43' telescopic vertical pole and radial field, and are most generally going to be quite long inverted L's... so I'm glad to have the suggestion as to not having to switch the cap from input to output. And I'll not be feeding with balanced line. I do have 100 feet of 450 ohm quality window line here to play with, but I don't yet really have any plan for that stuff.  It's all a game, and I'll find myself playing with it sometime or another.

I'll be visiting my best ham friend (Jeff K7ZSA - one call letter after mine, from 1963) in less than a month, and will begin to assemble this device and try to make it work then.  "Till then, thanks for the help.

Brian K7ZRZ
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Brian K7ZRZ
K7ZRZ
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« Reply #10 on: August 11, 2010, 06:23:24 PM »

Paul,

I tried sending you a message to the email address listed on QRZ.com - attorney@something, but haven't gotten a reply in a couple of days. Maybe you'll see it here first. I attached some photographs in the email... you might look there to see those.
 
I have my tuner up and running, in a rather primitive fashion. I have the capacitor and inductor ganged together inline, a bypass relay, 100' of control cable (the tuner only about 30 feet from the connector at the motorhome - the rest coiled up), and a 3-switch control box inside. I used the DPDT center-off momentary switches. One sends straight 12v and the other has a resistor in the circuit. The slower speed control does not stall the motor, but the motor does have a significant amount of "run-on,' causing me to have to flip back and forth a lot to try to get the perfect low-dip in SWR.
 
You mentioned in your dissertation, the PWM circuit board, and I though you might be able to elaborate on this for me... source, properties (such as will it help control the rotational inertia to any degree).  I'm hoping that your circuit will either damp that run-on or will allow a slow enough speed to not make it a problem anymore.
 
I still need to mount the roller-end indicator switches, which I have. And also I need to install one more relay to switch components around - probably the shunt device (which is L currently), switching if from leading the capacitor to following the cap. (I'm sure you know what I'm meaning here).
 
Thanks for helping me along with this... I deeply appreciate it..

--
Brian K7ZRZ
« Last Edit: August 11, 2010, 06:25:01 PM by Brian J. Ingoldsby » Logged

Brian K7ZRZ
K7ZRZ
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Posts: 279




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« Reply #11 on: August 11, 2010, 06:58:13 PM »

After looking around (Google) for PWM boards, I found this one http://www.superdroidrobots.com/shop/item.aspx?itemid=583

Does it look like something I could use for slow-speed motor control?  Thanks

Brian
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Brian K7ZRZ
W9AC
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Posts: 115




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« Reply #12 on: August 13, 2010, 03:28:19 PM »

Brian,

Although the one shown in the link looks fine, you might want to consider a board with a reversible switch like this one I am using:

http://tinyurl.com/2et9s62

The PWD board, being switch-mode based, may genetate RFI/EMI, but only when the motors are turning during the antenna tune function.  And, since tuning only occurs in transmit, you'll never hear it -- unless you're using a noise bridge in receive for manually tuning the ATU.  If so, consider using the "SWR Null Meter," a device I describe in the February, 2010 issue of QST.

Paul, W9AC
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K7ZRZ
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Posts: 279




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« Reply #13 on: August 13, 2010, 04:56:34 PM »

Thanks, Paul,

I put a bid on that board, or can buyonenow afterward.  You might try to explain the part about switch mode based.  My current slow-speed switch - a DPDT center-off momentary, just reverses the voltage to the motor. Seems like a pwm voltage connected to the switch center and then sent down the line forward or reversed, using the same switch configuration would work.  What other switching scheme is there?

Brian
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Brian K7ZRZ
W9AC
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Posts: 115




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« Reply #14 on: August 14, 2010, 11:47:28 AM »

Thanks, Paul,

I put a bid on that board, or can buyonenow afterward.  You might try to explain the part about switch mode based.  My current slow-speed switch - a DPDT center-off momentary, just reverses the voltage to the motor. Seems like a pwm voltage connected to the switch center and then sent down the line forward or reversed, using the same switch configuration would work.  What other switching scheme is there?

Brian

By "switch mode," I mean the technology used, not the use of a switch.  Like switch mode power supplies, a high-frequency (i.e., 100 kHz) pulsed square wave is generated, rather than DC or a 60 Hz AC sine wave. 

The unit you've bid on will accomplish the reversing function quite easily.  Mine works very well and the tuner motors can be moved in very small increments.  I used two boards -- one to control a vacuum variable cap, the second to control a linked pair of Collins ribbon inductors.

Paul, W9AC

     
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