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Thread: Micom Tuner Issues

  1. #1
    kd8gua No Longer Registered

    Default Micom Tuner Issues

    I have a Micom 2TS in my car, with an F2265 tuner and Mobat 12' fiberglass whip. I have used 2 gauge battery terminal cable to run from the tuner to the antenna mount. The antenna mount is a Hustler SSM-1 stainless steel ball and spring mount of similar design and construction as the Mobat ball mount, so much so that the drilling diameters are exactly the same. My whip is bent over the car from the ball mount on the rear quarter panel to the front fender. I have a 1.5' tall PVC standoff from which the tip of the antenna is tied securely to.

    My SWR readings with this setup were roughly 5:1 or worse (infinity) except for two or three particular frequencies in the 10, 24, and 28 MHz bands. I tried both adding a section to the fiberglass whip (16') and removing a section (8') and while at 16' I didn't get any improvements, while at 8' and standing upright, my 24 and 28 MHz bands had much better tunes.

    I was told to ground all of the mounting areas of the Micom. I had already done that. Then I was told to scrap the 2 gauge battery cable and get GTO neon sign wire. I was told to use the tuner's high voltage kit, but I got the tuner used, and can't afford the outrageous prices that Mobat/Royal charges for such items. The GTO wire was a second best scenario. Well, now I cannot get a match on any frequency, period. I'm at infinity SWR each time.

    What else can I do? I'm in Civil Air Patrol and have worked stations a few hundred miles away using far worse mobile installations. These installs used the WIMA antenna tuner/base combo however. But, even still, the 1/4" wide grounding braid on the WIMA, and the actually horrifying installs I've seen should have been recipes for disaster. One vehicle has its whip within 1.5' of the roof at maximum distance, and had the tip of the antenna tied and duct taped to a piece of 3" long plastic, that was bolted to a piece of sheet metal that was bolted to the van rain gutter. Another install had the tip covered by a tennis ball and the antenna tied down onto the luggage racks of the SUV. Yet, these antennas work, and mine won't. I don't know what else to do. I think my first order of business is to replace the GTO cable with the battery cable. At least I made matches on that... Also, please do not suggest buying WIMA tuning bases or Mobat/Royal ball mounts: I don't have the money to do that, and so it just will NOT happen.

    Thank you


  2. #2
    kd8gua No Longer Registered

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    Let me reply quickly with: I have found that my ground connection was loose, giving me the blanket poor SWR. So, now, if I go through the ALE channels I've sounded on, here are the SWR results:

    3791.0 USB Infinity SWR
    3996.0 USB Infinity SWR
    7185.5 USB Infinity SWR
    7296.0 USB Infinity SWR
    14346.0 USB Infinity SWR
    18117.5 USB Infinity SWR
    21432.5 USB 2.5:1 SWR
    24932.0 USB Infinity SWR
    28312.5 USB 1.4:1 SWR

  3. #3
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    If you bypass the tuner and put a quarter wave 10 meter whip on the ball mount and check your SWR on ten meters, do you get a low SWR?? Like REALLY low? Can you attach a standard piece of 50ohm coax from your radio output to the ball mount to do this test before you go any further? Are you ABSOLUTELY sure that the center insulated section of the ball mount is NOT grounded to the vehicle body?

    How far is the center insulator of the tuner from the center conductor terminal of the ball mount? Is it in free air, or is the single conductor laying on metal or other conductor along the way? Ideally, this conductor from your insulated output of the tuner should be as physically close to the ball mount as practical, and the wire from it to the ball mount should be LESS THAN a foot and a straight line, not near any metal.

    If you are concerned about high RF voltages you can take some good quality RG8 and strip the outer jacket and braid off and use the insulated center conductor for your antenna tuner cone insulator to the ball mount connection. With the stock output of the Micom this should not be an issue.
    "God as my witness" - Jeremy Dewitte - Felon

  4. #4
    kd8gua No Longer Registered

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    I can't do the 50 ohm coax test to bypass the tuner. I can shut the tuner off via the radio, and attach a 10 meter whip on the ball mount. I used to have a quarter wave 10 meter whip, but the threads sheared off on an old spring. Tests done a while ago when I used the 10 meter whip had less than 1.2:1 only while the antenna was vertical. While tied down, my SWR jumped up much higher. I have been able to get good SWR matches on 10 and 12 meters using the tuner and a vertical CB antenna. At no point is the center connector of the ball mount grounded to the vehicle body. I have tested this multiple times, from multiple angles with my multimeter, and there isn't even a flicker of conductivity.

    The closest I can get the tuner to the ball mount is about 14" with as straight a line as I can make. I cannot mount the tuner any closer due to the constraints of my trunk. I could try, but I'm not very sure it will fit anywhere else. The RF cable passes through free air, and also a piece of carpet lining the trunk sides. Even at the ball mount connection, I have a ring terminal, and have bent that to have the cable depart vertically out of the mount, instead of coming close to any of the grounded body connectors. I have also covered the whole connection on the inside of the ball mount with a moldable rubber sealant so as to avoid any RF arcing. The tuner came with the factory rubber boot over the insulated RF OUT post. I am currently using GTO wire, which is rated at 15000 volts, so even though it is 14 awg, I'm pretty sure it will do the trick. The 2 gauge battery terminal cable worked better, in my opinion, but I was told that GTO wire is the way to go with the high RF voltages that come out of this tuner.

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    Well, you have proven that the mount is good, if you can bypass the tuner and you get good SWR with a 1/4 wave resonant antenna. Remember that when you fold that whip over, you should NOT expect it to be even close to a match.

    Matches even 3 or 4 to one with such a short antenna are probably OK, at the antenna. Is the radio saying that is the match between the tuner and the radio? What happens when you put a very long antenna on there, something longer that 25 feet, which is, of course still very short for HF. Do you have a loaded whip or one of the spiral wound HF whips?
    "God as my witness" - Jeremy Dewitte - Felon

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    Duplicate.
    Last edited by com501; Jul 18, 2013 at 06:10 AM. Reason: Duplicate
    "God as my witness" - Jeremy Dewitte - Felon

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    Looking at the MOBAT ball mount, it appears to be exactly the same as the original Motorola TAB1012 ball mount which is NLA. The only difference I see, is the old ball mount used to cost about $100 and these new ones are $254. You can comb eBay for old MOTOROLA ball mounts, and they are of the very highest quality, if you want to look around. They will say Motorola on the plastic base piece, in Motorola's typical writing. I have never had one of those fail except for the one that I ran the fender of my truck into a parking lot bollard with. I don't think the Hustler is a bad performer, but you might want to carefully scrutinize your spring. The spring should have a piece of braid running up its middle that electrically shorts out the coils of the spring. If it is damaged, corroded or disconnected, its not going to be tuning right, at all.
    "God as my witness" - Jeremy Dewitte - Felon

  8. #8
    kd8gua No Longer Registered

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    The matches I am getting are being verified by an SWR meter I am placing inline between the radio and the tuner. The tuner data stream passes through the SWR meter no problem, so the matches I get with with the tuner are nearly identical while the SWR meter is present. The Micom has a power output display. Full power is 125 watts, which is displayed by full bars on the output display. All of the ALE sounding channels are programmed for full power, but I am lucky to get 25 watts output while the SWR is at infinity. This can be confirmed without an SWR meter by looking at the power output display, which only displays two segments. When I have a match around 1.5, my power output is measured at 80 watts, and I will see about 3/4 of the segments displayed on the control head.

    I do not have a longer antenna. I could, in theory, take a spool of insulated wire, strip one end, connect it to the RF terminal on the tuner, and throw it over a tree next to my car. Then I'd have an instant random wire antenna. Unfortunately I'd only still have my vehicle ground to work with, but I guess it would be a start.

    The antenna from Mobat/Royal is a quarter wave sectional fiberglass whip. Each section is 4 feet long. With two sections, this antenna is the same electrical length as a 10 meter quarter wave antenna. At three sections, the center frequency is roughly 21 MHz, which can be seen in the SWR results I've listed above. The F2265 manual states that this tuner will tune 3.8-30 MHz on an 8 foot quarter wave whip, and tune 1.6-30 MHz on a 12 foot quarter wave. Obviously, Motorola also suggests no less than a 25' non loaded whip, but not for vehicular installs.

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    Is this a new tuner or did you purchase it used?

    Are you using a spring on the ball mount? If so, I would definitely check it or bypass it temporarily by removing it.
    "God as my witness" - Jeremy Dewitte - Felon

  10. #10
    PRC148 No Longer Registered

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    Could the tuner be bad? Every time I've had strange band specific tuning issues it has been a tuner that has a relay or whatever else that has gone out.

    EDIT: just saw your post about verifying with an SWR meter for resonance. Hmmm ... still thinking.

  11. #11
    kd8gua No Longer Registered

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    The tuner is used. Got it from ebay via the reseller who buys their items from a 3 letter government agency. I will try removing the spring, but I'll have to use a smaller antenna, as I fear using the 12' whip without a spring will cause too much stress on the antenna and cause it to break.

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    I wouldn't drive around without the spring, this is just to test and see if the spring is the problem. You may very well have a tuner issue.

    Fortunately, most of these are relay driven, and a detailed physical inspection after a careful disassembly usually causes the culprit to become known quite readily.

    You can test the spring by sticking it in a vise and flexing it and looking carefully at the braid up the center with a bright flashlight. BE CAREFUL. There is a lot of tension when you have this thing spread open when its chucked up in the vise.
    "God as my witness" - Jeremy Dewitte - Felon

  13. #13
    kd8gua No Longer Registered

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    Yes, the F2265 is mostly latching relays. I will check the integrity of the spring's center braid before I remove it. The weight of the 12' whip lets the spring bend quite easily without any risk of whipping back.

  14. #14
    Radioconsult No Longer Registered

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    You didn't mention how is the tuner grounded to your vehicle.

  15. #15
    kd8gua No Longer Registered

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    The tuner is grounded to the vehicle body using 1" wide flat grounding braid connected to a grounding post which is also a DC ground for equipment, that way there is one common ground.

  16. #16
    Radioconsult No Longer Registered

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    How about DC voltage at the tuner, is this the same tuner that is used as part of the RDP package where DC is fed through the coax?

  17. #17
    kd8gua No Longer Registered

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    Quote Originally Posted by Radioconsult View Post
    How about DC voltage at the tuner, is this the same tuner that is used as part of the RDP package where DC is fed through the coax?
    It is not the same tuner as in the lid of the RDP. That tuner has a much more shallow form factor. It does however operate on the same principle: DC power is fed via the coax during the tuning process to setup the relays, and then when tuning is complete (or after 3 seconds of not finding a match) tuning stops and the DC voltage is removed. The tuner would not function if no or low DC voltage was present.

    Another interesting, completely random experiment happened today on the highway. I had packed my tuba (yes, the big concert band instrument) in the trunk of my car, next to the coax, radio, and tuner. Wouldn't you know it, that I start getting matches on 10 and 12 meters? How is that possible? I removed the tuba when I got to my destination, and I no longer had a match.

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    In mismatch conditions, a sort of skin effect occurs where the signal isn't properly contained inside the coax conductors and begins radiating or getting high and low voltage points that don't physically coincide with the antenna itself. This makes the antenna radiate poorly and makes the shielding of the feed line become part of the radiating element, essentially. This radiated "skin" energy was probably interacting with the tubing of the tuba like an air-coupled transformer.

    There is one hell of a joke trapped inside this trying to get out but for the life of me I just can't quite grasp it tonight. Oh, well...

  19. #19
    kd8gua No Longer Registered

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    Quote Originally Posted by Alpha View Post
    In mismatch conditions, a sort of skin effect occurs where the signal isn't properly contained inside the coax conductors and begins radiating or getting high and low voltage points that don't physically coincide with the antenna itself. This makes the antenna radiate poorly and makes the shielding of the feed line become part of the radiating element, essentially. This radiated "skin" energy was probably interacting with the tubing of the tuba like an air-coupled transformer.

    There is one hell of a joke trapped inside this trying to get out but for the life of me I just can't quite grasp it tonight. Oh, well...
    I tell you what... any time a tuba is involved, a joke isn't far behind. I get what you're saying though. That would explain why I couldn't contact anyone I heard.

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    You might get better results with a silver plated E-flat Sousaphone......
    "God as my witness" - Jeremy Dewitte - Felon

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    Quote Originally Posted by kd8gua View Post
    I tell you what... any time a tuba is involved, a joke isn't far behind.
    "That'll be 60 dollars." Bonus points if you get it.

  22. #22
    jlamanske No Longer Registered

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    Family Guy?