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eHam Forums / Elmers / RE: Internal tuner vs external tuner efficiency
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on: May 12, 2013, 11:21:41 AM
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There are other considerations besides just whether the tuner is internal or external.
The design of the internal tuner is of importance. For example, an internal tuner that uses relays to switch fixed capacitance and inductance in and out won't likely be able to keep up with an internal tuner that uses motor driven variable capacitance and possibly variable L as well.
But that isn't the whole story either, there are different tuner designs that must be considered as well.
Avoid the commonplace mistake of approaching a multiple-input problem by considering only one of the possible inputs.
All possible inputs must be evaluated in each scenario.
Whether or not the tuner is internal or external to the rig is likely one of the inputs that does not yield much in the way of the definitive.
73
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63
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eHam Forums / Amplifiers / RE: Tentec Titan 425 Blowing 20 Amp Fuses
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on: May 12, 2013, 08:16:06 AM
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At high voltages, I prefer the drilled hole to the slit.
Nice clean round hole, dressed with no sharp points, the idea is to eliminate any possible points that could conceivable arc over in future.
I would NOT use just a solder blob as a connection as mentioned above.
I would clean the trace, prepare and clean a Jumper wire and solder it cleanly across the broken trace, allowing enough length to guarantee current handling.
This is not a big thing, repairing board traces of every kind is a rather routine occurrence here.
73
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eHam Forums / Elmers / RE: Reflectors and Horizontal Wire Loop questions
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on: May 12, 2013, 12:02:15 AM
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Balanced Line, made of two coaxes, you won't need an exterior balun. You will need one in the shack, of course, mine is internal to the big manual tuner.
And there are other benefits to enjoy from doing it that way as well.
Stop heating feedline and start using more of the antenna, man.
73
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65
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eHam Forums / Amplifiers / RE: Tentec Titan 425 Blowing 20 Amp Fuses
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on: May 11, 2013, 11:59:24 PM
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That APL product is exactly the kind of stuff I keep onshelf for the purpose, Mark.
Don't be too concerned about the looks of the board, like I said above, if the carbon goes real deep, drilling a round hole there that is the diameter of the burn, completely through the board, won't hurt a thing and the resulting air instead of board material is insulator and then some.
73
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eHam Forums / Amplifiers / RE: Tentec Titan 425 Blowing 20 Amp Fuses
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on: May 11, 2013, 01:46:17 PM
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If that shown area is the only spot, it can be repaired.
if the black carbon cannot be scraped away using something like an exacto knife blade or perhaps a bit of fine work with a Dremel bit, consider simply drilling a hole right through the center of the carbonized area. Then solder a short length of solid copper wire across the edge trace to repair it, paying attention to have a smooth area with no raised points that could start an arc there again.
After resoldering the two thru vias, it would be a good idea to apply an electronics conformal coating to the area as well.
But I don't think you need to go for a replacement PCB here. At least, yours truly would certainly try the above first. Have repaired worse successfully.
73
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eHam Forums / Elmers / RE: Reflectors and Horizontal Wire Loop questions
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on: May 11, 2013, 09:07:54 AM
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I'm thinking of using coax out of the shack (as it is now) to my single ground point, then a 4:1 balun and ladder line (450 ohm) up to the feed point (50 feet). So 50 feet of RG-213 properly grounded, and 50 feet of 450 ohm ladder line vertically oriented to the feed point. How does that sound? thanks
I would use TWO coaxes as Balanced Feed from shack to antenna. All the advantages of balanced line with all the advantages of shielding. 73
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70
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eHam Forums / HomeBrew / RE: 11m Tuner for 2m Antenna
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on: May 11, 2013, 06:40:42 AM
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Um, that Shakespeare is called the "Sea Scout" antenna for a reason.
The "VHF" band there is the Marine Band VHF and it is not likely the thing was designed to work well in the 2 meter Amateur Band.
Also note that the antenna is a "Close Out" and seriously ask yourself WHY.
A few feet of coax, a mast, and an 11 meter stick, permanently attached to the 11 meter radio.
Again, I say that this would be best for the type of important communications, "disaster relief" or EMCOMM.
Multiple Operators.
Different skill levels.
The need for the best coverage you can obtain for each band.
Trying to feed a single antenna from the two different radios is a recipe for disaster in and of itself. One mistake can take out the finals on either or both radios and then what do you have?
The single antenna notion here is a very bad idea.
You've been told.
Twice.
73
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eHam Forums / Elmers / RE: Auto Tuners Vs Manual Tuners
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on: May 11, 2013, 06:31:35 AM
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If rotating the antenna truly results in a high SWR change while staying at the same frequency, changing to a manual tuner may get you into trouble, as the manual tuner will be tuned to that first situation, you rotate the antenna and the SWR changes, the manual tuner would not detect that. You may be able to keep transmitting, but you also may be forcing your PA into Foldback, or worst case scenario of damaging Output Tran$i$tor$.
**What you really need to be doing is finding out WHY the antenna is changing SWR when rotated. This may or may not be caused by the proximity to the house, at this point that is only an assumption as far as I can tell. Is there perhaps a Metal Roof involved?
**Your problem could very easily be caused by a bad connection somewhere in the antenna system. That is the first thing I'd investigate.
73
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eHam Forums / Elmers / RE: Reflectors and Horizontal Wire Loop questions
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on: May 11, 2013, 06:26:25 AM
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Feeding your Delta Loop with Balanced Line and appropriate balun/tuner combination would likely yield improvement over coax feed in terms of being able to cover more bandwidth efficiently.
Attempts at reflecting, while possible, would require a lot more space and also could eliminate signals that aren't in the direction of the reflections.
A big horizontal loop w/balanced feed and tuner to match worked very well for me when I had the space. I cut it long, to favor the CW portions of the 80 meter band, but found that using a big manual tuner (the old Heath bigbox at the time) allowed coverage from 80 on up to ten, to include the SSB portions of the bands.
73
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eHam Forums / Misc / RE: Ohm's Law
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on: May 10, 2013, 05:05:38 AM
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Most important, Murphy's Law supersedes Ohm's Law, Newton's Laws of motion and Cole's Law (shredded cabbage, carrots mayonnaise)
73 WB2EOD
You left out the all-important V. For Vinegar. 73
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eHam Forums / HomeBrew / RE: 11m Tuner for 2m Antenna
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on: May 10, 2013, 05:02:49 AM
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The OP states right off the bat that this installation is to be used for disaster relief work.
In that situation, separate antennas is not only the better path for reasons of efficiency of antennas and ease of use, it also would create a much better comm situation.
For example, while switched to 11 meters and working poorly at it anyway, any calls on the 2 meter band would be missed.
Couple that with the poor performance that the 2 meter antenna system is going to have on 11 meters and the whole thing just doesn't make sense at all.
Not when a separate length of coax attached to a vertical antenna made for the CB band can solve the whole problem nicely.
Couple that with the OP's admitted lack of knowledge on the subject, the wish to design something that the OP can't design and truth be told, the best of us might get something to make an impedance match appear good, but -- that does not mean the antenna system, 2 meters, is likely to work well enough to bother with -- and consider the amount of CONFUSION such a system would create for Disaster Relief Operators when every second counts makes this whole idea something in need of serious RETHINK.
73
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