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Old 07-18-2009, 11:36 PM - Thread Starter
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Didn't do anything with it today. I should have made my handle "Gomer". From what I see one answer for post #44 might be "yes, it receives backwards with the wrong/(NO?) resistor. I might be able to squeeze in a fourth wavelength and raise it to 20 something feet. (assuming a one inch gently twisted and soldered splice would be OK). I
johnpost, Guess if I get killed by a TV that would only be redundant if the one I have now has already killed me, but I don’t know it yet. Likely that is more likely. (but thank you)
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Old 07-21-2009, 11:13 PM - Thread Starter
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Got a regular 330 Ohm resisitror from my local computer fix-ti guy. Probably better I don't go up there in the dark, again. It's body is roughly the size of a carpenter ant. Result tomorrow.
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Old 07-24-2009, 11:28 PM - Thread Starter
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Again my thanks to all. The 3/4 wavelength rhombic maybe works a tad better for 3 (as planed) and 13. With weather and other signals popping up, then fading, as well as transmitter's changing..... Hard to tell if the resistor helped much.(didn't hurt!). All in all a sucessfull experiment. I'm 10/10.
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Old 07-10-2014, 12:29 AM - Thread Starter
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Now with digital I'm shooten at 520 and < 560

Howdy all. Now with digital I'm shooten at 520 and < 560 Hrz? Using the calculator below, I made a 9 director Yagi. (skunked). Three questions come to mind. Does it matter if the driven loop is squared or rounded at the "turn around" Should the total length of the driven loop be "on spec" or longer to account for where it makes the turn? I'm thinking longer to maintain the proper width.

Is there an, affordable, efficient signal amplifier that's worth anything? Power consumption is an issue.

I think I know the third. Vertical polarity would mean the antenna is mounted on edge?

http://www.qsl.net/w4hn/antennaCalc.htm

Marge and Bart (Simpson), are there (on fox) when the weather is just so.
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Old 07-10-2014, 12:58 PM
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OPTIMIZED Dimensions for a Folded Dipole depend not only on the spacing between long elements, but ALSO on the chosen DIAMETER of the Element. To the first approximation, the TOTAL LENGTH AROUND THE FOLDED DIPOLE is the determining factor, so if you want to round off the ends, you'll need to ADD a bit more length to make up the difference.....but since this is such a small fraction of the total length, it doesn't make much difference in the Frequency & SWR Curves. See fol. webpage for Optimized Dimensions for UHF, Hi-VHF & Lo-VHF Folded Dipoles:
http://imageevent.com/holl_ands/loops/folded

Although I haven't posted a 9-Element design, you may have an interest in one of the fol. Optimized Yagi designs, bearing in mind that ANY Antenna can be Rescaled from one band to another by multiplying ALL Dimensions (including Element Diameter) by the Rescale Factor = freq(old) / freq(new):
http://imageevent.com/holl_ands/yagis

Bear in mind that the calculator you used was no doubt a NARROW BAND, 50-ohm (200-ohm if Folded Dipole) type calculator (see 8-El K7MEM Yagi in frequency response charts in webpage cited above) which will NOT provide acceptable Gain and SWR across the entire Hi-VHF Band...for THAT, an OPTIMIZED design is needed....

UHF 8-Element Folded Dipole Yagi (with 2 Reflector Rods) is Optimized for the entire UHF Band and can be readily made LARGER by the Rescale Factor = 698 / 216 = 3.23 for operations in the Hi-VHF Band...(although a Re-Optimization might be just a bit better).

The 8-El Double Reflector was better than a 8-El Single Reflector Yagi, providing better Gain while meeting the F/B & F/R Ratio Goal of at least 20 dB and hence was a better expenditure of metal. If you just HAVE to have a 9 or even 10-Element Yagi, you can readily add more Directors to the front, using the same Length and Element-to-Element Spacings as the preceeding Element....it's ALMOST as effective as a fully Re-Optimized Design.

Last edited by holl_ands; 07-10-2014 at 01:13 PM.
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Old 07-10-2014, 01:21 PM
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Although I recognize that Rhombics were last discussed in this thread in 2009, in 2010 I analyzed a UHF Double Rhombic with various values for the Load Resistor (300-ohm was somewhat better). In 2011, I also analyzed a Small Rhombic Vertical Stack. As always, I included the 4nec2 files in case anyone wants to investigate modifications to these designs that "I found on the Internet":
http://imageevent.com/holl_ands/dipoles [Dipoles, Bowties and Rhombics, OH MY....]
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Old 07-10-2014, 06:52 PM - Thread Starter
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Much thanks for the info. I'm having trouble...three different browsers will not go to > http://www.k7mem.*********/Electroni...ed_dipole.html

The calculator in your link. I sure my thing (computer) has a stick somewhere it doesn't belong. If there were another appropriate calculator, I'm all ears!

Btw, 9 directors because of the boom length. (at 4-1/32 spacing, 9-5/16 length) then the reflector and driven for a total of 11. For 560 Mhz. I don't mean to bother anyone with "random" details, but I want to ask, does the number matter? (should something be odd or even?

The actual channels I'm shooten at are 22 and 28. Might be 520 is in the middle of 22, and 560 is the top of 28. Again, supper links hollands . I have a new balun coming in the mail, and some time to sort this out. Don.
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Old 07-10-2014, 11:34 PM
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Some K7MEM links have been tagged as being "untrustworthy" by some web browsers/website checkers because something was found SOMEWHERE on the host website, so ALL users are declared to be suspect.....or whatever...

Try these links...they work for me:
http://www.k7mem.com
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15313

===========================================
Sorry, I mis-read your post....a 9-Director Yagi would be an 11 or 12-Element Yagi depending on whether it had one or two Reflectors. So "UHF 12-El FD-Yagi-OPTimized" should be what you're looking for, with one Reflector or "UHF 13-El FD-Yagi-OPTimized" with two Reflectors.

I'm not exactly sure what you mean by "odd" and "even"....but it makes no difference other than the longer the Boom, the higher the Gain....and with any GIVEN Boom Length, increasing the number of Elements within that Length tends to increase the Gain.....but not by much....presuming that their Lengths and Spacings are determined via an Optimizer program (NOT an On-Line Calculator).

Good Luck trying to beat the Gain and SWR performance of these Optimized FULL-BAND Antennas using an On-Line Calculator to design a NARROW-BAND Antenna....which will need to be verified using (FREE) 4nec2 Antenna Simulation Program....
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Old 07-12-2014, 12:17 AM - Thread Starter
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OK Hall. I'm here and learning. Party tomorrow, my 55th. I DID get one to work> http://www.k7mem.com/Electronic_Note.../yagi_vhf.html

I played around with boom length to stay practical and still see good gain. 10 feet and near 15 Gb might be a thought. I confess, this and some stuff regarding motor/generator (and alternator) RF fields, can land with automatic transmissions and most of chemistry,that I do not now, and likely never will, understand. Women aside, I have most of the rest understood.

I should to re-visit the rhombotic! (I didn't even look at your link). Since I am so frequency specific....the 512-560 has to be allot more practical then the afore, Chanel #3 ) Btw I'm not above multiple antennas, and DPDT blade switches.

A question. "optimized"....On his "quick guide" , he shows varying lengths of the directors. Is that part of what you mean by optimized?

It suggests 1/4 inch dia. I happen to have a bunch of solid copper transmission line. It's 3/10 ths, (or a fat 3/16 th"s) . I gotta' wonder how "practical" he is being on his diameter, and what might be the parameters......

That said, I should talk to the engineers at CH# 22 and 28. (digital KBVU 28, KAEF 23) I bet they would love to tell their sponsors they are hitting someone nearly 80 miles away, way north in the north hills!

You gave me plenty to study and work on, much thanks! Where do I add that I'm off grid, so the whole area/wiring is permeated with choppy modified sign wave, AC, RF interference ? (from a modified sign wave inverter).

Is there a filter or cap or something for that?

Last edited by thatdonguy7; 07-12-2014 at 01:18 AM. Reason: if he how, deleted.....permeated
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Old 07-12-2014, 12:25 AM - Thread Starter
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Whoops! (I found "edit")

Last edited by thatdonguy7; 07-12-2014 at 12:33 AM.
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Old 07-12-2014, 02:04 AM
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nikiml's Python Optimization Scripts are a RANDOM SEARCH process, trying different combinations of the SYmbol Variables (e.g. ALL Yagi Element Lengths and Element-to-Element Spacings) to find the "best" combination, based on chosen performance Targets (e.g. Gain, SWR, F/B & F/R Ratio) and a chosen Target Function. My Target Function uses different "weights" to adjust the relative "importance" of Mismatch Loss (SWR), Raw Gain, F/B & F/R Ratios so that one doesn't unnecessarily "skew" the results trying to meet the Targets at all Frequencies, for example giving away a slightly better SWR than "needed" in exchange for a slightly better Gain Curve.

SMALL differences in Element Diameter won't make much difference...esp for a Wide-Band design...smaller diameter usually means a slightly worse SWR and only a bit of Gain Loss....but a 4nec2 run is needed to determine the actual difference.

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Old 07-12-2014, 04:47 PM
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"Where do I add that I'm off grid, so the whole area/wiring is permeated with choppy modified sign wave, AC, RF interference ? (from a modified sign wave inverter).

Is there a filter or cap or something for that?"

A modified sine wave inverter is really a modified square wave inverter.

I suggest that you use an Exeltech sine wave inverter. I use the XP125 12v 125w model for critical applications.
http://www.solar-electric.com/invert.../exsiwain.html

Make sure the coax shield is grounded to keep out RFI.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 07-12-2014 at 04:56 PM.
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Old 07-13-2014, 05:40 PM - Thread Starter
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Thanks Rabbit. Yea, been watching the price of "true sign wave" inverters creep down for years. And yea, the grounding. I drove a rod as far as the rock, 3-1/2 feet, and also laid 100 feet of copper in a ditch that goes through a wet area. That and various cages, even tried some sheet lead I happen to have around the inverter it's self...never noticed a difference. Guess all the wiring is transmitting. I have one of those wire tracing deals, where you clip a little transmitter on a wire, then go around with a little receiver to find the wire. That reciever will buzz anywhere near the house with an inverter on!

Even with a > $200 125W TSW inverter, the main one likely would still muck things up.

When I have some spare time I'll start straightening out some of that 3/16 solid copper wire. I could solder or braze the directors & reflector to copper pipe, that would be durable at least!
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Old 07-15-2014, 12:49 AM - Thread Starter
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Here I was noticing it has something in the column "vert" for KAEF, my main target. http://www.tvfool.com/?option=com_wr...e1c65a8f1e728e.
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Old 07-15-2014, 05:13 AM
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That's "Virt" under the heading of "***Channel***", not "Vert".

https://www.tvfool.com/index.php?opt...57#how_to_read
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Old 07-16-2014, 11:57 PM - Thread Starter
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Hi there Project! Long time no see.

Anyway I'm a bit fluumixed. I'm pretty capable with math and materials. Btw Hollands, I believe your son soldered, the 1/2 inch copper. It could be Brazed, but that is not common.

I'm feeling like I need to be "spoon fed", (and I'm 55 and normally people come to me for solutions). I can't seem to find a definitive solution that is worth the investment of time it will take to construct. My coumpter won't go to a number of links, then on-top of that, I just don't understand allot of what I DO find.

Maybe in a new thread since this one is so long, you guys could help me nail one or two. I think they are analogue 22 and 29. (23&28on my digital). In return I am willing to stick with it and build, weld solder, wire anything suggested, stick with it, and test it. I can't seem to locate an old vintage "antenna strength" meter I should have somewhere, but I do have a Radio Shack Field Strength/SWR tester.

Holland, I looked at the dual rhombotic you posted. Again, I have the skills to build about anything, but the dimensions and conversions, balun....I'm lost. or do I want that or a Yagi?

The yagi with the varying lengths of the directors intrigues me. I could solder the .3 inch solid copper on-top of a 1 inch copper tube easily enough. Fit the folded, insulated driven on a plane with the directors and reflector. (driven loop being 1-1/2 inch apart for the nearly 1/4 inch directors, and longer than spek to account for the rounded ends). Or should I use 1-1/4 inch copper tube? (would be significantly more rigid).

I'm sort of offering a deal. I have the ability to build about anything, use me! IN 100 years I will never understand the inner secrets you all take for granted, in return I have the tools and experience to manifest about anything material you can imagine. I'm at about 1,500 feet in CA, rite at the Oregon boarder with an ocean view. (95531). Barefoot, by CB can go to Gold Beach...40 -50 miles?

Attached is the meter I can find. It has the CB (PL259?) connectors.
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Old 07-19-2014, 06:33 PM - Thread Starter
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Copper pipe seems to have gotten too expensive. That and the comitment of soldering so much when just guessing cans that thought. If I go insulated on a rectangular aluminum boom I can experiment more freely. If I hit on something I'll post back. Much thanks for the info/links. Some amount of it I can understand!.
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Old 07-24-2014, 07:19 PM - Thread Starter
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This GE amp did nothing that I could see. The TV's signal bar did not move.
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