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160 and Small Antennas




 
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #25 on: October 02, 2006, 06:45:19 PM »

From what I've read (and from some observations during use) the impedance and loss of the brown crap ladder line can change when wet (in some cases drastically). Going with some strapping open wire line will remove this potential problem. 

For even less path loss across the line, don't use spacers at all, but pull the open line tight and keep it 2' apart for 75M. Air spaced open line, caw mawn. You need a strong center support and a bridal at both ends to pull it off, put it is bullet-proof in the hi hi FB bad WX, OM.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #26 on: October 02, 2006, 07:21:56 PM »

         "a better way to transition from the coax to ladder line in the attic with a shack in the basement??"

Sounds like a job for the










 


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WA1GFZ
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« Reply #27 on: October 02, 2006, 07:45:15 PM »

Frank find yourself some Johnson spreaders and you will be set for life. My 1983 #10 feeders spaced 4 inches with johnson spreaders still in good shape. I did tighten the tie wires once or twice. I'm lucky to have collected enough over the years to make another line for the new place. It never warms up and takes a lot of wet ice to mess it up....but QRO takes care of that.
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Steve - WB3HUZ
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« Reply #28 on: October 02, 2006, 07:51:37 PM »

Is the attic accessible? If so, put your tuner there.
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WU2D
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CW is just a narrower version of AM


« Reply #29 on: October 02, 2006, 09:59:47 PM »

This sounds like a nice Vertical.


* GOTHAMVERTICAL.jpg (391.25 KB, 1400x2176 - viewed 618 times.)
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The Slab Bacon
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« Reply #30 on: October 03, 2006, 08:00:02 AM »

Interesting. It's all about working and if the 4:1 works better, you go it. Can't argue with your signal.
One MORE thing (I keep thinking of things), do you notice having to retune with it's raining or snowing. From what I've read (and from some observations during use) the impedance and loss of the brown crap ladder line can change when wet (in some cases drastically). Going with some strapping open wire line will remove this potential problem. 

Well, there ya go, thinking again.stop thinking, it could be dangerous!!

Actually I have found the crappy brown stuff to be pretty stable in my situation. Dont forget that I am still running it way below its characteristic impedence. Ice will cause a slight change in tuning, if there is a large build up. But rain doesnt seem to have much effect on it.

One of the other problems with fat copper feeders that everyone seems to overlook is the weight. If your feeders are too heavy, you must have some kind of center support or use a car engine block as a bob weight to keep the antenna pulled tight and flat. this can create other engineering issues to consider.

Ed, You might try using a STRAPPING 4:1 balun if your tuna can handle the current. This will keep the coass from radiating and keep the operating impedence of the coass low to minimize losses from capacitive reactance. (just my thought)

                                                          The Slab Bacon
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Steve W8TOW
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« Reply #31 on: October 03, 2006, 08:34:51 AM »

My center fed 80m zepp is fed with the brown crap...I made a 1/2 wave tuned feeder,
then tap off it to the shack with more of the stuff...
that goes to a Johnson KW Mbox...
In in install, with just a drop of rain I am retuning the Mbox....
In the winter, with ice/snow it gets even worse.
I contructed HB  open wire, can't wait for a dry weekend to install it!
For 160m, I bought a ALpha Delta 40/160m  1/4 wave sloper...it was crap...
Next I took the coil, made a 2nd one to match it...
Then configured it as a 1/2 wave 2 band dipole...
This works ok, but this fall, it goes further out in the yard, higher up and fed with
HB open wire.. rather than coax.
This will go to a HB tuner (like a Johnson KW mbox) already installed
in the back yard in a wx proof enclosure!
This will give me 160 & 40m with good bw...
It will be broad side E-W and at 70 feet!

73 steve 8tow
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Always buiilding & fixing stuff. Current station is a "Old Buzzard" KW, running a pair of Taylor T-200's modulated by Taylor 203Z's; Johnson 500 / SX-101A; Globe King 400B / BC-1004; and Finally, BC-610 with SX28  CU 160m morn & 75m wkends.
73  W8TOW
The Slab Bacon
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« Reply #32 on: October 03, 2006, 09:39:15 AM »

While I am still thinking about this stuff, (here i go thinking again) there are a few things to look out for when using short antennas on lower bands. You can be very surprized how well they can work if EVERYTHING else in the system is optomized to work together. A shortened antenna is ALWAYS a compromise, but sometimes you gotta do what you gotta do. A compromised antenna is still much better than none at all! Dave, the apeman, has been running short antennas for years and puts out a strapping signal.

The first thing to do is MINIMIZE ALL LOSSES, make sure that all of your RF is going to the antenna. Heat=loss!! Anything that is getting warm or hot is creating loss, your RF is making heat and NOT getting to the antenna.

Use a strapping tuna, one that can handle the feeder current and not get warm. Mine is homebrew with 2 large bread slicers and a rollie duck from a broadcast transmitter. (it is as large as an R-390) It never even gets tepid under mormal operating condx.

If you must use baluns, find or build ones that dont heat up under heavy feedline current. Or If you dont like baluns, build a STRAPING balanced tuna.

RF ammeters in the feedline TO THE ANTENNA are really good indicators of how well things are working. TUNE FOR MAX FEEDER CURRENT.

Do not rely only on an swr meter between the tuna and the transmitta to tell you what is happening!! It doesnt tell the whole story.

Your tuna sometimes offers too many choices for a "good match". Especially if you are using a roller.  You really need something like an MFJ antenna analizer (or something better) to find the right combination of L and C for the best match. Tune for max resistive and min reactive load on the analizer. Any setting other than that is usually wasting power trying to heat up the tuna (or something else).

Look at your Feeder current (if possible) while tuning. Sometimes a setting with less than a perfect match will produce more current in the feeders. this is the setting you really want to use if you run into this scenario.

Use balanced line feeders if at all possible, they dont know what swr is, or care. If possible make your own using the heaviest wire you can, at least #12 or heavier.

If you must use coass for a feeder on a non resonant antenna, it will always work better with a short antenna than a long one. If you must sin with a high swr and coass feeders, keep the impedence as low as possible to minimize the loss from the capacitice reactance of the coass.

I have been using a 60' flat top on 75m for a long tome now and no one seems to have any trouble hearing me, even running lower power.

Sometimes you gotta do what you gotta do!! Wink

                                                         The Slab Bacon
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Steve - WB3HUZ
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« Reply #33 on: October 03, 2006, 10:02:35 AM »

Quote
Your tuna sometimes offers too many choices for a "good match". Especially if you are using a roller.  You really need something like an MFJ antenna anylizer (or something better) to find the right combination of L and C for the best match. Tune for max resistive and min reactive load on the anylizer. Any setting other than that is usually wasting power trying to heat up the tuna (or something else).


Good point about the tuners and loss. Most commercial tuners are of the T variety. They can give you an low SWR at more than one setting. But only one will be the lowest loss setting. That one is almost always occurs when the LEAST amount of inductance is used. You can see all of this in action at the URL below - a great Java T tuner simulation!

http://fermi.la.asu.edu/w9cf/tuner/tuner.html
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WA1GFZ
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« Reply #34 on: October 03, 2006, 11:54:11 AM »

My Tuner uses a pair of 5 KW broadcash inductors to avoid loss. There is a fairly wide range of adjustment but if I run the L too low the 10 KV caps flash over.
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The Slab Bacon
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« Reply #35 on: October 03, 2006, 12:23:05 PM »

My Tuner uses a pair of 5 KW broadcash inductors to avoid loss. There is a fairly wide range of adjustment but if I run the L too low the 10 KV caps flash over.

but can it tune up some eggplant?? or does it burn the eggplant when it flashes ova??
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WA1GFZ
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« Reply #36 on: October 03, 2006, 12:46:17 PM »

Frank,
Just got the word pickled egg plant will be on the menu Friday night.

The tuner can't do egg plant but handles the 4CX3000A FBOM

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The Slab Bacon
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« Reply #37 on: October 03, 2006, 01:46:02 PM »

Frank,
Just got the word pickled egg plant will be on the menu Friday night.
The tuner can't do egg plant but handles the 4CX3000A FBOM

Frank,
        I wish I could be there! But unfortunately due to family obligations I cant be that far away for that long. I can taste it from here!!

Always remember, you can tune a piano, you can tune a radio,
but you cant tuna fish!! Grin Grin Grin

                                                   The Slab Bacon
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W2VW
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« Reply #38 on: October 03, 2006, 09:31:36 PM »

And running the balun on the input side doesn't help. Neither the current balance in the output conductors nor the voltage across the balun are any different when the balun is put at the input or
output of the tuner.

Go with the simple link design. It has 70 plus years successful use behind it.

The best reason for using a BalUn in the input side of the "tuner" has little to do with balancing the system. It's much cheaper and easier to construct a BalUn to work from a 50 Ohm generator to resistive 50 ohm load rather than the very wide range of sources and loads found at the feeder end. The BalUn can now be constructed using leftover coax.
Almost every single antenna coupling scheme seen today has 70 plus years of successful use.
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Steve - WB3HUZ
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« Reply #39 on: October 03, 2006, 09:34:48 PM »

Dave:

Ref: Baluns on input side of tuner being better.

Not according to W7EL. Read his stuff here.

http://eznec.com/misc/ibalun.txt
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WA1GFZ
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« Reply #40 on: October 03, 2006, 10:24:31 PM »

My tuner had a 1:2 BB transformer on the input with 2 caps on the output having both rotors connected to ground. The secondary of transformer has a CT also grounded. The two rotors help balance things and the tuner seems to work better.
The feeder currents are balanced and the cores stay nice and cool. (6- 2 inch red iron 3 beside 3) Winding is 5 turns quadfilar #14 teflon. Two windings in parallel for primary and secondary is 2 in series. The caps are a pair of 300 pf cardwell 10 KV units (they are in series CT at ground) I also have a 50 PF padder from BC610 for 160M.
The inductors are 22UH each. I done a lot of testing and it seems to work fine and no better or worse than the KW matchbox. BB iron core transformers work better at low Z and that is why they belong on the input. They also don't like high voltage because wire breaks down and some materials conduct. High numbers of turns introduce leakage L loses. High Z needs lots of turns. So I can't agree with the article
fully. It is true with the effects but you have to look at the way the part wants to work. been my choice of tuner for 23 years way before Measures discovered it around '91. I came up with it in about '81 and built it when I came back to CT and collected the parts.
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« Reply #41 on: October 04, 2006, 07:46:39 AM »

Consider the extremes. The givens in some of those formula go out the door. I'd like to see Frank Witt's homework on that subject. I'm not associated with anyone in the BalUn business.
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« Reply #42 on: October 04, 2006, 07:52:21 AM »

I don't remember Measures claiming anything about discovering that tuna. He did however put the idea out for experimenters to make something useful. Needs no toaster wire. Similar tuner network is in pre-war ARL book.
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The Slab Bacon
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« Reply #43 on: October 04, 2006, 08:07:55 AM »

The best reason for using a BalUn in the input side of the "tuner" has little to do with balancing the system. It's much cheaper and easier to construct a BalUn to work from a 50 Ohm generator to resistive 50 ohm load rather than the very wide range of sources and loads found at the feeder end. The BalUn can now be constructed using leftover coax.
Almost every single antenna coupling scheme seen today has 70 plus years of successful use.

That was exactly what I found while experimenting with 1:1 baluns. They were all OK when they operated at their characteristic impedence at both ends. But when you strayed away from the characteristic impedence they ALL got pretty squirrely. I found that the 4:1's were much more forgiving.
                                                                   The Slab Bacon
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WA1GFZ
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« Reply #44 on: October 04, 2006, 08:24:39 AM »

Frank,
You have the same problem on 75 that I will have on 160 at the new place. I wonder if you could share the schematic of your tuner configuration and feed line length? This will give me an idea of component values I need. I don't think BB transformers like a lot of reactance but work well in a resistive transfer. I have a 250 foot spool of #8. I'm not sure if #8 will fit in the slot of Johnson spreaders but #10
will.  tnx, gfz
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The Slab Bacon
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« Reply #45 on: October 04, 2006, 09:03:18 AM »

Frank,
You have the same problem on 75 that I will have on 160 at the new place. I wonder if you could share the schematic of your tuner configuration and feed line length? This will give me an idea of component values I need. I don't think BB transformers like a lot of reactance but work well in a resistive transfer. I have a 250 foot spool of #8. I'm not sure if #8 will fit in the slot of Johnson spreaders but #10
will.  tnx, gfz

Frank,
        I am at work and dont have it here, but I have a scanned in drawing of my antenna system. Send me ur email and I'll send it to you.

The tuna is a nothing fancy, just srtappingly large. It is your basic "T" type with 2 large breadslicers and a rollie duck out of a broadcast transmitter. (edgewound thick ribbon coil)
I have a 6' piece of RG-8 coass coming out of the back of the tuna and going to the home made 4:1 balun on the back wall of the house. (too much metal in that area to run ladder line all the way to the tuna) The balun is ur basic center tapped coil 4:1 from any arrl handbook except it is uses 10 T-120 (or maybe 130) cores stacked like a pair of binoclears (5+5) and wound with large silver teflon stranded wire wound through the cores and not around them.

The ant is 120' of wire folded back on itself spaced at 10 or 11" to make for its 60' overall length. It resembles a 40m folded dipole, but doesnt make a complete loop. I have a second dogbone insulator above the feedpoint. (fed at the bottom) Sort of like 2 U's laying on their sides.

The feedline is the 14ga crappy brown stuff, random length, I guess somewhere around 50-60'.

The antenna was an experiment that worked so well that i just left it up and have been using it ever since. I only have about 65' of horizintal space to put up any kind of wire antenna, so you gotta do what you gotta do. As I said before a compromised antenna
is still far better than none at all! Make up for the difference with "antennas by Eimac"

                                                                   The Slab Bacon
                                                     



 
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WA1GFZ
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« Reply #46 on: October 04, 2006, 09:31:04 AM »

Wow my feed line may be 10 or so feet longer but the antenna length will be about 150 to 160 feet depending on which branch I catch on the trees. The feed line will come in the knee wall of the basement so just need to install some strapping feed throughs. Too bad you can't locate the tuner outside to eliminate the balun. Sounds like motor control would be cool. sounds like you could really improve the antenna but you do get out well. I wonder if you ever tried hanging vertical conductors at the end? Also how tricky is it to tune? It must be pretty sharp.
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« Reply #47 on: October 04, 2006, 10:19:51 AM »

http://www.arraysolutions.com/Products/bushcommantennas.htm

Here is an idea but use an antenna tuner and eliminate the dummy load
Three conductors rather than two
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Steve - WB3HUZ
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« Reply #48 on: October 04, 2006, 10:36:01 AM »

I've looked at those BushComm antennas before. Interesting stuff. What I can't quite tell is if the three wires in the flattop are all tied together, just making it a "fat" dipole, or if some sort of folding back or snaking of the wires are done to increase length. Some company in the NE area (IIRC) make such an antenna. It was discussed here on the forum a while back.
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Steve - WB3HUZ
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« Reply #49 on: October 04, 2006, 10:38:34 AM »

W3R might want to try this,




More info at http://www.iol.ie/~bravo/low_band_antennae.htm

Some ideas here too.

http://www.kn4lf.com/kn4lf2.htm
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