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Author Topic: 10 Meter Antennas  (Read 41963 times)
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W2VW
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« Reply #50 on: April 10, 2011, 07:14:18 PM »

I added a 16 ft 10M dipole element in parallel (as you suggested a few years ago) to my ladder-line fed 135 ft dipole.    It works great on 10M, the pattern is almost that of a dipole on 10M according to EZNEC and my experience with.




would that work ok scaled for 15 meters.

Did you check the coupler settings to load the 135 footer on 10 before adding the 16 footer?
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K3ZS
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« Reply #51 on: April 11, 2011, 08:44:42 AM »

I used the 135 ft for years before adding the 10M element.  The tuner settings were changed but that has nothing to do with the performance of the antenna.    I suppose adding a 15 meter dipole would be good for 15M.   The best thing is to model it using EZNEC and compare the patterns with those of a simple dipole at the same height.   I was mainly interested in 10M, the 40M and 80M patterns are not changed.  The other bands do not seem to have any advantages by adding the 10M dipole.
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« Reply #52 on: April 11, 2011, 08:57:21 AM »

I used the 135 ft for years before adding the 10M element.  The tuner settings were changed but that has nothing to do with the performance of the antenna.    I suppose adding a 15 meter dipole would be good for 15M.   The best thing is to model it using EZNEC and compare the patterns with those of a simple dipole at the same height.   I was mainly interested in 10M, the 40M and 80M patterns are not changed.  The other bands do not seem to have any advantages by adding the 10M dipole.


The reason I asked is it is possible for you to use either wire on 10 depending on your coupler settings. One setting will match the 135 foot antenna and another will match the 10 meter resin ant antenna.

You could most likely lose the 10 meter wire and substitute a 15 meter half wave and not experience very much difference in performance on 10.
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« Reply #53 on: April 11, 2011, 09:46:52 AM »

I thought about that also, but Tom K1JJ set me straight.    It is how the RF current divides itself, depending on the impedance of each dipole element.    There is only one tuning point.   It would be nice if you could vary the tuning and pick out the dipoles to use, but that just isn't what happens.    EZNEC is the best way to see if something would work.   I haven't tried different band dipoles in parallel with the 135 ft dipole using EZNEC.
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« Reply #54 on: April 11, 2011, 09:58:59 AM »

I just tried a 15M dipole in parallel with a 135 ft dipole using EZNEC.  It would work about as good as a dipole on 15M but the pattern on 10M is about the same as the 135 ft dipole alone.
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« Reply #55 on: April 11, 2011, 11:30:10 AM »

I thought about that also, but Tom K1JJ set me straight.    It is how the RF current divides itself, depending on the impedance of each dipole element.    There is only one tuning point.   It would be nice if you could vary the tuning and pick out the dipoles to use, but that just isn't what happens.    EZNEC is the best way to see if something would work.   I haven't tried different band dipoles in parallel with the 135 ft dipole using EZNEC.


I don't think that's entirely correct. The coupler and feedline combination should match either wire on 10 meters. Ideally the 135' wire will not accept much energy when the 16' wire is tuned. That depends as you say on the impedance of both. You would want a voltage feed on the 135 foot antenna while used on 10 meters since your 10 meter wire is current fed. 

If you only got one coupler setting with low SWR it may be both wire antennas are radiating on 10 OR one setting is out of range. 


If the EZNEC plot of the 15 meter wire in parallel is correct there may be some benefit in changing the 135' length around by a few feet so it has a different impedance than the 15 meter wire when used on 10.


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« Reply #56 on: April 11, 2011, 12:00:47 PM »

"You would want a voltage feed on the 135 foot antenna while used on 10 meters since your 10 meter wire is current fed."


Yes, this is essentially the idea. If the 10M legs make little difference then the 135' length needs to be adjusted so that it does not hog power (as a low impedance feedpoint) and produce that octopus lobe pattern on 10M.

Probably the best starting point is to model the three dipoles together and change all lengths until you see the best figure 8 patterns on the two higher bands. (10M and 15M).  The final lengths may surprise us and the patterns will be a compromise. I haven't modeled this specific antenna myself, only other versions - but may do it later today.

After the modeling, of course the real whirl effects are there, like effective height above ground, houses, ground conductivity, other antennas, etc.   But it should be close enuff.

Bob, you could try a reflector behind that antenna for you favorite band and direction too.

T

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« Reply #57 on: April 11, 2011, 12:39:19 PM »






I thought about that also, but Tom K1JJ set me straight.    It is how the RF current divides itself, depending on the impedance of each dipole element.    There is only one tuning point.   It would be nice if you could vary the tuning and pick out the dipoles to use, but that just isn't what happens.    EZNEC is the best way to see if something would work.   I haven't tried different band dipoles in parallel with the 135 ft dipole using EZNEC.


I don't think that's entirely correct. The coupler and feedline combination should match either wire on 10 meters. Ideally the 135' wire will not accept much energy when the 16' wire is tuned. That depends as you say on the impedance of both. You would want a voltage feed on the 135 foot antenna while used on 10 meters since your 10 meter wire is current fed. 

If you only got one coupler setting with low SWR it may be both wire antennas are radiating on 10 OR one setting is out of range. 


If the EZNEC plot of the 15 meter wire in parallel is correct there may be some benefit in changing the 135' length around by a few feet so it has a different impedance than the 15 meter wire when used on 10.



This would be true if the tuner was at the common feedpoint of the antennas.   I can't see how you could have two impedances at the end of the feedline however.   Interesting to think about, I am no expert on these things.
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« Reply #58 on: April 11, 2011, 12:49:36 PM »

While you are modeling how about a balanced line fed full wave in parallel with a half wave srtung 90 degrees different in azimuth.

That should yield a steerable pattern by changing coupler settings. Maybe not groundshaking but I don't see why it wouldn't work.

"You would want a voltage feed on the 135 foot antenna while used on 10 meters since your 10 meter wire is current fed."


Yes, this is essentially the idea. If the 10M legs make little difference then the 135' length needs to be adjusted so that it does not hog power (as a low impedance feedpoint) and produce that octopus lobe pattern on 10M.

Probably the best starting point is to model the three dipoles together and change all lengths until you see the best figure 8 patterns on the two higher bands. (10M and 15M).  The final lengths may surprise us and the patterns will be a compromise. I haven't modeled this specific antenna myself, only other versions - but may do it later today.

After the modeling, of course the real whirl effects are there, like effective height above ground, houses, ground conductivity, other antennas, etc.   But it should be close enuff.

Bob, you could try a reflector behind that antenna for you favorite band and direction too.

T


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Steve - K4HX
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« Reply #59 on: April 11, 2011, 02:04:26 PM »

The two feedpoint impedances would be in parallel and would look like one single impedance to the tuner. There would be no way to vary the power fed to the two elements without using two feedlines.
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« Reply #60 on: April 11, 2011, 03:14:14 PM »

The two feedpoint impedances would be in parallel and would look like one single impedance to the tuner. There would be no way to vary the power fed to the two elements without using two feedlines.
That settles it, otherwise it would drive automatic impedance bridges crazy.
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« Reply #61 on: April 11, 2011, 03:42:45 PM »

Think about how the ever popular "fan" dipole is supposed to work. Say, an 80 and 40 resonant wire pair fed with coax. Both impedances are in parallel there too but only the current fed wire works. Same idea but.

I'm not talking about a gradual change between radiators. Just one or the other would be used at one time.
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Steve - K4HX
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« Reply #62 on: April 11, 2011, 07:29:06 PM »

So, it's two separate but closely spaced antennas. One is fed and the tuner on the other is "tuned" to vary the directive pattern of both of them as a system. Do I have that right?
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K1JJ
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« Reply #63 on: April 11, 2011, 08:46:21 PM »

You guys are Taylor hybriding each other, right?   Wink

T
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« Reply #64 on: April 11, 2011, 09:12:08 PM »

EITCH  EYE!!!!!

I was just thinking the same thing and was about to bring it up.


You guys are Taylor hybriding each other, right?   Wink

T
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« Reply #65 on: April 12, 2011, 09:08:52 AM »

What is this Taylor thing?  I googled it and I got sites about guitars and golf clubs.
This is getting far from 10M antennas now.
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« Reply #66 on: April 12, 2011, 09:26:13 AM »

So, it's two separate but closely spaced antennas. One is fed and the tuner on the other is "tuned" to vary the directive pattern of both of them as a system. Do I have that right?

No a Taylor won't work here. You hafta use a Theremin capacitor.

I was being serious but forgot each antenna's load needs to be reactive and inhabit a different place on the Smith chart. Both would need stubs.

Make one j- and the other j+. Can you imagine that? Then put them in parallel.
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« Reply #67 on: April 12, 2011, 12:30:40 PM »

' Make one j- and the other j+. Can you imagine that? '


only the j-
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« Reply #68 on: April 12, 2011, 01:30:28 PM »

' Make one j- and the other j+. Can you imagine that? '


only the j-

Unreal!
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« Reply #69 on: April 12, 2011, 02:03:48 PM »

"  The old 2el stacked 10M Yagis have morphed into this homebrew stack at 33', 66' and 99' :  (On swing gates that cover 300 degrees)  "



T,

I hate you.

klc



YUP Tom is A CHANNEL master of sorts from 40M up.
90 over sigs into Iraq on 40M not too long ago.
 FRED
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