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Posted: 6/14/2015 4:11:25 PM EDT
Inspiration from this post by Goathiker: https://plus.google.com/+goathiker/posts/L5MBZHUuBKs And after a little googling I've started with this. (~50ft of CAT5). Let's see where this goes.

(corresponding flicker link: https://flic.kr/s/aHskc1imzZ )

Link Posted: 6/14/2015 4:37:07 PM EDT
[#1]
After 5-10 mins of meticulously slicing through the outer insulation with an exacto knife, I finally though to myself, "I wonder if I can just pull this string?" One of you guys could have told me earlier.



Garbage on one site, possibly 4 antennas on the other.

Link Posted: 6/14/2015 4:53:46 PM EDT
[#2]
Good start! wG0AT has a lot of good, portable, ideas.
Link Posted: 6/14/2015 5:18:16 PM EDT
[#3]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
After 5-10 mins of meticulously slicing through the outer insulation with an exacto knife, I finally though to myself, "I wonder if I can just pull this string?" One of you guys could have told me earlier. [img]http://www.ar15.com/images/smilies/smiley_confused.gif[/img
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Hey sburggsx, just pull that string on CAT5 and the wire just falls out.  
Link Posted: 6/14/2015 5:55:22 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:

Hey sburggsx, just pull that string on CAT5 and the wire just falls out.  
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
After 5-10 mins of meticulously slicing through the outer insulation with an exacto knife, I finally though to myself, "I wonder if I can just pull this string?" One of you guys could have told me earlier. [url]http://www.ar15.com/images/smilies/smiley_confused.gif[/img

Hey sburggsx, just pull that string on CAT5 and the wire just falls out.  


Thanks BD!
Link Posted: 6/14/2015 6:08:37 PM EDT
[#5]
Ok so untwisting one pair of wires from the bunch was tedious, but no where near as tedious as separating the two wires for the 22ft of the doublet. It was "bad.' This is definitely a "more time than money" project. First up, a pic of the pick.



Then next we have the final antenna! You'll notice I haven't untwisted the 28 ft of feed line. I am not positive that it needs to be, but if I'm wrong I'm sure someone will be along to tell me so. Throwing it on the food scale it came up to 3.5 oz. That's pretty light! I will do some SWR testing in a bit using a 20ft crappie pole as a mast in an inverted V. Right now it's still hot outside.

Link Posted: 6/14/2015 7:19:13 PM EDT
[#6]
can't you untwist them with a drill?  just chuck it up and pin the other end.
Link Posted: 6/14/2015 7:25:48 PM EDT
[#7]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
can't you untwist them with a drill?  just chuck it up and pin the other end.
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Probably not. It's a long stretch and the soild core wire is probably too fragile to survive it.

So far so good. Working out some details. 40m and 17m seems great.
Link Posted: 6/14/2015 7:30:30 PM EDT
[#8]
I've untwisted 33' sections of 24AWG CAT3 using a drill with no problem.  I'd think 50' would be doable.
Link Posted: 6/14/2015 8:12:48 PM EDT
[#9]
Ok, I have it set up in a very close inverted V. I did a quick comparison with the G5RV I have out back, no tuning. Lets see how this comes up.


Freq  --  G5RV  --  44' doublet
18.140  --  1.4  --  9.6
14.260  --  1.9  --  14.1
10.112.5  --  3.4  --  3,2
7.086  --  2.5  --  8.5
3.552.5  --  2.2  --  20.7


Not great numbers, but anything below 10:1 received pretty well. Using the KX3's internal tuner 20m was still 2:1 but everything else was low enough to work. I'll have to play with it a bit to see what changes things.
Link Posted: 6/14/2015 8:33:27 PM EDT
[#10]
OK, so that wasn't very readable. Sorry about that.

Next step, I took the two ends from being held down at their own length with tent stakes and I ran them both out to fence posts. One side was about 20ft away and the other was probably 40ft and slightly uphill. Both posts about 4ft high. With that I took the following readings.

17m  --  9.1
20m  --  12.1
30m  --  4.9
40m  --  8.9
80m  --  16.3

A little improvement, except on 30m, and still not very good. So I got to thinking.... where was my genuine BD certified UNUN? I put it in line and ran the test again.

17m  --  10.6
20m  --  3.2
30m  --  1.3
40m  --  13.9
80m  --  12.8

Not much difference on 17m, but I'd call both 20m and 30m useable! I don't have any other tricks up my sleeve for this evening, But it has been a learning experience.
Link Posted: 6/15/2015 9:00:02 AM EDT
[#11]
Looks like this is what you are trying to build.

http://www.norcalqrp.org/norcaldoublet.htm

The poor SWR might in fact be the fact your feedline is twisted. Though looking at the site it seems like they do use it with a tuner, so the SWR might be high on their version as well.

Link Posted: 6/15/2015 9:56:27 AM EDT
[#12]
Check out this guys take on the doublet antenna. His balun/transformers are not what I would call heavy duty, but the principles are sound. I've met him before and he's a smart dude.













Link Posted: 6/15/2015 10:01:16 AM EDT
[#13]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Looks like this is what you are trying to build.

http://www.norcalqrp.org/norcaldoublet.htm

The poor SWR might in fact be the fact your feedline is twisted. Though looking at the site it seems like they do use it with a tuner, so the SWR might be high on their version as well.

View Quote



That is one of the (many) articles I read before trying this. I'm staying with the twisted feed line until the very end.

If I get a chance to set it back up this evening, I'm going to check the lengths again. When I measured for the 22ft sides, I did it with the pair of wires twisted together, and added 4 inches for a way to secure the ends. I'm betting, and the SWR meter is backing this theory up, that the wires are longer now that they're untwisted.
Link Posted: 6/15/2015 10:15:02 AM EDT
[#14]
.
.
Well, the high SWR is more likely due to the design - it's just not going to be low Z current node fed on very many bands....  And the UnUn is not the right tool for the job.

Really, if you ARE getting low SWR on several bands, it would mean that you are doing something wrong, and that loss (or unpredictable lossy noisy common mode) has crept into the system!

You could gain some insight into how this thing works, or should work, and can do some optimizing if you give the old DOS program a try for balanced line fed doublets ----> http://www.w5dxp.com/goodbad/goodbad.htm

Or you could go with a nice proven multiband 33 ft design here ----> http://www.w5dxp.com/33ftdipT/33ftdipT.HTM    Of course, the various lengths of ladder line might be a killer for this idea, but at least it shows what can be done with this concept.  

And using the program above, you might be a able to get a good subset of acceptably matched bands that would make you happy.
.
.
Link Posted: 6/15/2015 11:02:44 AM EDT
[#15]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Check out this guys take on the doublet antenna. His balun/transformers are not what I would call heavy duty, but the principles are sound. I've met him before and he's a smart dude.

http://wv0h.blogspot.com/2014/05/the-wvh-park-portable-doublet.html



http://wv0h.blogspot.com/2015/03/ppd-junior-and-variations.html



https://lh6.googleusercontent.com/-7P2QPVx4uRs/U4VAFvbOfDI/AAAAAAAABpA/RZgRKJyVP_M/s640/blogger-image--1270492263.jpg

View Quote



I had to take a bit and read through the two posts. Great info! What he is doing with the chalk lines is very similar to the clothes line reels I already have. I may have to throw them up in this configuration and see what I get.
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