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Author Topic: Building a 2m Slim Jim Antenna.  (Read 25657 times)

gil

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Re: Building a 2m Slim Jim Antenna.
« Reply #15 on: October 30, 2012, 01:15:14 AM »
Small class, 4pm. We could work on your antenna before that, maybe get lunch, then build it, then train..

Gil.

Paul

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Re: Building a 2m Slim Jim Antenna.
« Reply #16 on: October 30, 2012, 07:05:14 AM »
This is one of those 'FWIW' thingys, nothing new to it, just a reminder.

The basic requirement for an antenna (of any sort) is that it has to be an electrical conductor.  It doesn't much matter what size/shape that conductor it, it just has to be able to conduct electricity.  It's a good idea to use such a 'size' that the current being dealt with doesn't melt that conductor, but that does not mean huge sizes by any means.
The typical transmitter can get really 'picky' about what's connected to it.  That's because what's connected to it usually ends up as a 'part' of that transmitter's circuitry and has to have particular 'values' so that it works correctly.  Those 'values' include impedance (dealing with the transfer of power), and resonance (dealing with efficiency, radiating ability).  There are a couple of other 'values' but those two are the biggies, sort of.
From there it's a matter of what you happen to have on hand (or can get), the amount of room you have to fit an antenna into, and your imagination.  The biggest problem with antennas is that there seems to be an obsession with having a 'perfect' one.  Unfortunately, there are no 'perfect' antennas for all occasions.  This one may be the 'best' for one particular situation, but it's probably going to be the 'worst' in another situation.  That 'best/worst' is a matter of degree and is different for everyone.  ('Butter-pecan' is THE best ice cream, your opinion doesn't count!  Right?)
For instance...
There are as many different versions of a 2 meter 'J'-pole as there are people making them.  If it works at all it means that the maker at least got into the ball-park as far as size/shape/electrical characteristics go.  I know of someone who built one onto a bed-slat.  I've drawn an antenna on paper using a carbon pencil.  Used foil burglar-alarm tape on glass.  They all worked.  I can't say they worked well, but they certainly worked.  You can make almost anything 'work' if you want to bad enough.

So, what's the point of this?  Keep an 'open' mind and don't 'rule-out' stuff just because...
 - Paul


Good luck with your class!


gil

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Re: Building a 2m Slim Jim Antenna.
« Reply #17 on: October 30, 2012, 10:26:56 AM »
Hello Paul,

I never pretended the Slim Jim was the panacea. Yes, it works well, and that's all there is to it. It's also cheap to make. I like using copper tubing because a larger conductor does increase bandwidth. In some antennas, conductor size also increases efficiency. Copper is also the best affordable conductive metal. Does that mean other antennas shouldn't be considered? Not at all...

Gil.

White Tiger

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Building a 2m Slim Jim Antenna.
« Reply #18 on: October 30, 2012, 02:35:17 PM »
I like pictures photo-blogs of practical builds accompanied by a reliable performance report - it makes me feel hopeful that even someone with limited experience (like me) could build!

Again, thanks for the pictures And step-by-step instructions...I'll let you know about Sunday!
« Last Edit: October 30, 2012, 02:37:55 PM by White Tiger »
If you're looking for me, you're probably looking in the wrong place.

CroPrepper

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Re: Building a 2m Slim Jim Antenna.
« Reply #19 on: February 27, 2018, 07:01:56 AM »
I tried to build one myself but in the end I bought the slimJim from N9TAX. I intend to use it on my baofeng F8HP on a telescope mast.

http://cro-prepper.com/wp-content/uploads/2018/02/IMG_20180217_152417_813.jpg

Can't tell much about the gain but the build quality is superb. As soon I got it, we were hit by a snowstorm and since then its very ugly outside for electronics.
« Last Edit: February 27, 2018, 07:06:30 AM by CroPrepper »

gil

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Re: Building a 2m Slim Jim Antenna.
« Reply #20 on: February 27, 2018, 07:06:36 AM »

C-ya

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Re: Building a 2m Slim Jim Antenna.
« Reply #21 on: March 05, 2018, 06:49:10 PM »
Hello!  My first post on the board.  I built a Slim Jim for 2m/440 and I love it.  It is mounted on my chimney for height.  For those needing to adjust SWR without moving the feedpoint, you can also adjust the gap between the folded ends.  I haven't found the need for it - I  must have gotten lucky with tuning that day! - but I have seen others do it that way.  I found one method of making the antenna that included a screw/bolt in one end and with turning the bolt, you increase or decrease the gap.

I screwed then soldered then covered with mastic tape (the weatherproof wrap tape) the connections onto the antenna and mine has been in service for many years.

Glad to have found the site!  I just ordered and received an MR100 antenna analyzer.  I'll post more in that thread.
« Last Edit: March 05, 2018, 06:56:24 PM by C-ya »

CroPrepper

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Re: Building a 2m Slim Jim Antenna.
« Reply #22 on: March 06, 2018, 06:33:50 AM »
I thought about getting the MR100 but in the end I discarded that idea. As far I understand is you can't use it in series with the rig? Another point is that a lot of people talk about calibrating, so the initial calibration is questionable and it does not cover VHF.

I will get a simple SWR meter (Diamong SX-20C for 80) that will be hooked up in line with the antenna. As soon I get my 817ND I intend to make a linked dipole for not yet determined bands in combination with the SWR meter. I still dont know if a tuner is necessary if I cut to resonate lengths, I guess SWR will vary everytime I install that thing on a different location.
SX-20C 3.5-30MHz, 50-54MHz,130-150MHz, 300 W

 

Radio Preppers

Re: Building a 2m Slim Jim Antenna.
« Reply #22 on: March 06, 2018, 06:33:50 AM »