6m antenna project

Frank Gentges metavox at earthlink.net
Mon Dec 3 08:58:21 CST 2007


Nice work taming a piece of RS crap.  I am looking forward to seeing 
your fine work before it gets all sealed up.


Michael Chisena wrote:
> All, I'm still working on finding antenna bases for the AS coil / whips 
> that Frank has.   After the Saturday Taco's meeting I got an urge to try 
> my hand at something.   Radio Shack of all vendors sells a base load 
> magnetic mount CB antenna that uses the AS style whip and base. This is 
> their 29.99 unit. I will bring it into tacos next Saturday if anybody 
> wants to see it.   In an old copy of the 'Handbook' there was an article 
> on how to tune similar antennas into ham stuff. I think the article was 
> for the 220 band.   Anyhow, I got to wonder how hard it would be to make 
> this work at 52MHz?   On the plus side, i! f I had killed the coil/whip, 
> I still had an AS style antenna base to work with. So the project would 
> not be a total loss.   I used my MFJ VSWR analyzer to do this. For those 
> of you with the VNA tool, that might yield a more precise result.   
> Couple of words about the antenna first. It's a loaded coil with a 
> fiberglass whip. It has about four inches of adjustment range.   A word 
> about plastic products. You know how some plastics feel like quality 
> products, and some simply don't. The plastic this was molded out of is 
> in the second category. Strong but brittle feelings, almost too shiny to 
> be real. The whole antenna radiated the feeling of 'cheap junk'. Just 
> for the record.   The antenna coil body seemed to be glued to the! 
> internal parts. At the time I didn't know how to remove this plastic 
> tube from the coil assembly. Ended up using a cut off wheel on the 
> dremmel tool.   You would expect a metal part connecting the coil 
> winding to the antenna whip. No so here. It's a chrome plate plastic 
> that makes the connection. I did say cheap. This thing is going to be 
> loaded with 'bi metallic' issues after a few years of service. The 
> copper wire is soldered to a brass pin, pushed into the plastic, making 
> contact with the chrome plating. It works, but for how long.  From the 
> day this antenna was assembled it starting to deteriorate due to oxygen. 
> Talk about a throw away product.   After some dust and noise, I was able 
> to cut a channel into the plastic, to the point where a screw driver can 
> be pushed into it, twisted and cracked the tube off the coil assembly.   
> Th! en the question of how to tune for a new frequency.   I counted the 
> windings. Five on the (lower) and 22 (Upper). With the stinger bottomed, 
> it gave me a vswr curve in the 28 MHz range. So if I over cut the 
> windings, I can compensate by raising the whip. I cut the upper coil.   
> So two turns at a time I removed windings. Then replotted the resonance. 
> Each time it moved a few MHZ up the dial. After a bunch of wire was 
> removed it actually tuned up on 52MHz. Not too bad.   I wish I knew more 
> about how these things worked. I think the magic number was about 28 
> inches (in 4 inch segments) off the top, and one turn off the bottom. I 
> saved the cuttings and the tune notes for Saturday.   Taking a t! urn 
> off the bottom was a wild guess. I did it because the Z Gage was more 
> than a little high. It proved out to be a right guess, but the how and 
> why is not clean in the mind. Call it inspiration, not based on logic or 
> thought.   Anyhow, I'm going to firm up the solder joints and make it 
> presentable. After the next taco's meeting I may spray it in plastic, 
> and cover with heat shrink tubing. I want the brain trust to look it 
> over and decide if it's sane or not.   If I need to do a second one, I 
> will boil the coil first to see if that frees up the glue the OEM used. 
>   Later kids Mike
> "You are, what you do, when it counts"
> The Masso
> "Gravity, the quickest way down"
> Mayor John Almafi
> "You ever drop an egg, and on the floor you see it break?
> You go and get a mop so you can clean up your mistake.
> But did you ever stop! to ponder why we know it's true?
> If you drop a broken egg you will not get an egg that's new?"
> MC Hawking
> ------------------------------------------------------------------------
> _______________________________________________
> Tacos mailing list
> Tacos at amrad.org
> http://www.amrad.org/mailman/listinfo/tacos
> ------------------------------------------------------------------------
> No virus found in this incoming message.
> Checked by AVG Free Edition. 
> Version: 7.5.503 / Virus Database: 269.16.13/1167 - Release Date: 12/3/2007 12:20 PM

More information about the Tacos mailing list