Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Slinky Antenna to Coax  (Read 1716 times)
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #15 on: September 07, 2009, 06:57:04 PM »

"One begs to ask the question, why on earth is one using RG6 which when I looked it up is 75 ohm coax when the normal average amateur uses RG 8 type of coax having 50 ohms imp?"

It's lightweight and real cheap for the performance it provides.

That's why I use it.  The loss on HF is similar to that of regular RG-8 (both by published specs and my spot check measurements just in case) but it costs about the same or less than RG-58.

Sometimes the impedance causes trouble... sometimes it doesn't.

73
Dan
Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KC9QEB
Member

Posts: 17




Ignore
« Reply #16 on: September 08, 2009, 06:14:15 AM »

Obviously I was in over my head when I bought the DSW. I thought I had done appropriate research, but I certainly did not. Many apologies.
Logged
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #17 on: September 08, 2009, 07:49:50 AM »

Don't quit before you've started...

Stick a wire in the radio's antenna jack and see what you can hear, like Dale said.

Go ahead and pick a random inexpensive aparment  antenna that lists 40m as a working band.  See what you can do with it.  Use the slinky if you've got that.  Why not?  As far as the step by step hookup, work through it... you probably need some of these:

http://tinyurl.com/mqh3hz

At this point in the sunspot cycle, 40m is probably one of the best bands on average to start on... the only trouble being that a 33 foot vertical or 66 foot dipole that would be possible for someone with more space isn't going to work for you.

And a three or six foot antenna like some of the apartment choices is probably going to make things a bit tough once you start transmitting.  A slinky is pretty bad too for transmitting, but it will probably work for receiving.

But the thing is you need to just do it.  We can't tell you how to do it because we actually don't know what's going to work for you in the end.  Some people have tons of fun with 2W and a six foot antenna.  Other people get totally frustrated that they can't work anyone.  Which one will you be?  I can't answer that.  Try it.

You've got a radio.  Now you need an antenna. Try one.

The *best antenna* overall on a small budget is not for sale.  That's a fact.  The best antenna *you* can start with on a budget may be a commercial one.  Buy an apartment antenna and coax with matching connectors from somewhere and plug it in.  

As you need more performance, come back here and look at the more complex advice.  

73
Dan
Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N5LRZ
Member

Posts: 0




Ignore
« Reply #18 on: September 08, 2009, 07:49:59 AM »

Re OX...

I have used cable TV cable on my loop antennas BUT So you are saying that the original poster is  poor aka living paycheck to paycheck aka living hand to mouth etc.  

Remember when you say that it is still my position that Amatuer Radio, much like the game of Golf,  never was and still is not nor should it be for poor people.  

BUT I will be fair and not jump the gun.   We have yet to confirm your poverty theory aka because its cheap theory with any certainty.   For this conformation we will have to await the information from the original poster.
Logged
WB5JEO
Member

Posts: 805




Ignore
« Reply #19 on: September 08, 2009, 08:06:04 AM »

I suggest you think in terms of mobile operation. You have a need for a small antenna that can easily be removed or folded, and you have limited ability to provide a ground plane. These are both fundamental limitations faced in mobile operations. The challenge of QRP with antennas that fit into this sort of scheme is significant but not impossible, so long as you are realistic about the limitations. It helps to read about others' experiences, because it gives you an idea of how you're doing within those limitations. And it's encouraging to see how well others have done with so little power.

If you search on QRP MOBILE, you will find a good many discussions and experiences of interest that focus on the problems of antenna limitations. One site is:
http://k4upg.com/

There are many others, but note about half way down the balcony setup using the center-loaded antenna and temporary counterpoise dropped over below the balcony during operation. There are many other sites, and QRP folks are generally always ready to offer advice.

There are a great many sites listed on:
http://www.w0ch.com/personal/personal_qrp_sites.htm

You'll see that they use both commercial and homebrew antennas, but are particularly interested in building antennas because they often are in the field. Because you are limited in both power and antenna size, you will want to weedle every bit of advantage you can get in terms of getting power to the antenna and out at a useful angle. The QRP crowd tends to know a lot about antenna matching and propagation, because of the need to be efficient and the common use of antennas mounted in ways that don't allow them to display the characteristics modeled in more conventional situations. The QRPers' advantage is that their systems can be built with little regard to power-handling capabilities.
Logged
KB7QOA
Member

Posts: 17




Ignore
« Reply #20 on: September 08, 2009, 08:15:27 AM »

Just a slightly different train of thought here, are you dead-set on 40m?  I was in a similar boat to you a few weeks back, had just upgraded to General, picked up my grandfather's old radio from my grandmother, and wanted to get up on the air right away.  While not in an apartment, I am in a rental so I have to be pretty careful with what I do.

I used to install satellites, so I had a spare spool of RG-6 in the garage, and plenty of connectors.  I ran to a good local electronics store (Rat Shack hardly has anything anymore) and picked up a PL-259 to F connector (as was recommended to you above.)  I cut a length of wire for a 20m dipole and cut it in half, soldered the center conductor to one wire and used a crimp connector to attach the (aluminum) shield to the other of the wire.  I created a common-mode balun at the feedpoint by using tape and wire ties to wind the coax into a coil of about 8-10 turns. I then laid the dipole in a lazy inverted-vee shape across the top of my house using those plastic Christmas light shingle clips to hold it all in place.

Next I ran the coax into the house through the window next to the air conditioner and put a compression F connector on it.  Attached this to the adapter, and plugged that into the tuner.  Voila, a quick and cheap 20m antenna.  I worked Louisiana, California, Ontario Canada, and many places in between on that antenna before I changed my configuration for now to a 40m a little higher up.  Ultimately I'll be using an 80m inverted-vee fed by ladder line to be used as an "all-bander" but quick and simple has me making contacts now.

Check with your local ham clubs and see if there isn't somebody there that can help you build a quick antenna, especially if they're willing to teach you to solder and crimp it yourself.  As others have said, soldering is a very simple skill that will serve you many MANY times in your career as a ham.  Don't worry too much about not knowing how much you want to learn yet, just learn this skill and start making contacts.  Some people want to learn before doing, and others want to start doing which drives the desire to learn.  To each their own.  That being said ham radio is definitely a learner's hobby, and you won't get nearly the enjoyment out of it if you don't treat it as such.

One thing you could do for now, build yourself a dipole (you should have room for a 20m or the "shorty forty" that was linked to you earlier,) attach a few ounces of weight from one end, attach the other end to your balcony and lower it down.  When you're done, pull it back in.  There you'll have a vertical dipole ("stealth" antenna since it won't be outside unless you're using it, probably after dark anyway) and it will perform as well or better than any of the cheap "apartment" antennas.

I hope that helps.  73!

Jeremy
KB7QOA
Logged
N3OX
Member

Posts: 8847


WWW

Ignore
« Reply #21 on: September 08, 2009, 09:16:12 AM »

"So you are saying that the original poster is poor aka living paycheck to paycheck aka living hand to mouth etc. "

I don't care what someone's financial situation is.

Why spend MORE for the SAME?  Nothing wrong with being on a budget.

I know how to use RG-6 type coax in a way where the performance is absolutely no different from much more expensive and heavier RG-8.

The only potential problem is impedance, and the way I do things around here requires pretty trivial changes to handle that issue when it comes up.

Some RG-6 type coax can be very good stuff for ham applications ... "cheap" and "inexpensive" are not necessarily the same thing, and this is a good example.  For feeding a high flat-top single band dipole with no center support, RG-6 type CATV coax could be considered *far superior* to RG-8.  About the same loss, but much less weight and windload.

And it and its connectors and the tool to install them properly are cheaply sourced locally, which can be very convenient if your coax stock is running low.

RG-6 type coax is cheap because it's a commodity product with much higher volume and takes advantage of skin effect to  use a very small amount of good conductivity expensive metal to do the same job as the much larger amount of copper in a comparable loss 50 ohm cable.

You do have to watch out for the loss on lower frequencies where the center conductor's copper flash may be a bit thin, but the particular stuff I use, which is Carol brand stamped with the number (and sold as RG-6/QS at Home Depot) has loss specs at 1MHz and 10MHz in the online brochure and measures appropriately to the accuracy to which I can measure that.

It's ridiculous to imply that you should not be in ham radio if you have to or wish to watch your costs.  You can have a lot of fun with a very inexpensive station.  I do it mostly because I choose to.  

73
Dan
Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WW5AA
Member

Posts: 2086




Ignore
« Reply #22 on: September 08, 2009, 11:23:36 AM »

I usually do not recommend commercial antennas...but in a situation like yours, I would bite the bullet and get the MFJ-1622, Price: $99.95. And yes, if you had the skills and knowledge it would be possible to build a better antenna for a lot less. Lacking those abilities the MFJ-1622 will get you up and running out of the box. Using CW will overcome many of the limitations and keep you interested until such time as you can improve your situation.

73 de Lindy
Logged
KQ6Q
Member

Posts: 988




Ignore
« Reply #23 on: September 19, 2009, 08:05:43 PM »

I second the motion - just get the MFJ-1622, get on 40m and make a few contacts. since a quarter wave is about 33' on 40m, you'll need to buy or build something to make the radio think it's got the right length antenna. The 1622 will do that for you in a single package.
Another alternative, for about the same investment, would be a hamstick dipole for 40, - the antennas and bracket would be about $65, and you'd still need a piece of mast to mount them on, and coax. Others will downplay that solution, but I have one, about 7 feet above my roof (height makes a difference) and work all over - but I'm putting 100Watts into it also, not QRP. You will make contacts with the DSW40 and an MFJ-1622, and they will be very satisfying, because they won't be easy, but you will make some. Get it up before the November CW Sweepstakes - there will be hundreds of stations looking for contacts, and some of they will answer you!
Fred Wagner, KQ6Q
Logged
KQ6Q
Member

Posts: 988




Ignore
« Reply #24 on: September 19, 2009, 08:13:56 PM »

I re-read your post. The slinky antenna needs to be strung between two points, to act like a shortened dipole. If you have a couple of trees or stairwells you can string it from, you're good to go, and RG6, with F-connectors and adapters to connect it to SO-239's will work (they're about $6 each from Radio Shack). I keep RG6 for longish temporary runs in Hospital support deployments. Running the slinky inside your apartment - the structure of the building, and the wiring and ducting in the walls, will absorb most of your QRP signal. You'll able to hear signals on it, but nobody will be able to hear you. And if you run more power to it (100W or so), your neighbors will hear you, because your signal will be getting into their home entertainment gear. At least with CW they won't know what you're saying!
If you can't spend any more money, and can't return the slinky, put it up as best you can, and try it in the November CW sweepstakes. If you can't get anyone to answer you there, you'll have to find another antenna.
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!