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: [1]   Go Down
  Print  
Author Topic: INTERCEPTER 10K  (Read 377 times)
KC2PHJ
Member

Posts: 21




Ignore
« on: December 03, 2008, 05:29:59 PM »

Does anyone have any experience with this antenna?
Can it be tuned in with a tuner for 12, 15 or 17M with a good tuner?

Dave (KC2PHJ)
Logged
AA4PB
Member

Posts: 12667




Ignore
« Reply #1 on: December 03, 2008, 06:59:11 PM »

Well, the specs say it is tunable from 24-44MHz. The DC grounded coupling system will look pretty much like a short circuit to your tuner on lower frequencies and the radials will be pretty much ineffective on lower frequencies. As a general rule you can't make an antenna work effectivly on frequencies it wasn't designed for by simply throwing a tuner on the end of the coax.
Logged
KC2PHJ
Member

Posts: 21




Ignore
« Reply #2 on: December 04, 2008, 12:25:30 AM »

If that is the case, how come some people can transmit via their rain gutters and using a tuner?
Logged
WA3SKN
Member

Posts: 5434




Ignore
« Reply #3 on: December 04, 2008, 04:27:43 AM »

If you use a tuner to operate on lower frequencies, you will just be using the coax as the antenna, the "connected antenna" will be operating as a top hat capacitor.
You can probably do better for the bands mentioned!
73s.

-Mike.
Logged
KB9CRY
Member

Posts: 4284


WWW

Ignore
« Reply #4 on: December 04, 2008, 06:07:19 AM »

how come some people can transmit via their rain gutters and using a tuner?



They can and do but it is not effective.  
Logged
KT8K
Member

Posts: 1490




Ignore
« Reply #5 on: December 04, 2008, 09:10:10 AM »

You will not likely be satisfied trying to tune a glorified CB vertical, especially to a lower frequency, and a simple dipole will beat the pants off of it.  If you don't believe me, whip one up and compare.

Dipoles are cheap, simple to build, easy to tune, and *highly* efficient.  You can add extra wires to your dipole to make it tune on several bands, too (the "fan dipole" concept).  One multi-element dipole can put you on 12, 15, and 17 meters and work SO much better than that interceptor.  

A dipole can be extremely stealthy, too.  If you use 18 gauge magnet wire, for example, a dipole is *very* hard to see from 15' away except in really bright sunlight or when covered in snow and ice.  
Best rx & 73 de kt8k - Tim
Logged
N3OX
Member

Posts: 8852


WWW

Ignore
« Reply #6 on: December 04, 2008, 11:01:55 AM »

"If that is the case, how come some people can transmit via their rain gutters and using a tuner? "

Any antenna, feedline, and tuner combination radiates a LITTLE bit of power at least.

If your Interceptor antenna is tuned for a good SWR on 10m, for example, and you feed it with coax and a good tuner on the 17m band, you end up with a TON of feedline loss and, therefore,  a very inefficient antenna system.

However, the cool thing about ham radio is that you don't need to radiate much more than watt or so to happily make *some* contacts.

People prove this every day by running 1W to good, efficient antenna systems.  I've worked Norway on the 160m band using approximately 1.25W effective radiated power.  

On 17m you could easily work DXCC with 1W power output (maybe not right this moment in the sunspot cycle, but it can be done).

So you can go ahead and "load up" your severely mistuned antenna on 17m and successfully radiate 1W out of your 100W applied from your barefoot HF rig, the other 99W going up as heat in the coax due to mismatched line loss or as heat in the tuner due to the nasty load the antenna will present.

That *WILL* make contacts.  You'll probably even get a few "you're a good 5 by 7" signal reports.  That doesn't mean your antenna system is working worth a darn at effectively radiating the power you're applying to it.

Now, the fundamental problem really is usually feedline losses.  If you actually put your matching network right at the feedpoint of the Interceptor, like if you had an autotuner or a remote controlled tuner, the Interceptor might work pretty well.  If it's a 5/8ths wave on CB it's actually pretty close to a 1/4 wave on 17m and with the tuner *right at the base* with no intervening coax cable, and with the interceptor's special matching network taken out entirely, it could be an OK 17m through 10m antenna.  It would help if you added radials for each band, or at least lengthened the ones that are there.

This is how the rain gutter folks tend to be most successful.  They buy an autotuner, and attach it right to the downspout or something, and attach the other side to some hidden ground radials, and they do pretty well.

When I was in an apartment, I compared the two approaches directly: tuner in the shack with coax and tuner out on the balcony, remote controlled, basically at the antenna feedpoint.  The difference on some bands was night and day, and probably to the level where I was radiating at most 1W or 2W of my 100W on those bands.

This is how I remote controlled my regular tuner:

http://www.n3ox.net/projects/servo

There are good ways and bad ways to feed random length antennas on multiple bands, but if you don't like to do a lot of planning and calculations, putting an automatic matching network at the antenna is often the way to go.  I do like to do a lot of planning and calculations, and I still tend to put the matching network at the antennna:

http://www.n3ox.net/projects/lowbandvert
http://www.n3ox.net/projects/sixtyvert
http://www.n3ox.net/projects/2017moxon

- - - - - - -

Anyway, if you want to try loading up the Interceptor through some coax, just be aware that making some ham radio contacts on it will be POSSIBLE even if the whole system is working VERY badly.

Probably the simplest way to get a really great antenna right now and to have the most fun using the Interceptor, if it is just a CB 5/8ths wave stick of aluminum is to turn it into a single band 17m groundplane by taking out it's matching network and adding a few 17m 1/4 wave radials.

15m and up are rarely open these days anyway.

73,
Dan







Logged

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

Monkey/silicon cyborg, beeping at rocks since 1995.
AA4PB
Member

Posts: 12667




Ignore
« Reply #7 on: December 04, 2008, 05:31:48 PM »

This antenna appears to be worse than most for trying to load it out of band with a tuner. It has a matching network that will act pretty much as a dead short on lower frequencies. The whole antenna is at DC ground. You'd probably be a whole lot better off loading the rain gutter on other than 10M.

As others have said, being able to get a good match for your radio with a tuner is NOT an indication that you will be radiating much power. My dummy load provides a near perfect load on all bands but it doesn't make a very effective antenna.
Logged
N3OX
Member

Posts: 8852


WWW

Ignore
« Reply #8 on: December 04, 2008, 09:57:15 PM »

"It has a matching network that will act pretty much as a dead short on lower frequencies"

Yeah, you'd have to take that out.

" My dummy load provides a near perfect load on all bands but it doesn't make a very effective antenna.
 "

Heck, many tuners will "load up" a dead short, but all the power will get dissipated inside the tuner itself ;-)

73
Dan
Logged

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

Monkey/silicon cyborg, beeping at rocks since 1995.
Pages: [1]   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!