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: Is it the computer, or the weather?  (Read 657 times)
AB8VE
Member

Posts: 11


WWW

Ignore
« on: February 08, 2006, 06:31:14 AM »

I recently had to purchase a new computer over the weekend.  My laptop of 4+ years decided to kick the bucket.  In hopes of having it live longer, I bought a desktop.  At the same time, the weather plummeted from average temperatures in the 50's, to an average temperature in the 20's.  I tried to fire up the HF rig for the first time today since buying the new computer.  I have a random length 14 ga.  dipole on the roof.  When I attempted to use my autotuner to tune it up, forget it.  The best SWR I could get was a 3.0.  Is this because of the new computer, or is the antenna frozen, or is it a combination of both?

73's
AB8VE
Logged
K0BG
Member

Posts: 9833


WWW

Ignore
« Reply #1 on: February 08, 2006, 06:42:54 AM »

I'd suspect the it is the way you have the antenna connected. You didn't say where the auto tuner was located, or what the feed line is. While auto couplers typically have a wide matching range, those built in to transceivers have a hard time with anything over 3:1.

If the antenna is coax fed, an auto coupler like an SGC SG237 may indeed match the antenna, the losses through the coax may be very high.

Temperature and humidity have all sorts of effects on antennas, but about the only thing a new computer can do is birdie up the receiver.

More info is needed here.

Alan, KØBG
www.k0bg.com
Logged

AB8VE
Member

Posts: 11


WWW

Ignore
« Reply #2 on: February 08, 2006, 07:39:13 AM »

I apologize, I suspect I could be slightly more specific.  The antenna is a random length dipole antenna that i built with a coax feed.  I have been using this setup for more than 6 months and it has been working great.  I have worked much DX on it.  The tuner is an LDG Z-100 autotuner.  For those not familiar with it, it uses a system of latching relays.  When the microprocessor finds a match, the relays lock and stay there.  It's really simple to figure out if you have a match.  After a tuning cycle, if you get a solid green light, you have an SWR of 1.5.1 or less.  When it blinks, 2.1 or less.  No green light?  No match.  This morning, the green light was blinking very fast which makes me think that it was between 2.1 and 3.1.  I didn't disconnect the radio in any way when I installed the new computer.  The desk has a higher platform for the monitor to set on.  The only thing i changed about the radio setup is I moved the tuner from the lower part of the desk to up next to the monitor to accomodate the computer speakers.    
Logged
K7UNZ
Member

Posts: 691




Ignore
« Reply #3 on: February 08, 2006, 09:49:44 AM »

It is possible that you are getting RFI from the monitor into the tuner control circuits.  Just move the tuner away from the monitor and see what happens.

Jim/k7unz
Logged
WB2WIK
Member

Posts: 20540




Ignore
« Reply #4 on: February 08, 2006, 01:43:34 PM »

It's the phase of the moon.

When the moon is in the Seventh House, and Jupiter aligns with Mars, then Peace and Love will guide your antenna tuner.

I think there was even a song about that...

Actually, although anything's possible I really doubt it's "the computer."

More likely something changed with the antenna.  You sure you don't have ice bridging any part of the antenna to your roof, or something like that?  Physical changes, including the presence of ice, can make big changes in the way antennas load but I've never seen a monitor influence an antenna tuner.

WB2WIK/6
Logged
AB8VE
Member

Posts: 11


WWW

Ignore
« Reply #5 on: February 08, 2006, 04:38:55 PM »

Thanks for the help guys!  Actually as the day progressed, and the sun rose, I tried it again, and there was no problem.  It took some time to get 17 meters to tune up, but 20 tuned up just like normal.  The antenna was just frozed or something.  Thanks for the clarification though!

AB8VE
Logged
K7UNZ
Member

Posts: 691




Ignore
« Reply #6 on: February 08, 2006, 05:54:00 PM »

Actually Steve, some of the older LDG models are very sensitive to, and even generate their own, emi/rfi, and depending on how well the computer system is shielded, it can cause problems.  Have a friend who literally threw away his LDG due to that.

On one model LDG even tells you in their manual that if the tuner is causing receiver hash problems, turn off the tuner lcd bargraph display. Don't know what good the tuner is without the SWR/power display operating...hi!

I currently have two LDG tuners, the AT-100Pro, and the AT-1000, and haven't had a problem with either.

Strange things do happen......

Jim/k7unz


Logged
K0BG
Member

Posts: 9833


WWW

Ignore
« Reply #7 on: February 09, 2006, 06:27:08 AM »

As Steve Katz said, it could be the moon phase. One of the problems is simply the way you feed your antenna. There is great loss in the coax on any frequency removed from it's resonant point. In fact, two things can happen.

First, the RF voltages can exceed the breakdown voltage of the coax even with just 100 watts of RF.This fact could also be the cause of your problem. Secondly, the amount of RF lost due to the very high SWR could be nearly 100%!

When using coax, the place for the auto coupler is at the antenna. You would need an RT11 or one of the SGC models that is weatherproof. Or, buy the balun LDG makes to go with the coupler and feed the antenna with ladder line.

Alan, KØBG
www.k0bg.com
Logged

WILLY
Member

Posts: 286




Ignore
« Reply #8 on: February 11, 2006, 04:38:49 PM »

 by WB2WIK on February 8, 2006     

" - - -
When the moon is in the Seventh House, and Jupiter aligns with Mars, then Peace and Love will guide your antenna tuner. "

No, no, no -

It's  "Then peace will guide the planets, and love will
steer your EME array."   Smiley




"I think there was even a song about that...  "

Aquarius (or Age of Aquarius - can't remember for sure)
-   Fifth Dimension  ,  circa late '60s.  



You're dating yourself.    And <ahem>, I'm not.   Smiley



 
Logged
KX8N
Member

Posts: 543




Ignore
« Reply #9 on: February 20, 2006, 02:17:14 PM »

Might be easiest to reach over and turn the computer off, and see if the problem persists.
Logged
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!