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

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: coaxial switch  (Read 13391 times)
W1GHR
Member

Posts: 28




Ignore
« on: January 27, 2015, 10:43:52 AM »

I'm not sure if this is the spot to post this but, I hope that if its not, I'll be okay with it. First off, I was given a Icom ic 746 ( not the pro ) and it was free. I have a 43 foot vertical antenna which, I purchased from zero five antennas and, it covers 160-10 meters. I have had a good SWR'S reading of 1:2.1 and I, purchased a coaxial switch for the three different antenna
PL- 259 . Well to make a story short, I hooked up the 3 way switch and when I, went to key up, I noticed that my SWR'S jumped all the way up to 3:0.1+. I took the switch out of my RG-8 and went back to having the coax directly to the back of the radio. Any suggestions as to why they jumped, would be very helpful.
Glenn
KC3DWC
Logged
K5LXP
Member

Posts: 6098


WWW

Ignore
« Reply #1 on: January 27, 2015, 11:31:30 AM »

It could the the switch of course but it could also be common mode.

Does the vertical have a radial field and appropriate unun?


Mark K5LXP
Albuquerque, NM
Logged
W1GHR
Member

Posts: 28




Ignore
« Reply #2 on: January 28, 2015, 11:44:15 AM »

First off, thank you for the response on this. Yes I have both of them and I also have a SWR meter in line before the radio. I had the same reading on the SWR in line before I hooked up the coaxial switch. Once again, thank you for the response and the information.
Glenn
KC3DWC
Logged
WB6BYU
Member

Posts: 18396




Ignore
« Reply #3 on: January 28, 2015, 12:00:24 PM »

Is that SWR measured straight down the coax to the antenna, or do you have a tuner in the line also?

Since the antenna is not expected to have such a low SWR by itself, my guess is that there is a tuner
(possibly in the radio) that is set to give a match.

When the coax is not perfectly matched, the impedance seen at the tuner will vary with the length of
coax used, even though the SWR is the same.  So when you added the switch, I guess that you also
added the length of a coax patch cable between it and the radio.  The tuner matches impedance
rather than SWR, so it sees a different load than the one that it was set to match.

Here is a way to test this:  connect the coax jumper to the incoming coax from the antenna using a
barrel connector.  Use the tuner to match this load so you get a low SWR.  Now swap the barrel
connector for the switch and check the SWR:  you may see a small shift due to the path length
through the switch, but I expect it will be much less of a change than you got from adding the
coax patch cable.

Note that there are other possible explanations as well, but this seems most likely.
Logged
W1GHR
Member

Posts: 28




Ignore
« Reply #4 on: January 30, 2015, 03:15:01 PM »

WB6BYU,
Thanks for that information. I will give that a try. I guess that I should have said that, I am running a Icom ic 746  (not the pro). Being new to ham radios and, never used a coaxial switch before, I appreciate the answer. Again many thanks.
Sincerely,
Glenn
KC3DWC
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #5 on: February 03, 2015, 04:58:32 PM »

43 foot verticals are a real mess on 160 meters. They have other bands where they have a pretty high SWR, also, but the 160 SWR at the antenna is about 100:1 on 160. 80 is quite a bit better, but still nasty.

It very well could be the antenna switch doesn't like the SWR, or as others suggested you have common mode in the system, or a bad switch.


 
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!