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Author Topic: I have intermittent that is driving me crazy  (Read 538 times)
VE7ALQ
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Posts: 349




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« on: September 16, 2005, 02:27:46 AM »

I have a number of Belden 213 jumpers each three feet in length going to the following

Linear -> External SWR Meter
SWR Meter -> Coax Switch (Daiwa)
Coax Switch -> RadioWorks Line Isolator (UnUn)

There is an intermittent somewhere here that is driving me nuts.  If I wiggle the jumpers to the Coax Switch or if I shoot some RF up the pipe, the intermittent fixes itself (for a while).  I am wondering if the Belden 213 is the wrong stuff to make jumpers out of.  It is stiff as all getout, and thus the PL-259 connectors may be FUBAR.  Also, I don't trust the Daiwa coax switch ever since I opened it up and found nickel plated contacts.

To solve this problem I have ordered five jumpers each three feet in length made from RG-8x (plus) from www.radioworks.com  I also have an MFJ coax switch on order.  I intend to swap the whole kit and caboodle, Belden 213 cables and Daiwa coax switch out for RG-8x (plus) cables (the plus means non-contaminating) and the MFJ coax switch.  At least MFJ assures me the contacts on their switch are copper against copper.  The extra jumper is so that I can use my ShinWa 30 mHz kilowatt low pass filter (not that I need it, as the neighbours are on cable)

www.radioworks.com assures me that their RG-8x will handle 1500 watts with 4:1 swr without problem.  I am a bit sceptical about this, as the manual for my Yaesu FL2100z says not to use thin coax for the RF output.  Nevertheless the FL2100z linear only puts out 600 watts when fully driven by my Icom IC-706mkiiG, so if the RG-8x cable will withstand 1500 watts at 4:1 SWR then it follows that the RG-8x cable can handle 600 watts at a 3:1 or lower SWR.
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W9PMZ
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« Reply #1 on: September 16, 2005, 05:01:57 AM »

There is also another possibility.

I had this same exact problem, an intermittent that I thought was in the coax.  Turned out to be a poor solder connection in the SO239 connector on my Kenwood TS-690S.

Have you used a ohm meter to check the cables?  The cables may not be the problem in the first place.

73,

Carl - W9PMZ
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AA4PB
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Posts: 13032




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« Reply #2 on: September 16, 2005, 05:23:18 AM »

I don't see why 3-foot RG213 jumpers should be any problem if they are made correctly and use good connectors. I've got some in 18-inch length on an antenna patch panel that have been in use for nearly 20 years and still going strong.

The RG-8X should also be fine for the jumpers. Loss won't be a problem, even on 2M, because they are short.

Other possibilites are a bad SO-239 (center contract spread) or as the previous poster stated, a poor connection on the back of an SO-239.
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K0BG
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« Reply #3 on: September 16, 2005, 10:08:50 AM »

You didn't state what coax switch. Some of the imports are not much more than junk. If you can take the back off, look for signs of heat.

Alan, KØBG
www.k0bg.com
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N4ATS
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Posts: 851




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« Reply #4 on: September 16, 2005, 10:29:00 AM »

It is most likey the Antenna Switch , what kind is it? Like the guy said above , most of the so called "Export" antenna switches are scrap. Look inside...
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X-WB1AUW
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Posts: 559




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« Reply #5 on: September 16, 2005, 12:00:03 PM »

<It is stiff as all getout, and thus the PL-259 connectors may be FUBAR.>

Why would a stiff cable make a connector FUBAR?  I use stiff cable, not for jumpers, and have never thought that the stiffness of the cable would alter/effect the PL259.

<I don't trust the Daiwa coax switch ever since I opened it up and found nickel plated contacts.>

I don�t see the relationship between nickel plated contacts, and an intermittent problem.
What happens if you don�t use the switch?

What happens if you run the antenna into your amp or rig?

Bob
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VE7ALQ
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Posts: 349




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« Reply #6 on: September 16, 2005, 12:14:35 PM »

The Coax Switch is a Daiwa.  With the switch in the circuit between the Amp and the Antenna, I definitely get the problem.  Without the switch, Antenna directly into Amp, I don't get the problem, but there are intervening short Belden 213 jumpers.

When I was young, I was taught that "What does not bend, breaks".  Thus I am going to substitute RG-8x (plus) for the Belden 213, have Radioworks make up five jumpers each three feet long with gold-plated PL-259 male plugs and gold-plated UG-176 adapters for RG-8x, the theory being that the professionally made 'gold' connections will be less likely to be intermittent, and the RG-8x (plus) will allow for easier manhandling of the jumpers.  I have been assured by Radioworks that their RG-8x (plus) is good for 1500 watts SWR 4:1  If this is true, I do not think that my 600 watt Yaesu FL2100z Amp should be able to damage it.

I have ordered an MFJ two position coax switch.  MFJ assures me that the contacts on this switch are copper.
If the issue is with the Daiwa coax switch, replacing it with the MFJ coax switch should solve the problem.
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N6AJR
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Posts: 9927




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« Reply #7 on: September 16, 2005, 12:33:29 PM »

I use a ton of jumpers and switches in the shack, ( see picture on home page, link on qrz.com at my cal) and I use mostly rg8x jumpers.

I find the 213 and rg8u to stiff to use easily and it could be the bending is pulling the connections out of contact.

I buy rg8x on ebay for $89 for a 500 foot roll from a seller  named GSSEC.  and I get connectors anywhere I can get a deal, like a 100  pl259's for $30, and I build my own cables.  any arrl handbook has directions for soldering up cable ends.

I keep a lot of coax on hand in different sizes as I am always putting up something different. I have 4 spools of 8x (2000feet) a hundred feet of 174 ( the tiny stuff. some 93 ohm cable for satalite antenna building, some 213 ( maybe a hundred feet), 500 feet of rg59, and 2400 feet of lmr-400, direct bury cable (its like really good rg8u)

I always have  enough for projects. the 2400 feet of lmr 400 cost me $600  shipped here in CA from Florida, so sometimes it pays to buy big, that stuff is usually over a buck a foot.

I like the 8x form jumpers, it handles power into a reasonable antenna, ( swr below 4:1 or so) and I have switches made bu diawa, mfj, opec, and others. all seem to be ok, I have had problems now and then but no particular brand is worse than the other.  sometimes flipping them back and forth a couple times will clean the contact.

good luck, find the problem befor something goes up in smoke..
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N0TONE
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Posts: 173




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« Reply #8 on: September 16, 2005, 03:54:53 PM »

You haven't told us the symptom yet.  Are you intermittently seeing high SWR somewhere or intermittently seeing no RF output, or intermittently having the receiver go dead?

Help us help you.

AM
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X-WB1AUW
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Posts: 559




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« Reply #9 on: September 16, 2005, 07:45:21 PM »

Do you have a double female that you can sub for your switch?

Copper oxidizes.

If I remember correctly, silver that oxidizes has slightly higher conductivity.

Bob
 
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W4XKE
Member

Posts: 66




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« Reply #10 on: September 16, 2005, 08:13:48 PM »

At General Motors we used to have a motto:

"Intermittant problems usually remain to be so for the service life of the equipment."

I have found that to be especially true in hamshacks.  Sad

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VE7ALQ
Member

Posts: 349




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« Reply #11 on: September 17, 2005, 08:19:52 AM »

The connection is intermittent on Receive.  On Transmit the exciter and/or the linear put through enough RF to punch a hole in whatever is causing the problem.

I have replaced my Belden 213 cables with professionally made up Belden 213 cables.  The intermittent is still there, but much less pronounced.  On Friday was couriered the MFJ coax switch, so I should be getting it sometime early next week.   Swapping out the Daiwa switch and swapping in the MFJ switch will help solve the problem.

I am also ordering from http://www.radioworks.com five RG-8x (plus) three foot long jumpers with gold PL-259 male plugs on the ends.  I have a theory that RG-8x would be better for jumpers, if only because it is flexible and less likely to break from metal fatique, etc.
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WK4KW
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Posts: 24




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« Reply #12 on: September 18, 2005, 02:42:30 AM »

You might look at a much simpler and more likely problem, your amplifier!! If the intermittent is only present in receive, it very well could be the T/R relay in your amplifier.The contacts may simply be dirty or they may be pitted and either way they may not be making properly when the relay opens. The problem of low receive would present with the amp on or off. You could also try a different length of cable between your transceiver and amp. Some amp makers suggest a particular length of jumper between the transceiver and the amp, others don't. I don't think anyone has suggested this as a possible solution, if so, please excuse the redundency.
73, Don
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VE7ALQ
Member

Posts: 349




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« Reply #13 on: September 18, 2005, 03:34:08 AM »

Wiggling on the Belden 213 going to my Daiwa coax switch causes the problem to appear and disappear.  After replacing all the Belden 213 coax jumpers with new professionally made Belden 213 coax jumpers, my problem "went away".  The linear is so heavy that manhandling the Belden 213 jumpers does not make it move in the slightest.

I am not enamoured with using Belden 213 for jumpers, as it is very stiff, and may induce connector failure if overly flexed.  I have on order from http://www.radioworks.com five jumpers 3 feet each in length, to have Gold PL-259 male connectors and Gold UG-176 adapters for RG-8x (super) installed.  I am also getting 20 Gold PL-259 male connectors and 20 Gold UG-178 adapters from them, in addition to the 10 male plugs going onto the five RG-8x (super) jumper cables.
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