Fw: [South Florida DX Association] TH-11 Problems

[K2EWB]

2nd posting. I've got intermittent cable service. First try may not have 
actually been sent. If you and the others on the reflector get two copies it 
wil be better than none at all.

LAK

----- Original Message ----- 
From: "K2EWB" <k2ewb at adelphia.net>
To: "Pete Rimmel - Marine Chemist - N8PR" <n8pr at bellsouth.net>
Cc: "SFDXA" <SFDXA at mailman.qth.net>
Sent: Sunday, January 14, 2007 11:20 AM
Subject: Re: [South Florida DX Association] TH-11 Problems


> Hi Pete,
>
> Perhaps the following will help. (Two people or more with two meter 
> hand-helds or cell phones will be needed.) I agree that using a 50 ohm 
> dummy load up on the tower should be tried first.
>
> 1. Remove the cable from the balun and the tranceiver, read the resistance 
> across the cable. It should be infinity.
>
> 2. Short the cable at the tower end and read the resistance in the shack. 
> It should be close to zero.
>
> 3. If the above don't check out OK, check out any double female connectors 
> that may be in use if the cable is not one single piece. I've seen these 
> collect salt if used outside in our climate, even if taped.
>
> 4. If the tower and or the antenna has ever been hit by lighting the coax 
> might be "cooked".
>
> Good Luck,
>
> Regards,
>
> Leon,   (K2EWB)
>
> **************************************************************************
> ----- Original Message ----- 
> From: "Pete Rimmel - Marine Chemist - N8PR" <n8pr at bellsouth.net>
> To: "SFDXA" <SFDXA at mailman.qth.net>
> Sent: Sunday, January 14, 2007 9:44 AM
> Subject: [South Florida DX Association] TH-11 Problems
>
>
>>>>Wally and interested members,
>>
>>>>The SWR is 5:1 on all bands as measured both in the shack and at the
>> antenna...
>>
>> Wally wrote:
>> 12 meters never had a good SWR.  Always hovered around 2:1 and the 746 I 
>> had
>> at the time would shut back the output power unless I used the internal
>> tuner.  I remember that the SWR started to climb at the high end of 20 
>> and
>> 15 pretty quickly.
>>
>>
>>>>Two of us put it together and triple checked everything.
>>
>> Make sure the correct traps are mounted in the correct positions.  If the
>> antenna was sitting on a wall waiting to be installed and water moisture 
>> got
>> into the vents you could have a problem.
>>
>>>> We have built, repaired and/or rebuilt many antennas, and did not use 
>>>> too
>> much or too little No-Al-Ox on the antenna joints.
>>
>> Dont go too crazy with the penetrox.  It isn't DX-butter!  All it is
>> supposed to do is to keep metals from seizing together.
>>
>>>>> NO, this did not happen.
>>
>> If you get a bunch of it in your pipe clamps they can loosen prematurely.
>>
>>
>>>> I discovered that the BN-4000 is a 1:1 balun and it seems to be OK...
>> Putting the dipole connection in line should have also been a 50 ohm 
>> match
>> aothough unbalanced to the antenna, but it did not seem to be much 
>> better...
>> 3:1 on most bands, but I did not write it all down...  On the low end of 
>> 10
>> M it came down to 1.5:1   Go figure !!
>>
>>>>I used my MFJ antenna analyzer with a 50 ohm resistor across the output
>> both with and without the "impedance matching" coil across the balun and 
>> got
>> about 1.2:1 on all bands from 1.8 to 30 MHz and all freq's in between.
>>
>>
>> I used a hy-gain balun  on my antenna.  Don't recall any issues with it.
>>
>>>> We did check the Coax  with a 4 watt  ~50 ohm load on the coax, and got
>> less than 1.5:1 on all bands.  The coax is old, but I don't think it is 
>> the
>> problem.
>>
>>>> the MFJ on the antenna, directly with a 2 foot jumper,  showed the same
>> 5:1 SWR as in the shack.
>>
>>
>> Isolate the problem.  Is it in the coax?  Pull the coax off the antenna 
>> and
>> put a known 50 ohm load on it.  PL-259's Okay?
>>
>>>>Yes traps  are holes down...
>>
>> Look at the bottom of the traps.  Vents down?
>>
>>
>>>>Again. everything was triple checked and all dimensions are to spec.
>> checked by two of us...
>>
>>
>> Then, look at your OAL and spacing measurements.  An inch here, an inch
>> there..... Can cause a problem if you miss something.
>>
>>>>  We have about 28 man hours in the construction of the antenna...  we
>> really took our time and made sure it was AOK.
>>
>>>>We double checked to see if there were any shorts or kinks in the 
>>>>matching
>> network after it was up, and all is FB.
>>
>>>>  I was really hoping that it was the balun, but now, I have no idea 
>>>> where
>> to go next... we really don't want to take thaantenna back off the 
>> tower...,
>> That would take another 4 hours and crew of 10...
>>
>>>>>>>>>ANYONE HAVE ANY OTHER IDEAS???
>>
>>>73,
>>>
>>>PeteR  N8PR
>>
>>
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>