[TowerTalk] Need balun advice

[Jim Brown]

I don't think it's coax, I think it's simply interaction between 
antennas and Les's misunderstanding of the importance of SWR as an 
indicator of antenna performance.

Repeat after me --

SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.

OTOH -- the "balun" used should be exactly what the antenna designer 
recommends. The word "balun" is used to describe (at least) a dozen 
different things that are VERY different from each other. The operation 
of the antenna, as well as the match between antenna and feedline can be 
greatly affected by which is used.

So -- study the instructions for the antenna, use exactly with the mfr 
recommends, and if you want to minimize RX noise, ADD a common mode 
choke on the coax side of the mfr's recommended matching device, as 
described in by Cookbook. k9yc.com/RFI-Ham.pdf

73, Jim K9YC

On Tue,11/10/2015 1:38 PM, Les Kalmus wrote:
> Chris,
>
> I had a similar problem that turned out to be the coax. It leaves the 
> top of the tower over an arm, then hangs. The center conductor 
> migrated at the top of the arm.
> I had to cut that section out and remounted everything but hung the 
> coax from the arm with a cable grip from McMaster. No problems since.
>
> From your description, you should probably recheck the coax and make 
> sure there are no points where there is pressure that could cause the 
> center to migrate and change as the tower is raised.
>
> Les w2LK
>
> On 11/10/2015 12:54 PM, Chris Wynn via TowerTalk wrote:
>> OK, see if this changes any opinions. When I put up the A3WS at the 
>> towers nested height of about 30 feet, 12 meters swr was flat, 30 
>> meters was flat, and 17 meters was around 1.8:1....
>> Now, with the A3WS MOUNTED OVER THE th-7, 12 METERS is 1.8:1, 30 
>> meters is 3.1:1, and 17 meters is 1.0:1........
>> I have the A3WS mounted about 10 to 12 feet above the TH-7. While 
>> talking to Mark at DX Eng., he brought up the issue of spacing 
>> between the TH-7 and the A3WS..... Originally, I thought that the 10 
>> to 12 feet of space between the two would be enough.  However, at 
>> this point, I HAVE NO CLUE! Would it be worth moving the TH-7 above 
>> the A3WS?????
>> While coming home for lunch,  I worked the 5Z4 on 17 meters with the 
>> tower nested.... Hell if I know at this point!!!
>> AS TO THE QUESTIONS ON HOW I MEASURED THE SWR, I have used both the 
>> MFJ 259 and the radio's (FT-1000 field) and get the same 
>> measurements.... And have measured the swr at the end of the coax 
>> connected to the balun on the yagi.....
>> The TH-7 is working just fine......
>> I appreciate all of the help and advice...My XYL is livid with me as 
>> I have been totally consumed with these problems, and as much as I 
>> like RF, I LIKE "THAT" better and don't want to end up divorced;)
>>
>> Chris
>>   Christopher L. Wynn
>> Attorney-at-Law
>> Christopher L. Wynn, ESQ., P.C.
>> 8473 Earl D. Lee, Suite 300
>> Douglasville, Ga., 30134
>> (770)942-8661 (Landline)
>> (770)577-1626 (Telecopier)
>> chris at chriswynnlaw.com
>>
>>
>>       On Tuesday, November 10, 2015 10:40 AM, "K7LXC at aol.com" 
>> <K7LXC at aol.com> wrote:
>>
>>    >  Last week I had the antenna back on the ground and disassembled 
>> every trap on it, and found nothing out of the ordinary. ?     So 
>> what was the swr when it was on the ground? Did you check it?     You 
>> need to first ascertain that your antenna looks like an antenna; i.e. 
>> it has a dip somewhere. Put your antenna analyzer on the antenna and 
>> work your way back from there.      BTW many times an "antenna 
>> problem" turned out to be something in the shack; e.g. coax jumper, 
>> coax switch, etc. Cheers & GL,Steve      K7LXCTOWER TECH
>>
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