[TowerTalk] Six meter balun

[Joe Subich, W4TV]

On 2022-07-03 6:43 AM, Dave Sublette wrote:
 > The antenna is working now.  I'm suspecting the relay position on the
 > remote switch.  As soon as it stops raining, I will check it out.

The RCS-10 is a poor design at higher frequencies ... it has one relay
feeding two relays that feed four relays to select among eight antenna
positions.  That means three relay contacts in series for any antenna.
Not only is it three times the places for trouble, it is three times
the inductance and a much longer non-50 Ohm "path".

73,

    ... Joe, W4TV

On 2022-07-03 6:43 AM, Dave Sublette wrote:
> I just checked the coax I used.  It has the stranded center conductor.  I
> can't find the part number on it.  I would hve to find the invoice.  But it
> is the mil spec teflon/silver coax.
> 
> K4TO
> 
> The antenna is working now.  I'm suspecting the relay position on the
> remote switch.  As soon as it stops raining, I will check it out.  Thanks
> for for all the advice.
> 
> K4TO
> 
> On Sat, Jul 2, 2022 at 11:57 PM Grant Saviers <grants2 at pacbell.net> wrote:
> 
>> A minor matter, but RG142 center conductor is SCCS - silver plated
>> copper coated steel.  That makes it very strong but fatigue prone.  Some
>> are concerned about TFE creep from the solid conductor and recommend
>> stranded RG400 as a result.  However, I've not had problems in FT-240
>> toroid chokes wound 10 years ago with 142 made from Mil 17/60-RG142 spec
>> cable.
>>
>> Paternack specs their 142 at 2400w average power at 100MHz.  It will get
>> hot, but the TFE handles it.  Best to provide easy dissipation of the
>> heat as K9YC recommends.
>>
>> Another possible issue is to keep ferrite toroids away from the boom and
>> other conductors as the coupling can cause problems.
>>
>> Grant KZ1W
>>
>>
>> On 7/2/2022 16:13, Jim W7RY wrote:
>>> Agreed.
>>>
>>> RG-400 works well to. The only difference between RG-142 and RG-400, is
>>> that RG-400 has a stranded center conductor. RG-142 has a silver plated
>>> solid hard drawn copper center conductor.
>>>
>>> 73, Jim W7RY
>>>
>>>
>>> On 7/2/2022 6:09 PM, john at kk9a.com wrote:
>>>> The 50MHz power average rating for RG142 is several kilowatts, why do
>> you
>>>> think it is inadequate?*If it is a balun problem it is most likely
>>>> connection related.*
>>>>
>>>> John KK9A
>>>>
>>>>
>>>>
>>>> Dave Sublette k4to wrote:
>>>>
>>>> My six element 6M LFA is showing a high SWR and severe loss of receive
>>>> signal.  This happened this afternoon as I was working the band with 500
>>>> watts from my KPA500.
>>>>
>>>> To this point, the antenna was very nicely matched with a 1:1 SWR over
>>>> almost 1 MHz of bandwidth. The antenna is home brew and I made the
>>>> matching
>>>> balun per the instructions from K9YC using two toroids with six turns
>>>> each
>>>> of high quality teflon insulated, double shielded silver braid. I
>>>> think it
>>>> was RG142 purchased new from a reputable vendor in Tennessee. It has
>>>> worked
>>>> perfectly at the 100 watt level for three or four years.  I had looked
>> at
>>>> the specs on the coax and thought it would be good for 500 watts.
>>>> Evidently not.
>>>>
>>>>
>>>> 73,
>>>>
>>>> Dave, K4TO
>>>>
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