[TowerTalk] Cushcraft XM240 & Shunt fed tower

[K8RI on Tower talk]

>I heard stainless is not good for carrying RF current.

All else equal, the clamp is only for grounding and should not be carrying 
any current.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com

>
> 73, Keith NM5G
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Pat Chiles
> Sent: Monday, June 12, 2006 12:08 PM
> To: Kelly Jones
> Cc: towertalk at contesting.com
> Subject: Re: [TowerTalk] Cushcraft XM240 & Shunt fed tower
>
> Kelly,
>
> I shorted the reflector of my XM240 when I initially installed it.  This 
> was
> after I noticed no difference between shorted and unshorted.
> Characteristics seem to be very close to what CC publishes.
>
> I shorted the reflector by using a stainless steel hose clamp around the
> middle and then screwed the hose clamps "tail" to the boom.
>
> Pat, K8PC
> ----- Original Message -----
> From: "Kelly Jones" <kjones at virtualcohesion.com>
> To: <TowerTalk at contesting.com>
> Sent: Monday, June 12, 2006 11:46 AM
> Subject: [TowerTalk] Cushcraft XM240 & Shunt fed tower
>
>
>> Hello TTs,
>>
>> As some of you may recall, I'm in the process of shunt feeding my shorty
>> tower for 80/160.  On top of this tower is a Cushcraft XM240.  Some have
>> suggested that I may need to ground the reflector in order to get enough
>> top
>> hat loading.   Some have also suggested this in order to prevent arcing 
>> at
>> high power from the boom to element as well.
>>
>> Well, I had an interesting event take place yesterday afternoon.  We had
>> what was essentially a "dry" thunderstorm come through.  The air was very
>> "charged".  You could just feel it.  I happened to be in the back yard 
>> and
>
>> I
>> kept hearing this "tick, tick, tick" noise.  After a little 
>> investigation,
>> this noise appeared to be emanating from the back of the XM240.  Then I
>> happened to notice that every time there was a cloud-to-cloud lightning
>> strike, the "tick" would become a "crackling" noise.  The intensity of 
>> the
>> "crackle" would depend on how close the lightning strike was.  On a 
>> couple
>> of occasions, I noticed the area around the rear of the XM240 light up
>> with
>> white light when it would "crackle".  This caused an extremely uneasy
>> feeling!
>>
>> I was not brave (or dumb enough) to walk out underneath the antenna to 
>> see
>> if I could visually see where it was arcing, but my gut tells me it was
>> between the reflector and boom.  So my question is has anyone put a 
>> ground
>> strap between the reflector and boom?  Would this change the
>> characteristics
>> of the antenna?  I tried contacting CC to bounce the idea off of them, 
>> but
>> trying to get to a real person doesn't seem possible.  I know that the
>> older
>> 402CD did use a ground strap but for whatever reason the XM240 does not 
>> do
>> this.
>>
>> I am pretty certain this will change the my shunt feed project as well,
>> hopefully for the better, but I obviously have an issue that needs
>> addressed.  I suspect if I do nothing it's just a matter of time before
>> the
>> smell of ozone is in the air (and in my shack).
>>
>> 73
>> Kelly - N0VD
>>
>>
>>
>>
>>
>> _______________________________________________
>>
>>
>>
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>>
>
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