[TowerTalk] antenna choices for K4XS

[Doug Renwick]

>From my Mosley catalogs the TA-33 jr is rated at 0.5kw cw, the MP-33 is
rated at 1.1kw cw,  the TA-33M, TA-34, TA-53, TW-33, CL-33, CL-36, are rated
at 1.5 kw cw and the PRO-57,67 are rated at 2.5kw cw.  Yet except for the
TA-33 jr they are all rated for 600w RTTY.
Compare that to the Hy-Gain yagis.  The TH3jr is rated at 600w PEP and 300w
AM.  The TH6 is rated at 1kw AM.  The TH7 is rated at 1500w PEP one place,
no other ratings shown, and then maximum legal in other places.
I am beginning to think that some of these power ratings, like gain ratings
from years ago, are developed by marketing rather than engineering.
Doug 


-----Original Message-----


On 2015-04-19 12:35 PM, Doug Renwick wrote:
 >>From my CL-33 manual that I have on file:

The Classic 33 and Classic 36 (along with the newer CL-33WARC and
CL-39M) are a completely different design.  The feed point is
"balanced capacitive" with no ground strap like the MP, TA and PRO
series antennas.  Of course, the Classic series still uses the same
traps - with losses so high that Mosley rates the Classic antennas
- like all their trap antennas - for only 600 W in constant carrier
modes (AM, FM, RTTY, AMTOR).

73,

    ... Joe, W4TV


On 2015-04-19 12:35 PM, Doug Renwick wrote:
>>From my CL-33 manual that I have on file:
> "You can use a R.F. Choke if you want to ensure keeping R.F. off the outer
> shield of the coax.  This can be simply made by coiling 5 turns of your
feed
> line into a 6" diameter as close as possible to the attachment point of
the
> PL-259."
>
> Doug
>
>
> -----Original Message-----
>
>
> You may think that, but Mosley's documentation does not say so.
> How many inexperienced antenna builders know enough to ignore
> what the manufacturer says?
>
> 73,
>
>     ... Joe, W4TV
>
>
> On 2015-04-19 11:48 AM, Roger D Johnson wrote:
>> It stands to reason that you would remove the grounding strap when using
>> a balun.
>>
>> 73, Roger
>>
>>
>> On 4/19/2015 11:43 AM, Joe Subich, W4TV wrote:
>>> On 2015-04-19 11:20 AM, Kevin Stover wrote:
>>>> A balanced feed point fed with unbalamced line needs a choke or 1:1
>>>> balun or you get feedline radiation and screwed up pattern from
>>>> common mode current on the coax shield.
>>>
>>> Mosley's TA series antennas are not balanced feed points.  They strap
>>> one side of the driven element to the boom - that severely unbalances
>>> the antenna *even if one uses a balun or choke*.  Depending on the
>>> antenna height (impedance of the tower at the antenna DE), it may be
>>> nearly impossible to make a choke work properly and keep the feedline
>>> and/or tower from radiating.
>>>
>>> 73,
>>>
>>>     ... Joe, W4TV
>
>
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