Hello Mike,
I would like to know more as well. The antenna is very high Q when
using the loading coil. I indicated that the BW was 40 KHz previously but
it really is closer to 10 to 20 KHz when using the loading coil. So if
power is changing the inductance due to heating then it is easy to see how
the SWR might increase.
My SPE amplifier being solid state is not tolerant about SWR
approaching 2:1 without retuning. So this is a problem. If I run 400W CW
then there is no problem but this is not on for a HP contest entry. On
40M up the antenna is great.
73 Doug EI2CN
PS I have a SteppIR 4 element on the higher bands at 80 Ft with 40M trombone
so seldom use the BigIR.
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of W0MU
Mike Fatchett
Sent: 08 December 2017 17:08
To: towertalk@contesting.com
Subject: Re: [TowerTalk] BigIR question
I am a mod on the SteppIR yahoo group and I have never heard of this
before. We have many many BigIR users and if this was the case it would
be a big issue. It does sound like there is a problem with this
particular setup.
Has SteppIR been contacted about it? If not it is hard to fix problems
they don't know about.
W0MU
On 12/7/2017 10:42 AM, john@kk9a.com wrote:
> If that is really what is occuring and if Doug is only using 1500 watt CW
> there is a design flaw. This can be easily remedied as you suggested and
> it would be worth trying, even if the SteppIR is not his primary antenna.
>
> John KK9A
>
>
> Sent via the Samsung Galaxy 7 edge, an AT&T 4G LTE smartphone.
>
> On Thu, Dec 7, 2017 at 11:56 AM, Grant Saviers <grants2@pacbell.net>
wrote:
>
>> On 80 and 160 a matching ferrite transformer such as used in the CrankIR
>> is subject to heating with QRO rtty. The solution is a larger core -
>> larger diameter core or a stack or lower power on these lower
frequencies.
>>
>> Grant KZ1W
>>
>> On 12/7/2017 0:06 AM, turnbull wrote:
>>
>>> Starts at about 1.2 and heads for 2 to 1. The BE is maybe 20 kHz.
>>> This is a Hi Q device when using the loading coil. 73 Doug EI2CN
>>>
>>>
>>> Sent from my Samsung Galaxy smartphone.
>>> -------- Original message --------From: Keith Dutson <
>>> kdutson@sbcglobal.net> Date: 07/12/2017 00:58 (GMT+00:00) To: 'Doug
>>> Turnbull' <turnbull@net1.ie>, john@kk9a.com, towertalk@contesting.com
>>> Subject: RE: [TowerTalk] BigIR question
>>> What is your SWR on 80?
>>>
>>> Keith NM5G
>>>
>>> -----Original Message-----
>>> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>>> Doug
>>> Turnbull
>>> Sent: Wednesday, December 6, 2017 9:56 AM
>>> To: john@kk9a.com; towertalk@contesting.com
>>> Subject: Re: [TowerTalk] BigIR question
>>>
>>> Dear OMs and YLs,
>>> I have a BigIR mounted on an extensive radial field and also with
>>> the
>>> 80/60M loading coil. In contests, I am allowed to run 1500W - I find
>>> that
>>> on 80M the antenna does not stay in tune while transmitting for a while
>>> and
>>> assume this is to do with heating but am not sure. Normally I would
not
>>> operate with more than 500 W for a contest on 80M then there is no
>>> problem.
>>> On 40M to 10M there is no such problem.
>>>
>>> This is not my prime antenna but is a useful fallback. It is an
>>> excellent vertical.
>>>
>>> 73 Doug EI2CN
>>>
>>> PS Only in contests are we allowed this higher power level.
>>>
>>> -----Original Message-----
>>> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>>> john@kk9a.com
>>> Sent: 06 December 2017 12:23
>>> To: towertalk@contesting.com
>>> Subject: Re: [TowerTalk] BigIR question
>>>
>>> This is a much better antenna than the fixed height 43' vertical that is
>>> so
>>> popular.
>>>
>>> John KK9A
>>>
>>>
>>> To: Frank VO1HP <invl160@gmail.com>
>>> Subject: Re: [TowerTalk] BigIR question
>>> From: Ed Richardson <ed_richardson@shaw.ca>
>>> Date: Tue, 5 Dec 2017 19:44:07 -1000
>>>
>>> Jim. The bigIR can be tuned to a quarter wave on all frequencies from 7
to
>>> 54 MHZ. On frequencies from 21-54 MHz you can select a 3/4 wavelength
>>> mode.
>>>
>>> I have used this antenna with raised radials, tuned stub radials and a
>>> ground mounted radial field. Works well in all cases. It is still a
>>> quarter wave vertical.
>>> No magic
>>>
>>> Ed. Ve4ear
>>>
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>>
> _______________________________________________
>
>
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