There are two possibilities.
One is what Jim Brown suggested about a large change in impedance that is
not being properly matched.
Another possibility is that somehow the balun/core has changed the airflow
around the radio either by causing a repositioning of the radio or by just
blocking some air.
----------------- Wes Attaway (N5WA) -------------------
1138 Waters Edge Circle, Shreveport, LA 71106
--- 318-393-3289 (Cell) ---
Computer Consulting and Forensics
-------------- EnCase Certified Examiner ---------------
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of David Cole
Sent: Friday, June 20, 2014 2:26 PM
To: rfi@contesting.com
Subject: Re: [RFI] Ferrite Question...
Hi,
I should have asked a different question... Any idea why the rig is
getting warmer than if no ferrite's...
Here is some more information...
A fellow wrote me off list asking for more info...
Antenna is on roof, and AC wiring is I am sure in attack area. About
three feet of coax between the tuner and radio. He is running 30 watts,
no grounds, all bonds are via coax, one ground to tuner. No balun on
the OCF...
I get that the OCF makes things very unbalanced, (he has no balun on
it), and I get that a single ferrite won't correct this, (he did no
winding), but why might the rig get warm? I thought I had a handle on
how this stuff was working, but for the life of me, I can't imagine why
the rig gets warm... It always sees a 1:1 because he is tuning it the
feedline to 1:1 as it feeds the rig...
--
Thanks and 73's,
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On Fri, 2014-06-20 at 09:18 -0700, Jim Brown wrote:
> On 6/20/2014 4:53 AM, David Cole wrote:
> > What is happening here, any ideas?
>
> First, because it's off-center fed, it's wildly unbalanced, so there's a
> lot of common mode current on the feedline, which makes it part of the
> antenna. The path for that current is through the tuner to ground.
>
> Second, I'm guessing that he didn't wind turns through the ferrite
> cores, simply clamped them on. That adds inductance to the common mode
> circuit, which changes the tuning.
>
> Study k9yc.com/RFI-Ham.pdf
>
> 73, Jim K9YC
>
>
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> RFI@contesting.com
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