[Elecraft] AGC behaviour

[e72x]

When I listen on ANT1 and switching to ANT2 (not connected to anything)
> I can hear pretty good signals on ANT1 on all bands! What is wrong?

regards,
E72X,





Jim Brown-10 wrote:
> 
> On Wed, 24 Sep 2008 07:59:36 -0400, Monty Shultes wrote:
> 
>>I have very high white noise in my K3 on 75 meters when connected to the 
>>serial port computer interface. Removing this connection greatly reduces
the 
>>noise.  If you use HRD, LP-BRIDGE, or any control software, you can also 
>>hear a pulsing noise related to polling the K3 over the serial port.  I 
>>believe this can be lessened, but have not tried as yet.  Here in Florida, 
>>USA, the level of thunder storms creates a naturally high noise level in
the 
>>summer, but the effects described above are clearly noticeable.  I use the 
>>Elecraft KUSB as serial interface.
> 
> I suspect that either the computer or the K3 are dumping RF trash onto
> your 
> serial cable, which, like any antenna, is radiating it, and your 75M
> antenna is 
> picking it up. I suggest that you wind the serial cable around a toroid to
> form 
> a common mode choke tuned to 75M. Fair-Rite #31 is the best material to
> use, and 
> a 2.4-inch o.d., 1.4-inch i.d. toroid is a convenient size. Fair-Rite #43
> will 
> work, but you'll need more turns. This size is commonly called FT-240 in
> the ham 
> world. 
> 
> See http://audiosystemsgroup.com/RFI-Ham.pdf for tutorial information
> about how 
> and why this works, as well as measured data for chokes with 1 - 14 turns
> around 
> #31 and #43 toroids. Ferrite beads clamped onto the cable will NOT fix
> this 
> problem on the HF bands. They WILL help on 2M. :) 
> 
> 73,
> 
> Jim Brown K9YC
> 
> 
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