Topband: RX antenna switching - unused ports

[Herbert Schoenbohm]

Brad, I have a 12x1 commercial Panasonic video switcher which is passive 
and terminates in 75 ohms all unused ports.  I used 1/2 wave feed lines 
which conceivable repeats the 75 ohm termination at the Beverage 
matching transformer.  I also use several 1:1 (DXE) isolation boxes 
about 30 feet from several Beverages to reduces feedline pickup coupling 
back into the Beverage matching transformer.


On 6/8/2017 8:06 AM, Maciej Wieczorek wrote:
> Hi Brad,
>
> what I can say from my perspective - in the last 10 years I have tried 
> both grounding and terminating through 75ohm resistor. With the 
> terminating I see absolutely no pattern distortion on my Beverage's, 
> which was not so obvious when direct grounding was used.
>
> My Bev's often are crossed 45 deg, height is 1,8-2,0m.  I use only 
> isolated transformers / separate windings.
>
> 73's
> Mac SP2XF / SN2M
>
> ----- Original Message ----- From: "Brad Denison" 
> <brad.denison at gmail.com>
> To: <topband at contesting.com>
> Sent: Thursday, June 08, 2017 1:54 PM
> Subject: Topband: RX antenna switching - unused ports
>
>
>> All,
>>
>>  I am working a homebrew RX antenna switch box for my beverages, 
>> flags and
>> shared apex loop array and am looking for design advice.  Can someone
>> educate me on the proper way to handle unused ports:
>>
>> 1)  Leave all unused ports open
>> 2)  Ground all unused ports
>> 3)  Terminate unused ports to 75 ohm
>>
>>
>> I have seen various commercially available switch boxes with all of 
>> these
>> configurations but it is not clear to me if any of these variations are
>> best, i.e does it matter?
>>
>> Thanks,
>>
>> Brad, W1NT
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