[Test-Equipment] Does it really make a difference over the short haul ????

[Bill Weinel]

I used Trompter patch panels in my former occupation for routing L-band 
(950Mhz~1500Mhz) as well as HD video for 15+ years and they worked 
great. Some models do have internal termination resistors in circuit 
when no plug is inserted (it depends upon the model... not all have 
them.)  As others have stated, be careful to match the type of BNC 
connectors used with the impedance rating of the patch panel as there 
are differences in the diameter of the center pins (...which can do 
damage to the BNC jacks to the patch panel rear connectors if too large, 
or can cause intermittent connections if too small.) As far as impedance 
differences, at worst using a mismatched connector will cause a slight 
bump in the impedance plot on a VNA. In my experience it usually isn't 
significant.

73 Bill W4WHW

On 9/1/20 10:23 PM, Glenn Little WB4UIV wrote:
> I worked in broadcast TV.
> Internal to the jack may be a chip terminating resistor.
> On the panels we used this could be removed by disassembling the jack.
> I would use the 75 Ohm panel as a receiver patch panel without 
> question, if you are using HF or low VHF.
> It might get iffy at UHF and above.
> I would not run power through the jack without removing the 
> terminating resistor as it would probably burn.
>
> 73
> Glenn
> WB4UIV
>
> On 9/1/2020 8:00 PM, Doug Hensley wrote:
>> This question is for the experts on this list.
>>
>> The Trompeter Company in California for many years manufactured 
>> patching panels that were used by both military & broadcast 
>> operations.  Some were 50 ohm but most were 75 ohm for video patching.
>>
>> All these panels used BNC's on the rear and the famous Trompeter 
>> barrel socket on the front.  50 ohm set ups were made but most 
>> readily available are 75 ohm.  The distance from the rear BNC center 
>> pin to the Trompeter barrel pin is less than an inch.
>>
>> Question 1:  Given 50 ohm cables are used front & back, does using a 
>> panel that is rated for 75 ohms really amount to a hill of beans 
>> regards ham use?
>>
>> Question 2:  If the panel itself has negligible affects, can short 75 
>> ohm patch cords be used for RF without degrading the signals?
>>
>> Not sure how else to ask this.
>>
>> Does anyone know?
>>
>>
>> Doug W5JV
>>
>>
>>
>>
>>
>>
>>
>> Visit https://www.qrz.com/db/W5JV for some great vacuum tube finds.
>>
>>
>> ______________________________________________________________
>> Test-Equipment mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/test-equipment
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Test-Equipment at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>