Topband: F connector question

[Michael Tope]

It is certainly true that 50 ohm N and 75 ohm N connectors are NOT 
physically interchangible (a N-50-male with trash a N-75-female). I 
don't recall for sure about 50 and 75 ohm BNC. The 75 ohm BNCs I 
remember using were on the return loss bridge for Wavetek CATV sweep 
generator. I believe that the nested dielectric cylinders that are 
present in the 50 ohm BNC are removed entirely from the 75 ohm BNC in 
order to raise the impedance of the structure, but I don't recall for 
sure about the center pin/receptacle diameters.

Mike W4EF..............

k8gt at mi.rr.com wrote:

>With all due respect, Frank, but 50 and 75 Ohm BNC connectors are very compatible and in the TV and Video production businesses, we have been using them since the '60's.  When we changed from UHF connectors to BNCs, we only had 50 Ohm types, it was a little later that the 75 Ohm connectors were available.  In analog video it didn't make any difference, but when we got to SD video and now HD video, it definitely did make a difference.  Obviously at VHF anf UHF RF, it makes a great difference.
>
>Your description of the difference in connectors is spot on.
>
>73, Gerry, K8GT
>
>
>
>---- donovanf at starpower.net wrote: 
>
>=============
>75 ohm BNC connectors are specialized connectors used primarily above 100 MHz by in high definition television production studios, telephone, and satellite communications industries.  Unless you work in those industries, you're not likely to need them.  50 ohm BNCs work fine with 75 ohm cables for applications below about 100 MHz where the connector is very short compared to a wavelength.
>
>The dielectric in 75 ohm BNCs connectors has a obvious different configuration than the dielectric in 50 ohm connectors.  The dielectric in a 50 ohm BNC is extends along the inner surface of the  shield.  The dielectric in a 75 ohm BNC does not extend along the inner surface of the shield.
>
>http://www.lifebeforelandfill.com/item/cameras_photo/professional_video_equipment/cables_wires/canare_bnc_cable_m-m_75ohm_lv-61s_45-ft/images/00179_canare_bnc_cable_m-m_75ohm_lv-61s_45-ft_img_01_gall.jpg 
>
>IMPORTANT: 50 and 75 ohm BNC connectors are not usually compatible or interchangeable.
>
>73
>Frank
>W3LPL
>  
>