[time-nuts] Distribution Amp 75R socket compatability

[Robert Atkinson]

Hi Dave,
The "old" thin pin 75R BNC sockets are rare these days. Most equipment now uses intermateable sockets that use the same size contact as 50R but with reduced diameter dielectric to maintain the impedance match. Fully compatible with 50R without damage. The only small drawback is that the old thin pin plugs (if you have any) may not make good contact.

HTH,
Robert G8RPI.




________________________________
 From: Dr. David Kirkby <drkirkby at gmail.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
Sent: Thursday, 8 August 2013, 12:08
Subject: Re: [time-nuts] Rb video
 

On 6 August 2013 09:37, Raj <vu2zap at gmail.com> wrote:
> Found this on Hack-a-day
>
> http://www.youtube.com/watch?v=chrzrod3tQY
>
> Cheers
>
> --
> Raj, VU2ZAP

Interesting video. I decided to but one of the distribution amps. I
already have the rubidium. There were a few things that struck me in
the video.

1) Having a PIC to control an LED seems a bit OTT. Personally I'd just
stick a second LED - one as a power indicator, the other as a lock
indicator, rather than make it flash when warming up, and solid when
locked.

2) If one does have a flashing LED, it would be better if it is
slower, in case there are any epilepitcs about. As someone who suffers
from photosensitive epilepsy, I would not want it flashing any faster
than 1 Hz. He should just about be ok, but I'd feel a bit happier if
it was slower.

3) I'm not really convinced there is a need to change the output
impedance from 75 to 50 Ohms. The impedance mis-match is pretty small.

4) More concerning to me would be the fact the output connectors are
75 Ohm, and so would be damaged with the larger male pin of a 50 Ohm
connector. I guess one might get away with it given one is not going
to be disconnecting this a lot, but I think I'd buy 75 Ohm BNC plugs
to put on one end of the cable, and 50 Ohm BNC plugs on the other end,
sticking a bit of heatshrink on the 75 Ohm end of the cable so I know
they are not standard BNC cables.