[time-nuts] TAPR TICC and TADD-2 Minis

[Tom Holmes]

Frank...

What is interesting is that all of your traces appear to be identical except for the vertical scale factor, which suggests that the ringing you are seeing, which is much improved from your earlier plots, is still a little bit of a problem. I am going to guess that , as Bob pointed out, is probably due to a reflection problem in the input side of the attenuator. Could be the attenuator input impedance is not a good match to the source, or could be a cable impedance issue. 

I hope that suggests some things you could try experimentally and educationally to sort it out.

Tom Holmes, N8ZM

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Frank O'Donnell
Sent: Tuesday, June 02, 2020 1:19 PM
To: time-nuts at lists.febo.com
Subject: Re: [time-nuts] TAPR TICC and TADD-2 Minis

On 6/1/20 9:11 AM, Bob kb8tq wrote:

> Scope basics:


Thanks for the comments. Very helpful as background beyond this immediate project.


> A 10 db pad ahead of the feed through is another way to deal with this. It should at
> lest get you into the 20 db return loss range.


I have a nice JFW variable attenuator, and inserted it between the TADD-2 Mini and the scope to capture the Thunderbolt's 10 MHz signal converted to square wave with 0, 3, 6, 10 and 20 dB attenuation. Screen shots are attached (very small, but there are five of them).



> One of the reasons there are compensated scope probes is to get around this
> issue. There are a variety of them out there with a range of capabilities. Yes, the
> fancy fet probes cost more than something simple ……. 


Currently the only probes I have is the stock pair that came with the Siglent digital scope (an SDS1202?X-e). I also recently bought a vintage Tektronix T922 analog scope, but it didn't include probes. Thus I might be in the market for a good set of probes. If there are suggestions for any that aren't more expensive than, say, a T922 or a used Thunderbolt, I'd be very interested.


Thanks again,

Frank