Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Thomas Garson

This is very interesting to me, but the description of the device on the eBay sale page is very difficult to follow. They discuss spectrum analyzers as if this is one. I don't see how that can be.

However, even if it is only a "flat" white noise source, I can see the utility it offers. My normal MO for testing receivers is to use my Marconi generator swept over the required spectral range while observing the output of interest on my 7000 series 'scope. This works quite well, but can be somewhat cumbersome. I have considered trying to acquire a tracking generator for my 7L12, but those are relatively rare and have been somewhat expensive.

I never considered using a broadband noise source as an alternative to the tracking generator. From your post, it appears that you have done so, with at least acceptable results.

It's kind of funny, because I work more in audio than RF and for years, prior to the advent of low cost computer "sound card" based analyzers with tracking generator, used noise with an analyzer for sound system measurements. Duh.

Any comments, hints or suggestions welcome.

Thank you.

Thomas Garson
Aural Technology, Ashland, OR
By my calculation, the dynamic range of the universe is roughly 679dB,
which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps.

On 12/27/20 7:50 AM, Nenad Filipovic wrote:
On Sun, Dec 27, 2020 at 05:31 AM, Attilio wrote:
Can you give an indication as to which source noise should I buy ?
I've got one very much like this:
It's reasonably flat and worth the price. You might find it cheaper on Aliexpress. Do not buy the PCB only version (no metal box, unless you intend to put it in one) as it will pick up all sorts of RFI from your environment.

What can I do to reduce the possibility of damage the first 7L13 mixer using
an active probe?
Same as what Chuck already said, care and discipline during usage. 7L13 attenuator offers fair protection on its own at -20dB and higher settings. Insertion of clamping diodes will provide additional protection but it may also disrupt the complex impedance of the input, which may impair the accuracy of measurements on higher frequencies.
Best regards and Happy Holidays,
Nenad FIlipovic

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