Hi:
In addition to just the SRD there are things called "comb generator modules" that consist of a raw SRD diode (not in a
package) and an input matching circuit, typically for 100 MHz, all housed in a hermetically sealed cylinder about 1/4"
in diameter. For example HP 33002, 33003 and others.
Here is a packaged diode on eBay (item # 202135267844) advertised as for a comb
generator for $30, but I don't read Russian.
Using the eBay search term "(srd,step) diode" shows many Russian SRDs under $10
and words like 100 GHz.
Item 201976756657 has some specs, $4 and may be the same as item # 202135267844?
The HP 8406 lab bench comb generator uses a SRD, but I don't know what lifetime
it has.
https://www.prc68.com/I/HP8406.shtml
Cheng Lai, founder of Herotek came up with a way to make a comb generator module that has a wide band input. It would
be interesting to learn how he did that.
--
Have Fun,
Brooke Clarke
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
Most of my SRD stock resides on old junked PLO brick boards - that way they won't get lost, and I can possibly use
some of the associated circuitry. I have quite a few good PLOs, and have used a number of them in various projects.
The ones that I have from the 1960s -1980s seldom run the oscillator above about 2-3 GHz. The higher frequency types
usually have a high power oscillator around 1-2 GHz, and tap off power to - you guessed it - an SRD multiplier,
followed by a filter. For higher multiplication or power, there may be a class-C power amp stage in between. The
highest fundamental PLO I have is around 3 GHz. Everything above that uses SRD multipliers.
So, I think the SRDs used in the sampler/PLL sections won't quite reach the Rb frequency, since they only need to be
effective to around 1-2 GHz, maybe 3. But, you never know - it may be worth a try.
The old PLO bricks are very popular I think, because they're useful, versatile, and easy to work on. They can usually
be adapted for lots of situations and frequencies outside the nameplate. For example, about ten years ago I built a
portable Rb standard unit, and I wanted to have decade frequencies as high as I could go. I had in stock a 9.6 GHz or
so PLO that ran from 80 MHz reference. I took it apart and figured out the scheme. As I recall, it was an oscillator a
little over 1 GHz, driving a power amp driving an SRD for around 8 or 9 times multiplication, then the filter. I
modified it to run right at 1 GHz, added a tap for that output, retuned the filter for 10 GHz, and tweaked the SRD
network to maximize output power there, for X10 multiplication. The reference drive needed no change - it uses 100 MHz
from a VCXO locked to the Rb 5 MHz, and the 10 MHz comes from the PLL divider. So there you go - 10 MHz to 10 GHz in
one box. I couldn't have gotten the 10 GHz in there without this two-in-one source. It's no slouch either - the 1 GHz
is about +15 dBm, and the 10 GHz about +10 dBm.
Ed
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