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If the only thing wrong with the 7L13 is a broken knob, then I think $1k
is a reasonable price. Microwave spectrum analyzers are always
expensive. Though a 7L13 or 7L14 is on the low-end of the frequency
range, it might be OK for many people, without the $3k . . $5k . . .
expense of getting something with a higher frequency range.

One potential advantage of the 7L13/14 is that the schematics are
available and there is no power supply or display electronics to worry
about. I think more modern or similar vintage but more capable spectrum
analyzers which are not 7000 series plugins would have a lot more
electronics to go wrong, including power supplies, firmware-based
microprocessor stuff, CRT displays etc.

I recently bought a 7L14, in the 2.5GHz version (without a 1.8GHz LPF
and input limiter) for $650 or so. I knew it had problems, and I fixed
some of them - multiple dead tantalum capacitors. I now suspect its
input mixer needs its diodes replacing, since its sensitivity was very
low, and there needs to be quite a lot of work to make the displayed
frequency match what the device was actually responding to. At present
it is not responding to any signal. Now I know more about these
devices, I realize I need the 1.8GHz LPF, but fortunately MiniCircuits
make one which should work OK - and the cost is under $50.

I have now acquired three of John Griessen's <john@...>
excellent 7000 series extender kits:



so I will be able to work on this beast. Its not for everyone, but I
liken this introduction to microwave electronics to buying my first
vehicle - a clapped out 1961 VW Kombi van - and the years of learning
experiences as I rebuilt various engines, always imperfectly, and
successfully refurbished the gearbox and many other parts.

It can't be ruled out that I am crazy too, but I only bid this because
someone else was ready to bid a little lower. One fellow in Western
Australia has a 7L14 (1.8GHz version) with the TR502 tracking generator
- bought on the understanding it was fully working for ~$1.5k. That
seems reasonable to me, but it turns out that it is lacking sensitivity
and so probably in need of diode replacement in the input mixer, plus
potentially other faults.

- Robin


Magnus wrote: