Re: Testing the Measurement Rcvr

Nick Kennedy

I went to the 5.528 MHz IF solely in the spirit of trying to use parts that
are in my junk box. It certainly has no advantage over the frequency chosen
by Jerry H.

Some of the other stuff I did is hard to explain now. Possibly I wanted to
not use a heat sink on the output amplifier. And I felt that the PHSNA has
plenty of dynamic range. It's definitely a good design as-is though.

Yes, Farhan's SPECAN is very interesting. Who wouldn't love to have a
spectrum analyzer? And he claims it's easy enough to build and not
expensive. Maybe that one should go on the stack.


Nick, WA5BDU

On Thu, Jan 3, 2019 at 11:47 AM Nigel Maund <> wrote:

Thanks for your feedback Nick,

I am intrigued as to why you may have changed to the 5.528 MHz frequency
of operation?

And, also the decisions to go with lower amplifier output.

In researching other types of analyzers, I came across Ashar Farhan’s
“Specan” design.

He used a 12 MHz filter.
It occurs to me, that I could build the front stages of his design, and
“tack them on” as front stages to the Measurement Receiver.

Let me start by getting the Measurement Receiver built (it has been, like
4 years on the back burner!).

Thanks and interested to hear from others that have implemented the
Measurement Receiver.


On Jan 2, 2019, at 8:31 PM, Nick Kennedy <> wrote:

It's been 4+ years since I built mine, but I have some notes,
Your idea of testing in sections is certainly a good one. I had to do a
of troubleshooting, although not generally due to the design or concept
due to having a couple of bad mixers.

Also, I made a lot of changes so I had to be sure I'd done them
I used some 5.528 MHz crystals I had on hand so that changed the
frequency, the diplexer, the L-matches and so on.

Shooting through the crystal filter and its L-matchers before connecting
the rest of the world is definitely a good idea. And since you have that
nice PHSNA instrument sitting there, why not?

I like to measure my critical component values pretty closely and also
simulate the circuits in LTspice, so sometimes I don't actually feel the
need to adjust trimmers. My notes say I pre-set my L-match trimmers to
required value. But I could see plotting the filter curve and playing
those trimmers until you got a nice flat response curve might be a good

I substituted an ERA-1SM for the ERA-3+ which changed other component
values a bit. It's easy enough to verify the gain of that stage acting
alone before installing the mixer.

For whatever reason(s), I didn't feel the need for so much oomph out of
output amplifier so I changed the biasing to reduce standing current to
about 10 mA and didn't need a heat sink.

I did take a look through the diplexer before connecting it to the
and driven stages. I had already modeled it on LTspice and seen that, by
design, you don't get sharp peaks but you do get a constant load over a
wide range of frequencies. Which I guess is its function.

So getting back to testing in stages. Yes, especially on through-hole
projects, it's a great idea. Sections can be hard to break apart after
fact. And as I guess I've suggested already, you could easily build and
test separately the MMIC amplifier, the diplexer, the crystal filter plus
matchers and the output amp. Or combine the output amp with the filter.
This can be accomplished by holding off on installing the mixer until
testing the boards separately, and maybe keeping C15 out until you've
tested the filter and output amplifier separately.

On the fuse and blocking diode - your proposal to share them seems
reasonable. I don't remember exactly what I did there.

73 & good luck with the project,

Nick, WA5BDU

On Tue, Jan 1, 2019 at 6:40 PM Nigel Maund < <mailto:>> wrote:

Dear PHSNA testing community;

I am finally building the Measurement Receiver.

I wanted to ask advice on how to test/tune it as I build it in sections?

Here are my thoughts:

1) using the PHSNA, sweep the Xtal filter alone, and adjust the trim
capacitors to get a flat response curve
2) add the 2n2222 Amplifier, to then see the sweep with a 20 dB gain

Next steps - how would I make sure that the Bridge Tee Diplexers are
properly tuned?

Is it simple enough to wire up all the components and go for broke.
Or, is there a way to perhaps add in the Diplexer circuit and sweep it
using a 3.2768 MHz (spare crystal) oscillator,. If I were to use a
loss bridge would this then give me some interesting way to use all the
test components and actually see the Diplexer working?

I am thinking of how best to test each of the two boards separately,
the PHSNA and Power Meter, before connecting them together.

One final question: the schematic shows only one power connection
circuitry (200 mA resettable fuse, shotkey diode) but both boards have
locations for this circuitry. Is it acceptable to simply wire one board
with this circuitry, and jumper the 12 volts supply to the 2nd board.
do both boards need a 200 mA resettable fuse?

Nigel, Va2NM

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