Can anyone suggest a decent inexpensive spectrum analyzer, that I can look
for used on ebay, that would be suitable for evaluating SSB transmitter
output for spurs, harmonics, etc.?

I have a cheap RM Italy former CB amplifier that has been heavily modified
to work on 80 through 10, and has a set of low-pass output filters in a
box with a band switch, all of which I am using with my FT-817. Its
provenance is suspect, at best, and I'd like to be able to check it from
time to time to make sure its output stays clean.

Also I have an old TS-120S that seems to have some serious transmit
problems, part of which is probably spurs and harmonics and
self-oscillation in the finals and God knows what else.

I don't mind paying a fair price for a good spectrum analyzer but I don't
want to pay big bucks for a high-end unit with features I'll never use.

Thanks...

In article ,
"Rick (W-A-one-R-K-T)" wrote:

Can anyone suggest a decent inexpensive spectrum analyzer, that I can look
for used on ebay, that would be suitable for evaluating SSB transmitter
output for spurs, harmonics, etc.?

Rick-

If you have a signal generator, you can use it as a local oscillator for
a Ham panadapter. The Heath SB-620 HamScan can be set up that way. I
used one many years ago to troubleshoot a Regency HR-6 and BTL-301 spur
problem.

I also had the TS-120S which had spurs. I took it back to the dealer,
who had a good technician at the time. Apparently incorporating all the
Kenwood tech bulletins will solve the problem unless you have a
defective component. Mine was clean as a whistle when I sold it.

Fred
K4DII

Fred McKenzie wrote:
Rick (W-A-one-R-K-T) wrote:

Can anyone suggest a decent inexpensive spectrum analyzer, that I can
look
for used on ebay, that would be suitable for evaluating SSB transmitter
output for spurs, harmonics, etc.?

Rick-

If you have a signal generator, you can use it as a local oscillator for
a Ham panadapter. The Heath SB-620 HamScan can be set up that way. I
used one many years ago to troubleshoot a Regency HR-6 and BTL-301 spur
problem.

I also had the TS-120S which had spurs. I took it back to the dealer,
who had a good technician at the time. Apparently incorporating all the
Kenwood tech bulletins will solve the problem unless you have a
defective component. Mine was clean as a whistle when I sold it.

Fred
K4DII

I used just that technique to marry my SB620 'Scanalyzer' to my TS-120S and
TS-130S xcvrs (with buffer amplifiers inside the xcvrs). The 620's input
amplifier has an RFC to ground from the cathode. A capacitor is switched
from bypass of the RFC, to coupling from an RCA jack on the rear apron.
That turns the input amplifer into a mixer. My '620 came to me setup for
Heathkit's 3.395 MHz IF. I made a dead-bug oscillator using a ~ 12 MHz xtal
that was intended for a rock-bound 2m xcvr. A slight tweak of the '620's
sweep oscillator, and I was in business.

Another potentially inexpensive spectrum analyzer scheme is based on a
varactor-tuned frontend from a cable box (it utilizes your generic
oscilloscope for display). You can build a basic unit, or add modules for
more function. Take a look at http://www.science-workshop.com/, home of the
"Poor Man's Spectrum Analyzer".

73,
Bryan WA7PRC

Can anyone suggest a decent inexpensive spectrum analyzer, that I can look
for used on ebay, that would be suitable for evaluating SSB transmitter
output for spurs, harmonics, etc.?

A few years ago I picked up an HP 8557 analyzer plugin, in a 181T (I
think) display mainframe, at a local hamfest. It's simple, and its
bandwidth range isn't super-wide by today's standards (it's rated for
..01 MHz to 350 MHz), and it isn't the most precisely tuneable or
rock-stable analyzer around, but it has been extremely useful over the
past few years. It's plenty good enough to look at the HF spectrum
and at the basic performance of a 2-meter radio (although it won't
tune up far enough to see the third harmonic of 2-meters or to be
directly useful on 440).

The tuning dial is analog, and tends to require a tweak to the
calibration-zero when you move more than a few MHz away from your
previous location. Having a decent crystal calibrator or comb generator
isn't a bad idea (I built one using a 10 MHz oscillator can, a 10:1
decade divider, and a MMIC amplifier chain deliberately driven into
saturation... works great).

The newer 8557A has a digital frequency display - I don't know whether
it's fundamentally any more stable or precise than the analog tuning
and indicator dial on the older 8557.

I've used the 8557 to help identify some local QRM problems. Hooked
to a directional 2-meter antenna it let us track down the source of a
drifty "buzz on the squelch-tail" signal which had been plaguing
several local repeaters (turned out to be a bad Ethernet switch,
"singing" loudly enough to be heard for miles!).

More expensive, wide-bandwidth spectrum analyzers might not work as
well, in your application. A lot of the wideband ones don't work at
all below 10 MHz (one of their IF frequencies, I suspect).

My repeater group was recently gifted with a used Tek 491... a
wide-band model. It turns out to have a very interesting and
significant quirk - the 10-to-200-MHz band uses a non-balanced mixer,
and input signals can "blow through" right into the 150-to-250-MHz
first IF. This creates some *huge* non-tunable spurs in the display.
As a result, I *dis*recommend this model if you have any thought of
hooking it up to an antenna and looking at your ambient RF
environment... pager and public-safety-band transmissions will show up
as non-tunable spurs which can exceed the signal you're looking for!

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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