Notified last night that it may arrive next Wednesday. I never had a spectrum analyzer in my life until the little $110 unit from China and now this.....

Took a course a week or two back from the county and they had a $30,000 service monitor with built-in Spectrum analyzer.

Retiring from the practice of medicine January 10, 2020. Will have a lot more time!!

Tons to do!

Gordon

Now you will be a radio doctor... ?

How about links to the siglent and the spectrum analyzer that you mention??

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Congrats for the nice tool! I have always asked myself whether one could also use an SA as a low phase noise receiver or at least a part of it.

Gordon,

Congrats, you will learn a lot from an analyser.

You will also need some attenuators and dummy load type power attenuators.

A 30db power attenuator rated for more than 100W will suffice even for commercial rigs. For uBitx and such
25W should do.

You will also need optionally a variable attenuator, one that has 0-9db and 0-90db steps. With this you can
set any power input to 0dbm at the SA input.

Raj

What I use is similar to this one below and this is fixed after the big dummy attenuator below. This brand will be expensive.



At 12/04/2019, you wrote:

We won't hold Gordon to making great advances with the acquisition of? this nice tool, but bonne voyage on having the dBs and MHz's presented.? (Okay he is welcome to further solve the v3 and v4 remaining spurs that his nice circuit board design partly cures).?

Yes the kind of stuff Raj shows is very familiar and quite useful.? I suggest if one does not plan to do lots of work up at UHF, one can scrounge useful-enough hardware at hamfests/surplus that works at HF or low VHF.?

Iz - I recall (but never used myself) some HP portable spectrum analyzers that indeed contained analog demodulators that allowed it to function as a receiver.? These items can easily be home assembled - see if this or another spectrum analyzer contains an IF output, then you have a path to making it a receiver - even an SDR or a multi-SDR/analog receiver.? As for low phase noise, look carefully to see if it has a lower phase noise than even a uBITX -- it might be similar or only slightly better.? The ubitx hears just as well as my K2 -- both have nice PLL's (I have not put the ubitx to test with large adjacent signals but I imagine the ubitx to be pretty good).? yes get and analyze some real numbers before assuming its an advance over what you already possess).?

Glad to see enthusiasm for the radio art - everywhere around the world.?

73 Curt

On Fri, Apr 12, 2019 at 05:22:41AM -0700, Curt via Groups.Io wrote:

We won't hold Gordon to making great advances with the acquisition of? this nice tool, but bonne voyage on having the dBs and MHz's presented.? (Okay he is welcome to further solve the v3 and v4 remaining spurs that his nice circuit board design partly cures).?

I have a Siglent that I have been wanting to find time to throw
the uBitx on. Time is something I have in short supply right now. ;)

I'll let the group know once I find some time.

Yes the kind of stuff Raj shows is very familiar and quite useful.? I suggest if one does not plan to do lots of work up at UHF, one can scrounge useful-enough hardware at hamfests/surplus that works at HF or low VHF.?

Iz - I recall (but never used myself) some HP portable spectrum analyzers that indeed contained analog demodulators that allowed it to function as a receiver.? These items can easily be home assembled - see if this or another spectrum analyzer contains an IF output, then you have a path to making it a receiver - even an SDR or a multi-SDR/analog receiver.? As for low phase noise, look carefully to see if it has a lower phase noise than even a uBITX -- it might be similar or only slightly better.? The ubitx hears just as well as my K2 -- both have nice PLL's (I have not put the ubitx to test with large adjacent signals but I imagine the ubitx to be pretty good).? yes get and analyze some real numbers before assuming its an advance over what you already possess).?

Yes there is a demodulator on the Siglent but I have not looked into it too
much yet. Time.

Glad to see enthusiasm for the radio art - everywhere around the world.?

73 Curt

--
- db@... db@...

I'm not so sure there is much point in buying a special high power 20dB attenuator.
Even at 10 Watts, a 20dB attenuator would be rather expensive.

You probably already have a 50 ohm dummy load suitable for use with your transmitter.
If you plan to work on your transmitter at all, you should have a dummy load.??
A 12 Watt 50 ohm dummy load could be built with four 3 Watt 200 ohm resistors in parallel.
You can get ten such resistors for one dollar from Mouser,? part number 283-200-RC
Forty 2000 ohm resistors in parallel can dissipate 120 Watts,? Mouser 283-20K-RC

To reduce transmitter power by a power ratio of 100), must reduce the voltage by a factor of? sqrt(100) = 10.
So add a 450 ohm resistor from the top of your 50 ohm dummy load into your 50 ohm step attenuator,?
The step attenuator must be capable of dissipating 100 milliwatts if the transmitter is giving 10 Watts.

The 50 ohm step attenuator sees a voltage that is reduced by a factor equal to its 50 ohms divided by
the total resistance of that leg, or 50/(450+50) = 0.10, which is a factor of 10 as computed above.

The transmitter will see 50 ohms in parallel with (450+50) ohms, or 50*500/(50+500) = 45.5 ohms,
close enough for government work.? Could correct this 10% error by making your dummy load
look like 55.55 ohms instead of 50 ohms by adding a 1/8 Watt 5.55 ohm resistor in series with it.?
(The 5.55 ohm resistor only sees 1/10'th of the transmitter's voltage, so only 1/100'th of the power.)

Kees has a kit available for a step attenuator at a good price, kit number 13 here:
? ??

Jerry, KE7ER

Correction:
The 2000 ohm 3 Watt resistor is Mouser 283-2.0K-RC

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Thank you guys, but I already had a series of adapters, series of of BNC attenuators, a 6 dB N rated at 2 watts and heathkit Cantenna ?with a homemade attenuator and now a commercial 50 W dummy load with a 30 DB tap