[Amps] Tiny SA

[John Lyles]

I use a R&S FSVR7 and Hp 8560E at work with big RF amplifiers, and have 
had a Tek 7L13, 7L14, Hp 8591E in my home lab over the decades. All of 
those boat anchors are gone now. My current favorite SA for home is a 
Rigol RSA3030 with TG. I am spoiled having the real time mode (both the 
FSVR and the Rigol have 40 MHz real time FFT bandwidth). On those I can 
spot a parasitic, high order microwave mode, or observe frequency 
hopping for some 915 MHz Digi SX wireless links that I have been 
implementing in a system. They will get a 40 MHz wide swath of spectrum 
in a few microseconds, something that a sweeping SA can't do. Looking at 
normal harmonics is fine with a sweeping SA, as long as you notch or 
attenuate the fundamental to prevent it from overloading the front end 
and generating harmonics internally. And of course you must know when to 
set the RBW to 1 MHz, 300 KHz, 10 KHz etc. Since I deal with pulses at 
work a lot of the time, this is very important to know. The trade off of 
RBW vs sweep time is a big one.

I also use a R&S FSH4 at home that I got for a steal on Ebay from Korea, 
and it just needed a new Lithium battery pack. This is used very often 
for antenna work, setting up cellphone boosters, television antenna 
(Free OTA of course), WIFI links, and super portable. Its color LCD and 
has great ability to save and print spectra. Something like this or a 
used Field Fox (from Agilent) is very useful in the ham shack if you can 
find it for a good price and condition used.  Their are plenty on Ebay 
and other places as ignorant companies replace them when the battery 
gets weak. They have real calibration signals at 50 MHz and calibrated 
attenuators.

I got a Tiny SA as a door prize at a ham function last year. In my 
opinion, it is a novelty, but it can serve a purpose, like is my signal 
where i think it is? Is it modulated? But for precise measurements of 
overtones (harmonics) in -dBc, I would say not good enough for 
repeatable measurements. Don't even try to use it to observe any close 
in noise, sidebands due to power supply ripple, or phase noise of a 
carrier. All of these are things I do with SA.

I took it on a field trip last fall, and also brought the TIny SA as 
well as the Rigol RSA. I was very frustrated as I tried to observe a 0.5 
watt signal off a homemade loop on 30 meters, modulated with PSK31. I 
was using the little telescoping monopole that comes with it. I could 
not even see the difference in end fire and broad side signal and I was 
not overloading it. The carrier (resting idle tone) was all over the 
place, would not come to the same peak level even if I didn't hold it in 
my hand. Frustrating.

73

John

K5PRO


> Date: Wed, 26 Apr 2023 09:26:16 -0700
> From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> To: amps at contesting.com
> Subject: [Amps] Tiny SA
>
> Have any of you folks used the tiny SA  (spectrum analyzer) or any other
> version of it ?   It goes down to -100db.  Used with a suitable attenuator,
> it would be a good tool to look at the harmonic content of an amp.  And
> also IMD on a SSB signal, 2 x tone tests etc.   Reasonably priced vs a
> megabuck ....'real one'.
>
> Tnx..... Jim   VE7RF
>
>