Handheld Spectrum Analyzers vs Benchtop Spectrum Analyzers

OPERATIONAL RANGE

Desktop SA test units have narrower temperature and humidity operational ranges as well as lower IP levels compared to hand held rugged SA like FPH from Rohde & Schwarz and Fieldfox from Keysight, former Agilent, ignore some Nintendo-like gadgets that are sold with a sticky on it reading 'spectrum analyzer'. 

By IP meaning Ingress Protection (British BS EN 60529:1992, European IEC 60509:1989), the scale that rates any envelope capacity to stand ingress, from 'can't look at it' to bullet proof, long term immersion in water or buried in dust, so on so forth.

WHAT CAN YOU MEASURE

Broadly speaking, hand held SA have higher internal noise than desktop counterparts. 

This implies that certain phase noise dBc/Hz measurements, better test with, or can only test with desktop units.

In general terms, hand held spectrum analysers have lower frequency accuracy than desktop analysers because the box allows for temperature control circuits, and I mean sort of 'internal air conditioning' that allows measurement corrections that hand held devices can only approximate.

FPH and the Fieldfox, Anritsu's Site Master is also a very reliable hand held SA, among others, are ideal to climb masts and check right on the antenna connector that everything is ok 'up there' and then go backwards down to the indoor unit.

Desktop spectrum analysers allow for more processing power, that in turn allows for complete standard test capabilities like multiple mobile comms standards in one box.

It may be possible to measure BER with a hand held SA, but hand held devices have a limited range of standard specific built-in measurements, while desktop units are best option when designing products because the whole standard to comply with may be available without additional hardware.

For instance, I don't know if Keysight hand held units have such option but some Keysight test units have the option for a MATLAB licence along with the unit.

Hand held spectrum analysers, at least without additional personalities, have lower frequency ranges than desktop unit.

With hand held SA units, you may have to carry a good laptop around, while with a desktop SA unit, some after-measurement processing can be done with the same box. 

POWER SUPPLY

The FPH and the Fieldfox have battery power. Desktop units may have battery packs, some models, but they need AC supply. 

One can even build a custom battery pack for small desktop SA but again not all operators have the back and muscle to carry around up and down a bulky heavy box, day in day out, compared to the tablet-like design of FPH and Fieldfox.

Desktop SA units may have more ports, more set-ups are possible, larger displays, and consume more. 

VIBRATION AND DROPS

Hand held SA units, again ignore the ones that look like Nintendo consoles, may stand certain drops.

Do not, never, ever, drop, or let drop, a desktop SA unit without compromising measurement capacity, the whole of it. The desktop unit may not stand a 1.5m fall from a lab bench, while a Fieldfox, may, cross fingers, stand a fall from a 20m cell mast.

 OTHER APPLICATIONS

You can use desktop units to tell whether a new recruit is lazy or not, by bringing them to the lab, and tell them to move a particularly heavy SA desktop unit from one bench to another: in some cases you will be surprised how uncorrelated are top academic marks and hard work pro attitude. There's a reason why some desktop units come with handles.