Having used a small gadget called a 'Watts-up' previously with my sons RC Electric flying (where we measured just a shade over 3kW out of 48V Lipo packs!) I had a quick look on eBay for something similar but with more info.
I found thishttps://www.ebay.co.uk/itm/223677371570 which is pretty much the same thing and will certainly cover any planned amplifiers! It duly arrived and was soldered to a m/F pair of XT90 connectors in the line from my battery to fused distribution block (another eBay find to which I added an eBay Voltmeter - useful to see). The XT's allow for a quick disconnect is things go wrong by virtue of yanking....
The unit was set in line and left running throughout the day. Base load was mainly my FT857 talk-back and a Portsdown 4/minitiouner/Lime/USB and preamps etc.
Small 12V PAs were used on 2,70,23 with a Purple Stealth on 13 (responsible for the peak draw of 364W) and then a 20W stealth on 9cm and a Ferranti amp for 6cm.
Pictures tell the story, just a shade under 30A/Hr used so easily capable of a longer harder day, unlike the operator!
The generator wasn't needed although it could have powered my 70cms & 13cms amp (Nokia Dolphin and my QO-100 Nokia pallet conversion which both use around 10-12 amps).
Signals did not necessitate their use and the battery is clearly in good shape. My main Portsdown 4 ran all day from a large Toshiba Laptop pack (with a little connector board I made that enables the contents) and on recharging that it took nearly 6A/Hr from the available of just over 7. (10.8V nominal).
Other successes were trying a cheap eBay preamp on 23cms after the interdigital filter - excellent improvement and using my small 70cms 'brick' amp as a receive preamp as it had filtering on the output. Unconventional but it worked.
Especially pleased with TX capability on 3.4, a Bi-quad feeding a old BSB minidish. I had to turn the power down a bit......and on receive, I used the same dish assembly to feed a probe in the 3.4GHz LNB waveguide tube. Solid copy resulted. Moving the 6cms, the tx worked as I hoped, Express DVBTransmitter on my laptop producing the RF from a Pluto and a Ferranti amp upping the watts to a 23.6dBi flat-plate. Copy was maintained down to about 1/4 Pluto power and it had a nice broad beam too. For RX it was over to my 'wing and a prayer' assembly of sundry parts. A DDS, eBay 6GHz preamps, sundry pipe cap filters, (one on the DDS, one into the LNB probe) and a loaned microwave mixer.
RX in via band filter, into a preamp (eBay 6GHz), into the mixer. IF port, DDS set to 2360MHz, pipe cap tuned to 2360, attenuator, eBay preamp into Mixer IF port. Output into a 3.4 GHz pipecap feeding the 1/4 wave probe in the 3.4GHz LNB all running from a 5V phone boost pack. Longmynd set to receive 1749MHz. And it worked in the field 10GHz was a near mis, I used a Bullseye LNB mounted to another BSB minidish and was able to use the bandscope to see about +10dB of Noels signal. My TX was a bit lacking, and my waveguide feed at 90 degrees to where it should have been, so that aspect needs work. Parts acquired.....
Pictures tell the rest of the story....