Re: HP Power Sensor wanted

Neil Smith G4DBN

I have an HP33330B 18 GHz Low-Barrier Schottky detector that I use with a set of Radiall attenuators.  I calibrate it now and then against my 8481A and 8481D heads on an HP436A. I'm thinking of building an interface to it with an A/D converter and PIC and building that into a 435 case with a rechargeable battery and a USB interface for charging, updating the calibration curves and reading the output using a 436A or ACPI emulation.

OK, I could build it into a small case with an e-ink display, but I like the big analogue meter when tweaking things.  I have a 435B that is very clean and works well, so I'd have to find an unloved one to gut and re-purpose.  Having it run on batteries would make it a lot more useful.

Neil G4DBN

On 25/09/2020 11:05, Mike Willis wrote:
On Thu, Sep 24, 2020 at 09:25 PM, Paul Randall G3NJV wrote:
There are plenty of HP8484 heads on Ebay for not unreasonable prices between £100 and £200. If you want professional test gear I am afraid you have to pay a little bit of money to get it. Not a lot compared to the new price. My advice is not to but the thermal heads you will blow them up, eventually. The over power capability of the 8484 diode head is much greater relative to it's upper power limit than the 8481.

You can always go for the cheaper solutions, not as accurate, but maybe accurate enough. Usually you don't really need to know the amplifier output exactly. After all you usually then connecting it via coax where the loss is not exactly known, through several connectors and relays to an antenna so you have really no idea what the actual EIRP is to within a dB or so. Knowing the PA power output to better than 2% doesn't really figure against the other errors.

Mike G0MJW

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