Mike,
Lord, I don't know. I just got it and am investigating. Do you have test cases to propose? With the chipping markings sanded off it's a puzzle what chip it's using. I'm guessing an HMC602 from the specs given.
At the $32.32 price with free shipping I think it's an excellent start to a budget power meter. Add 60 dB of JFW rotary attenuation and use the tinySA as your power reference at -10 dBm.
Peregrine makes 0.5 and 0.25 dB step 31 dB attenuators. Add a couple of those and a 10 W 30 dB power attenuator, frequency counter and UI and you should be all set. Caveat emptor, programming required. Would make a cool group project.
Bottom line. It's quite usable with appropriate technique as is. However, it's got much more potential than that.
As this list is about T&M design and construction, I thought I should call it out as having significant benefit to a budget RF lab with some development work.
Have Fun!
Reg
On Friday, December 15, 2023 at 09:42:26 AM CST, N2MS <mstangelo@...> wrote:
Reg,
Thanks for the feedback. Does this power meter measure peak power or does it just measure average or RMS power? I'm looking for a portable instrument to measure the PEP power from my QRP SSB rigs.
73, Mike N2MS
> On 12/14/2023 11:49 PM EST Reginald Beardsley via groups.io <pulaskite@...> wrote:
>
>?
> Just using the 8648C and a pair of JFW attenuators as reference, it appears to have an acceptably accurate dynamic range of 0 to -56 dBm? The FW is terrible and doesn't even? debounce the keys!? But it does work decently.? I suspect that with good FW it would be an excellent piece of lab kit. Annoyingly, all the chips have been sanded.
>
> Response is highly variable with frequency.? But I consistently found 56 dB of dynamic range within the limits of the 8648C after adjusting the offset and trying the step attenuators.
>
> The big question is how to calibrate it on a hobby budget.? With the addition of a couple of Peregrine attenuators? and a frequency counter it could look up a correction factor and be a very useful lab instrument.
>
> However, I've never checked the power output accuracy of the 8648C so the attached photos might be more accurate. Or not.? However, a 2nd tinySA gave the same result.? For $33 I'm impressed.
>
> Have Fun!
> Reg
