[NLRS] power measurement

[John P. Toscano]

Ken Boston wrote:

> Bottom line, an all-in-one power meter for 1-24 gig, power rating 10
> milliwatts to a KW probably does not exist. (unless there is some super
> expensive top of the line meter out there that does this)  You will end
> up with a collection of a decent , older power meter with some sensor
> heads, power attenuators, and directional couplers that cover the bands
> that you need them for.  Cruise the swapmeets, conferences and E-Bay,
> and expect to spend some money.

Hi, Ken, and everyone else contributing to the thread.

I didn't really expect a single unit to do it all, from milliwatts to 
kilowatts, but was hoping for one meter, a manageable number of slugs or 
plug-in sensors, and if necessary, a small number of attenuators or 
directional couplers.  My thought was that the meter would be the most 
expensive part, but looking at the price of sensors, that doesn't 
necessarily seem to be the case, especially if it will take more than 
one or two to do the job.  The Marconi/Aeroflex 6960B that I originally 
asked about covers 30 KHz to 4.2 GHz and measures -30 dBm (1 microwatt) 
to +20 dBm (100 mW), but they make other sensors for the 10 MHz to 
either 20 GHz or 46 GHz range, and with just two of the right ones, you 
could measure between -70 dBm and +35 dBm.  But the chances of finding 
just those two sensors in working condition for less than the price of a 
new mortgage on my house? slim and none.  Likewise, an HP/Agilent 432 
with a type 8481B sensor spans 0 to +44 dBm at 10 MHz to 18 GHz, so that 
would come awfully close to being a perfect combination for my needs. 
(Not quite up to 24 GHz, but who knows when or if I'll get there, and 
not quite up to the full power I will have on 2304 and 3456, but one 
good high-power -10 dB attenuator or -10 to -20 dB directional coupler 
would fix that.)

So, I've been scanning eBay for attenuators and directional couplers. 
It is easy to find -10dB attenuators but most of them seem to be rated 
only to 1 or 2 watts at 0 to 2200 MHz, but the problem is that an 
attenuator is needed the most when there's more power than only 1 or 2 
watts which needs to be sampled.  I've not yet had success finding an 
attenuator that has a high enough power rating and a wide enough 
frequency rating, but I will keep on looking.  I suppose in the worst 
case, if I found a 100 watt -10dB attenuator that was, for example, only 
rated to 2200 MHz, I could have someone sweep it to the higher 
frequencies and develop a "calibration curve" for the actual attenuation 
at the higher (out-of-rating) frequencies.

Most eBay listings I've seen so far for directional couplers don't seem 
to mention anything about power ratings.  I guess from the theory of how 
it is supposed to work, you put RF in one end, and 1% (-20dB) comes out 
the sampling port and the other 99% comes out the output end, and there 
is minimal power to actually dissipate within the device itself.  So am 
I correct in assuming that I could probably put 100 watts into it, have 
a dummy load or antenna on the ouput end, sample my 1 watt from the 
sampling port (which now is within the power range of one or more 
inexpensive -10dB attenuators as needed), and not worry about blowing up 
the directional coupler itself?

Thanks for all the input, and the kind offers of help with setting up my 
systems.  I will definitely be looking forward to the day (hopefully 
soon) when I get things assembled to the point where I'll be ready for 
using some of that help.

73 de W0JT