[NLRS] RF power meters

[Gerald]

On Wed, 2006-02-08 at 21:55 -0600, John P. Toscano wrote:
> 
> Hello, all.
> 
> I've been thinking about obtaining a reasonably accurate RF power meter 
> that covers the higher frequencies.  I have relatively inexpensive 
> SWR/power meters that cover 50-450 MHz, and one slightly more expensive 
> model that has switch-selectable coverage of the 902 and 1296 MHz bands. 
>   I don't know how accurate it is, but at least it is actually designed 
> for those bands, and probably good enough for what I need on those bands.
> 
> I would like something that will work on the 2304, 3456, and 10368 MHz 
> bands, and if economically feasible, my ideal meter would be one that 
> would work properly from 900 MHz to 24+ GHz (in case I ever get that 
> high in the bands) and measure power levels from 1mW (0 dBm) to 100 W 
> (50 dBm).
> 
> My first thought was a Bird model 43 with appropriate slugs, but there 
> don't seem to be any slugs that cover 3456 MHz or higher, and a few 
> dealers I checked made no mention of having a slug for 2304.
> 
> I have found a used Aeroflex 6960B meter with the 6912 power sensor, all 
> supposedly in excellent working condition, on eBay.  This sensor covers 
> 30 KHz to 4.2 GHz at -30 to +20 dBm.  Although it misses 10 & 24 GHz, it 
> otherwise covers any frequency I'd expect to need for the near future, 
> but the 100 mW maximum is of concern, since I'd like to be able to 
> measure higher power than that.  There exists a type 6930 power sensor 
> that covers 10 MHz - 18 GHz at -5 to +44 dBm (0.3mW to 25 W), which 
> seems like excellent coverage to me other than not going up to 24 GHz 
> and not quite reaching my target of 100 W.  But I have no idea what such 
> a sensor would cost.  Googling around the internet yielded some places 
> claiming that a good used one would be 595 British pounds (around 
> $900?), and others claiming to have this sensor available for a mere 
> $2500, and lots of places that refuse to quote a price!  Yikes!
> 
> Anyway, I'm looking for opinions on this.  The Aeroflex 6960B + 6912 is 
> being auctioned with a starting bid of $499.99, but the listing does not 
> mention whether or not there is a "reserve" price, so I assume that 
> there is.  So I don't know what the item would actually sell for on eBay.
> 
> If there are better choices out there, perhaps an HP model that is 
> abundant in supply and therefore low in price, with decent prices on 
> power sensors, I'd love to hear those opinions also.
> 
> Thanks in advance.
> 
> P.S., even if I don't actually buy any such thing soon, I will probably 
> want to get someone's help in setting up the drive levels on my 2304 and 
> 3456 transverters so the PyroJoseph PA's (60W and 50W out, respectively) 
> don't go up in smoke when I get them on the air.  But I'm not ready for 
> that just yet...
> 
> W0JT

Generally the HP 430 to 436 family of RF milliwatt meters are universal.
They can be had with coaxial heads good from HF to beyond 10 GHz and
with  waveguide heads. They typically are only good for 10 milliwatts so
they need to be protected in higher power situations with attenuators or
directional couplers. The earliest do drift a lot and for the later ones
often heads cost more than the meter as many times the he heads seem to
have been damaged or tossed separately from the meters.

I don't know of any meters that will work from a MW to 100 watts without
external attenuation.

It would seem like that the new generations of logarithmic RF power ICs
that work to 6 or 8 GHz would do the fundamental work and with some
mixers do the higher microwave bands quite well, though they probably
don't have the predictability of the HP 43x family that are often
supplied with mirrored scale meters for better readability.

Because of the delicacy and the drift of the 432 on my bench, for
frequencies under 1 KHz, I more often use a RF millivoltmeter, mine is
from HP, Boonton made good ones too. Their limits are about 3 volts RMS,
but attenuators give higher ranges.


-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson