[Boatanchors] how to read microvolts

[Gary Schafer]

The 1400 / 800 series measurements units were pretty good generators but
only went down to 25 MHz on the low end.
But the old model 80 and ts-497 were very leaky. The HP 608 is not bad but
still leaks at low signal levels a little. The URM-25 and 26 are terrible
leakers. They are very nice and very useful generators but not for making
accurate low signal level measurements.
I have owned all of the above units over the years and have gotten rid of
all because I had use of much better stuff. I do now own a URM-25 that gets
used once in awhile when I need a low frequency signal source. But to make
an accurate low level measurement below 1 microvolt, it can't be done.
They are great for tuning up a radio and trouble shooting etc. 

73
Gary 

> -----Original Message-----
> From: Glen Zook [mailto:gzook at yahoo.com]
> Sent: Monday, April 02, 2007 4:28 PM
> To: garyschafer at comcast.net; boatanchors at mailman.qth.net
> Subject: RE: [Boatanchors] how to read microvolts
> 
> Those generators have been used in the commercial
> two-way field for decades as well in many laboratories
> during the period up to at least the 1980s.  All of
> them are at least double shielded with solid metal
> shields around the oscillator and double shielded
> coaxial cable to the attenuator.  You can definitely
> measure signal levels down to under 1 microvolt with
> any intact unit.
> 
> Now a 6 dB attenuator definitely needs to be attached
> directly to the output connector and these attenuators
> were "stock" when the generators were shipped new.
> This is necessary to match the output of the generator
> to 50 ohms and to provide additional shielding.
> 
> Now if modifications have been made, shields removed,
> and so forth, then all bets are off.  But, as
> originally designed those signal generators that I
> mentioned previously are definitely capable of low
> level measurements.
> 
> Glen, K9STH
> 
> 
> --- Gary Schafer <garyschafer at comcast.net> wrote:
> 
> While those generators mentioned are very handy and
> can be used for tuning things up and measuring levels
> above a few microvolts they are not good for making
> accurate low level signal measurements. They all have
> too much leakage and trying to measure below 1
> microvolt with them is impossible. The attenuator
> reading does go below 1 microvolt but the signal level
> doesn't follow because of leakage around the
> attenuator. Still much better than the heathkit type
> generators though. I have a URM-25 that I drag out
> once in awhile when I need a low frequency signal
> source.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Glen, K9STH
> 
> Website:  http://k9sth.com
> 
> 
> 
> __________________________________________________________________________
> __________
> Now that's room service!  Choose from over 150,000 hotels
> in 45,000 destinations on Yahoo! Travel to find your fit.
> http://farechase.yahoo.com/promo-generic-14795097