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Re: [Amps] How to read the 3-500Z spec sheet?

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Subject: Re: [Amps] How to read the 3-500Z spec sheet?
From: Patrick Barthelow <>
Date: Mon, 24 May 2010 08:15:23 -0700
List-post: <">>
For some years now, after acquiring some things from the Bill Orr (W6SAI)  
Estate, I have stored a Specialized spectrum Analyzer  (TS-1379A/U) and a 
precision mil spec two tone generator, that Bill used for Intermod Studies of 
High power amplifiers.


Maybe I need to find a ham garage/lab to set this up to verify some of the 
theories of intermod in amps.   It is a big box, mid sixties, but perfect for 
the job.  

There is a ham near me (Mike, N6IGA) who builds a lot of amps, that might be 
the right place to set this up.

I will post some other PDF images of the instrument on the web.


Here is a page from the front of the manual, that sort of summarizes what it 
can do.


NAVSHIPS 0969-094-3010

The Spectrum Analyzer TS-1379A/U is a sensitive, high resolution test instru-
ment of the automatic scanning, superheterodyne receiver type.

The primary application is in testing Single Side Band (SSB) transmitters and
receivers for measurement of third order distortion of the transmitted or 
s ignal.

The Spectrum Analyzer permits analysis of one or many signals simultaneously,
Each signal within the band scanned (sweep width) is displayed on the CRT 
as one of a series of "pips". The pip amplitude indicates the signal level. The
pip position along the horizontal axis indicates the signal frequency.

Any one of six parts of the rf band - the "Band Scanned" - within the 2mc -
30mc range of the Analyzer may be selected by means of the Band Selector tunable
oscillator, and the "Scanning Width" may be selected by the Sweep Width 
The Sweep Width Selector positions provide eight different degrees of frequency
separation of the signal display. A preset operating mode automatically adjusts
Sweep Width, Gain, Resolution, and Scanning Rate at each one of the Sweep Width

The Band Selector tunable oscillator is a high stability continuous tuning 
generator designed to provide local injection signals over the frequency range 
2. 5mc to 30mc. It is a fully transistorized, precision, variable capacitor 
oscillator. The 0. 3 volts rms output signal is the first local oscillator in 
hetrodyne system. The tunable oscillator is free from spurious signals, hum and
noise are suppressed at least 60db below signal level. The unit is particularly
suitable for use in intermodulation testing.

The Spectrum Analyzer is also valuable for monitoring a frequency band for
the appearance of or disappearance of and shift of signals. A display of 
distribution can be obtained by selecting the Sweep Width, bringing the "Scanned
Band" into the narrowest position (150cps) to enable examination of signals so
closely adjacent in frequency that their corresponding "pips" normally are 
together. At this reduced Sweep Width (150cps) signals with an amplitude ratio
of 60db separated by 50cps are clearly indicated. One of the internal 
features, the Internal Dual Frequency RF Test, simulates such a test.
Best Regards,   
73, de Pat Barthelow AA6EG
> Date: Sun, 23 May 2010 16:55:46 -0700
> From:
> To:
> CC:
> Subject: Re: [Amps] How to read the 3-500Z spec sheet?
> On 23-May-10 3:49 PM, Joe Subich, W4TV wrote:
> >
> > I don't care what kind of transition Joe has programmed into the
> > DSP. The rise time/wave shaping makes little difference with a
> > class C amplifier because the sharp turn on/turn off characteristic
> > and saturated operation will always square up the pulses.
> There is no turn on/turn off. That's what I'm trying to tell you. The 
> smooth phase transition that occurs as the tones change from one to the 
> other is exactly the same as slowly turning the knob on a linear (as 
> opposed to a PLL digital) VFO. NO CLIX!!!
> >
> > A Class C amplifier requires a certain level of drive to "turn on"
> > and operates in saturation ... the turn on threshold will remove
> > much of the low level ramp up and the saturation will create sharp
> > "corners" at the top of each pulse. Even the most basic measurement
> > with a dual trace oscilloscope will show the difference between a
> > linear amplifier and one run in class C. Run a string of dits
> > through a class C amplifier and compare the difference between
> > the drive signal and the output.
> Any time you turn on and off a "signal" you generate sidbands (sinX/X). 
> You can modify the wave shape and reduce the sidebands (also known as 
> clix) but you cannot eliminate them entirely. At least not until the 
> signal is either on all the time or off all the time or looks like a 
> sine wave. If the keyed wave form looks like a sine wave there will be 
> no sidebands generated.
> >
> > The clicks are not receiver generated ... they are generated in
> > the transmitter/amplifier by pulse squaring and eliminating the
> > wave shaping created in the exciter. W7AY has done extensive
> > work with wave shaping and can show the "damage" caused by non-
> > linear amplifiers in FSK and AFSK systems.
> Strong RTTY does indeed generate clix in some receivers, at least they 
> do in my "economy" DSP if filterd radios. NB makes it worse in those 
> radios.
> If the RTTY tones are "keyed" as you imply above, then yes I agree they 
> can and will make clix. However if the tones phase is seamlessly 
> transitioned at the zero crossing, there will be no clix. It all 
> depends on who did the DSP programming on a SSB type setup or who 
> designed the radio internals on a direct keyed setup.
> An amplifier that is only conditionally stable "in band" will also 
> generate clix as it tries to self oscillate over a small portion of the 
> RF cycle during phase transitions. Not common, but I've seen it happen.
> >
> > > Last I looked Duty Cycle was defined by the ratio between ON time and
> > > OFF time. No time limit specified.
> >
> > Any calculation of "duty cycle" must include a time limit ...
> Why "must" it? Duty cycle specified on transformers, motors, is not time 
> limited. Duty Cycle implies unlimited time operating normally. Normal 
> operation of a ham amplifier includes RX periods as well as TX periods. 
> By your definition, CW has a 100% duty cycle since you only want to 
> count the time when it's actually transmitting. I think we are confusing 
> duty cycle of the modulation envelope verses duty cycle of the SYSTEM.
> >
> > Simply put, when one limits the calculation to transmission
> > periods, AM, FSK/AFSK, WSJT, etc. are 100% duty cycle modes.
> > CW is a 50% - 60% duty cycle mode (depending on message
> > content) and SSB is up to 60% (depending on compression or
> > clipping levels). If you start adding "receive time" all
> > of those numbers will decrease but it still does not eliminate
> > the fact that AM/RTTY/WSJT/etc. are as much as four times as
> > taxing on an amplifier than CW at a similar peak power level.
> By the above numbers, FM/RTTY/WSJT is still only 2x taxing. 50% CW vs.x 
> 100% WSJT/FM/RTTY. AM is not even close. 100 watt carrier is 25% of the 
> 400 watt PEP of an AM signal. With modulation at full PEP assuming tones 
> not voice the average is still only about 50%, so same same as CW.
> >
> > Good for you ... however, the Eimac data sheets clearly show 400 mA
> > single tone (CW) plate current in AB2 service at all plate voltages
> > from 1500 - 3500 (
> I stand corrected, that spec sheet does indeed show 400 ma. As much as 
> those things cost these days even 350 makes me nervous!
> 73, Larry
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