[Boatanchors] HP 606 vs. 608

[Carl]

The HP-8656 and 8656A have the 2nd worse phase noise in HP's history 
with the #1 position being the 8660/8660A. There is a good reason they 
are so cheap as no serious ham shop would have one. Many on Epay are on 
the 2nd or more rebound since they left commercial labs where the 
problems werent relevant to their use.

You probably wouldnt notice it since the IC-745 is in the same phase 
noise class. Its one of those radios that comes up "Phase Noise Limited" 
in IMD tests.

Before anyone makes a mistake in their choice I suggest joining the HP 
Yahoo forum, ask questions, and look in the files for several plots.

hp_agilent_equipment at yahoogroups.com

The non synthesized HP-8640B and its military HP-8640B Opt 323 aka 
AN/USM-323 variant are still the standard in the affordable category. 
The HP-8657A is acceptable for many uses but its price reflects its 
acceptability status.

Carl
KM1H





----- Original Message ----- 
From: "Don Buska" <dbuska at wi.rr.com>
To: <boatanchors at qth.net>
Sent: Wednesday, February 11, 2009 4:07 PM
Subject: Re: [Boatanchors] HP 606 vs. 608


>I understand our love for the BA's, but for me I want my test gear to 
>be
> the "standard" in my lab.  Since the early part of this decade (after
> the DOT COM bust) newer used test instruments have really taken a big
> price hit.  With our latest economic problems this has only added to 
> the
> amount of equipment out there at very reasonable prices.   It may be
> time to move out that 1950/60's test gears and buy some 1980's stuff.
>
> In my case I bought an HP 8656A Signal Generator off eBay a couple of
> years back for around $300.  What it gives me is a modern synthesized
> generator that does 100kHz (see below) to 990MHz with internal AM/FM
> modulation.  Using the internal frequency standard I only experienced
> about a 1kc error max across the whole frequency spectrum.  Also, even
> though it is rated to have a lower frequency limit of 100kc it will
> accept lower frequencies entry.  I just aligned my SX-115 50kc IF 
> using
> it and the frequency and output levels were spot on.  I used the HP
> 8656A and selected external AM modulation supplied by the output of my
> HP 3325A function generator sweeping from 10Hz to 10KHz,  and then
> monitoring the IF output on an Advantest TR4171 spectrum analyzer (the
> only SA I know of that also has a Hi-Z input channel).  Immediately 
> you
> can see what a difference it makes to fine tune IF alignments to get
> symmetrical sidebands on each side of the carrier.  I quickly found 
> out
> that peaking the IF's for the carrier frequency won't do that. 
> Actually
> I quickly discovered my cause of a noticeable difference between my
> signal levels under AM-USB and AM-LSB on my SX-115.  I would have been
> head-scratching for days if all I had was an old RF generator and 
> VTVM.
> This is a perfect setup for performing stager tuning of IF's if that 
> is
> necessary aka HQ-170-180's.
>
> Bottom line is many of us are willing to invest thousands in our
> stations, but then only a couple hundred, if that much, in test gear.
> Good modern RF generators can be had for well under $500 if you look 
> for
> them.  Sweeping audio generators for much less and good spectrum
> analyzers for a bit more.  Also, another excellent signal generator is 
> a
> transceiver.  My older Icom IC-745 has a transverter output which 
> simply
> operates the rig minus the final amplifier.  The RF output control 
> still
> works so I can generate an RF signal from 1.5MHz through 30MHz at a
> level up to 50mW.  I think IC-745's sell for around $300 these days. 
> A
> good signal generator that can also make QSO's, hi.  Plenty of the
> high-end solid-state function generators, with sweep, will go to 20MHz
> and are great for IF alignment too.  Don't go to the surplus equipment
> houses, keep your eyes open on eBay.
>
> BTW, I gave my two 608C's away a couple of years back.  I'm glad I 
> don't
> have to fool with those anymore.  I'm not getting any younger and if 
> I'm
> going to pull a muscle it will be on an BA transmitter and not my test 
> gear.
>
> 73 es take what you want and leave the rest.
>
> Don N9OO
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