Alignment Tools?

The extra load only dropped the levels, it didn't cause any distortion. Of course I wouldn't operate it like that knowingly any more!

I didn't hear any relays in there so I think it really does have the electronic attenuator as evidenced by the front panel sticker. There's an 8121 on eBay right now that is the same way and I also saw one without the sticker.
 
I doubt very much that there is not any relays in the attenuator, why!! well I do not know of a electonic method to attenuate a signal over such a large range. Usually they use "PIN" diodes for small range of control(0-5dB) and a relay for a larger range 5-100+ dB. It might be because the design of the RF relays are jsut quiet ones. I would not know 100% unless I look at the schematics, which I have not been able to retrieve thus far.
is this the one you are refering too?
http://www.ebay.com/itm/PANASONIC-V...166?pt=LH_DefaultDomain_0&hash=item2c836bf806

here is a Wavetek sweeper/marker SG that I think can be used as a IF sweeper
http://www.ebay.com/itm/Wavetek-Swe...454?pt=LH_DefaultDomain_0&hash=item1e944e2646
looks new or very clean!!
 
That's the 8121A I saw with the "electronic attenuator". I suppose you're right on the relays.

I do have the manual but registering a Google drive was more frustrating than I had patience for. The schematic spans 30-40 pages and I'll endeavor to take a look for the attenuator section tomorrow.

That sweep gen is an old boy but in good shape. Wavetek was in San Diego in the mid 1980's and the sticker says Indiana on it. I've already way overshot the budget lately though! :D
 
The attenuator is done with high frequency switching ICs. They are Macom SW-277's and are good up to 2.5Ghz. They are a "GaAs Absorptive Switch with ASIC Driver". Don't ask me to explain as I can't! They are 50 ohms in impedance and have an insertion loss of 0.75dB and isolation of 30dB. They are listed on Mouser but labelled obsolete. Here's a link:

http://www.mouser.com/ds/2/249/SW65-0313-356277.pdf
 
Good luck with that Leader LSW-333 marker/sweeper, hope it does the job for you.
BTW, I bought this diamond in the rough of late, been looking for one for a long while now and it was too good to turn up.
http://www.ebay.com/itm/301375703995?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Don't look like much but it has lots of potential.
I can use it for my HP 8901A modulation analyzer cal/check-out and as a very low noise/THD AM & FM source.
Will have to get a old HP instrument case and build a low noise power supply to power it. It will also need a low THD audio oscillator that can drive 50 ohm input Z, so I plan on using this or similar
http://www.ebay.com/itm/Ultra-low-d...rator-assembled-and-tested-PCB-/321567802656?
and a LME49600 or LME49610buffer.
 
Something to note is that the SG-165 generates a 10.7 MHz swept signal and has center and side markers. The Heathkit IG-37 and IG-5237 generate only their 100 MHz swept signal. You tune this through the front end and it gets mixed down to 10.7 by the tuner oscillator.

The result is pretty much the same, and has the advantage of not having to find a suitable injection point for the IF. The Heath does however only have a center marker, so you have to find some other way to tell how flat to make the IF response curve.

The Heath will get the job done and is way easier to work on, but given a choice I'd go with the solid state SG-165 over the tube based Heath. For modern low THD tuners/receivers, you really need an ST or other higher performance unit.
 
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