Just acquired a "Precision" E410C sweep gen with marker gen

[wa2ise]

Picked this up yeaterday at the BARA ham club auction, and trying to figure out how to use it. Yes, I have the instruction manual, but some things are not clear, or I didn't see them .

First, the frequencies as marked on the dial are way off (so much for "precision" ), and took the covers off the generator, but found nothing I could adjust. So I just remarked the dial as to what frequencies it does generate (using my Icom HF ham transciever to find the frequencies it does generate. I set the Icom to say 20MHz, and see where to position the dial to have it produce 20MHz, and mark it accordingly. Okay..) And the marker generator crystal oscillator works. But what I'm having trouble using is the section where I inject the "receiver response" (you tap some point of the IF you're aligning to feed back into this machine) and mix it with the marker. And there's a "scope vertical" that you use to feed to the vertical input of your scope (I have a modern reall scope, a Tektronix 400MHz job, with 50 ohm input impedance, which may be an issue.)

Thing is, I don't see anything on this "scope vertical" output. Looking at the machine's schematic in the manual, I can see that the scope's 50 ohm impedance would not play nice with the megohm range mixing circuits in the machine. So that's one issue to resolve. Maybe build a cathode follower stage to convert the high impedance to an output that won't mind the 50 ohm load.

Question: Should the connection cable that I use to feed the "receiver response" have a detection circuit, like an AM detector in an radio? This would be for use in a circuit that hasn't been detected in the radio yet.

One thing I want to do is look at the response of say a ceramic IF filter. Maybe I need the diode detection in my "receive response" cable?

[wa2ise]

Originally Posted by wa2ise

Thing is, I don't see anything on this "scope vertical" output. Looking at the machine's schematic in the manual, I can see that the scope's 50 ohm impedance would not play nice with the megohm range mixing circuits in the machine. So that's one issue to resolve.

Some progress: I found an old chip, an LH0032c high frequency op-amp driver chip. I found its data sheet, and wired it up as a unity gain circuit. High input impedance, and low output impedance, adding a 50 ohm resistor as source impedance to match the cable and scope load (and the resistor provides some short circuit protection). Seems to work for me. Some of the RF generator's RF leaks into it (but this thing is not a lab grade instrument). But I can use this leakage to my advantage, as this leakage will interact with the marker generator. I can see a dip when the generator and marker frequencies coincide. And as my scope has two vertical inputs, I can view the output of the device under test on one channel, and see the marker dip on the other channel.

Ideally I'd want a sweep generator/ spectrum analyzer, but that's not in my budget...

[miniman82]

Are you trying to perform alignments? If so, it's much easier to get a B&K 415. It makes alignment a breeze, but you can't do the early 20mhz IF's with it only later stuff.

[jr_tech]

Originally Posted by miniman82

Are you trying to perform alignments? If so, it's much easier to get a B&K 415. It makes alignment a breeze, but you can't do the early 20mhz IF's with it only later stuff.

These seem to be pretty cheap on the 'bay.... do they *usually* work ok, or require a lot of troubleshooting/or at least new ps caps to get going?
Are there 2 different versions? I think that I have seen at least one with all bnc connectors on the front panel... perhaps a user mod?

jr

yep, I would also love to have a spectrum analyzer/tracking generator

.

[wa2ise]

My main objective was to be able to see the passbands of various ceramic and other filters, and it turns out I have the equipment to make it happen. A frequency generator (VC2002 function generator), a sweep generator (Heath 1274 sweep function generator, and a scope (Tek TAS465). The setup:
The other two pix show the low end freq and the high end freq.
I can adjust the amplitudes on both generators. I can see the shape of the bandpass (linear, not dBs though) and I can also see the amplitude of the marker frequency outside the passband of the filter on the scope. The scope is triggered from the sweep gen. The marker is always on. But the marker has to go thru the filter to get on the scope, and changing the marker frequency I can see when it drops to half amplitude and thus the 3dB points, high freq and low. The marker also beats with the sweep generator (which doesn't really show in the pictures) when the frequencies of the two happen to coincide.

The Device Under Test (DUT) is a ceramic filter at 455KHz, and has a little more than 20KHz bandwidth at 3dB. Which would be good for 10KHz of AM radio station audio, the max the FCC allows. Hifi AM. Okay... Yes, channel spacing is 10KHz, but not in the same town.