[ARC5] Signal generator selection

[Kenneth G. Gordon]

On 5 May 2021 at 12:39, Craig via ARC5 wrote:

> Hey all: Looking for some guidance on buying a signal generator for the 
> bench. Scope and power supply are already in place, but too many options 
> on generators on what's out there and what is sufficient for working on 
> the SCR and AVT stuff.  New or used, but I'd like to keep it under $300 
> total. Audio thru ?... Definitely don't need anything with a bus, as I'm 
> manual only.

Well, Craig, it depends a lot on what you are going to use it for, and what "features" you will 
need.

I have several instruments here which I use for signal-generator duties, from the very 
"un-handy" to those which were designed as signal-generators.

The simplest and least-"handy" are two BC-221-AK units. To align receivers, I can set one at 
one end and the other at the other end of a band. The AK versions also include modulation, 
like most (all?) LMs, which makes aligning an AM receiver far easier. Despite being +70 
years old, they are very stable, and quite accurate. They are also fun to use.

I also have two very cheap Eico model 324s to which I have added a connection to drive a 
frequency counter since their "readout" is quite crude. However, despite their simplicity, they 
are quite stable. Those are "adquate" for many things. I use those to align receivers like the 
NC-57s which I give to "newbies".

Then I have an HP-8640B, which I use regularly and which has just about everything needed 
to accurately align our more modern rigs. However, the 8640B is noted for not being 
particularly reliable. I know mine isn't, but it isn't all that difficult to keep going either. One nice 
thing about the 8640B is that one can "FM" the output by feeding the saw-tooth output of a 
sweep-generator into it, and then you can use that same sweep-generator to synch a 
'scope's horizontal sweep to give you a visual indication of the shape of, say, a receiver IF 
stage. The amount of FM range is limited, though, to about 10% of the frequency output. For 
instance, at 85 kHz (the IF frequency of a BC-453 or R-23/ARC-5) the 8640B will only "FM" 
around 10 kHz, which isn't really wide enough to give you a complete picture of the IF 
"shape". But it suffices.

This method is also very useful to bandpass-align receivers which use staggered tuning to 
get a wide, flatter, bandpass

I was recently given an HP-606 signal generator by a very kind Skip Magnuson W7WGM. I 
have not yet been able to use that generator due to some health issues which are, for the 
moment, keeping me tied up, but I plan to make it a main part of my bench alignment setup 
as soon as I can.

Lastly, I have a URM-25D here which needs refurbishment, and like Hugh, I see it as a lot of 
work. However, because it will output a signal down to less than 50 kHz, it will help in the 
alignment of such receivers as the Hallicrafters SX-101, and Hammarlund HQ-180 with their 
50 kHz IFs.

Almost all of this equipment was given to me by various folks, so I have not had to buy any of 
it. I did buy one of the BC-221s for $5.00 from a local.

I make it a practice to get equipment, and not only test equipment, which "needs work", 
because my skills outweigh my income....by quite a bit.

The Rigol unit sounds absolutely delightful, and I am going to have one of those as soon as I 
can convince the Chancellorette of the Exchequer (my dear wife) that we can afford it. ;-)

I hope this helps.

vy 73 for now,

Ken W7EKB