wmartin@brl-vgr.ARPA (Will Martin ) (03/12/84)
Just in case there are people on the net who do electronic repairs, testing, or just fiddling around on something other than digital circuitry... I have been perusing the mail-order electronics equipment catalogs and have noticed a curious discrepancy. You can buy cheap audio signal generators, cheap frequency counters, cheap multimeters, and various other low-cost gear, but it seems there is difficulty in buying a reasonably-priced RF signal generator! Does anybody know why this is so? It seems to me that it should be little more difficult to build an RF signal generator than an AM radio; the circuits have much in common, as the oscillators in a superhet essentially do the same thing. Accurate dial calibration and linearity should be the main cost factors, but, with cheap counters being sold by every electronics outlet, who needs such accuracy in the generator dial any more? I have a decent counter, and I need an RF generator to do occasional alignments on shortwave and FM radios. Heath makes the only low-cost (kit) RF generator I have found; the IG-5280, at $47.95 less the ubiquitous 10%-off coupon. It runs on batteries, or requires a separate power supply (which powers a set of 5 different instruments in this series). Does anybody have any comments on this device? Are there any other low-cost, solid-state RF signal generators available out there, either kit or assembled? I know I really would do best to frequent hamfests and probably would find one there, but circumstances make that impracticable. I have tried to read the QST classifieds, but haven't seen anything like this advertised. Advice and comments solicited. Will Martin (...!brl-vgr!wmartin or WMartin@Office-3)
parnass@ihuxf.UUCP (Bob Parnass, AJ9S) (03/13/84)
I've had a few tube type Heath RF signal generators. They
drifted and tuned very coarsely. For fine tuning, I varied
the distance between the generator and my hand (ala "hand
capacitance").
I too am curious about the newer solid state Heath genera-
tor, although I am not curious enough to buy one.
The AN/URM25 and 26 series of military sig jennies are
decent. Although they have AM/CW/PULSE output only, the
output is much closer to sinusoidal. Cheapies have perver-
ted output waveforms so the harmonics can be used on the
higher frequencies. I have a 26 made by Boonton. It was a
hamfest special at $15. I rewound some coils and installed
a tube (the last owner didn't realize that the oscillator
tube was missing!). Unfortunately, the bolometer assembly
is defective, so the output calibration circuit is inopera-
tive.
The Precision Apparatus (forerunner of B&K Precision) E200-C
is often found at hamfests. It's an old model, with tubes.
My $15 was well invested. It's much better than its Heath
and Eico counterparts. It was made for real (?) techs, and
has a good amount of shielding in its inner construction.
The E-200D is B&K's solid state replacement. I've heard
second hand that this unit drifts a lot for a solid state
generator. It's always priced over $100 at the local
fests, usually much more.
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Bob Parnass, AT&T Bell Laboratories - ihnp4!ihuxf!parnass - (312)979-5760