tchrme wrote:
A question for those with Hammarlund experience,
I have just restored my first HQ rcvr and the manual says I need a
sweep generator and a scope to align the IF. On most of my other rcvrs
(Hallicrafters), I just use a signal gen and a VTVM. Is this really
necessary or can I just peak the IF's? Mike KF6KXG

I have one of those, exactly, and I just peaked the IF stages. What was
interesting was getting the frequencies on the dial to be exact. I used
WWV as much as possible and A.M. radio stations that I knew the
frequency of. If you want it to be absolutely right on you will need a
signal generator (digital preferred) and a counter if you don't have a
digital generator. A sweep generator is nice to have but not that many
people have them laying around the bench.

Good luck with that, my 129X picks up the whole world quite nicely and I
think you will be very happy with it.

Bill Baka

Bill wrote in :
tchrme wrote:
A question for those with Hammarlund experience,
I have just restored my first HQ rcvr and the manual says I need a
sweep generator and a scope to align the IF. On most of my other rcvrs
(Hallicrafters), I just use a signal gen and a VTVM. Is this really
necessary or can I just peak the IF's? Mike KF6KXG

I have one of those, exactly, and I just peaked the IF stages. What was
interesting was getting the frequencies on the dial to be exact. I used
WWV as much as possible and A.M. radio stations that I knew the
frequency of. If you want it to be absolutely right on you will need a
signal generator (digital preferred) and a counter if you don't have a
digital generator. A sweep generator is nice to have but not that many
people have them laying around the bench.

Good luck with that, my 129X picks up the whole world quite nicely and I
think you will be very happy with it.

If you're lucky enough to have a ramp or triangle generator and an RF
signal generator that will do DC-level FM, you can feed the ramp or
triangle output into the siggen's FM modulation input and get a very
good approximation to a sweep generator. I do it with a ramp fed into my
HP 8640B's FM modulation in. Feed the stage output into the Y on your
scope and the ramp input into your scope's X, and you get to see (modulo
tweaking things so that the scope display, sweep rate, start and stop
freqs all are what you want) a really good idea of what the response
curves look like.

A dead-simple ramp generator is a constant-current generator (read LM117
or LM317 or LM318 with one resistor, if I recall correctly) feeding a
cap of the right value, a 555 to reset things periodically, and maybe a
few other components. The LM117/317/318 datasheet at national.com has
schematics for constant-current regs; I think I'll play this weekend.

--
Mike Andrews, W5EGO

Tired old sysadmin