[ARC5] Visual alignment of BC-454

[J. Forster]

Generally, fast sweep rates causes artifacts. You need tosweep slowly
enough that the circuit is in essentially sinusoidal steady state all the
time.

It is easy enough to build a solid state triangle or sawtooth generator,
using am opamp and comparator or a timer chip.

Best,

-John

================



> On 22 May 2013 at 19:31, Dennis Monticelli wrote:
>
>> Ken,
>>
>> I would be very interested to view those sweep photos.
>
> I have ONE photo up at the moment:
>
> Go here:
>
> http://www.w7ekb.com/Personal/BC454/BC454IF-1.jpg
>
> The receiver is that 10 meter BC-454 I struggled with a month or so ago.
>
> You will notice some "jitter" on the trace, which I am almost certain is
> coming
> from my B&K 3025 Sweep/Function generator. It is not a very good piece of
> gear, but it is all I have at the moment, and it does work OK.
>
> The IF bandwidth is quite broad, and the regenerative IF causes that peak
> that you see to the left of the main "hump". Also, the shape of that trace
> shows very obvious overcoupling.
>
> I have set the HP-8640B to sweep 10 KHz, and the limits (above and below)
> points are almost exactly 10 KHz: I am sweeping from a little more than
> 1408.5 to 1418.5 KHz. which appears to be centered. This shows that the
> IF's center-frequency is not 1415 KHz, but more like 1413.5 KHz or so.
>
> However, I don't see how that really matters much with this receiver.
>
> I am using the B&K's "Sweep Output" on the back panel to drive the HP and
> to sync the scope. The waveform of that Sweep Output is supposed to be a
> sawtooth, but it isn't a particulary GOOD sawtooth, and the slower I set
> the
> sweep, the more rounded the sawtooth gets.
>
> I have the sweep rate set at its highest setting, which isn't very high.
>
> I am going to try to feed another signal generator output to the receiver
> to try
> to get some sort of moveable cursor to see how wide the bandwidth at the 6
> db points actually is. I think that is going to be difficult to accomplish
> with this
> setup though.
>
> So, what do you all think of this so far?
>
> Ken W7EKB
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