[HBR] Initial test of 1st and 2nd IF coils

[Peter Bertini]

Hi Cal

How are you coupling the scope and the low impedance output from the signal
generator to the IF transformers?  You need to use a very small (a few pF at
most) coupling cap in series with the sig gen output.  The scope will add a
few pF capacitive loading that will affect the tuning slightly as well.

Pete K1ZJH

On Sat, Jul 10, 2010 at 2:54 PM, C Eus <catman351 at gmail.com> wrote:

> All:
> My Hitachi V-355 scope just came in and after fiddling with  it and my
> Elenco SG-9500 signal generator, I was able to obtain some interesting
> results with the initial testing.  I only tested one coil per IF circuit
> and
> a Miller 262 kcs IF coil was actually resonating at 187 kcs while a British
> 1600 kcs IF coil resonated near 1080 kcs.  Definitely off frequency but I
> suspect after tweaking, I can get them at the correct op. freq.
>
> BTW, when measuring bandwidth on these coils, are they measured at the -6dB
> points? I take it that -6dB down would be at the half power/voltage value
> of
> the peak resonant frequency. Is that right?  If so, I put in about 3v p-p
> on
> the Miller 262 kcs IF coil and it looks like it goes down to 1.5 v p-p at
> 184 kcs and 191 kcs respectively, or about a 7 kcs bandwidth (which seems a
> little wierd since I was expecting a symmetrical bandpass but it turns out
> to be slightly assymmetrical instead). Looking for comments on these
> findings and thanks. Cal, N6KYR/4.
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