FW: HW-101 step 4

[Jordan Arndt]

Clark, John wrote:
>
> Doug, I'm looking at your suggestions.
>
> This oscillator has two stages, the A & B side of a 12AT7.
>
> The crystals and DC test point are on grid of the first stage.
> The plate of this first side is tuned by the second wafer of the
> select switch.  The first 3 with L&C, and next 5 with only L.
>
> The plate output is then Cap coupled to the B side grid. I think this B
> side is called a "Cathode Follower"
>
> The output is taken from the Cathode of the B side via a 100 uuf cap.
>
> I took my frequency readings from the far side of this Cap, heading to
> the
> "Second transmitter mixer and to the first receiver mixer"
>
> To follow your suggestion I lifted the DVM from the test point while
> watching the frequency,
> no change.
>
> Unfortunately the KB9JJA web page does not have the schematic for this
> radio listed.
>
> Your comments have been so helpful, I would like to send you a copy to
> help me along.
>
> Got a FAX?
>
>     ---------------------------------------------------------------
>
> Subject: Re: FW: HW-101 step 4
> Date: Thu, 13 May 1999 07:21:00 -0600
> From: "k5cr at juno.com" <k5cr at juno.com>
> To: "john.clark at STATE.CO.US" <john.clark at STATE.CO.US>
>
> John:
>
> The freq of the crystals is changing due to the plate load impedance
> changing as you tune the oscillator coils.   I see that they all look to
> be on the low freq. side of the stated crystal freq.   Is there a chance
> the freq counter is loading the oscillator and shifting the freq down??
> It is possible that when you disconnect the freq counter the osc. freq
> is
> going up.
>
> I would set the tuning to 80 to 90 percent of the peak grid voltage and
> let it go.   The way to tune the crystals on freq would be by changing
> the oscillator load cap. (reducing the capacitance that the crystal).
> Usually as the crystal ages the freq goes up but I see that your list
> showes they are lower than the marked freq.  This makes me think the
> freq
> counter is loading the oscillator.
>
> Hope this helps.
>
> 73
>
> Doug/K5CR
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Hi... for all the Heath SB/HW rigs I have ever worked on I have never
seen one where all frequencies are "Netted"... the -1.5 Vdc is a "Good"
starting point, and is the recommended setting for many Heath rigs...
given that the HW-101 has 5khz dial increments, and that even with
careful adjustment even the SB series with 1 Khz dial increments has a
+/- 7.5 khz adjustment range, and uses basically the same cktry, don't
expect the frequencies to be the same unless you are extremely lucky...

You are not trying to set the frequency with the adjustment made and
measured at the TP, you are simply trying to ensure proper crystal
action and start of oscillation when each crystal is selected... I have
seen SB series rigs with a 10-12 khz difference between zero spots on 80
and 20 meters... now if you use a 5Khz dial reading, it may seem like
they way off, but it would be worse , or at least more apparent with a 1
Khz indicator...How much are the crystals off from nominal??? I do have
the HW-101 manual also... also , have you tried to see if the offset is
uniform accross the band??? ie if it is 5khz at 0 is it still close to
that at 500??? If not does it change uniformly across the band? If not ,
then I suspect that your VFO is not properly aligned... Hope some of
this is useful... 73 de Jordan...

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