[ARC5] The not-so humble BC-221/LM-xx frequency meters. - zero-beating with WWV

[Bill Cromwell]

Hi Howie,

I have a couple of radios here with the so-called 'logging' scales. I 
made some 'charts' for those using a spread sheet. During the process I 
noticed that the tuning isn't really in a straight line either. Close. 
But not quite. As we tune from one end of the dial toward the other end 
the amount of frequency change per turn of the knob (or degree of 
rotation) changes. I use the graphing function of the spread sheet to 
give me an X-Y tuning graph. The line from the lower left to the upper 
right has a clear, subtle curve. I made one for each band on the RAK and 
I have to make some new ones for the SW-3 as I am making new coils for 
it - one graph per coil.

The so-called 'direct reading' mechanical dials on our newer gear have 
those pretty linear scales. The tuning varies across the tuning range on 
those too - some better than others but all of them are bent. That's why 
the calibrators are there. One of mine has pips at 25 kc and 100 kc 
intervals and the fiducial should be set at those intervals if we expect 
to actually copy a scheduled net when it comes on - or more important - 
if we are operating near a band edge. Just because we hear other hams on 
a frequency doesn't mean they are actually inside the band edge! It's 
our own individual responsibility.

It's been an interesting thread. I'm in the seventh inning stretch of 
preparing a holiday meal for the XYL and me. Here's wishing all of you a 
merry Christmas and happy holidays. Hug the grandkids and great 
grandkids if you have 'em.

73,

Bill  KU8H

On 12/24/2016 02:08 PM, howard holden wrote:
> I'll concur with Ken's comments. The rise and fall of signal as they go
> in and out of phase is easy to hear. And you can do it either at near
> zero for a direct read, or, with a little patience, with the WWV carrier
> at an audible pitch. You just have to make sure you are coming at it
> from the correct frequency direction in this case, otherwise you'll be
> off something like a Kc or more.
>
> Using that method to make sure my crystal was "on frequency" about 10
> years ago, I came to 47 CPS off of a W1AW frequency measuring test,
> extrapolating off the LM-18 dial. Probably a fluke, but that was also
> with a calibration sheet that I made up for 3.5 to 3.6 Mc, as the one I
> have didn't come with a cal book. It pays to spend some time with your
> meter to see the change per dial setting with change in frequency, as
> the rate does change with frequency. in the 3.5 to 3.6 Mc range mine
> changes an average of 2.08 dial divisions per Kc.
>
> It's certainly good enough for my needs, and I'm using it as it was
> intended. Amazing that 70-plus year old stuff does so well, and with all
> original components.
>
> Howie WB2AWQ/7
>
>
> On 12/24/2016 10:42 AM, Kenneth G. Gordon wrote:
>> On 24 Dec 2016 at 12:37, Bill Cromwell wrote:
>>
>>> In recent years I have made my comparisons to WWV using sound card
>>> software. We can identify the WWV carrier on the spectrum display and we
>>> can watch the secondary standard as we tweak it creep up one side of the
>>> WWV pip, reaching the top at *zero beat*. We can't hear zero Hertz but
>>> we can see that display quite easily.
>>>
>>> I am not sure how the ancients did it but zero beating to references or
>>> standards is *NOT* new.
>> Well, some regard me as an ancient, and here is how I do it: I listen for the rise and fall in
>> the background noise when I check the crystals in my BC-221s against WWV. Using that
>> method it is easy to get within a fraction of a cycle/second (Sometimes it hurts to say Hertz).
>>
>>
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-- 
bark less - wag more