[ARC5] Question about charts

[Bill Cromwell]

Hi,

Some new, homebrew gear has logging scales and a "chart". Those can be 
more accurate and much easier to maintain the accuracy. When it was 
built, that equipment had some tables (not charts) and you found the 
nearest value in the tables and then interpolated or extrapolated to get 
the values in between the table values. The next step up is an actual 
chart with an x-y curve so that any value can be found along the curve 
(or curves for mult-band) equipment.

While those are quite accurate maintaining the accuracy over a long 
period of time (years) is more troublesome. However, with computer 
spread sheet software it is easy-peasy to generate a new curve and toss 
the old one as the equipment ages. I made a set of curves for my RAK-7 
regen receiver. I can not only reset the frequency to a previously 
logged station and be right *ON* it, but can look at the curve for a 
band and preset it to a new, never used frequency before and also be 
right *ON* it. I can find the frequency of a newly found signal on the 
air. I found that my unit has drifted a little bit in 70 years but is 
surprisingly close to the logged information in the table that was 
supplied when I got the used receiver.

As for the digital gear and the displays that readout directly in 
frequency, resistance, capacitance, ohms, volts, etc we have to 
periodically check those too (alignment) and that be a lot more 
troublesome than plugging a few points into a spread sheet and printing 
a curve.

You puts your money down and you takes your choice. Some of us prefer 
blondes, others prefer redheads - etc. Some of us like them ALL.

73,

Bill  KU8H





On 05/08/2015 09:04 AM, J Mcvey via ARC5 wrote:
> Why is so much of the pre-war equipment dependent upon charts?For example, the BC654 has a limited frequency range, yet the transmitter dial is not calibrated in frequency, but the receiver in in freq. Why is that?The previously mentioned RLC meter needs a chart, when direct reading dials would have been simpler, IMO. ( I have an ancient RLC meter that has direct reading dials).The heterodyne calibrator is also useless without a chart.Then there is the National log dial...and the list goes on...It just seems like an unnecessary extra step.
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