[ARC5] BC-221 question

[Bill Cromwell]

Hi,

Ken Gordon who is a member of this list AND is dabbling in this thread 
has a computer program to generate the cal book. If he still has it you 
might find it on his webs site (assuming he still has it). Ken might 
speak to that himself. If he no longer has it I am sure I have it in my 
bitstash.

I use a spread sheet and enter some reference points into it relating 
the dial settings to some known frequencies. Then graph the curve of 
those points with the spreadsheet. The more points we enter the nicer 
the curve. I have not had to do that for an LM but I did it for each 
band on my RAK.

Tedious? For all of the bands on my RAK I spent a couple of evenings 
playing with the radio. I once spent several weeks plotting the response 
of a Hammarlund xtal filter in it's various settings with a pencil and 
graph paper. Now *THAT* was tedious. Later I found identical curves in 
an obscure manual. By that time I already was wringing maximum 
performance from that receiver. It worked exactly the opposite of the 
recommendations in the ARRL Handbooks. No wonder they thought the single 
xtal filter is not worthwhile. "Tedious" efforts can give nice rewards.

73,

Bill  KU8H

On 5/22/20 8:05 PM, Richard Knoppow wrote:
>     The crystals are in cans like metal tubes. I don't know the type as 
> far as the crystal cut. I also have a BC-221A/K and use it. The A/K is 
> the one with a modulator and an AC supply stuck in the battery 
> compartment. The cabinet is supposed to be sealed but getting the 
> crystal on frequency is a PITA unless you drill a hole to access the 
> trimmer from outside. Before you do any drilling make sure there is not 
> something in the way. I think there is on mine would have to open it up 
> and look.
>      The key to the BC-221 and the similar LM is having the calibration 
> booklet. Its possible to make one with a modern counter but its a 
> tedious project. I saw an article (and may even have it) on how the 
> calibration charts were generated originally.
> 
> On 5/22/2020 4:31 PM, Kenneth G. Gordon wrote:
>> On 22 May 2020 at 23:19, Hubert Miller wrote:
>>
>>> I do not have a BC-221, so can someone remind me, this crystal 
>>> frequency and package
>> type?
>>
>> I have, and use, two BC-221-AKs. Both have 1 MHz crystals in them. I 
>> can't remember the
>> type.
>>
>> Ken W7EKB
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-- 
bark less - wag more