[ARC5] Crystal Filters in BC-455

[Kenneth G. Gordon]

On 29 Oct 2015 at 16:14, Fuqua, Bill L wrote:

>   I have been working on a homebrew receiver for the ARRL Frequency Measurement
>   Test.
> There are two receivers, one has crystal filters for 4 WWV frequencies. The
> other is the test signal receiver Anyway, I have used 2.5 MHz crystals from
> mouser to make a filter with less than 100 Hz bandwidth. Naturally that can be
> widened by lowering the Q. 
>   It occurred to me that 2.5 MHz is not far from the IF frequency of the BC-455.
>   In fact
> Digikey has a 2.949 MHz crystal which is even closer to the 2.830 MHz IF.
> Naturally the Local oscillator would have to be aligned but being only 4% shift
> in IF it should still track and match dial fairly good.
>   I remember some earlier discussions about using crystals in ARC5 receiver IF's
>   but don't recall the 
> outcome.  
> 
> 73
> Bill wa4lav

Hello, Bill:

I had thought of that idea too, and, in fact, Mike Murphy WU2D has a 
youtube video of a BC-455 in which he did exactly that and the video shows 
the very effective results.

He, apparently, found a 2830 KHz crystal, and although I have been 
searching for one, I have, so far, never found one that was inexpensive.

Your idea has great merit, and I thank you for it.

Be aware that the BC-455 and the R-27/ARC-5 have two different kinds of IF 
transformers: I forget the models, but the IF transformers in one model 
consist of only one coil, whereas those in another model consist of two coils 
like the lower frequency models have.

vy 73,

Ken W7EKB