[ARC5] ARC-5 Double Conversion

[Kenneth G. Gordon]

On 5 Apr 2018 at 14:45, DSP3 wrote:

> One might also try modifying the three IFTs by moving the lower coil 
> downward.  I wrote it up in ER magazine and it works great.  The BW on 
> the 80 meter receivers is better than halved.  On forty meters, not quite 
> as narrow but it really helps.  Not as good as using a second receiver, 
> but......
> Jeep - K3HVG

Your method is a great improvement. In fact, I had hit on the same idea some time ago, but 
never followed it up with any sort of write up.

However, one should be aware that there were two distinctly different IFTs for the 6 - 9.1 
MHz receivers: 1) all IFTs have a single large winding, and 2) the IFT has two separate 
windings like the 3 - 6 Mhz receivers.

The two-winding IFTs can have the two windings separated as much as possible, but the 
single-winding versions cannot (obviously), so another method must be used to enhance 
selectivity in those receivers.

Mike Murphy WU2D turned that 1st IFT in his 6 - 9.1 Mhz receiver into a single-crystal 
crystal filter, but finding 2830 kHz crystals is NOT trivial.

Ken W7EKB

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