[ARC5] The "new" MF band.

[Bill Cromwell]

Hi Ken,

I have been using batteries for both the heaters and the B+ (90 volts) 
on mine. I noticed a small frequency shift whenever my space heater 
blower kicked on off. The batteries got rid of than and reduced the 
power line crud too.

73,

Bill  KU8H

On 09/16/2017 12:02 PM, Kenneth G. Gordon wrote:
> I, along with some others, have been using a refurbished BC-453 on that band for receiving.
> I couple mine to my computer which has various pieces of software on it.
>
> The BC-453 and the R-23*/ARC-5s work very, very well there.
>
> There are some modes being used on that band which require very high stability, and the
> "ARC-5" receivers, although they are quite stable already, can be improved by using
> regulated DC on the filaments.
>
> As to whether or not the resultant stability is sufficient for those modes remains to be seen,
> however.
>
> Of course, regulated B+ must be used too. In addition, that B+ should be kept "low". As I
> have mentioned here before, a B+ voltage of around 170 VDC appears to be the optimum.
>
> Even the small variations in line voltage cause obvious instabilities due to the changes in
> filament voltage with some of those high stability modes.
>
> If you decide to use the lower B+, it is a good idea to move the screen voltage feed from the
> original midpoint of the two filament voltage divider resistors to the hot end, increasing the
> screen voltage to a point closer to that required by the tubes' specification.
>
> Too low screen voltage causes a significant worsening of overall sensitivity.
>
> Measured MDS sensitivity for my refurbished "ARC-5s" is 0.1 microvolt on that band.
>
> Ken W7EKB
>
>
>
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-- 
bark less - wag more