[ARC5] Suppressor Grids and pentodes

[Kenneth G. Gordon]

On 31 Jan 2013 at 23:08, Paddy Ryan wrote:

> Hold on!...does this mean a BFO solution for the BCB receivers with
> the BFO coil missing?

Possibly: this is, apparently, used in some "communications" receivers which 
normally don't have a BFO.

>..if so which tube is modded and does it work on
> the ARC5?

Well, the ARC-5 receivers HAVE a BFO, so it wouldn't be needed for that. It 
could probably be used in the ARC Type 12s, which don't have a BFO.

The tube/stage that is normally "modded" would be the first IF stage. 

Some of those cheaper receivers in which this is used have only one IF 
stage.

This mod makes the IF stage into a controllable oscillator. Although this does 
work as a BFO (sorta), you can't change the "pitch": it is fixed-tuned.

As a BFO, I view it as a total kludge. It DOES make that stage more 
selective, kind of like a "Q"-multiplier does, but not as well.

Ken W7EKB