Bush DAC90

[Ed_Dinning]

Hi Folks, I had noticed that the LW reception was very poor on my DAC90 in comparison to the more modern DAC90a. As a work round this I added a long wire to the red (LW) frame aerial lead and was rewarded with the signal (and noise ) coming right up. This gave me an Irish and 2 french stations as well as R4 LW.

This could however be hazardous, so I suggest it is only done on your own sets if you understand all the implications and with the following additions

Aerial wire connected from a 4mm socket housed in the ventilation holes a the top left of the back panel. This runs to 2, 1nF class Y caps connected in series . These are totally oversheathed with heatshrink sleeving and are connected to the red wire going to the frame aerial.

Ed

[FERNSEH]

Hi Ed,
for an aerial and earth connection, would it be possible to add extra winding(s) to the frame aerial?
A number of turns around the MW and LW coils, both connected in series.
Alternatively, a single coil interposed between the LW and MW coils.

DFWB.

or an aerial and earth connection, would it be possible to add extra winding(s) to the frame aerial?

I did that on my '90a it works well, I posted the result here. https://www.vintage-radio.net/forum/...ad.php?t=56889

[Heatercathodeshort]

I have a card box around 8" X 5" X 2" wound with around 50 turns of wire connected between my outdoor 50ft aerial and earth mounted underneath the work area of the bench. The RF coupling has improved enormously. The workshop is too well screened to pick up only the strongest MW/LW stations without it. John.

[Ed_Dinning]

Hi Gents, all those ideas are possibilities and seem to work.
My concern was to do them in a manner that addressed any live chassis safety issues.
An earth connection is not necessary as far as I can see, bit if required could be achieved in the same way as the aerial connection.
To follow good practice, 2, Y caps should be used in series to cover single point failure. The whole assembly should then be oversheathed in heatshrink tubing.
I believe this covers the spirit of the regulations governing earthing of or aerial connection to, a live chassis set and as commonly used on TV sets.Any lawyers /H&S specialists inputs most welcome

Ed

My concern was to do them in a manner that addressed any live chassis safety issues.

Mine does, the additional coil is insulated as are the two original coils, double insulated or treble insulated if you count the air gap.

[Ed_Dinning]

Hi Merlin, that would be fine, but I decided to go for "known tech" as it keeps the regulators happier if there is a problem, rather than then having to think about insulation levels, creepage and clearance etc.

Ed

[mister valve]

I don't want to state the blinking obvious, but could it just be that 'T.C.2' (LW aerial trimmer) needs adjustment to peak at 200kHz ?

[Ed_Dinning]

Already peaked thanks

Ed