Radio Caroline 648kHz

[Geordie McBoyne]

Connected to the tunable frame aerial Radio Caroline was last night coming in loud and clear through the Philips TRF receiver model 634A, the "Ovalteeny" model of 1933.
Very faint reception this morning.

Geordie McBoyne.

[Murphyv310]

Excellent David.
I find the 472 on weak stations gets even sharper so its actually the only set that gives readable reception up to around 4pm when the signal improves. On even a decent superhet with selectivity switch on the narrow setting its far too lacking in treble for any form of clarity whereas the 472 is much sharper.

[Geordie McBoyne]

Hi Trevor,
I'll try out the other Philips Superinductance radio tonight, the 1932 model 834A. Actually when you think about it because these Philips radios have two tuned RF amplifier stages and coils made to the highest quality possible such sets should perform as good as any 4 + 1 superhet. Having no noisy multi-grid frequency changer valve must help as well.

Geordie McBoyne

[pwdrive]

I've never seen one of those Philips's in the flesh, I would think that the high impedances primaries of the RF coils are set to resonate below the MW band to help maintain equal sensitivity across the band along with varying the grid bias.

Lawrence.

[Old Sparky]

For quite a while now I've had a Philips 274A 'Superinductance' Radio in my 'to do' section, and am working on it on behalf of it's owner. I have the service manual, but haven't fully studied it. You could be correct in ho=w it works, Lawrence.

[Murphyv310]

Don't forget these sets have AGC, very unusual on a TRF, on a weak station they are on the brink of oscillation but get throttled back on strong stations, this slightly widens the effective bandwidth to give excellent audio quality.
Sparky be very careful when restoring a Superinductance. It is very important to rigorously follow the layout used by Philips, even changes in component size and position can effect alignment and stability. I'm convinced mine works so well as its virtually original.

[Geordie McBoyne]

The Philips 834A was the first of the "Superinductance" series of TRF radio receivers. Yesterday evening the 834A was connected up to the frame aerial, the results weren't as good as the previous reception test with the 634A. However, I don't think the set was to blame for this, Radio Caroline was last night subject to fading. At times the station came in really loud and clear and then would fade away to a noisy mush.   Unlike the 472A and 634A the 834A doesn't have AVC so perhaps that doesn't help much when the signal fades.   The 834a employs an anode bend detector whereas the later sets use diode detectors, an SD4 diode-tetrode in the 634A and a 2D4A double-diode in the 472A.

This evening it's the turn of another early thirties TRF receiver, the Murphy A3.  

Geordie McBoyne.

[Geordie McBoyne]

Can't use the Murphy A3A this evening, the loudspeaker field coil has been found to be open circuit. The frame aerial is now reconnected to the Pilot X65B. Reception from Radio Caroline is absolutely hopeless this evening.

Geordie McBoyne.

[Old Sparky]

Perhaps a seeperate thread is required, but I'm following the original layout as closely as possible. I've put modern yellow capacitors in the paxo;in sleeves which housed the original caps, and am remounting them in their original positions. Something which puzzled me was the use of bare tinned copper wires for most of the connections, including some which carry HT. Presumably the use of sleeving would add capacitance, and thus upset the alignment? As to the subject of this thread, I haven't yet been able to receive R. Caroline on 648, despite having tried several times on 2 or 3 AM radios, including a 1964 Cossor Transistor Portable, which is one of the most sensitive radios I've come across in recent years!

[Murphyv310]

Good here David on a Matsui clock radio with its tiny ferrite rod aerial.