My Latest Junker. Courier AM Car Radio.

[Herald1360]

Mistweaked aerial trimmer?

[Radio Scotland]

I was probing the detector diode and accidently broke one of the legs, Replaced it and she burst into life, The original Diode either had a weak output or a bad solder joint.


Would never have suspected that was the issue, Pity i spent ages recapping it But most were out of spec anyway,


Pretty sure shango066 was caught out with this too after spending ages trying to find the cause of low volume,

[Radio Scotland]

Anybody know how you adjust the pre-set on this ?

[Nickthedentist]

Aerial trimmer?

[Radio Scotland]

Originally Posted by Nickthedentist

Aerial trimmer?

No it's not that nick, Presume it must be one of the inductors either side of the preset switch

[Graham G3ZVT]

Nick,
Looks like the (far better looking) LW/MW original



was morphed into this MW only model with that awful logging scale, and the wave change button reassigned as a 208m preset.

Could equally be a 1500m preset I suppose.

[ms660]

Mods permitting for ID only etc ?:

https://www.ebay.ie/itm/144650943104...YAAOSwK7BinKBg

https://www.service-data.com/product...06/9943/m22306

?

Lawrence.

[Radio Scotland]

Originally Posted by rambo1152

Nick,
Looks like the (far better looking) LW/MW original

Attachment 265091

was morphed into this MW only model with that awful logging scale, and the wave change button reassigned as a 208m preset.

Could equally be a 1500m preset I suppose.

It's set to 1500m Radio 4

Anybody know why car radio's use inductor tuning ? presume something to do with ignition noise

[Radio Scotland]

Originally Posted by ms660

Mods permitting for ID only etc ?:

https://www.ebay.ie/itm/144650943104...YAAOSwK7BinKBg

https://www.service-data.com/product...06/9943/m22306

?

Lawrence.

Is there a point to posting the ebay listing ?

[ms660]

Originally Posted by Radio Scotland

Is there a point to posting the ebay listing ?

Yes there is because it looks very similar to yours, the service info for it is available in the link I posted, which might help in future if the circuit etc is the same as what's in yours should your receiver develop another fault in the future, I don't have a copy of that service info but it might give alignment/adjustment instructions which would also be a bonus if required.

Lawrence.

[Radio Scotland]

Originally Posted by ms660

it looks very similar to yours,
Lawrence.

It is mine

[ms660]

Originally Posted by Radio Scotland

It is mine

Which was unbeknown to me at the time because you didn't provide any model number information.....

Lawrence.

[Mr 1936]

Hi

Car radios use inductive tuning because:

It is physically smaller

It is electrically more suited to a short rod antenna. In a traditional design the first tuned circuit has a fixed parallel capacitor made up of the capacitance of the antenna, plus a short length of special low capacitance coax, plus the aerial trimmer, plus a fixed value. Since the first two are outside the control of the designer, the trimmer is used to ensure alignment.

Since FM came along this has all gone out of the window, and a FET preamp with no trimmer is used.

[Radio Scotland]

Originally Posted by Mr 1936

Hi

Car radios use inductive tuning because:

It is physically smaller

It is electrically more suited to a short rod antenna. In a traditional design the first tuned circuit has a fixed parallel capacitor made up of the capacitance of the antenna, plus a short length of special low capacitance coax, plus the aerial trimmer, plus a fixed value. Since the first two are outside the control of the designer, the trimmer is used to ensure alignment.

Since FM came along this has all gone out of the window, and a FET preamp with no trimmer is used.

Cheers for that, Makes sense ,


Jay

[Graham G3ZVT]

Originally Posted by ms660

Which was unbeknown to me at the time because you didn't provide any model number information.....

Lawrence.

I think he means he bought that actual specimen.

[ms660]

Originally Posted by rambo1152

I think he means he bought that actual specimen.

Yes, which was unbeknown to me at the time....as I already stated....

Lawrence.

[ms660]

Originally Posted by Radio Scotland

Anybody know why car radio's use inductor tuning ?

Permeability tuning also solves the potential problem of capacitor tuning gang microphony.

There's also less change in selectivity and gain when tuning across the band.

W.J. Polydoroff did some work with permeability tuning back in the early 1930's, there is an article by him in the 1933 edition of the proceedings of the IRE which starts on publication page 690 in the link below for anyone that might be interested:

https://worldradiohistory.com/Archiv...RE-1933-05.pdf

Lawrence.

[Radio Scotland]

Originally Posted by ms660

Permeability tuning also solves the potential problem of capacitor tuning gang microphony.



Lawrence.

Interesting, Never thought of that as obviously a car radio is subject to a lot of vibration