Permeability Tuning

[pwdrive]

I'm wondering if it would be worth trying permeability tuning on my experimental Regenerodyne Receiver (RF amp stage only)
Pro's Con's Ideas anyone?

Lawrence.

[pwdrive]

Would anyone know what the difference (if any) is between the core material in the VHF permeability tuner and the broadcast band permeability tuner?

Lawrence.

[Andrewausfa]

My (the) Ekco A28 uses permeability tuning but only for one of its short wave band ranges. The way it's done is quite novel. Per 'Trader' it uses iron dust cores.

Andrew

[pwdrive]

My (the) Ekco A28 uses permeability tuning but only for one of its short wave band ranges. The way it's done is quite novel. Per 'Trader' it uses iron dust cores.

Andrew

Thanks Andrew, the brief for my idea is to have (if possible) one type/grade of slug that will cover the shortwave spectrum, the reason being is that I am aiming for my Regenerodyne project to have plug in coil packs, mechanicaly I can do this no problem if only one type/grade of slug is used but if I need different types/grades for different bands then it's going to be a no no.
The plan would be to have one panel mounted RF tuning control operating two ganged slugs within the plug in coils (RF amp grid tuning & Mixer grid tuning)

Lawrence.

[AlanBeckett]

Andrew,

The slugs I've used in my limited efforts with rf have been quoted by the Manufaturer for a maximum frequency. I don't remember a minimum being quoted.
These were Neosid ferrite 6mm and 4mm screw in ones. One variety was used at rf - 140 to 170MHz - and the other at IF - 10.7MHz.
If I remember rightly they had a different coloured strip on them.

Alan

[pwdrive]

Well a bit of progress, I have found out that the Barlow Wadley receiver used a single ferrite slug for the RF bandpass filter tuning (via switched coils all on the same former) covering the full shortwave spectrum, question now is what grade of ferrite did they use? and is it likely to be pretty broadband given the nature of the Wadley loop system?

Lawrence.

[pwdrive]

Andrew,

The slugs I've used in my limited efforts with rf have been quoted by the Manufaturer for a maximum frequency. I don't remember a minimum being quoted.
These were Neosid ferrite 6mm and 4mm screw in ones. One variety was used at rf - 140 to 170MHz - and the other at IF - 10.7MHz.
If I remember rightly they had a different coloured strip on them.

Alan

Thanks Alan, the ones in the R1155 are colour coded (dot) I seem to remember, I have considered using standard tuning slugs as found in old RF coils but I suspect I wouldn't get the tuning ratio, Ideally the ratio needs to be the usuall 3 to 1 or there abouts, wonder if I could glue 2 o 3 of them length wise to get the required inductance change? Next time I'm at the bench I could try that and check the inductance swing on the bridge.

Lawrence.

[AlanBeckett]

Lawrence,

I suspect a scrap car radio is your best bet for a start, but they're probably only good for 2MHz or so.
TV ones with a hex hole would give you a higher prequency and allow you to join them together. However, I fear you might get steps.

Alan

[pwdrive]

Yes, one with VHF as well as AM, also done a web search, ferrite rod is available to 100 Mhz plus eg: Fair Rite do such stuff.
I might be on to a loser with this permeability tuning idea but I will give it a go.

Lawrence.

[AlanBeckett]

When did the first VHF car radios come in?
Were they permiability tuned.
Modern ones are all synthesized I fancy, and before that varicap tuned.

Alan