UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Ferrite rod antenna and RF amp for Valve radios

Christoffrad · 5th Oct 2019, 7:41 pm

I am building an antenna system for my valve radios ussing an old ferrite rod which has been recovered from a transistor radio.
It seems to work fine on Long Wave. A good resonant peak and clear directionality when turning the rod. But I'm having some problems on Medium Wave. The ferrite rod antenna consists of two coil sets. The Long Wave coil primary is 4.85mH and secondary is about 10uH. The Medium Wave coil set has a 1mH primary (approx) and 5uH secondary.
If the MW secondary is connected one way round the antenna doesn't seem to resonate with the tuning capacitor and if the secondary is reversed it becomes unstable.
The circuit is shown below.

Any suggestions?

5th Oct 2019, 7:41 pm	#1
Christoffrad Hexode Join Date: Jun 2018 Location: Cambridge, Cambridgeshire, UK. Posts: 262	Ferrite rod antenna and RF amp for Valve radios I am building an antenna system for my valve radios ussing an old ferrite rod which has been recovered from a transistor radio. It seems to work fine on Long Wave. A good resonant peak and clear directionality when turning the rod. But I'm having some problems on Medium Wave. The ferrite rod antenna consists of two coil sets. The Long Wave coil primary is 4.85mH and secondary is about 10uH. The Medium Wave coil set has a 1mH primary (approx) and 5uH secondary. If the MW secondary is connected one way round the antenna doesn't seem to resonate with the tuning capacitor and if the secondary is reversed it becomes unstable. The circuit is shown below. Any suggestions? Attached Thumbnails