Hi Peter,

 

here also FT1000MP and also observed lower senestivity arround 500 kc.

Wonder if you have built a preamplifier in order to overcome this ?

 

Uwe, dk1kq

Hullo Uwe,

 

Yes, I made a simple preamplifier that solved the problem of low sensitivity and removed the spurious signals from my local medium wave broadcast stations.

 

The input circuit is a small 465 KHz I.F. transformer in a can 2 x 2 x 3.5 cm, possibly from and old transistor radio.  The coils are tuned by 330pF capacitors and one of the windings has a low-Z tap.  The Q of each coil is about 75 at 500KHz.  I use the low-Z tap for the aerial input and the secondary winding feeds the gate of a BF244A FET amplifier with its drain directly coupled to a 2N3906 transistor emitter follower. It is actually a circuit for an LF band preselector that I published more than 25 years ago in the now defunct Short Wave Magazine.  I have seen a very similar circuit for 500 KHz somewhere on the internet but can't remember where.  However, any simple tuned preamp should work fine at this frequency.

 

With the preamp in circuit I operate the FT1000MP with the IPO button 'on' and the ATT set to give a low S-meter reading on local noise picked up by the antenna.  Sensitivity is now more than adequate and there is no trace of spurious on the Spectran waterfall.

 

73 Peter, G3JFS.