432 MHi IN

Fig, 1. 432 mhz FET prearnp.

Parts List

LI - 1" long x W wide copper strip. Center tapped-

L2 L3 - 1V4" long x wide copper strip. L4 - 1" # 18 wire coupled to L3, Ln - 2-4 turns #22 ^3/8 long x 3/16" diameter slug tuned. FET - UC734 Union Carbide-

After the usual mistakes were corrected the preamp started to perform. Once the first stage was neutralized, which wasnnt too difficult, I had a very hot preamp.

This was fed into an old uhf TV converter employing just a crystal mixer, but retuned to cover the 435 MHZ band. The results were excellent. Local signals, as well as one


Fig. 2. 435 mhz FET preamp.

Fig. 2. 435 mhz FET preamp.

Parts List

LI - rW copper strap - center tapped. L2-L3-L4-L5 - copper strap.

L6-L7-L8 - 1" #18 wire parallel to cold end of output strap* FET - Union Carbide UC734-E.

Fig. 3, 2 meter FET preamp.

Parts List

L3-L5 - 2T pickup loop

FET - UC734E Union Carbide (1st choice) -

mpf!02 Motorola about 100 miles distant, were received with S9 copy. Please note the only antenna at this time was a home brew 3 foot reflector with a dipole in the center.

After such astounding success with the two stage unit, I "naturally" concluded that four stages would be better,

I proceeded to build another preamp of that same configuration cxcept for two additional stages of grounded gate. WOW, was that unit loaded with problems. I spent several weeks trying to tame il down but achieved little success. 1 then changed the input stage to a grounded gate and experienced the same problems. It became apparent that my shielding was inadequate so 1 put shielding on top of shielding until I had completely enclosed each tuned circuit. This cured the problem very well, I realize now that the circuit as I had originally built il would have worked very well if I had been much more careful in the way I had used the interstage shielding.

Both 436 MHZ circuits employed the UC734H FET mounted in sockets. Copper clad board was used for the base and also for the between stage partitions. Capacitors are all Arco # 400 miniature trimmers which are very inexpensive, but do a very good job.

It should he pointed out at this time, that all the accepted vhf techniques should be employed in this type of construction or

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