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AO40 The Easy Way by VK3CJS

CONIFER MODIFICATION - Page 4

My next experiment will be to alter the local oscillator crystal to bring the IF out on 2 metres to suit my ICOM all mode rig.

The LO works by multiplying the fundamental crystal frequency X 256.

Hence in this case 256 X 7.621 = 1951 mhz. So our frequency of 2401 - 1951 gives a first IF of 450 mhz. In order to convert to 145 mhz we would need a crystal frequency of 8.8125 mhz.

Providing the lower converter is disabled there should be no image problems. Likewise the IF filter coils can be easily rewound for 2 metres.........

If you care to follow the circuit on the board, you will see that the coils are scattered all over the place. This is to reduce mutual coupling between them. On the lower frequency board the VHF coils are wound horizontally on surface mount formers. Any PCB pad with a hole in it simply connects through to the ground plane behind.

Addendum since last posting: Fool that I am, I didn't pay attention to the patent numbers written on the downconverters. The related documents make fascinating reading. You can also follow the threads to other patents and so on.

The US patent number search is . If you can't see the document pix, go to HELP and download the viewer... it's quite painless.
Conifer patent numbers: 5,202,699 5,300,941 5,394,115
Hills / Pacific Monolith: 5,015,968 5,280,412 5,317,291

So there it is.... the extent of our adventures so far. (September 2002)

Further progress will be reported in these pages on the Central Goldfields Club website....

Please feel free to contribute any thoughts or corrections to this article.

73 de Chris VK3CJS