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Welcome to Magnums' way of doing things. (Back then)

As said earlier - the thing is Negative Ground Only - which may not matter or become the bane of noise pickup.

The earlier version of this radio used a dual gate FET RF Front End amp similar to what Cobra 148 and Grant XL's used for their IF mixers, in an attempt to make the RF amp work similar to a Pre-selector/attenuator to reduce imaging problems this chassis develops along certain specific receiver section - like Birdies. Fine, but the original board I had, they silkscreened a transistor part - like the 1674, but what they put in on the bottom of the board, a 4-legged beast that made me go back to the original design of 3-legged transistor. With that redesign, it had it's own issues but receiver side worked better because the RF amp worked more like impedance matching and buffer than a IF amp filter and preselector they tried to squeeze in there.

Only that "Birdie" problem is an inherited artifact of the Xtal synthesis that goes on in there. Several areas of the board need to stay isolated from the others so they tried various methods of communication including the CPU controlled "Switchyards" but they seem to be more like antenna arrays for that IF imaging problem to propagate to other parts of the board thru the power supply buss feeds.

<blockquote data-quote="Handy Andy" data-source="post: 658149" data-attributes="member: 52309">Welcome to Magnums&#039; way of doing things. (Back then)As said earlier - the thing is Negative Ground Only - which may not matter or become the bane of noise pickup.The earlier version of this radio used a dual gate FET RF Front End amp similar to what Cobra 148 and Grant XL&#039;s used for their IF mixers, in an attempt to make the RF amp work similar to a Pre-selector/attenuator to reduce imaging problems this chassis develops along certain specific receiver section - like Birdies. Fine, but the original board I had, they silkscreened a transistor part - like the 1674, but what they put in on the bottom of the board, a 4-legged beast that made me go back to the original design of 3-legged transistor. With that redesign, it had it&#039;s own issues but receiver side worked better because the RF amp worked more like impedance matching and buffer than a IF amp filter and preselector they tried to squeeze in there.Only that &quot;Birdie&quot; problem is an inherited artifact of the Xtal synthesis that goes on in there. Several areas of the board need to stay isolated from the others so they tried various methods of communication including the CPU controlled &quot;Switchyards&quot; but they seem to be more like antenna arrays for that IF imaging problem to propagate to other parts of the board thru the power supply buss feeds.</blockquote>

[QUOTE="Handy Andy, post: 658149, member: 52309"] Welcome to Magnums' way of doing things. (Back then) As said earlier - the thing is Negative Ground Only - which may not matter or become the bane of noise pickup. The earlier version of this radio used a dual gate FET RF Front End amp similar to what Cobra 148 and Grant XL's used for their IF mixers, in an attempt to make the RF amp work similar to a Pre-selector/attenuator to reduce imaging problems this chassis develops along certain specific receiver section - like Birdies. Fine, but the original board I had, they silkscreened a transistor part - like the 1674, but what they put in on the bottom of the board, a 4-legged beast that made me go back to the original design of 3-legged transistor. With that redesign, it had it's own issues but receiver side worked better because the RF amp worked more like impedance matching and buffer than a IF amp filter and preselector they tried to squeeze in there. Only that "Birdie" problem is an inherited artifact of the Xtal synthesis that goes on in there. Several areas of the board need to stay isolated from the others so they tried various methods of communication including the CPU controlled "Switchyards" but they seem to be more like antenna arrays for that IF imaging problem to propagate to other parts of the board thru the power supply buss feeds. [/QUOTE]

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