You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

Dudmuck -
At first glance I agreed with you about dc current flowing through the antenna coax braid if the radio negative battery lead opened up. But after thinking about it a little more, I remembered that rf /earth ground (connected to the chassis of the radio) is separate and is isolated from DC ground. They are capacitively-coupled, but not dc-coupled. I verified this by opening up my 2950, and ,sure enough, the pads for the mounting screws that hold the board to the chassis were not connected to the circuit except through several 470 pf caps. You can easily check this by hooking up an ohmmeter between the negative power lead and the chassis. The only time it will show conductivity is if one of the caps is shorted. Now I don't know if this is the case with amplifiers, but it seems to be true of most radios. My old TRC-458 (circa 1977) was set up the same way. So, it would seem that the antenna system couldn't be a component in a dc ground loop, but Murphy will probably prove that one wrong too. LOL.
- 399

<blockquote data-quote="unit_399" data-source="post: 112878" data-attributes="member: 7311">Dudmuck -At first glance I agreed with you about dc current flowing through the antenna coax braid if the radio negative battery lead opened up. But after thinking about it a little more, I remembered that rf /earth ground (connected to the chassis of the radio) is separate and is isolated from DC ground. They are capacitively-coupled, but not dc-coupled. I verified this by opening up my 2950, and ,sure enough, the pads for the mounting screws that hold the board to the chassis were not connected to the circuit except through several 470 pf caps. You can easily check this by hooking up an ohmmeter between the negative power lead and the chassis. The only time it will show conductivity is if one of the caps is shorted. Now I don&#039;t know if this is the case with amplifiers, but it seems to be true of most radios. My old TRC-458 (circa 1977) was set up the same way. So, it would seem that the antenna system couldn&#039;t be a component in a dc ground loop, but Murphy will probably prove that one wrong too. LOL.- 399</blockquote>

[QUOTE="unit_399, post: 112878, member: 7311"] [FONT=Times New Roman]Dudmuck -[/FONT] [FONT=Times New Roman]At first glance I agreed with you about dc current flowing through the antenna coax braid if the radio negative battery lead opened up. But after thinking about it a little more, I remembered that rf /earth ground (connected to the chassis of the radio) is separate and is isolated from DC ground. They are capacitively-coupled, but not dc-coupled. I verified this by opening up my 2950, and ,sure enough, the pads for the mounting screws that hold the board to the chassis were not connected to the circuit except through several 470 pf caps. You can easily check this by hooking up an ohmmeter between the negative power lead and the chassis. The only time it will show conductivity is if one of the caps is shorted. Now I don't know if this is the case with amplifiers, but it seems to be true of most radios. My old TRC-458 (circa 1977) was set up the same way. So, it would seem that the antenna system couldn't be a component in a dc ground loop, but Murphy will probably prove that one wrong too. LOL.[/FONT] [FONT=Times New Roman]- 399[/FONT] [/QUOTE]

Top Bottom