"Robert Donnell" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- I used to have a DC-3, for my TR-3. It has no provisions for running an R-4 or any 120V output. Both the DC-3 and DC-4 are of the design family of switching voltage alternately to one half of the center-tapped low-voltage primary of a large power transformer. And the operating power for the transmitter tube filaments is gained by using a series/parallel string arrangement, so that all can be powered from 12 VDC. I'd bet part of the design trade in the DC-4 that allows running the R-4 on a 120V winding is that the T-4X series isn't capable of as much output power (and hence not as much HV power consumption) as the TR-3/4, so there's a bit of reserve transformer capacity.
Also consider that inverter transformers are designed to work with square waves, that being the output of the switching transistors. Applying square waves from the output of an inexpensive inverter to an AC-3 or AC-4 transformer may not be especially good for the long-term health of the transformer, and unless the transformer is potted or tarred, will probably cause it to buzz audibly. I'm guessing (hoping?) Drake kept that in mind when providing for operation of the R-4 on 330 Hz from the DC-4. At least one of the benefits for the DC-3/4 is that by using a frequency above 60 Hz, the transformer didn't have to have as much iron to function correctly as would be needed for an equivalent capability 60 Hz operation. Generally speaking, the "big transformer" type inverters are not as efficient as the current state of the art in inverters, which is that a small high-frequency switching power supply is used to generate a 160V (roughly the peak voltage of 120V sine wave) and then to alternately connect the positive and negative outputs of that power supply to the two power pins on the AC power output connector. Part of that is because of the use of MOSFETs in current designs, which have a lower voltage drop in the on state than do germanium transistors. Germanium transistors were the favorite in the early 60's for this application because of the voltage drop and power dissipation saved when using them in that high-current application. But with MOSFETs having no fixed minimum voltage drop, and ON resistances expressed in low milli-ohm values, they're now a better choice. Hope that helps! 73, Bob, KD7NM ---------- Original Message ---------------------------------- From: [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] Date: Mon, 9 Jan 2006 15:59:17 -0500 (EST) > >[EMAIL PROTECTED] made an utterance to the drakelist gang >---------------------------------------------------------------------- > >Question about DC-3 or DC-4... > >Wondering how the 110VAC is supplied to an R-4any from the supply. Also, >i'm wondering if the DC-x supplies are more efficient than using an >inverter to power a set of twins. > >thanks > >-- >73 Jason N1SU >http://n1su.com/ >---------------------------------------------------------------------- >Submissions: drakelist@www.zerobeat.net >Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body >Hopelessly Lost: [EMAIL PROTECTED] - help in body of message >Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net >---------------------------------------------------------------------- > ________________________________________________________________ Sent via the WebMail system at webmail.pioneernet.net ---------------------------------------------------------------------- Submissions: drakelist@www.zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
