"Jim Pruitt" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Hello Jim.
According to the article itself (mods done on a late R4C with 6EJ7 first and third mixer). "Major Features:" "High performance LM1875 audio amplifier (THD at 20 W/1 khz of 0.15% typically" "12v regulated supply (+12v and -12v) for solid state circuitry." "SN602 product detector" "SN602 as R4C third mixer." "MiniCircuits SBL-3 double balanced mixer (+7dbm LO) as R4C second mixer." "MAV-11 MMIC to increase IF gain after the R4C second mixer." "Sherwood 600 Hz first IF CW filter, with realay switching so the stock 8khz wide first IF filter is retained for SSB/AM operation." "Completely new three speed hang AGC system after the second IF crystal filters and allows the gain of all the stages before the R4C's third mixer to run at maximum. The AGC has one speed for very fast CW (35wpm-plus), plus one for slower cw and one for SSB." One thing that did not set well with me was that the author drilled a hole and installed a small toggle switch on the front panel. The artilce was written because the author had a basket case R4C and wanted to do the mods that W8JI had done but W8JI did not document his mods and the NC0B and K8RRH mods used parts no longer readily available. As one other Drakelister pointed out to me off list was that the author does not recommend the mods on a good and working R4C. I did not read that but did read that it was done on a basket case. In reading the article I did keep thinking that the guy was sure not improving resale value but as the author stated, he has no intention of ever selling his modified R4C so the estetic value was totally unimportant. I contacted Fred at FAR circuits and asked if he was going to make pc boards for this article (the article used only dead bug and breadboard). Fred said he had no plans to make any pc boards and I can understand that since it would not be a popular mod (for one thing, a lot of us do not have the late R4C). I did wonder about the LM1875 audio amp (20 watt). My R4C needs work (motorboats) and I wanted to do the Sherwood PS4 mod and the audio amp. I have a Velleman audio amp kit that I was going to use but in reading Bob Sherwood (NC0B) mods a few decades ago in Ham Radio Magazine made me wonder how my Velleman audio amp would work since Bob said to be careful about lead lengths (had to be exact lengths or would oscillate). So the LM1875 audio amp was the one mod I was considering but did not want to butcher my R4C. Hope that information was helpful. Thank you. Jim Pruitt ----- Original Message ----- From: "Jim Shorney" <[EMAIL PROTECTED]> To: "DrakeList" <drakelist@www.zerobeat.net> Sent: Sunday, January 22, 2006 8:02 AM Subject: Re: [drakelist] Has anyone done the mods from the Jan-Feb 06 QEX for the R4C? > > "Jim Shorney" <[EMAIL PROTECTED]> made an utterance to the drakelist gang > ---------------------------------------------------------------------- > On Sat, 21 Jan 2006 17:57:13 -0800, Jim Pruitt wrote: > > >Has anyone on the list done any or all of the mods from the QEX Jan-Feb 06 > >article "The Harmonized R4C-A High Performance Analog HF Receiver" by VK6APH > >and VK6VZ? > > Can you briefly describe the mods? > > > -- > TR7/RV7, TR6/RV6, T4XC/R4C, L4B, NCL2000, SB104A, R390A, GT550A/RV550A - all vintage, all the time! ---------------------------------------------------------------------- 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 ----------------------------------------------------------------------
