Gene, Thank you very much for the time you took to share your experiences.
I apologize for the poorly framed question... kind of like "what kind of car is best?".... :-) My applications for this rig will be CW DXing, and since I've got two stations, I can dedicate one to be tweaked (if appropriate) for that application. I'm not one to change, just for the sake of modding ... in fact I generally leave older rigs original, as so many ham "improvements" aren't. I think some or all of the Sherwood mods stand the test of time, and do not fall into that category. The rig I've been thinking of allocating for this purpose is a very nice original w/Drake 500kc filter, and works well. I'm going to go study your response some, and think on this (along with pulling out Drakemods and reading that discussion again). Thanks once again for getting me such good information. 73 John K5MO At 02:41 PM 9/19/04 -0500, Gene McCalmont wrote: > >Hello John; >Your post caught my eye this afternoon, so I thought I'd share my experience >with you while the Redskins get trounced by the Giants in the background. > >The first question you should ask yourself is "What do I intend to do with >this once I'm finished?" > >Not all of the modifications from Sherwood are needed if you intend to >operate only CW or only SSB or listen only to AM. Also, I'd ask "What is >reasonable for me to spend?" A "full boat" R-4C can be an expensive >proposition. I know, I've built 6 of these machines for myself and for >others. They are remarkable receivers and perform very well when compared >with more modern rigs. > >I'd also ask myself "what level of performance do I expect?" That is to say, >a R-4C with the appropriate 2nd IF filters and the installation of the >"GUF-1" upgrade 1st IF filter from INRAD, produces an excellent receiver >with not a lot of investment. I'd suggest the 6Khz crystal filter if your >operation is mostly CW/SSB. If you use your radio to listen to SW broadcast, >then the 8Khz filter would be a better choice. If you have installed the >4NB, then the 8Khz filter is again your best choice. It allows the noise >blanker to perform it's job better, with less pumping of the AGC. > >One of the most popular and biggest bang for the buck mods from Sherwood is >the upgrade power supply board and the R-4C audio amplifier, AMP-4. These >modifications solve two of the most annoying problems of the rig. The >Sherwood web site explains the upgrades in good detail. These mods are >relatively easy to perform and your cash outlay is less than $100. >Everything gets progressively more complex and expensive from this point >onward. > >I almost always replace the diode product detector in an upgraded RC-4 with >the Sherwood PD-4. It gives the receiver improved headroom in the presence >of strong signals. It's more difficult to install, in my opinion, but still >well within the capability of most Hams. You must pay close attention to the >instructions and be able to identify various components on the Drake factory >circuit boards. > >The MIX-4 is the last upgrade I do, but only when the particular R-4C I'm >working on is having problems in this area. A problematic 3rd mixer presents >a noticeable hum in the audio and the typical "snap crackle pop" of a noisy >6EJ7. It is one of the more difficult mods to install. Since 6EJ7s are cheap >and plentiful, I first try to find a tube that will solve the problem before >resorting to the MIX-4 upgrade. > >Last but certainly not least are the first IF crystal filter upgrades. This >is where you are going to spend a lot of money but the results are very >dramatic. If operating CW exclusively, or just "a lot", the 600hz crystal >filter will DRAMATICALLY improve the receiver's ability to isolate >individual signals and gives the CW operator a truly superior machine. It is >difficult to describe how unwanted signals just disappear when the 600Hz is >switched into the IF chain. > >The upper and lower SSB filters dramatically improve the receivers 3rd order >intercept performance with a resultant improvement in MDS in crowded band >conditions. There are few receivers that offer the kind of performance these >filters bring to the R-4C. The "roofing" filter approach is one of the >reasons the TenTec Orion has won such acclaim for it's performance. However, >installation of the filters and attendant switching circuits is not for the >faint of heart. > >I hope this information helps out some, John. Perhaps others have differing >opinions worth considering. > >Best regards; >Gene > >W5DDW >Gene McCalmont >270 Oak Ridge Ln. >Argyle Texas 76226 > > > >--- > >Checked by AVG anti-virus system (http://www.grisoft.com). >Version: 6.0.727 / Virus Database: 482 - Release Date: 7/26/04 >
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