Construction Activities


John H. Bryant <bjohnorcas@...>
 

I've finally finished the tile work and most of the rest of my home projects and I've been able to spend the last few days on Ultralight construction projects.

The first effort was to create the final dial for the National SRF-39 Table Model. I spent about a day on this using a signal generator for both the Western Hemisphere and Eastern dials. I spotted individual frequencies below 1000 and did each 50 kHz or so above... then interpolating. The FM dial was strictly listening, recording known frequencies and then SWAGing the dots on that dial.  I'm really pleased with the results. I can read the dial to the 9/10 KHz below 1000 with full confidence and can usually guess correctly above. I'm not sure just how much I'll even use this set to DX, but I've always wanted to make something like this. It was even more fun than I expected.  The radiating station names are on there just for decoration, tho' they also represent a decent hit list for me from the Northwest. Most of us have always loved the old radios with city or country names on the dial. I'm certainly no exception.


I also put together two identical cabinets from specimen wood. One, from 60 year old recycled Arkansas walnut, houses the radio. A second of identical dimensions is a speaker enclosure. I was originally going to house a small stereo amp and speakers cannibalized from an Ipod dock... to provide speaker-level volume for the SRF-39 and for my mp3 player, etc. However, despite Nick's good technical counsel, I managed to burn that little amp out immediately.  Since the unit cost me almost nothing and I managed to salvage the four little speakers, it wasn't a total disaster.  I eventually did a search on line and found Canakit in suburban Vancouver that makes a wonderful line of kits and assembled units. A "Walkman" stereo amp, 5 watts per channel, is on its way to me now. The speaker unit cabinet, out of salvaged tropical hardwood similar to ebony, will have the four little speakers in the front panel along with stereo controls, a power switch and a switch to throw the stereo output either to those four little speakers or out the back to a pair of outboard larger stereo speakers.  As soon as I get the stereo amp (late next week) installed, I'll post photos of both units.... I'm really pleased with how they both look and what testing I've done with the National SRF-39 hooked up to serious antennas, it looks to be an excellent DX receiver.

I had completed modifying my Sangean DT-200VX to accept an outside antenna a couple of weeks ago, but I'd delayed writing the article until I had the time and found the nerve to tackle the Eton E100  for a similar mod. You might remember that I'd gotten the back case off the e100 and been unable to go further in disassembling the radio.... I lost my nerve and tiptoed back out of the radio. Well, after a lot of thought and some more study of the interior photos posted on line by HongKongRadioer, I restarted the E100 project this morning. I had guessed correctly and things went reasonably well. If you know how, taking the radio apart is really not bad at all. Its a shame that Eton does not make Technical Manuals available. I took good pictures and will write up the disassembly instructions in the next day or two.

Installing an external antenna port inside the e100  case proved impossible with this tightly packed radio, but I was able to install a "PC board-type" phone jack mounted on the upper edge of the outside of the case.  This leads inside to the typical pick-up coil wrapped around the stock ferrite bar antenna. I've not had a chance to test this unit much, but it seems to work well on an outside antenna on at least the upper half of the dial. There seemed to be less sensitivity than I expected below 600 KHz. Also, when I briefly tried it late this afternoon, I noticed some overloading from my local daytimer (1 mile away), so I'm only cautiously optimistic about  performance of the e100 with an outside antenna. 

I did notice, though, that the e100 is PERFECT for a transplant of a larger rod. The coil on the stock ferrite bar is a simple single coil with connections only to each end of the coil (no center tap, etc.) The two solder points for the antenna coil are right in front of you as you open the back of the case.  It would be simplicity itself to unsolder the two wires from the board and solder in cabling to an appropriately sized coil on a much larger bar, outboard to the case... the Transplant strategy that Gary DeBock is pioneering.

Well, as you can see, I've been having loads of fun getting ready to return to the DX beaches of the NW. I'll upload that e100 disassembly information Monday.

Hope Gary DeB does only moderately well in his Grayland  visit :>)   

John B.
Stillwater, Oklahoma, USA
Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods)
Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version)