Month: June 2017

The Philmore Fixed Crystal Detector

I was at the Manassas, Virginia hamfest on Sunday. An old timer had a box of crystals for sale. It was obviously the kind of “box of rocks” that many of us have in the shack. There was a very wide variety of crystal packages in there, perhaps the widest range of possible styles. In among the modern computer crystals and WW II FT243s, I found one from the earliest days of broadcast radio. The Philmore Fixed Crystal Detector is really just a chunk of galena with a phosphor bronze cat whisker held in place by a spring. Philmore apparently went ahead and found a “sweet spot” for you.
N2HTT was working with on of these last year: https://n2htt.net/2016/01/17/a-complete-digression/
Of course, I liked the New York City connection.

I will see if this old thing still inhales.

KM4FNQ’s FB Michigan Might Mite

Bill:

transistor: 2n2219a metal can with homemade aluminum heat sink
resistors: 27 ohm 2w 5% metal oxide; 10k ohm 1/4w 5% carbon film
polyvaricon capacitor: from an old am radio 9pf to 149pf
capacitor: 0.047uf polyester film (473)
coil: 1.25in. pill bottle with electric motor magnet wire: 0.017in.
primary: 45t, tap: 15t, secondary: 6t
crystal: hc49/u 3.57 mhz

key: momentary-on switch from radio shack going-out-of-business sale

board: fr4 1oz copper, 3inx4in

pads: me-squares from qrpme.com

dummy load: six 300 ohm 3w metal film resistors

next step: low pass filter.
73 de Ken KM4FNQ

LTSpice .asc file for the Organic Chip NE602 Rig

A link to the .asc LTSpice file for the NE602 rig appears below. Perhaps some brave soul more skilled in LTSpice than I am might want to turn this drawing into a real simulation. Some of the parts (like the NE602s) have actual simulated components behind the drawings. Others (like the relays and the LM741 and LM386) are just drawings. But go ahead and flesh this thing out. Who knows, it might come to life in the PC and start making QSOs on 40!

Here is the .asc file: http://soldersmoke.com/NE602 Rig.asc

My Organic Chip Rig with an LTSpice Schematic

CLICK ON IMAGE TO ENLARGE

This is a rig that came together through a process of Spontaneous Construction. It started out with an innocent effort to get an Organic Light Emitting Diode display to work with an Si5351/Arduino combination. Then I figured I’d make a superhet receiver with it. Then Pete said I should make it a transceiver.

Most of my earlier transceivers so closely followed the schematics of Farhan or others that it didn’t really make sense for me to prepare a new schematic. This one was different. So I decided to prepare a proper schematic. I tried a few of the free-ware CAD or drawing programs, but each of them had a learning curve at the entrance. So I turned to LTSPICE. I have already climbed that learning curve.

The results appear above. Click on the image to make it bigger. I’m sure there are errors in there. And I think some of my parts choices might be less than optimal. But it works well.

The filter was deigned with the help of AADE software.

The idea of using two NE602s with a filter between them came (I think) from the Epiphyte.

The band pass filters were designed with ELSIE software.

The RF power chain is mostly from Farhan’s BITX40 module, with the pre-driver and driver modified for a bit more gain. Farhan’s amp is the most stable power amplifier I have ever used. It hasn’t given me any trouble, even at 20 Watts. Strongly recommended.

The microphone amp is derived from the 741 op amp circuit used in the (in)famous Wee-Willy DSB rig.

The receiver AF amp also comes from Farhan’s BITX40Module.

Please let me know if you spot errors or have suggestions for circuit improvement.

A link to the .asc LTSpice file appears below. Perhaps some brave soul more skilled in LTSpice than I am might want to turn this drawing into an actual simulation. Some of the parts (like the NE602s) have actual simulated components behind the drawings. Others (like the relays and the LM741 and LM386) are just drawings. But go ahead and flesh this thing out. Who knows, it might come to life in the PC and start making QSOs on 40!

Here is the .asc file: http://soldersmoke.com/NE602 Rig.asc

KY3R’s Metalized Cigar Box Rig Enclosures

Bill,

Bob, KY3R, here. Haven’t written to you in a few years (although do manage to run into you most years at the Vienna Wireless Society hamfest ).
Anyway, was watching your visit with Farhan, and you mentioned your penchant for building projects into wooden hobby boxes, and using copper flashing for shielding. I want to share my solution.

I snatched up any old cigar boxes I come across. For shielding I use “metal repair tape.” This is the stuff used for joining or repairing dryer lint vent ducts, and it is available at any hardware store. Very lightweight, and you just cut the desired lengths, peel off the backing, and press onto the inside of the box. The only drawback is that it is aluminum and doesn’t take solder very well, but it is easy enough to add one or two short lengths of wire from the circuit ground plane to a terminal bolted down onto the case interior.

The attached photos show my current project–a Por Larranaga cigar box in the process of being converted into a home for a BitX-40! I haven’t yet fully decided exactly how to position the unit in the box, but as shown in one of the photos, it fits with plenty of room for later mods. As for other decisions, I toyed with the idea of painting or covering the outer box, but I am leasing toward leaving the original cigar box labeling. Arguably adds a bit of “soul,” plus who needs a clean panel and all that fancy stenciled lettering anyway. I’ll know which knob is which!

73, and as always, thanks to you (and Pete, of course) for your continued work on the SS podcast.
Bob Keller, KY3R