Monday, July 30, 2007

Antennas, etc...

I bought one of these antennas on eBay for $20, reasoning that it was cheap enough to take a chance, and if it works it would serve as a travel/portable/emergency HF antenna for my KX1 - and, short-term at least, as the main antenna at the house. The seller, Bell Imel Group LLC, says:
This system requires NO GROUND and NO COUNTERPOISE. It only requires a minimum of one support and it can be configured for vertical polarization, horizontal polarization and NVIS operations. It tunes from 40 meters to 10 meters using an internal tuner on your rig or an external tuner.
Sounds good to me.

It arrived by Priority Mail in about a week. Upon first inspection it looks like a 50 ft. length of zip cord with one of the twin-leads cut at the halfway point. It terminates in a BNC connector.

First test was to hang it from a hook off my deck, running it along the front of the house, around the corner and through the door into the shack. In this configuration the KX1 tunes it up fairly well on 20m (3.1 SWR) but SWR is pretty high (9.9) on 40m (as measured by the KXAT1, which may or may not be calibrated correctly..); I'm hoping both of these figures will improve if I get it up high and in the clear, and away from the side of the house. On receive, the antenna works quite well. And quiet - even with the plasma TV on there was less broadband noise than I typically encounter with a random wire or the Jeep-mounted verticals (Outbacker and mono-band hamsticks). So in all, it's $20 well spent.

The only question is: What exactly is it? A J-Pole ? A Zepp? Damned if I know. I can't find any similar antenna design on the web or in any antenna books in the shack. From what I can tell it doesn't seem to be cut for any particular frequency as it requires a tuner to match it to 50 ohms. But it appears to work.

Some links regarding end-fed wire antennas:
While in antenna mode I took some time to properly attach the TerraFlex mounting brackets on the Jeep, drilling through the transom and bolting them firmly to the body. While doing this I had a close look at the HF connector and found it to be pretty much shot. I originally salvaged this from a 3-magnet mount that was on my old SE-R; I guess I got my money's worth out of it, but it's time for something new - the High Sierra Sidekick is the #1 candidate to replace the Outbacker.

Until then, I bought a new 3/8-in-to-SO239 mounting stud and installed it along with a short grounding wire from the underside of the stud to one of the screws which hold the door latch thingy. Now I can tune the 40m hamstick to under 2:1 - without the ground wire the antenna was a basket case, reaching 50 ohm resistance down around 6.2 MHZ with an SWR dip a bit lower. I adjusted the whip for lowest SWR in the CW portion of the band. So now I have at least one antenna that loads up properly. The JST-245 has no problem matching it even up in the phone segment. Of course it's still about 8 ft. away from the plasma TV, so not much use until the living room is shut down for the night. Been too hot and sticky to do anything with the hamsticks for the other bands, but the Outbacker, once cleaned up, loads up nicely on all bands except for 10m. The JST-245 is getting some use now; might try some RTTY next chance I get.

With the mobile antennas out of the way, I relocated the end-fed wire antenna to the back of the house, running it out the bedroom window and along the side of the house - still not in the clear, but it works well enough for me to SWL and practice my CW at night with the KX1 before I fade. I'm still too chickenshit to actually attempt a QSO, though I'm finding myself on occasion able to copy CW without realizing that I'm copying it, a sure sign that it's starting to stick. I did some tuning during the IOTA contest this past weekend and was able to copy some of the higher-speed QSOs - but contest QSOs are relatively easy because they're predictable.

The KX1 has turned out to be a real pisser of a radio; despite crappy band conditions and RFI I've had lots of fun tuning around and getting to know all the menu-driven features to the point where I can operate the rig without the manual. I'm hearing a lot of stations in the midwest and south during my midnight tuning sessions, plus the occasional European.

Monday, July 16, 2007

Elecraft KX1: Building the KXAT1 Automatic Antenna Tuner

This was an easy job, taking but a few hours. Once again I am at a standstill regarding calibration until I get a dummy load and a resonant antenna, but I tried it out on the 40m hamstick and it seemed to handle a mismatch of around 9:1 without giving any error message or releasing any smoke.

I'm not sure what all the hand-wringing over winding toroids is about; after reading the Elecraft reflector all these months I was expecting this to be a difficult, painstaking process that would surely end in disaster. Not so, this went smoothly for me during both the KX1 and KXAT1 builds.

So now two of the three major components are done, only the 80m/30m kit left unbuilt. I will give that a go maybe next weekend. An end-fed dipole antenna is on the way, so I will hopefully have the chance to make first QSO soon. Meanwhile, I'm listening as much as can and my CW skills are steadily improving. Who knows, maybe I'll be contest-ready by the time CQWW rolls around...

Elecraft KX1: Assembly Parts II & III, Final Assembly and Initial Tests

The second part of the assembly process (receiver section) was completed over the course of two days - I spent a couple of hours on Wednesday night installing the resistors and inductors, and completed the section early Friday evening. I probably spent more time looking at the the inductors under a magnifying glass to make certain I was reading the color bands correctly (did I mention color blindness sucks?). Apparently I did OK, because all of the tests and check at the end of Part II were satisfactory and, upon firing the radio up with a DMM probe stuck in the BNC connector as an antenna, I was able to copy CW signals on both 40m and 20m bands!

Since it was still early, I decided to proceed with Part III, the transmitter section and final assembly. This all went smoothly and quickly, and by 2am I was finished mounting the board in the case and sticking the rubber feet on the bottom. I proudly present Elecraft KX1 S#1763:

I still need to perform the final transmitter tests once I get my hands on a dummy load (the Elecraft DL1, perhaps). For shits and giggles I attached my Diamond RH77 VHF/UHF rubber ducky and tuned around on Saturday night during the IARU HF contest and was able to copy a bunch of stations, though not well enough to hear both sides of any QSO. On Sunday I tested it briefly with the Datong AD-270 active antenna that has been in the attic in Closter since forever, that seemed to work though the receiver gain was still not what I hoped it would be - had to turn AF gain nearly full, and thus got lots of hiss.

This morning I tried it in the Jeep with a 40m hamstick and the Outbacker set for 20m. Both antennas are poorly tuned, probably because of the lack of adequate grounding on the mount. Not much to be heard on 40 other than the growls from the plasma TV which is about 10 ft. from the antenna. Also noted what seemed to be lower gain on 20m. But again, this may be more an indicator of how poor my antenna systems are than anything else; I had to use a PL-259-to-BNC adapter which is of questionable quality. More tests to follow...

Saturday, July 7, 2007

Elecraft KX1: Assembly Part 1

So after 3 months, I decided it was time to melt solder.

The first step of assembly - the control circuitry - was completed in about 5 hours. This included about a half-hour of measuring all of the resistors with the DMM, taping them to the inside of the cardboard box, and penciling in their resistance values; color blindness sucks.

The Hakko 936-12 soldering station worked very well, but the Kester .020" solder I bought didn't flow - it just balled up on the end of the iron - because (I found out later) I bought 'No Flux' solder. I wondered why it was so cheap... I found some old, thicker Radio Shack solder that I had in the junk box and used it as carefully and sparingly as I could, mindful of numerous warnings about the hazards of using excessive amounts of solder. The PanaVise circuit board holder is the best thing since peanut butter, I can't believe I worked without one in the past.

The KX1 passed all tests at the end of Part 1 - all voltages were within spec, the unit powered up, the white LED lit, everything that was supposed to work seemed to work.

First Component

WW2PT Advanced Resistor Identification System (patent pending).

Instant Electronics Lab - Just Add Clutter.