I made a couple of contacts with a relatively low power 2200 meter CW transmitter I built from a schematic at http://electronics-diy.com/electronic_schematic.php?id=1065 I could not get the power I expected out of it but I did manage to work 4 stations with the best DX of 165 miles with about 70 watts output. I decided to QRO and built a legal limit class E amplifier. See https://kb8u.home.blog/a-high-power-2200-meter-amplifier/ Now I have to get a rig to drive it that will work on digital modes and rebuild my antenna.
630 meter variometer
Last summer I built a variometer so I could adjust the match on my top loaded vertical to compensate for changes in operating frequency, ground moisture and etc. I followed the instructions at https://wg2xka.wordpress.com/the-variometer I tried to keep the Q high by leaving a little space between windings. I had to decrease the inner (rotatable) inductor size to keep from having the tuning be too critical. The Q was well over 200
I shortly afterwords added remote tuning capability. I use a small, waterproof servo motor driven by a Raspberry Pi. Abbreviated instructions for installing the code is at https://github.com/kb8u/web-servo
I had been using a 40m dipole with the coax conductors shorted together at the bottom. Since the picture was taken, I replaced the vertical radiating element (coax) with wire to lighten the antenna since it had fallen down in a big wind storm. Also, the wires to the servo proved irresistible to a rabbit (which chewed through them) so I repaired it and covered the wires with a plastic cover.
Initially it worked flawlessly, but now sometimes the servo doesn’t turn at first until I run the control back and forth. I have not yet diagnosed what’s wrong. It is exposed to the weather so covering it would probably help. For now the problem is just an annoyance.
SPE Expert 1.3K-FA amplifer on 630 meters
I happened to stumble on an amplifier made in the UK that works on 630-6 meters http://www.linamp.co.uk/gemini_HF.html
The specs say it’ll do 1KW on 1.8MHz and above, and up to 200 watts on 630 meters “with an external low pass filter”. That made me wonder if the SPE 1.3K-FA would also work on 630 meters (since it is also a power MOSFET amplifier).
I set the SPE amp for the 160 meter band, added my 630 meter diplexer filter https://kb8u.home.blog/a-diplexer-filter-for-the-icom-ic-7100/ and tried it out. On 630 meters, it has roughly the same gain as the other bands and it runs cool at 200 watts indicated output. The load resistors in my filter run cooler at that power than with the barefoot IC-7100 at 40 watts! The SWR meter in the SPE amplifier accurately indicated low SWR, and the power meter seems accurate (but I did not verify it).
I increased the drive and the maximum power I saw was about 450 watts. At that power, the amplifier temperature rose quickly, and my 8 watt diplexer load resistors would have soon burned up so I only ran it for maybe 15 seconds at that power. I can’t verify if the amplifier will run at that power without overheating. I’ll test it further once I get some larger load resistors for my diplexer.
With my antenna system, I don’t need that much power to get to 5 watts EIRP anyway. My guesstimate is 200 watts is sufficient, so I run the amplifier set to LOW power (32 volts on the drain) and the IC-7100 set to 7% output or so at it has been working fine at 200 watts output for the last week.
KB8U QRV on 630 meters
February 10, 2019
In late January 2019 I made my first contacts on the 630 meter band. I’ve been on for about 2 weeks now and have worked 22 states and two Canadian provinces. I thought I’d be lucky if I got out to 500 miles, but I’m happy to say that my expectations have been exceeded. My best DX is to Washington state (from southern Michigan).
I’m stuck on one frequency for now since my matching network is not adjustable (other than moving the loading coil closer to or farther away from the tower).
I’m using an Icom IC-7100 with an external diplexer filter of my own design to attenuate harmonics. Total power output is 13 watts. The antenna is a 40 meter dipole with the coax shorted together and fed as a marconi. The feed goes up about 120 feet from the base of the tower, where it is connected to a large loading coil and shunt inductor to get a 50 ohm match to the rig.
IC-7100 630 meter diplexer filter details
I created a page detailing the filter I made: https://kb8u.home.blog/a-diplexer-filter-for-the-icom-ic-7100/
I haven’t blown anything up yet, the radio and filter even survived me transmitting into a bad load when I discovered today that half of my dipole had fallen down and was hanging from a guy wire on the tower. I climbed the tower and fixed it even though it was below freezing and the wind was blowing. Brrrr! Next time I won’t use rope from the big box store.
KB8U ham radio 