This is the homepage of Lars Thunberg in Sollentuna, Sweden. Amateur radio callsign SM0TGU e-mail lars(at)larsthunberg.se For information about my satellites and amateur radio activity please see this page where most of the info are in english. Also see all the posts about amateur radio or use the web page search .
Step by step for changing the mainboard of a Rot2Prog rotor controller. Time aprox. 20 minutes.
First of all – remember to point your antenna to Azi = 0 degree and Ele = o degree! If anything goes wrong you know 100% where your antenna is pointing.
Remove the top cover and then the old mainboard (see red markings)
Carefully move the PROM from the old mainboard to the new one
Lift up the old mainboard
Lift up the cables marked in red from the old mainboard in place it at the same location on the new mainboard
Place the new mainboard in the metal enclosure and align in so all the push buttons on the front is working. Tighten the board screws and then mount the top cover.
I have been looking for a headset for my IC-9700 and read that many are very pleased with the Koss SB-45 (SB/45) PC headset with electret microphone element.
I got one for 20 EUR via the Swedish eBay site Tradera. I made a DIY adapter for the Icom standard 8-pin Mic connector – just connected pin 7 ”Mic ground” and pin 1 ”Mic input” to a 3.5mm female connector.
8 pin MIC adapter DIY
This is the pinout for the Icom 8 pin connector:
Icom Mic pinout
Here are some very short audio samples – first with the standard Icom mic and the second with the Koss SB-45. I’m using USB and maybe not exactly on the correct frequency when I did the recordings:
Icom HM-219 original micKoss SB-45 controlled with VOX
When my End Fed Half Wave antenna wire broke I decided to try a new type of HF antenna. I google and many seen happy with the Skyloop (or Deltaloop) antenna so I decided to try that type. I will not go into detail about this antenna, there are tons of articles on Internet – just google and read. My primary source of info for my constructions is from this page at HF-Kits.
The antenna feedpoint is as below. You can also see the MFJ RT-100 remote antenna tuner I’m using. This is needed as the loop only has 50 ohm at 3.5 MHz and 7 MHz without use of 2:1 balun (see the SWR charts below). I’m not sure about the exact length of the wire for the loop, around 84 meter.
It was not possible to tune the WARC bands with this setup so in the next installation I used a 2:1 balun.
Second installation – with 2:1 balun and no Choke
In order to be able to work the WARC band (with my MFJ tuner) I decided to try a 2:1 balun. Balun design can be found at many sites but I used this one:
And in the box:
I skipped the Choke balun this time to see if it should work anyway as I’m only working max 10 watts. I can not see any RF problems without the RF Choke. Below in the SWR graphs you can see the result.
SWR measurements
At antenna feedpoint, without Choke balun. I didn’t need to cut the antenna wire much to get a good match. Strange to see the good SWR at 3.5 and 7 MHz, as the loop has 100 ohm impedance.
Without 2:1 balun, only Choke
Next, with first version of 2:1 balun, antenna has the same length. You can see the much better SWR but the antenna is tuned a little low in frequency. At 3.5 MHz the SWR is now higher but better at all other frequency.
First test with balun
Below is the result after the balun is mounted in enclosure and antenna wire is cut/tuned a little. It is very good for 40m, 20m, 15m band and OK for 10m low end of band. 80m and WARC bands can be tuned with the remote tuner, that was not possible before without balun.
With this setup, the loop antenna can be used without tuner on several bands if needed.
Final version with balun and trimmed wire
Results and performance
I’m very happy with the result of this antenna! I have not been able to compare with my End Fed Half Wave (EFHW) antenna, so I can not back up my ”feelings” of the antenna result with actual numbers and facts. What I see when running FT8 and looking at PskReporter is:
My signal is heard at the same distance as I can receive, that was not possible with the EFHW antenna.
Received and sent signal reports are more equal now compared to the EFHW antenna.
I you have space for this antenna I highly recommend it. A 7 MHz version is just half the size of the 3.5 MHz version. It can be a little tricky to set up as four (or three for Delta Loop) support points are needed. Also, I recommend to use a 2:1 balun. In my case, the Choke balun was not needed.
Some initial results from PskReporter FT8 and WSPR with the second version with balun:
First 5 minutes with the antenna, 2:1 balun – 10 MHz FT8 with 8 watts. I was heard in VK.WSPR over 24h, aprox. 200 mW. 433 unique spotters heard my signal. No VK this time…30 min FT8 40m to 10m at 16:00 UTC. Some TX on 30m (10 MHz), as you can see my signal heard in VK.Same evening, 30 minutes CQ with FT8 on 20m (14 MHz).