Class D 600 Watt Topband Amplifier Mods

After some tests on Topband a few modifications were made. The 40A bridge rectifier failed and was replaced with 50A one mounted on a better heatsink, the problem appears to be the ability to handle the peak repetitive forward current charging the 30mfarrad capacitors -the specs for the rectifier don't show this value - only average forward current i.e. 50A. A front panel transmit/receive switch was also fitted to replace (temporarily) the control from the FT817. The FT817 transmit control line currently does not provide sufficient delay (pretty sure it can be programmed for sufficient lead-in) to ensure the antenna relay is properly made before the amp delivers full power. The final mod was to the microwave oven step/slow start protection circuit. Instead of a 22 ohm series resistor limiting the primary current, the two 50 ohm resistors were connected in series giving 100 ohms which limits the primary inrush current to 2.4 amps (24 amps in the secondary). The protection relay timing capacitor was also increased from 50 microfarrad to 250 microfarrad.

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FT 817 Power Amplifier

This very simple 2 Fet power amplifier easily achieves 250W output with an FT817 5W drive. The key design details as follows: 3:1 broadband input transformer matches the 5.5 ohm gate load resistor (4 x 22 ohms in parallel) to the 50 ohms required by the FT817 . The 4:1 output broadband transformer presents 3 ohms (16:1 impedance ratio) to the balanced HEXFET pair each mounted on a 3mm copper heat spreader which is insulated from the 2 1w/degC heatsinks. These are blown cool by a fan underneath. The power supply required is 28v at 30 amps. The amp is around 50% efficient with a standing 750mAmp temperature compensated bias. An IC 703, with 10watts output will drive the output to around 400 watts. The output filter shown is a 5 pole topband filter with T130-2 torroids and 400v silver mica caps. Peak output voltage on 160 metres with 5 watts drive is 160v or 320v p-p in 50 ohms equating to 250watts. This is slightly higher than the reading on the 3kw MFJ power meter. The inline F...

Splunk Cheat Sheet (Linux)

1. set root's password: sudo su passwd root Enter new UNIX password: < new_root_password > Retype new UNIX password: < new_root_password > passwd: password updated successfully # su - 2. Remove any existing Splunk directories & create user etc: # rm -rf /opt/splunkforwarder # userdel -r splunk # this will remove as above if user splunk's home directory # groupadd siem # useradd -g siem -s /bin/bash -d /home/siem -m siem # vi ~/.profile # chage -I -1 -m -0 -M -99999 -E -1 siem If above fails because of multiple passwd fails: # pam_tally --reset check with #chage -l siem # uname -a # check OS version # dpkg -i splunk-4.3.1...........intel.deb # chown -R siem:siem /opt/splunk # su - siem : $SPLUNK_HOME/bin/splunk start --accept-license : $SPLUNK_HOME/bin/splunk edit user admin -password newpassword -role admin -auth admin:changeme 3. vi ~/.profile (as follows) (OR .bash_profile) # ~/.profile: executed by the command interpreter for log...

Beautiful Soup HTML parsing The following Python code fetches the specific windspeed web page and extracts the timestamp, average windspeed, direction, gust speed and writes out data to a date stamped file named say /home/user/wind_data/windspeed_date(2015-04-21-12).txt. Schedule a cron job to run this every day at midnight say. The windspeed file can be selected for a particular day and processed by graph.py. #!/usr/bin/python import os import requests import time from bs4 import BeautifulSoup date_stamp = time.strftime('%Y-%m-%d-%H',(time.localtime(time.time()))) outfile = os.path.join(os.path.expanduser('~'), 'wind_data', "windspeed_%s.txt"%date_stamp) f = open(outfile,'w') list = [] r = requests.get("http://xxxxx.wwww.yyyyy") soup = BeautifulSoup(r.content) table = soup.find("table", {"id":"grid"}) for line in table.findAll('tr'): for l in line.findAll('td'): ...

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