Back in September/October 2010 timeframe, I was looking to start working satellites after making contact with the International Space Station (ISS) from the car. I would end up buying a Yaesu 5400B az/el rotor, Tracking system, M2 2m circular polarized antenna and sell my Icom 746 for a Yaesu FT-847. I was set, or so I thought.

I would go on to burn out the motor twice on the 5400B rotor, with the already $1200 investment I had in the project, I would need to add an additional $900 on a 440 circular polarized antenna, and pre-amps for both. Needless to say what’s left was the 847, 2m antenna and tracking system, which most likely would go on ebay.

Recently I started getting back into digital modes, RTTY, PSK and CW and found that the 847 was quite sloppy on the receive side when trying to get selective on the station you are trying to work. With some research, I found the 847 itself had a 2.7k receive filter which was used on both SSB and CW. Quite wide for work below 170hz wide and nearby stations would end up desensing the receive causing the intended station to merely disappear.

What to do? Add filters of course! I opted to go with a different radio instead, and I’ll tell you why.

I’ve read a number of reviews about filter options for the radio including this one, which gave me hope of increasing the receive performance of the 847, although there is a fairly major flaw with the way Yaesu designed this rig. The filter that is already in place is a 2.7k and it is on full time. If I were to replace that with a 2.1 or 1.8, that would be fine for SSB phone work. Same thing with CW, drop a 250hz INRAD in the second slot and CW performance would most likely be spectacular. But what about PSK and RTTY? Both as SSB modes. Unlike the 746, there is no menu setting that I can change that would use a CW filter for SSB digital modes.

If I were to then replace the 2.7k filter with a 250hz filter for use on RTTY or PSK, the radio would then be useless for SSB Phone, because that filter would be on full time. Not exactly flexible in that respect.

So the thought was to replace this rig with a Kenwood TS-480HX and have it serve in the shack on a temporary basis, until I acquire a Flex 3000. The 480 would then go in the mobile in place of the 706 which came into the shack on the YL’s desk during the last PA QSO party.
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On my particular rig when I enable noise reduction (NR) I tend to get a fair amount of ringing in the filter, an artifact of the older DSP technology. In addition to that Icom’s PBT (PassBand Tuning) only goes so far. My 1900hz filter in the rig could clean up the IF stage of the receiver, but I needed something more to make QRM filled receive audio more tolerable. I also started thinking about the possibilities with RTTY and PSK31.

After listening to Idiom Press’ audio samples on SSB phone and CW, I was sold. I decided to go with the kit form to save a few bucks and experience the challenge of building a kit. Since my last kit (D-Star hotspot) was a success, I was up for the challenge. $90 and 3 days later the kit arrived.

The included instructions were very clear and very consise and the kit assembled exactly like they had stated. One issue I encountered was wrong resistor (miscount). Where I required a 3rd 10k ohm, I had a 100 ohm. No biggie, nothing that I can’t get at my local Radio Shack. Thankfully mine still sells common electronic components. The other issue was trying to figure out the pin ID on the DPDT switch. Unfortunately I soldered mine backwards and the switch is keyed to install in only one direction. All this really means is the UP position is OFF and DOWN is ON. Again, no big deal.

I had most of the kit assembled in the course of 3 hours while I was carrying participating in my usual 8PM net on 1900khz. Today I was able to pickup the remaining resistors and also some audio cables to interface it into my rig setup. I decided to place it between the AF output of the radio (accessory audio output) and the rig audio input of my Rigblaster. This way I could utilize it for digital modes on the computer, which is a direct feed to my monitor speakers. The filter has 2 audio outputs, one for headphones and external speaker audio. The kit gives you the luxury of choosing which size jack 1/4 or 1/8 inch you wish for either function as well as if you want stereo or mono. Since it’s ham radio and the most audio bandwidth I’ll ever hear (from a properly tuned transmitter) is 6khz (on AM), I decided to go mono for both.

Upon powering up the filter for the first time, I was happy to hear the exact results I had heard on their website as well as nothing blowing up (reverse polarity electrolytic capacitors become missiles). The instructions call for you to adjust the internal potentiometer, but I had found the audio to be consistent with it set to the middle.

Check out the photos below and also take a look at the audio spectrum I had captured with the filter in line as well as out.

So far I’m happy with the results and look forward to using it during contests and busy digital waterfalls.
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First I started with G1TLH’s download documentation. It references a file named usdbraw.gz which was unfortunately unavailable at the time. After a brief google search, I found the file, expecting it to only contain states and cities, but instead it IS the US FCC callsign database. The newest one I found was from 2004. Importing this database would make state filtering spuratic at best since so many new callsigns have been issued in the US of the course of the last 5 years and DXspider would only filter callsigns it knew about.

The FCC provides a daily updated database archive on their site available for download. Their database structure by itself is not compatible with DXspider and requires massaging of the data to ready it for import.

A huge find in this process was G1TLH’s USDB generation script. Dirk’s script takes the compressed FCC archive and converts it into DXspider format which happens to be output as usdbraw.gz.

Taken that process, then reverting back to the download documentation, then importing the database renders a newly up-to-date reference to apply state filters against.

This is great, but new callsigns are generated daily and I wanted to keep DXspider as up-to-date as possible with little to no administrative intervention from me. Introduce a little scripting and the use of cron.

My shell scripting skills a disasterous at best but it does function as advertised. I named my script usdb-update.sh and wrote it in /spider/local_cmds. It seemed to be the most obvious place for it at the time. Now let’s step through the script:

#!/bin/sh
SPIDERDATA=/spider/data
SPIDERPERL=/spider/perl

wget -P $SPIDERDATA http://wireless.fcc.gov/uls/data/complete/l_amat.zip

$SPIDERPERL/gen_usdb_data.pl $SPIDERDATA/l_amat.zip

$SPIDERPERL/create_usdb.pl $SPIDERDATA/usdbraw.gz

rm $SPIDERDATA/l_amat.zip
rm $SPIDERDATA/usdbraw.gz

At this point if all has gone swimmingly you have the US callsign database waiting for you in DXspider. We now have to load it to make it available to our cluster users.

Telnet to your cluster, login as your privileged callsign and load the database:
load/usdb

30 5 * * * run_cmd('load/usdb')
So my cron entry above executes the command load/usdb within the cluster environment every day at 5:30AM GMT.

Since the previous cron entry only works within the cluster environment, I need to execute the data collection process external to DXspider.

[sysop@dxspider1 ~]$ crontab -e
Append the following entry into the sysop user’s crontab
00 5 * * * /spider/local_cmd/usdb-update.sh

I’ve decided to run the usdb-update.sh we detailed earlier at 5:00AM GMT. In practice I’ve found the data collection and processing only took 5 minutes so to execute the actual load of the database in DXspider 30 minutes later was plenty of time. This allows for internet or server slowness. Feel free to set these times however it suits your needs.

Below are the files I’ve referenced in the above documentation:
G1TLH’s gen_usdb_data Perl script and my data collection script

usdbraw.gz created 12/23/09