Hi There Topband enthusiasts,
I know it's an old chestnut and I hadn't taken much notice previously up
until this year, but after I received two complaints about key clicks during
the Stew Perry Memorial Contest from G stations I took up cudgels in an
effort to reduce the width of my CW transmissions on 160m. I viewed the W8JI
website, archive info on topband@contesting.com and the information provided
by International Radio with their key click modification kit.
I felt that an easy option first would be to do the mod on the IF board
suggested by International Radio. A capacitor and resistor are placed across
a surface mount capacitor on the bottom of the IF board. A very cheap mod
but a risky business with my rather poor eyes. I did it and there was
absolutely no improvement in clicks with that mod. If anything my signal was
wider. There appeared to be extra key click sidebands created further out
than previously. So I removed the RC network and put the rig back together.
It was then I noticed my S meter wasn't working but everything else was. The
S meter on the Sub RX was fine.
I delved into Tom's (W8JI) website and decided I would go for the full
gallon. Total cost of the best available components was £3.28 UKP or $5.15
USD. That was for 3 capacitors, two multiturn miniature variable resistors
and a 4 way terminal board. I don't have the test equipment that Tom has,
so I pressed into service my standby Yaesu FT847 as a monitor receiver with
a 2" screw in the antenna socket. To simulate true transmitting conditions I
ran 20 watts of FT1000MP clicky RF into my normal topband TX antenna . The
results on my monitor Rxer before and after WERE ABSOLUTELY STAGGERING. I
also tested the click bandwidth of the FT847 as a comparison. That rig
remains unmodified and is quite acceptable. My S meter is still broken I'm
sorry to say, and Yaesu UK are giving me some pointers as to what I may have
disturbed. Suffice to say that's a minor problem that I be able to resolve,
or even pay to get resolved, but having completed this mod I can go back on
160m with confidence that my signal is clean. Thank you Tom W8JI for the
excellent guidance. In my opinion it's much less risky to solder one wire
each on the RF and IF boards and then route to a small terminal board as
suggested by Tom than to try and solder fixed components onto the boards
themselves. My results below:
FT1000MP S/No. 9C390068 Monitor Rxer Yaesu FT847 S/No.8H090447
7th January 2003 1500z 7th January 2003 1500z
TX Antenna: 3/8 inv L RX Antenna: 2" screw (RX in shack)
Power out: 20w AGC on - Bandwidth normal 2.2 KHz
Pre Mod Key Click Tests - dots at 28 wpm:
Freq: 1816.8 KHz Clean - no sigs audible on 2" screw
Freq: 1818.3 KHz Solid clicks just starting to break
up
Freq: 1825.1 KHz S1 All clicks
Freq: 1826.2 KHz S3 A little tone but mostly clicks
Freq: 1828.3 KHz Centre TX freq S7 (monitoring on FT847 in shack)
Freq: 1828.85 KHz S3 A little tone but mostly clicks
Freq: 1829.5 KHz S1 All clicks
Freq: 1836.6 KHz Solid clicks just starting to break
up
Freq: 1837.1 KHz Clean - no sigs audible on 2" screw
antenna
Pre W8JI Mod: Click Bandwidth on shack monitor FT847 = 20.3 KHz
======================================================
FT1000MP S/No. 9C390068 Monitor Rxer Yaesu FT847 S/No.8H090447
8th January 2003 2100z 8th January 2003 2100z
Antenna: 3/8 inv L Antenna: 2" screw (RX in shack)
Power out: 20w AGC on - Bandwidth normal 2.2 KHz
Post Mod Key Click Tests - dots at 28 wpm:
Freq: 1824.5 KHz Clean - no sigs audible on 2" screw
Freq: 1825.9 KHz S1 Tone no clicks
Freq: 1826.4 KHz S3 Tone no clicks
Freq: 1828.3 KHz Centre TX freq S7 (monitoring on FT847 in shack)
Freq: 1828.7 KHz S3 Tone no clicks
Freq: 1828.8 KHz S1 Tone no clicks
Freq: 1829.0 KHz Clean - no sigs audible on 2"screw
antenna
Post W8JI Mod: Click bandwidth on shack monitor FT847 = < 4.5 KHz
====================================================
Extra Click Tests on monitor transceiver FT847:
Yaesu FT847 S/No. 8H090447 Monitor Sub RX FT1000MP S/No.9C390068
7th January 2003 1600z 7th January 2003 1600z
Antenna: 3/8 inv L Antenna: 2" screw
Power out: 20w AGC on - Bandwidth normal 2.4 KHz
Key Click Tests dots at 28 wpm:
Freq: 1823.6 First freq LF when clicks are gone
Freq: 1825.3 S1 A little tone mostly clicks
Freq: 1825.4 S3 Mostly tone Freq: 1828.3
Centre TX freq S7 (Monitoring on FT1000MP above)
Freq: 1829.4 S3 All clicks
Freq: 1829.7 S1 All Clicks
Freq: 1831.7 First freq HF when clicks are gone
Click Bandwidth of unmodified FT847 = 8.1 KHz
====================================================
We got a result - pre mod the FT1000MP was twice as nasty for key clicks
than the FT847. Post mod the FT1000MP is now twice as nice as the FT847.
Many thanks to Tom W8JI for doing all the technical spadework, providing
his website and helping me make this mod an undoubted success.
I just hope that the keying now isn't too soft, but if it is I can just
adjust it with the variable resistors!
I hope manufacturers realise the importance of CW signal bandwidth. I had
the same problem with an FT107M in 1984, but couldn't improve
it despite various mods so I ended up selling it on. So I have to say, it
doesn't look like things will change in the short term.
73 and Good DX
Phil Catterall G4OBK
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