Signal Intelligibility and CW key-click problem

*** B. Amateur radio and related equipment ***

FT-902 with
Transverter selector
RX antenna patch
2m transverter
136kH converter

The KEY-CLICK Problem.
If you are care for other operators, the first thing to do is to make sure that your transmitter is OK, the
worst problem is the KEY-CLICK problem. Many plastic radio operators believe they have the right
to transmit whatever they want if they use the latest junk on the marked. If you are among those lids, don't
read further, the following information is not meant for you, in opposite case see what W8JI writes on
or for FT1000

SM5BSZ has also provided some material on the problem, but did not show how to solve it
in practice according to his theory. We had some dissagreement in early 80's and I went to my
lecturer who made the maths in his xmas holidays. Have a handwritten paper for ASK and FSK
(Amplitude shift keying and frequency shift keying), but it is in Norwegian - although the formulas
may not be in a particular language.......

If you understand the problem, you only need to add some capacitors - and in some cases - resistors,
to reduce the problem dramatically.Often manufacturers like Yaesu are aware of the problem, and they
have taken steps to avoid it without knowing that have increased the problem instead of improving
(FT-7/FT-221/FT-225). Almost as bad as not having proper time constants in the keyed circuits,
is when you have different time constants in two or more keyed stages. Very simple mathematics
is needed to understand time constants, and the key-on/off threshold levels are also important
to understand. This means that you cannot key a stage very far beyond cutoff and expect to
have proper timeconstant in this and that it follows another circuit, the keying may sound bad with
poor intelligibility of the signal.

CW key-filter specifications.
W8JI writes: The ARRL recommends a 5 mS rise and 5 mS fall time for CW, based on data in section 2.202 of FCC
rules and CCIR Radio regulations. But this is only a simplified version. The 5milli-second timedelay applies to a
first order low-pass-filter which is a very poor, but satisfactory mean to avoid key-clicks. You may just as well use
a 500Hz third order low passfilter using some stages of semiconductors or simplified with op-amps and
CMOS-devices. I've got good reports from local OPS using this, and the transmitter is also capable of transmitting
2000LPM (400 WPM) morse without too much distortion. I worked UA1ZCL on 2m (2000km) on cw
meteorscatter and other with this speed, but now such speed is regarded as slow.

The importance of Signal intelligibility
LA4O club should operate LA1X at an exhibition in Oslo in 68. We had got the latest Japanese rubbish
on the marked, but nobody cared to approach the stand. It was an obvious demonstration of operation for
certain strange persons and the public avoided us. So Gudmund, LA2DL understood that something was
going really wrong. He got home and collected his own Drake TR-4 rig and later installed it at the stand.
And just as we had removed the Japanese junk and installed the Drake rig, the stand caught considerable
interest, now the public suddenly understood that what was going on on amateur bands was conversations
which everybody could cope with. LA2DL's initiative was important and after this I was even more
critical to improper designed rigs. Still sometimes I hear somebody comment that
"don't know about the receiver, but the transmitter is good". So, for a period I accepted only Drake equipment
for the good intelligibility from the receiver sound, got the 2-B in december 68, TR-4 in 74, and R-4C in 76,
and another 2-B in 77, but some Japanese equipment has been useful, and I've also learnt how to improve the
sickness, which is usually caused by improper AGC time constants and in two occasions, improper product
detector, but quite simple modifications - when you learnt what was to remove or add. Have therefore
kept FT-7 since 82, FT-902 since 88, IC202 since 85, had Trio TR7010 and Sommerkamp FL-dx-500 for
a period of time until they were donated to some friends.

Old YAESU rigs
The first and most important point to mention for such old rigs using edge-contacts on the PCBs, is
that the rig starts to fail after 15-20 years. I had some intermittent frequency stability problems in FT-902,
and believed it was the 6V regulator. This was modified and worked fine for some years. OZ1HDA has the
same problem with his FT-901. Got a tip from a service-man, he said it was important to clean the edge-
contacts with iso-propanol (blue windscreen washer liquid works fine), use a brush and cover the contacts
with a very thin layer of vaseline afterwords. It solved all my problems with FT-902, and it is still my main
transceiver, operating with it on HF as well as VHF/UHF with different SSB transverters.
FT-101B, FT-221, FT-225 has some serious problems which seem impossible to solve.
The carrier oscillator spreads signals through the receiver, and you will see that if you
remove the carrier connections to the product detector it will still demodulate SSB.
I spent a week trying to solve this for FT-221, and reduced the problem somewhat,
but not by far as much it was needed. Spent also several weeks with FT-101B, it
is totally impossible to build IF-derived AGC detectors for this, so I used it only as
transmitter with Drake R-4C receiver. FT-7 and FT-902 have not this kind of problems.

see page B.52 for FT200/FT250

I hate VOX, and it is disabled on all my equipment (now FT-7, FT-901 and FT-902). Believe it might
work in some equipment, but not in the rigs I have, so it is possible to use the available front controls
for some better purposes, like CW drive level control, SSB-squelch (AGC derived) and other

The ideal key filter is shown here. But application of this is only possible when you build the
transmitter yourself, normally you cannot decide to have the so easy task......

Se forøvrig følgende artikler om Yaesu/Sommerkamp utstyr:
FL-DX-500 Ombyging av sender                  LA8AK  QTC 87-12-530
FL-DX-400/500 Forbedringer  +150V REG         LA8AK  AR  75-01-008
FL-dx-500 på 30m bandet                       SM7VY  QTC 85-05-185
FR-dx-500 på 30m bandet                       SM7VY  QTC 85-05-185
FT-221R modifikasjon                                 AR  81-09-256
FT-221R ombygging                                    AR  81-10-293
FT-101ZD på de nya banden                     SM5RN  QTC 85-03-091
FT-221R forbedring (3)                               AR  79-10-274
FT-221R forbedring (2)                               AR  79-06-176
FL-DX-500 Forbedret ALC                              AR  74-12-275
FT-277(FT-101B) Forbedring av følsomheten            AR  80-04-104
FT-101B Nøklingstrinn (FT-250/FLDX500/FTDX500)LA8AK  AR  90-03-071
FT-250 Interferens fra 40m kringkastere              AR  83-07-203
FT-480R Modifikasjon                                 AR  85-12-337
FT-7   Rent CW-signal (max 1000 lpm)          LA8AK  QTC 83-03-086
FT-901-DM    Modifikasjon   (1) Klikk og NB   LA3ZL  AR  79-06-175
FT-77   Forbedring av selektiviteten                 QTC 88-01-009
FT-250 Tilkopling av converter/transverter    LA8AK  AR  71-05-108
FT-7   TX-gain                                LA8AK  QTC 87-01-010
FT-757GX Datorstyring av -(QTC 85:03: )       SM6CPI QTC 85-05-191
FT-901-DM    Modifikasjon   (2) Noiseblanker  LA3ZL  AR  79-08-212
FT-7   SSB-squelch                            LA8AK  QTC 85-07-282
FT-7 Forbedring af-(10m/xtalcal/transv etc)   LA8AK  OZ  83-02-.6.
FT-101 Forbedret AGC                          OZ6WP  OZ  78-03-119
FT-7   Utvid 10m, transverter tilkopling      LA8AK  QTC 85-09-325
FT-221R Forbedring av nøkkelklikk                    AR  82-02-060
FT-221R forbedring (1)                               AR  79-02-045
FT-250 Modifikasjoner                         LA8AK  AR  69-11-239
FT-221R Forbedring av følsomheten                    AR  80-04-104
FT-7   SSB squelch for mottaker               LA8AK  AR  83-12-339
FT-480R Modifisering (2) -tillegg             SM0LBR QTC 83-04-128
FT-480R Scanstart for-                               QTC 83-10-336
FT-901/902   Forbedringer (2)                 LA8AK  AR  90-07-206
FT-901/902   Nøkling                          LA8AK  AR  89-06-165
FT-100 Forbedret AGC                          OZ4DX  OZ  70-09-321
FT-7   Omkopling av xtal-kalibrator           LA8AK  AR  84-02-040
FT-7   Feil i tidlig utgave                   LA8AK  AR  83-02-041
FT-901/902   Forbedringer (1)                 LA8AK  AR  89-02-038
FT-726  Forbedringer                    LA7BI        AR  89-04-124
FT-726 - forbedring av produkt detektor LA7BI LA8AK  AR  93-10-277
TR-7010 - produkt detektor      LA8AK  AR  93-10-277 
FT-101B med transverter,boks for utkopling av PA-rør AR  83-04-127
FT-7   Regulering av uteffekten, TX-gain      LA8AK  AR  83-10-275
FT-250 Forbedret AGC                          LA8AK  AR  78-04-101
FT-221 Kritisk undersøkelse og modifikasjoner  LA8AK QTC 89-07-
FT-200/250 Forbedring av AGC                  LA8AK  OZ  78-03-120
FT-DX-100/150 MOSFET i HF trinnet                    AR  73-12-293
FT-290R Svakheter i transceiveren                    AR  82-06-197
FT-901/902   Noise-blanker                    LA8AK  AR  89-02-039
FT-250 Drive-problem                                 AR  78-05-133
FT-250 Intermodulasjon fra xtal kalibrator           AR  77-01-004
FT-902 Xtal kalibrator kan gi intermodulasjon  LA8AK AR  89-04-105 
FT-101B eliminering av nøkkelklikk                   AR  81-04-100
FT-901/902   Processor (RF-clipper)            LA8AK AR  89-02-039
FT-757GX Datorstyrning av                   I/SM6CPI QTC 85-03-100
FT-757GX Direkte frekvensinntasting/brukertest LA6PB AR  88-03-070
FT-26, test av yaesu                                 OZ  92-01-017
FT-5200 2m/70cm, test af-                            OZ  92-03-141
FT-7   Xtal kalibrator kan gi intermodulasjon  LA8AK AR  89-04-105 
FT-736, Amatørradioklubben Københavns teknikum måler- OZ  94-03-143
FT-747GX styring av-                                 AR  94-03-069
FT-890, test av -                                    OZ  92-10-556
FT-901/902 forbedringer for HF/VHF            LA8AK  OZ  93-07-407
FT-901/902   Forbedringer af -                 LA8AK OZ  93-07-407
FT-901/902 rettelse for OZ 7/93                      OZ  93-11-661
FT-990, test af -                       OZ5RM OZ1AWJ OZ  92-05-258
FT-726 og TR-7010 SSB RX kvalitetsproblemer  TR-122  AR  93-10-277

Mods Intro

Need your help:
In 1967-68 I borrowed a Starflite 390(?) transmitter - with Heath VF1 VFO - from NRRL, but later I have found no
references about this rig. So I would be very interested if somebody would give me some more info, possibly circuit diagram
and data.

Built my own 80m 5W PEP solid state SSB transmitter in 1967, based on an article in CQ-DL (DJ8MC?), it was
described as a mobile transceiver, but I never needed the receiver since it transceived with my Heath SB-300. Purchased
an HX-20 transmitter in 68, and when I've tested 49 modification on it I sold it to LA6VM, who had already bought my
Drake 2-C, and I bought Sommerkamp FT-250, which was combined with Drake 2-B, I was surpirsed how good it
was and immediately decided to get rid of SB-300 and buy 2-B, but I never liked the 2-C which I had one and a
half year earlier, the worst was that it didn't cover 10m and had no passband tuning.

Have made extensive experiments and modifications for the following sets:
Collins 51-S, Drake 2-B, R-4C, TR-4, Heathkit HX-20, SB-300/301, Trio TS-500, TR-7010, IC255E, IC202E,
Yaesu (Sommerkamp) FT-7, FT-101B, FT-250, FT-902, FL-dx-500,
May publish more information if it is some interest for it, and I find time to dig into old books, but please note that


Need info and schematic for this: FDK AC/DC Multi VFO