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All sorts of interesting stuff about Ham Radio and old gear from Steve G3ZPS, near London in the UK

Yaesu Musen

Yaesu started as a communications equipment company in 1959 under the stewardship of Sako Hasegawa JA1MP. His initial plan appears to have been to produce domestic ham and commercial radio equipment. In this regard Sako had remarkably similar ambitions to Robert Drake in the USA and Rowley Shears (KW Electronics) in the UK. Yaesu quickly started producing valve transmitters and receivers in the early 60's and established the 'F line' as a brand that would soon become familiar to just about every radio ham on the planet. The early HF SSB equipment used the same mechanical filters as Collins and KW, but Yaesu quickly switched to crystal filters. Their 1960's FL100, FR50, FR100 and FL1000 were not remarkable in themselves and other manufactures did not pay any great attention - even as the units started to appear in USA, EU and Australia...but Yeasu had hardly got started !!!

One thing set the Japanese manufacturers apart from KW and Drake in this period..the speed of development of new products...the shear pace of Yaesu  R&D coupled with either the introduction of new models or revisions to existing models was dizzying. Yaesu quickly started targeting different aspects of the ham radio market - with innovative part transistor designs (valve / solid state 'hybrid'), heavyweight ' boat anchor' stations for use as fixed stations and low power 'novice' equipment. The first hybrid design was the FTdx100 and appeared in was a quantum leap ; AC and DC supplies built in, 80 - 100 W output,  just plug in a Mic and go!!. The FTdx100 was refined over a 4 year period into great little transceiver for base or mobile use..and the next step would create a legend

The next HF transceiver - THE FT101 - is arguably the single product that started the slow death of KW, Drake, Collins and other manufacturers of Ham radio equipment. Yaesu built on their experience with the FTdx100 and came up with a global winner. The FT-101 series of transceivers first appeared internationally in 1970 (in the US in January 1971). It gained overnight approval of amateur radio operators for its quality of signal, flexibility and for professional attention to workmanship and design. The modular design of 10 solid state circuit boards on a common chassis with a rugged tube output stage was a revelation for the price. There were no extras to was stable,  did not run hot and was built to a very high standard on a large production line..other manufacturers were left in the dust !. Of course markets like the USA continued to buy homegrown products, but it was too late - the tide would become unstoppable.

The FT101, was the start of a revolution in Ham radio equipment and the other major Japanese manufacturers (Icom and Trio/Kenwood) were just behind..and along with Yaesu they were destined to become the major global players. Yaesu kept up the fast pace of development, revising designs and bringing out new models. The first FT101 I owned in 1979 was from the 'Z/ZD' variant, this major revision saw Yaesu re-design to keep costs down by doing away with plug in boards and moving to 6146 output valves - not really the same radio but the name had become iconic. The 101Z series all had excellent receivers (although not the widest dynamic range), and I really couldn't find any weaknesses, for non contest use it was 1982 I got married changed jobs and packed away the 101 in its box...for 20 years

Yaesu Collection

My 1979 FT101Z MK1   came out of retirement in 2002..and worked straight out of the box. It has AM fitted - there was a MK0 which had no AM position on the function switch. The AM receive is dreadful as they use the SSB filter in that mode - no easy provision for an AM filter although some have put a 6KHz filter in the CW position and done some re-wiring to have it in circuit in AM mode. Still working fine in 2016. Compared to the KW and Drake these radios are light years ahead, when you have them apart you can see the great attention to detail in the wiring and PCB board labelling

I was offered another FT101ZD in 2003 that had also been little used, it also worked OK after many years out of service. This 101ZD had a CB crystal in place of one of the 10m band positions but it had not been abused - The PA still gives good power out and there is no evidence of  stress in the PA compartment. Although these MK1 radios are not shown as FM capable, the FM board can be fitted (works in the AM position) - a squelch control needs to be added. In this example a small preset variable pot has been added to the connector on the FM board that would normally go to the its preset and works fine.  It can only have been used on CB for a short period in the late 70's. Its only fault was an intermittent 'clarifier' control which turned out to be one of the pesky little 12v DIP relays..a quick repair.

FT902 DM 

My next acquisition from another mate was a pristine FT902DM (similar to FT901DM) complete with Speaker and ATU. This is a fabulous bit of kit and has been my main rig for 13 years. The receiver is still in the top 30 for close in dynamic range on the Sherwood website and I have never found a single weakness in the RX performance even on 10m. Yaesu pushed the boat out with the 902DM and it was one of the very best 'hybrids' ever produced - and at the time of its release one of the very best receivers (billed as a contest capable rig). It has a keyer, CW filter, IF width, Proper AM and FM, Audio Filter, Notch, Memory, Tune Up timer etc...oh.. and its very heavy!

I quickly added the FV901 digital VFO..only 100Hz steps but dead stable, the FTV transverter followed and then I started to run out of room. Driving an AL811 linear this set up has become my main station..perfect.

I have had remarkably few problems with any of my Yaesu gear - a testament to the design, build quality and the quality of components used. The small black 12 V DIP relays appear to be a week spot wherever they get used on ham gear. I have had 2 relay failures - one on the speech board in the FT902 and one in the clarifier of my FT101ZD - they only cost a few pennies to replace.

Yaesu FR50B Receiver

Another bit of kit that came to me through a Silent Key clearance. This is one of Yaesu's earliest receivers as part of their mid 60's 'novice' set up. Its a pretty simple design and very easy to work on and they are quite rare in good or working condition. The radio uses the dreaded 'switched VFO' that does away with a crystal premix arrangement and saves money..same as the Swan 350 / 500 and KW Atlanta..makes alignment very tricky and a bit temperamental. Before agreeing to buy this RX (for not much money) I downloaded the manual and checked the web for any obvious problems. All the pictures showed 2 simple (and small) mechanical filters in series in the IF, and no one had reported problems..oh how wrong can you be!.

When I got the RX home and opened it up I saw to my chagrin that unlike any internet pictures it had a large Kokusai mechanical filter (as used in my KW gear)..where the hell did that come from??. It was clearly a factory fit and I suspect it was a transition FR50B from the earlier FR50 model which I suspect had this filter installed..damn!...and of course it was as dead as a dodo . As with my KW gear I bypassed the filter with 1000pf and found I had a working radio. Luckily I have spare Kokusai Mech filters and a few Murata ceramic SSB filters at 455KHz. In the end I fitted a Murata CFJ455 and appropriate matching transformers. I also like the variable BFO, no need to worry about carrier crystals !

The internal speaker is truly awful, but I had a shock when I attached a Drake MS4 - the audio sounded really great - A check of the schematic revealed that the designers had put some negative feedback around the valve output stage - sounds really 'smooth' and easy to listen to. I also noted that even after alignment it was bit low on IF gain, i used the old trick of a few pf across the IF transformers and things improved, and its a very quiet receiver with the antenna unplugged..I listened to it every day for a week on 80m..the reported VFO drift was acceptable after warm up as well 

The Cosmetics were next - the case was a bit marked in places and had some rust spots - out with the wet / dry sandpaper and Hammerite 'satin' black. This is how I paint the Drakes as well...4 light coats give a near flawless finish. Cleaned all the knobs and it looks and sounds great...time to get its big brother the FR100 ! 

Sommerkamp FT277ZD / FT101ZD MK3

Came to me through the local radio club as part of a silent key sale - The club noted it had been extensively modified and whilst it powered up and put out some RF power in 'Tune', the internal speaker was missing and no further testing was possible. There was a tin box hanging off the back connected to the PA fan and a lot of scribbled documents relating to complex mods

Once home on the bench I set about working out what its late owner had done - or more accurately tried to do. FT101ZDs can have either an FM or AM board fitted - but not both. Our late colleague decided he wanted both options and set about achieving his aim. He managed to screw the 2 boards beside each other, one had the correct connectors but the other had to be wired in some sort of parallel arrangement. He then had to fashion an AM/FM switching mod so added another push button and LED on the front panel (above the Clarifier switches)

He also had a bright idea - In AM mode perhaps he could use the wider 455KHz ceramic filters off the FM board to also drive the AM detector on the AM board?..this gets around the normal use of the narrow 9MHz SSB filters in AM mode (a drawback with AM on these radios). So he tapped into the FM board just before the discriminator and then tapped into the AM board before just before the AM detector (the AM board operates at the 9 MHz IF)...but I worked out what happened next..there was insufficient 455KHz IF gain to drive the AM detector properly, so - yet another bright idea ; use part of an old AM transistor radio IF strip (I’m not kidding - its in the picture!)…nowhere to put it ? - so remove the internal speaker and leave this funny extra IF strip hanging in the case. What a friggin' mess

None of this worked and probably never did. SSB seemed to be OK so I removed the worst parts of the conversion to test the rig and re-installed the speaker. After a few hours I ended with correct operation on SSB and FM only. The PA fan mod was so that the fan only came on with heaters..I took it out..after all its not a noisy fan.

After verifying I had a working radio I set about removing the rats nest of wiring between the 2 boards and the radios wiring harness. What a mess -  took me 5 hours to clean up the rig at each step referring to the service manual and 2 other FT101ZD's. Along the way I learnt that the FM boards have 2 variants (not documented), and the RF unit connections (coloured cables) are reversed on the MK III unit.. He had even hacked into the PCB  tracks on the AM board

Pic above shows the radio all restored to original condition. Quite why our late friend embarked on this complex and foolhardy mod is something I will never know. After a touch up alignment it works great on SSB, but he probably came close to ruining a perfectly fine radio..a lesson there somewhere. Radio ham bodgers and twiddlers - you've got to love them...maybe not

Yaesu HT capacitors 'Orange Gunk'

Quite a few auction sites and websites talk about the Yaesu HT capacitors 'Orange gunk or goo' - and point to the fact they are leaking all over the PCB and must be changed. Although there is no harm in changing caps (and the EHT ones probably should be changed), this is misleading ; the Orange gunk is not the caps leaking its the cement that Yaesu used to hold the caps on the PCB - they probably didn't need it but they were very thorough on the these radios. Its especially visible on the 'Rectifier A' don't rush to change them when you see it

 S Meter Bulbs FT902

Changing the S Meter bulbs on the FT902 is a really fiddly job. The bulbs in most variants of the radio are small axial filament bulbs rated at 8V.  Getting to them is another matter..hee hee !. First the front panel must be removed - I had to use the workshop manual to work out how to do this.  Remove the  case and ALL the knobs (you will need a small screwdriver for the concentric knobs) the VFO must be removed - this requires the removal of the counter board and the bracket holding the frequency display. THEN take out the 4 allen key bolts that hold the VFO in, and start to ease it out..THEN you must release the VFO earth strap (this really caught me out)


On my one the VFO earthing strap was on the bottom right screw at the front of the VFO case and the wire disappeared into the bottom of the radio - this is where I discovered a rare Yaesu error - the earthing strap should be on a solder tag under one of the many screws..but mine was soldered to a lug on  the underside of chassis..once removed all was OK and I got the VFO out (a tight fit). The bulbs are actually inside the meter housing which you prise off - and the two bulbs are small - even smaller than my replacement ones - in fact in my 902 they are 2 different sizes. Its never been apart so must have been  built like that.

After reflection over a coffee, it looked like a very tight fit to get my bulbs inside the meter - and I could never face taking the radio apart again if they failed. I hit upon another solution. There is room to slide a bulb in above the meter without taking  half the radio to bits - so I put one of my bulbs in a clear heatshrink sleeve (so both wires came out one end) and slid it in to the small gap between the meter and the front panel - wired it to the 8V supply (blue wires) and voila. Not quite as sexy to look at but works fine and is an invisible mod.

IMPORTANT -  the countersunk screws holding the front panel on may have washers under them..BUT ONLY THE TOP SCREWS - there are no washers on the two bottom screws. The front panel is a very precise fit and if not put back properly you may find the right hand push buttons bind a little (you can push them in but they stay in!)..Yaesu puts the washers in to ensure the front panel fits OK..if you put washers under the bottom front panel screws it may make the push switches stiff..only a mm or 2 !!..I reckon its a manufacturing error that needed a bit of adjustment . Well that was a happy 4 hours !