Saturday, 10 September 2016

Waste not want not.

I've just recently gone around the house swapping out all the 50W GU10 spot lamps for their LED equivalent. Prices on the web have dropped to well bellow £3.00 each when purchased in bulk. The only trouble is I now have a box full of partly used 50W incandescent spot lamps.  However, as I have a workshop and a little used studio, all populated with old drawing office angle-poise lamps I decided to re-cycle the lamps in these beautiful old fittings. The CFL (compact fluorescent light) spot lamps are really expensive and give a very poor light when they get old. So having dredged through several of the auction sites I came across these nifty little adapters shown below. 


I know using the 50W lamps is wasting energy but throwing them away is too. However, they were use four at a time in the fittings we have in each room, that 200W just to light the lounge, reusing theses lamps one at a time isn't too bad! I reckon my supply of pre-used lamps should see me OK for the next twenty years. These adapters are also available in ES (Edison Screw type). You could,  if the fitting allows, use them to put LED spot lamps in your favourite retro angle-poise! When looking for these adapters use the terms "BC to GU10" or "ES to GU10 adptors". 

73 Rick G6AKG




Monday, 27 June 2016

UT5JCW 4 Meter Transverter Reveiw

I was lucky enough to spend this weekend playing with an old Deecom 4m HB9CV beam antenna and as this coincided with the 4m cumulative contest I decided to give my portable station a workout. This flurry of activity was spurred on by the many thunderstorm that have triggered sporadic-E openings well into this summer. My hope is to go and activate a local SOTA site this Autumn.

My backpack station now consists of a 70MHz transverter, a fishing pole mounted HB9CV beam antenna, a Yaesu FT817ND transceiver and a homebrew 12V power pack.

Supplied transverter PCB
Serge (UT5JCW) produces transverters for bands from 50MHz right though to 430MHz and I can confirm the 4M PCB is slightly larger than a credit card, it makes use of mainly SMD components with the exception of Inductors and the PA transistor. The PCB is supplied fully aligned and produces in excess of 10W when running from my gell-cell portable power pack. After carefully adjusting the transceiver drive level I did some quick tests which proved a nice clean output on 70MHz, with a second harmonic 39dB down on the fundamental. The close in emissions noted at 84MHz (2 x the local oscillator crystal at 42MHz) were better than 40dB down on the output signal.

So after extensive bench testing, I've finished boxing up my transverter and made several successful 4M band SSB contacts using my newly acquired Yaesu FT817ND as the driver. 

Rear of supplied transverter PCB
The receive sensitivity seems similar to that of the drive transceiver on 28MHz and the only problem noted was a slight frequency skew in transversion, of plus 5.8kHz. However, I didn't view this as a deal-breaker as this can be programmed out in my home QTH transceiver and mentally accommodated when out portable .

Serge did suggest that a suitable inductor could be connected in series with the crystal to drag it on frequency, but the PC board is so neat it seemed a shame to start hacking it around. Surge commented that in order to keep the price down of the product he had used computer grade crystals that were not noted for their accuracy.

Included in my box is a variable 30dB power attenuator, as suggested by Serge in the application data, as the transverter only requires 100mW drive - maximum! I also added to my project an RF activation circuit to operate antenna changer-over relays, as the barefoot transverter PCB has no switching hardware. A separate socket was added to make use of the grounded PTT line which is available on the ACC socket of my FT817. 

My boxed transverter including power attenuator and relays, the heat sink is from a faulty industrial PC
Overall this transverter represents good value for money and since I purchased mine, Serge has added some accessories that make its application even easier - as he now offers a ready made relay and power attenuator PCB. In fact you can buy a whole kit including the case for approximately £80 - see his  Ebay Transverter Store.

Many thanks to Serge UT5JCW for his prompt help in answering my technical queries and use of his circuits diagrams and photos in this blog. 

Transverter technical specifications
  • RF range  -   70 ... 72MHz
  • IF range  -  28 ... 30MHz
  • IF input power  -   1 ... 100mW (0.1W max.) or 0 ... 20dBm
  • LO frequency  -   42 MHz
  • LO frequency stability  -   +/- 3ppm
  • Output power  -   10 ... 15W
  • RX gain  -   typ. 20dB
  • Noise figure  -   typ. 1.0dB
  • Image rejection  -    typ. 70dB
  • PTT control  -   Contact closure to ground
  • Supply voltage  -   +13.8V DC (+12 ... 14V DC)
  • Current consumption  -   typ. 2A (TX)
  • TX Output transistor  -   RD16HHF1
  • RX Input transistor  -   BF998
  • Dimensions (mm)  -   80 x 45






Sunday, 22 May 2016

FT817 RF Clipper Microphone Review

DF4ZS RF Clipper  

A couple of months ago I purchased an audio RF clipper module, designed by Joachim Münch DF4ZS (SK), to fit inside the microphone of my new FT817ND. I based my purchase on some enthusiastic reviews posted on eham (www.eham.net/reviews/detail/2732).

I had previously built and tested an audio compressor based around the SSM2216 chip which was trialed on a fellow amateurs FT817 (thanks to Mark 2E0VOV).  It suffered terribly with RF feedback problems, even though standard EMC design practices were adhered to, with respect to layout and earthing. Needless to say it did leave me with the impression that any audio circuit left out side the transceiver chassis was going to suffer a similar fate.



When the RF clipper arrived I eagerly unpacked it and inspected the hand crafted PCB with its mix of conventional active devices and surface mount discrete components - all looked to be in order however, my heart sank when I saw that there were no installation instructions included - just a QSL card! I need not have worried, as all the data I required was available on Joachim's website , I also found it useful to download the MH-31 microphone data provided by Roy Frettsome G4WPW web pages.
 
Circuit diagram of Yaesu MH-31 mic.
I sat and pondered all the information for a while and once I'd  got my head around taking spare components out of the mic.  PCB and adding a 1.2k resistor, the installation of the clipper went easily. I even re-wired the tone switch to enable the processor to be switched in and out of circuit.
 

Note: There is a service offered by the supplier of the module to install the clipper for you, although  once you've factor in the postage both ways for the microphone it looses its appeal. However, for those not gifted with the necessary skills it is a nice option.

The newly modified microphone uses an electret type insert mounted of the rear of the clipper PCB, which I though was a neat idea (more of that later). Once the Clipper PCB was wired in place I button up the microphone assembly and it all worked first time, I found it necessary to reduce the transceivers microphone gain down to approximately 15 (with the clipper out of circuit) and adjust the clippers output to match the normal microphone setting using a small preset on the clipper PCB (I was a bit premature completely reassembling the mic!).


The mic. gain and ALC adjustments were made by ear, aided by the use of a second receiver fitted with a decent pair of over-the-ear headphones, to prevent audio feedback while monitoring the FT817 transmission.  Setting the FT817  ALC is very "hit and miss" using the LCD bar graph provided, however, I did managed to eventually adjust the gain settings to produce  a few meter bars on speech peaks, both with and without the clipper. 

After satisfying myself that I was not overdriving the transmitter I finally re-assembled the microphone and then did a couple of videos showing the modulation envelope of the transmitted RF signal, with and without the clipper in circuit. I'm sure once you've viewed both videos you'll be able to instantly see the increase in peak envelope power made by the clipper. 

video
Un-processed 

video
Processed

I decided to perform a couple  on-air tests with another amateur, fortunately Mark 2E0VOV lives within 2 meter QRP range so I set a schedule using both FM and SSB. Mark can always be relied upon for an unbiased audio report, he's spent some time with me fine tuning his FT817 audio, which now uses an electret microphone insert, his logbook bares whiteness to its clout in chasing QRP DX.

It's fare to say the results on both FM and SSB were disappointing, the overall increase  in average signal level was good but the audio quality was very poor - this was using the supplied electret mic. Mark commented that both microphone setting were like listening to me through a wet sock, at this point I got frustrated and a little confused, as the audio was poor with and without the clipper in circuit! After some thought I decided to try mounting the  supplied mic. insert in a baffle plate (as shown), after all this is the way Mark and so many other amateur have modified their standard Yaesu microphones to take an electret insert.

The upshot of my experiment has finally produced audio  quality that now matches the increase in talk power provided by the clipper. :0)

However, I can only recommend this mod. to those with a steady hand, a good set of eyes and decent fine tipped soldering iron. 

73 to Ivonne Glaser (DO2AL) and Harry Gödde (DO5AL). Thanks to Harry and his partner for all their help in perfecting this modification, they have now taken over the production and development of the DF4ZS RF clipper.

Note: Having discussed the above modification with Harry, he has promised to investigate my findings once he has finished re-designing other products in their range. The clipper sells well as it is and my modification just adds icing to the cake. 

I hope you have found the review useful and interesting, I have yet to do any serious DX chasing with the RF Clipper Microphone, because as soon as the project was finished HF propagation took a very rapid downturn.  I live in hope of better times with the onset of the  sporadic-E season. 

73 Rick DE G6AKG 

Thursday, 19 May 2016

Another FT817 interface

FT817ND VOX Interface

A month ago I built a rough copy of the Wolphi VOX interface to go between my Yaesu FT817 transceiver and my Android Tablet - its shown on my defunct FB blog. It worked OK with the Tablet but was somewhat "hit & miss" on my Chinese copy Samsung phone. The Wolphi interface uses the DC bias available on the Tablet audio port to power a single stage audio amplifier, it's normally used to supply an electret microphone in a headset.

It would appear this DC level is not standard across all Android devices and on my phone it was a dismal 1.4V, far too small to provide a decent rail to power the audio amp. This resulted in my interface failing to key the FT817 in several of the digi modes I tested, even with the phone volume set to maximum. 


Needless to say I was rather disappointed, but to be fair if I'd used a Darlington pair transistor rather than an FET to control the PTT line, as in  the original design, it would have worked. The FET requires twice as many volts to put it into conduction - so there's nothing wrong with Mr. Wolphi's design. I'd decided to use an FET because it's is less likely to be biased on by stray RF fields which are often present in portable installation where RF grounds are less than perfect. If  the interface were to be effected then the transceiver PTT line would hang in transmit mode, because the PN junction in the control transistor rectifies the RF and biases it self permanently on.


I finally settled on a circuit designed WA8LMT which uses a step up transformer rather than an audio amplifier to generate the high level of audio needed to drive the VOX circuit and in order to make the rectifier circuit more efficient I used a Schottky diodes which have a much lower forward volts drop, of approximately 0.2V, giving me more power to switch the FET.



Modified WA8LMT VOX interface circuit.

My interface uses transformers culled from my extensive scrap box, however, after a search I found some suitable replacements available from Rapid Electronics. Unlike the original interface design mine has additional flying leads enabling the use of  Notebook PC in place of the Tablet - the number of digimodes available for Android is still relatively limited, so I like to use FLdigi and MMSSTV as well.


Just as a final note, if you see any old PC keyboards floating around at the tip or a junk sale, the type with a light green PS2 plug, salvage the cable with plug, as it  can be used to connect the interface to the data socket on the FT817 (same plug :).


Monday, 16 May 2016

I need the Sea


Hamworthy Sunsets

I couldn't live away from the sea its in my blood, three generation of my family have work, next to, or on the sea. My maternal grandfather George was a shipwright diver, my father Gordon was an Electrician in Bolsons Ship Yard and I worked for Greenham Marine as a marine electronics service and installation engineer. I was born under a water sign, if you believe such stuff and away from the sea I get restless. Here are a few of my Poole Harbour sunset photographs taken from the Hamworthy shoreline - they are a comfort to me when I'm inland. :0)

Sunset from Lake Pier, the dolphin (mooring post) is
a relic of WWII when a shorts flying boats would
have been stationed here as a coastal patrol.

Low tide at Hamworthy Park (late winter)

Same sunset but earlier on, boy it was cold.


Saturday, 14 May 2016

Singing is good for the Soul


I Love to Sing

I've loved singing since a pre-pubescent kid at school. My voice breaking at 13 years saw my choir career cut short as they had no use for an unsteady baritone. Just before leaving school my music master Mr John Blackett took it upon himself to organize a school opera in which I played a Royalist Office in "All the Kings Men".



A dress rehearsal of the Kings Men opera
Middle age saw me suffer the curse of the Ayley family - depression and after ten years of taking pills I decided it was time to tried something else. I started singing with a friend, accompanying his folk songs with dodgy harmonies and it wasn't long before I noticed the singing was giving me a natural high - rather than the Real Ale! 

After my friend took an away job driving, I felt somewhat of loss and one Christmas, while singing at the midnight service, somebody suggested I join a choir as I had a pleasant voice. Clearly not reading music left me short of joining a professional choir, so after a searching the internet I found a local community choir in Bournemouth. They are now called the "Chicken Soup Choir" and I've had the pleasure of singing with them for in excess of six years now. The are a fantastic group of people, of whom I've made many firm friends and needless to say the depression is now a thing of the past; my fix of singing every week has seen to that.
 

A group photo of the Chicken Soup Choir in London
photo by Lou Pack
Singing in a choir is slightly more expensive than proscription drugs but you have a lot more fun! I now also sing with a village community choir called "Just Sing" which have just received a major boost in their numbers after singing backing vocals with the famous Operatic foursome G4.


Group photo of Just Sing at the Wimborne Folk festival 2015
Just Sing are performing again this year, in the Wimborne Folk Festival on the 10th, 11th & 12th of June, both on the main stage in the town square and in Wimborne Minster. I can thoroughly recommend singing as a cure for depression, being lonely and helping to boost self confidence - go on give it try what have you got to loose!

End Fed Matcher

EFHW Tuner & Link Multi-band Half Wave Antenna


The project shown in Figure 1 is a loose and improved copy of a Hendrix End Fed Half Wave (EFHW) antenna matcher. Mark 2E0VOV gave me all the parts and assisted me getting the number of turns right on secondary, Hendrix say it should 20 turns on the secondary of T1, however it ended up as 18. I added a press switch to connect a 4.7k artificial antenna load enabling the matcher to be tuned off air - which is an added feature .

This is the third version of this project and it incorporates a transformer coupled absorption VSWR indicator which gives a sharper response than the Hendrix version. The matcher also covers the 60m band using a 220pF silver mica capacitor connected, via switch, in parallel with tuning capacitor C3 and by experimenting with the trimmers on the back of the poly-varicon capacitor (C3) I found it possible to make the match box tune from 40m all the way up to 15m! My modifications has provided two extra bands which I think made all the tinkering worth while.

I have now constructed a linked half wave radiator, shown in Figure 2, making it easy to plug and play on all the bands covered by the matcher. The antenna has not been field tested yet, so the wire lengths are approximate for each band center. I feel its a good place to start pruning - highest frequency bands first. The matcher is designed for portable QRP use up to 5W CW although it will probably survive 10W SSB.

Figure 1
Figure 2.