Bank Holiday Monday - Mast preparation :)

After my last post on 6M I got to thinking about how I could get a better antenna for 6M, and perhaps 4M and then there's always 2M as well isn't there !

I've had in my mind for several months the idea of a 'temporary' mast to enable me to quickly get some decent (perhaps 6 element 6M beam) up in the garden for weekends and contests.

The basic criteria would be -

1 - Temporary - most important after studying the planning regulations, I didn't want to apply for permission for a mast, especially as I live in a conservation village, whilst I might find antenna's pretty special others (including the xyl) might have other ideas. A 'temporary structure' is defined as one that is not permanently fixed to a building - or other structure.

2 - It must be fast to put up and take down - I want to do radio not build masts etc.!

3 - Would be high enough to get above the house from the back garden

4 - Would be able to be assembled as dis-assembled  by one person (me!)

5 -  Would have minimal impact when taken down (ie must be temporary, not visible and not a structure when taken apart)

I've been thinking about it for some time and in the end decided that an ex mod pump up mast would be best.

Not a SCAM12 - those are massive, and whilst built like the proverbial 'brick out house' they weigh a ton and are designed for a small army to assemble, so what next ?

Then I came across (again via eBay what would I do without it) a Hilomast NK9, a lot more manageable - when pumped up 9M, 2.3M when retracted, 22Kg's of head weight and it weighs approx 21KG, which whilst bulky is manageable for a lard ass like me :)

It was advertised as "possibly in need or refurbishment"  I took a punt and won it just over £100, with semi local collection, I picked it up in my 7 series - couldn't do that with a SCAM12 :)

This was autumn of last year, I got a seal pack from SMC Communications (£70+ ouch!), and then did nothing with it.

Then my 6M post |(and an upcoming 2M low power contest), and I thought I take a closer look at how I could use it.

Well after 6 hours or work, I've replaced all the seals, and now know intimately the inner

The construction of a Hilomast
(c) Hilomast (SMC)

workings of the Hilomast !! - if you've any questions just ask !

I'm was very impressed with the build quality, really good stuff, great to work on, perhaps the equivalent of a BMW or Audi in engineering terms, when I dismantled it, I discovered a hand written note on one of the upper tubes, that it was re-built in 1994, so I doubt that its been touched since then. The top section is slightly damaged, but has no effect on the use of the mast at all.

I did check before working on it and it didn't pump up at all :(  and now after working on it, it not only pumps up, but also stays up (without using the locking handles), so now all I've got to do is work out how to put together a ground mount to help me put it up, and also how guy it to make sure it doesn't fall over with the antenna's on top !!

I've already decided that the cables would be permanent from the house to ground level down the wall in a weather proof box. I've already go a method of getting cables from the loft to the outside world using the a waterproof hole in the soffit (or is it barge board) of the roof, with a removable, flying cable up the mast, including the rotator control cable, to enable quick set up, and keep things tidy.

I recon that I should be able to get it set up for weekend working (I'd have to choose the antenna obviously !) in about 45-60 minutes and then take it down in about the same.

That should give me great gives flexibility  (Contests are only at the weekend, and actually I'm only around then to play radios's), a reasonably good antenna for my favourite bands 6M,4M,2M, and no planning problems as its temporary, I can even drop it down to 7ft when I'm not using it to avoid neighbour problems.

I should be able to store the antenna vertically at the side of the house safely and so not too much disassembly should be needed, and if it does need this its a small price to pay I think.

So next step now I've got a working mast is to get the ground mount sorted out, and get the cables put in permanently. Thinking cap on, I've a few ideas already.

Sorry there's no pictures, I didn't really think until I was finished, that I'd write it up on the blog, silly me :( - I will when I do the ground mount, and of course the final result.

Now how big is a 40M three element beam (!!!) :)

73's

Chris

6M - Truly the magic band !

I thought I would get some time in the shack today (Sunday), I've got several projects on the go, some of which I've written up on my blog - such as the TS-570DGE and several which are still on the bench (like the Ameritron 811 Linear amplifier)

I switched on the 756 PRO to see what going on, and found to my delight the 50Mhz was wide open again (it was yesterday) and so spent a very pleasant couple of hours working into France, Germany, Austria, Italy, Spain.

Heard far more than I worked - but then there is a reason......

I only run the 756Pro barefoot (100W) and my 3 element 6M beam is located in my loft !

Yes its pointed south and its in my loft - so had over 35 contacts right across Europe - not too shabby :)

I've plans for getting a better (ie external !) aerial for 50Mhz later in the summer when I can get some spare time, but in the meantime .....


A station in Italy pretty much refused to believe that my antenna was in the loft space as my signal was so good

Just proved what can be done - don't give up hope anyone who can't get an external antenna for  50Mhz when its open internal antennas really can work.

Great fun - truly 50Mhz is a magic band !!!!

Kenowood TS-570DGE Repair - lets get started (and finished as it turns out!!)

So....

Got it home and found some time to have a closer look at it.

Sure enough, as described, everything works, but its as deaf as a post :( , the TX side is fine, giving 100W out, so that's good.

I'd already downloaded the workshop manual prior to bidding (to check what components I might need to check the circuit configuration - well its best to know what your in for isn't it :) ) and so knew where the front end components, protection diodes, bandpass filter switching diodes etc.

So removed top and bottom covers, as usual the bit I want (rx input etc) is on the 'bottom' of the radio !

I start the investigation, no obviously damaged components from the top, no smell (remember that the seller said he thought that some had transmitted into it by accident) of burnt or damaged components.

I test the protection diodes - all ok - good
I measure the switching diodes on the bandpass filters - to my surprise there are all - so a moral there never believe what you are told :)

I have a break and a think at this point, I had expected this to be the problem.

I decide that I will fall back to normal fault tracing, and so inject a strong signal into the aerial socket and start tracing.

Circuit is below for this area so you can see my work ;)

Partial TS-570DGE circuit - copyright Kenwood Communications

1 - Signal at the antenna connector on the board - yes  (CN1 above)

2 - Signal at  R2 - yes3- Signal at R2 end of L4 yes4 - Signal at tp4 - NO (!!!!!!!!)These test are a little tricky as everything is surface mount, but no real problems, so I decide to inject the 14.100Mhz signal into TP4.Result is an end stop signal on the radio.So L4 is at fault ? - remove from the PCB and yes its open circuit :) - fault number one. I temporarily jump out L4 and sure enough - receiver works perfectly, pre-amp fine, all looks great :)Whilst in this situation I give it a really good check out - seems to work perfectly, have a few short qso's all fine, so a suitable surface mount 0.25u inductor goes on the part list.Whilst checking it out I notice that the attenuator doesn't attenuate (!) , so I chase the circuit and discover that R1 (56R) is open circuit - I have a suitable surface mount resistor and so remove it and replace - Check again and now the attenuator works - result !I then check around the circuit testing voltages as per the  workshop manual - (BTW - I really like Kenwood / ICOM service manuals as the have really comprehensive voltage / voltage tables for TX and RX - Yaesu don't seem to - why is that ?)At this point I check again all the bandpass switching etc - all is fine, I notice however that on TX the voltage on the rx line should drop from ~10V to 0 - ie muting the rx line, but it doesn't - another fault.I remove the PCB (as Q2 is mounted under the board) and as I lift the board - what do I find ? a rather burnt Q2 - so its added to the component list for repair.So conclusion ? - well it must have had some RF into it I would have thought. my guess is that the attenuator was switched in and it took out the 56R resistor, then the inductor and then Q2, thankfully it was transient and so no further damage was done.Components ordered, arrived and a pleasurable 10 minute install of the inductor L4 (if you should do this watch the soldering iron on the relay !!!, then removed the board and replace Q2.Re-assemble it all, check and check again - all works perfectly.I then do a full alignment check as per the workshop manual, everything is spot on, nothing to adjust or change.I then spend a little time cleaning it up a little and then a very pleasant afternoon on 40M and 18M having so very pleasant QSO's - all works perfectly.So the conclusion;Yes there was some damage, someone (or something) did take out some front end components but whatever it was must have been pretty short lived as none of the normal protection components or bandpass switching diodes were damaged, my guess is that L4 and Q2 went, L4 going open circuit effectively acting as a fuse / protection component :)So a little time (about 2 hours fault finding) 3 faults and total component cost of £2.45 - I have a working really nice TS-570DGE  working really well - RESULT :)Now to keep or sell - I wonder ?  

TS-570DGE Repair

Well I couldn't resist could I ?

Recently, well a few weeks ago actually, on a well known auction site, a TS-570DGE that was faulty. TX fine but RX was as deaf as a post, didn't have a good picture at all (see below)

Should I or shoudn't I  ? - surface mount doesn't frighten me, the owner hints that it might be the siwtching diodes in the bandpass filters, but then if its had higher power RF into it then who knows ?

I decide (as with all my bids) what I think its worth, place the bid and wait.

I win it for for quite a bit lower than my top limit :)

Its reasonably local, so I go and pick it up, its in excellent condition, is a DGE version, has a box with the packing, microphone, manual and power lead.

During our chat, he says that he has had the case off (bad sign) but was not impressed with all the surface mount and so didn't touch it (good sign !), he did say that when he touched around the input side of the receiver (!!!!) the receive side did pick up (it received signals!) - so might be a dodgy connection. He demonstrated that the TX side worked (it did :) ) and also that the rx side was as deaf as a post (it was !!).

He also had people email him saying this was a common fault and it was the swithcing diodes in the front end. I did some research on the net, and looked at the circuit diagram, but came up with nothing that was a 'common' fault. Yes there were faults reported and yes there are plenty of switching diodes in the from end but 'common' no.

So I pay the money, and retire home, pleased with my purchase and keen to find out what the real reason for the poor receive is.

Down East Microwave - 144-28 Transverter Repair - Helping out someone else.....

I've been very busy at work recently and so not had much time for the 811 or any of my other projects 

BUT

When I was on 40M a few weeks ago I had a really great QSO with someone that had a 144 to 28Mhz  transverter that needed repair, and I talked about some of the repairs that I do, he had a look at this blog and my QRZ.com page and well ........ I ended up offering to take a look (with no guarantee's though !!!)

When it arrived a couple of weeks  it was a top end (Down East Microwave) transverter with a 28Mhz IF, low level input (0dBm). The report was that it didn't transmit. It did a manual with it, although when I opened it up it didn't seem to match the actual layout of the board although the circuit looked pretty close !

First things first, a close visual inspection - nothing to note  here no burnt components (to the naked eye), no overloading by the look of it. The owner did  say that he thought it might have had a near miss with lightening (!!) and so I had expected the worse, but no.

I was very impressed with the build quality, absolutely superb :) here's a picture of it on the bench ;

So i powered it up (via a current limited supply) - checked the Local Oscillator, right frequency - has a wonderful temperature stabilised arrangement - worth looking at the circuit really good for frequency stability, warms the crystal up and keeps it there - very clever, i've seen it in professional kit but never in a transverter before !

Got a suitable IF transceiver (in this case a ten tec as it has a nice transverter output at the right level and does key output for the ptt) connected it up and...................

RX worked fine - injected a -127dBm 2M signal from my test set and this was easily detectable in the IF transceiver so no problems there - great news !

Checked the input level from the transverter correct at 0dBM (224mV into 50R), accroding to the manual this should give more than 10W out on 2M from the transverter.

Key down on CW (as per manual suggested setup) - nothing out into the Bird ThruLine :(
well after putting it onto the test set it was actually giving out ~300mW !!

PA block failure perhaps ?

So worked my way down (or is it up ?) the tx chain, after swtiching the 28Mhz IF signal goes through a MAR 3 MMIC amplifier to take it up from 0dBm and yes 0dBm in but -6dBm out - so the amplifier is an attenuator  :) might be a problem !

Check the voltage supply in the area / biasing and all looked reasonable - so decided to bypass the amplifier effectively making it into a higher input power transverter, injected 1W from an FT817 on 28Mhz and w and behold ~20W out on the Bird.

So a fault MAR3 MMIC, after finding the right manual it said this should be a MAR 6 anyway which was a little confusing, the owner didn't know why and had never changed it so perhaps it was built this way ?

So after chatting with the owner via email, I ordered some MAR 3 and MAR 6 MMIC's (always good to have a small stock and I didn't have any !!). 

Arrived last Friday, quick change (photo of new one installed below) a new MAR 6 was installed as per the circuit diagram (the scratches where its mounted were already there, this is where the track was cut to insert the option MMIC in the TX chain to allow lower drive levels, its detailed in the manual);

For those readers who don't know what a MMIC looks like its the small black dot with 4 legs in a star arrangement above the orange disc ceramic capacitor :)

Fired up the Ten Tec as the IF on 28Mhz and the result is shown below ;

The meter on the left is showing the RF input to the PA Hybrid at 1.6V which is 50mW (what the manual says it should be) and the output on the Bird is showing 35W - this is using CW as per the manual suggests. I set the input control (the lower blue variable resistor on the MAR6 photo)  to give the 50mW input required.

So all fixed and working, gives approx 23W on speech peeks, and the output is nice and clean - see below (apologies for the poor photo!)  each graticule block is 50Mhz and the large spike (!) is of course the 144Mhz signal.

After a few more email conversations with the owner, his IF transceiver gave a little more output than mine +10dBm (100mW) and I wanted to check that the input into the PA block hybrid didn't overload anything and so I constructed a 20dB attenuator and used a 1W input into this from an FT-817 to give 100mW and then adjusted the input resistor pot (as above) to give the right input level of 50mW.

I then gave it a really good test over several hours at that level with simulated long overs etc with breaks etc, the unit get warm but not overly so, and so I think this is fixed - result.

Now Ii've just got to post it back to the owner - hope he likes it - its certainly working better now than before !!!!